A dual-controlled tunable broadband terahertz absorber based on a hybrid graphene-Dirac semimetal structure is designed and studied. Owing to the flexible tunability of the surface conductivity of graphene and relative permittivity of Dirac semimetal, the absorption bandwidth can be tuned independently or jointly by shifting the Fermi energy through chemical doping or applying gate voltage. Under normal incidence, the device exhibits a high absorption larger than 90% over a broad range of 4.06–10.7 THz for both TE and TM polarizations. Moreover, the absorber is insensitive to incident angles, yielding a high absorption over 90% at a large incident angle of 60° and 70° for TE and TM modes, respectively. The structure shows great potential in miniaturized ultra-broadband terahertz absorbers and related applications. Terahertz (THz) absorbers have been widely investigated due to their wide applications in electromagnetic radiation, radiation, sensation, and thermal imaging ,2,3. A cIn this work, a dual-controlled ultra-broadband THz absorber based on a hybrid graphene-Dirac semimetal multilayer structure is proposed and studied. By simply shifting the Fermi levels of graphene and Dirac semimetal, the proposed structure shows tunable absorption over a broadband wavelength range. The simulated results show that under normal incidence, the device exhibits a high absorption larger than 90% over a broad range of 4.06–10.7 THz for both TE and TM polarizations. Moreover, the absorber is insensitive to incident angles, yielding a high absorption over 90% at a large incident angle of 60° and 70° for TE and TM modes, respectively. The physical mechanisms are also elucidated by the impedance matching theory and electric field analyses.It is known that graphene is a potential material to design reconfigurable THz devices due to the tunable surface conductivity  formula :(1)σg(ω)In the THz range, the relative permittivity of BDS can be expressed as :(2)ε=εb+σ can be written as [The dynamic conductivity itten as :(3)Reσ=erated as :(5)θ(t)=From Equations (2)–(5), we can see that the permittivity of BDS can also be controlled by Fermi energy. 2O3 layer with a relative permittivity of 2.28 and loss tangent of 0.04, BDS complementary pattern layer, lower Al2O3 layer, and gold layer with conductivity σ = 4.56 × 107 S/m from top to bottom. In this work, AlCuFe is used as the BDS material [The schematic diagram of the dual-controlled ultra-broadband THz absorber is illustrated in material .2O3 layer is to provide resonance absorption space, and the bottom gold layer is used to reflect the incident wave. In order to satisfy the polarization and incident angle insensitivity, we have designed a symmetrical structure as shown in The top graphene patterned layer is to match the impedance of free space at a specific working frequency band, so as to achieve no reflection of the incident wave. The BDS pattern of the middle layer is to expand the absorption bandwidth. The basic function of the Al1, w2, R1, R2, and R3 to construct circular rings and square channels in the graphene pattern. (2) In the design of the patterned BDS structure, on the one hand, the method of designing multiple small channels similar to the graphene layer is continued to be used; on the other hand, the structure is supposed to complement to the upper graphene pattern. In this case, the two absorption layers would resonate at different frequencies, thus extending the absorption bandwidth of the structure. In our proposed structure, the BDS pattern is controlled by w1, w2, a, and b. (3) In the conventional absorbing material model, in order to ensure that the wavelength in the dielectric layers forms a stable standing wave of electromagnetic waves, the thickness of the dielectric layer satisfies h = (2n + 1) λ/4, where n = 0, 1, 2.... In that case, the incident electromagnetic wave would interfere destructively with the reflected wave from the bottom metal layer, leading to the absorption of the electromagnetic wave energy by the structure. But for the metamaterial absorber, the thickness of the dielectric layer does not need to be a quarter wavelength as the dielectric constant and permeability of the metamaterial are controllable, which facilitates the realization of the absorber structure. In our work, the size of the two dielectric layers of graphene-BDS hybrid absorber is 4 μm and 2.8 μm, which are obtained from scanning optimization in the simulation software in consideration of the requirements of structural miniaturization and high absorption performance.The reasons for designing this structure are as follows: (1) In the patterned graphene structure, due to the localized surface plasmon resonance, most of the electric field will be limited to the edge of the annular graphene. This resonance can effectively capture light energy to enhance the absorption rate. More circular channels in the graphene pattern can be arranged to limit the electric field distribution on the edge of the graphene, thereby increasing the absorption rate. Therefore, in our proposed structure, we use w21 = 0 and absorbance A = 1 − |S11|2. The detailed dimensional parameters of the proposed absorber are listed in Ansys HFSS is used for the simulation of the proposed structure. The THz wave impinges on the graphene pattern from the air. Periodic linked boundary conditions (primary and secondary) are adopted in the x- and y-directions and Floquet port excitation in the z-direction. To better describe a graphene film, the graphene layer is considered as a two-dimensional conductive surface with the impedance boundary of resistance and reactance in the software simulations. For BDS material, the relative permittivity is created by importing relevant data obtained from Equations (2)–(5). Since the thickness of the bottom gold film is considerably larger than the skin depth, the electromagnetic waves can hardly be transmitted through the bottom metal plate, leading to SThe absorption properties of different structures under normal incident TE and TM polarizations are shown in Next, we studied the influence of graphene Fermi energy on absorption performance. BDS offers another possibility to tune the absorption performance of the hybrid structures. To sum up, owing to the tunability of absorption bandwidth by graphene Fermi energy and the control of resonance absorption peaks by BDS Fermi energy, our proposed absorber combines the advantages of being broadband-controlled and frequency-adjusted.For THz absorbers, the sensitivity of polarization and incident angle is a significant issue in practical applications. Here, the absorption properties of the proposed structure under different polarization waves and incident angles are investigated, as shown in d is the travelled distance and k0 is the propagation constant of the wave at free space. The calculated values of the constitutive parameters for three absorption peaks are listed in To clarify the working principle, the absorption peaks located at 4.49, 6.738, and 9.66 THz are explained according to the impedance matching theory. The relative impedance (Zr) is calculated using Equations (6)–(10), where x and y directions and the internal oblique gaps, while the electric field distribution of the BDS layer is mainly concentrated in the wide channels along the x direction. At 6.73 THz, the electric field of the graphene layer is concentrated in each slit except for the four internal oblique slits, while the electric field of the BDS layer is scattered in the square blank channels. At 9.66 THz, the electric field of the graphene layer is concentrated in each slit except for the four slits in the x direction, and the electric field of the BDS layer is concentrated on the four sides of the x direction of the outer frame.In order to illustrate the working principle more intuitively, the electric field distributions on the x-y plane at frequencies of 4.49, 6.73, and 9.66 THz corresponding to absorption peaks I-III for TE polarization are shown in x-axis and induce tangential electric fields on both graphene and BDS layers, which will cause energy loss. The energy consumption inside the loss materials including graphene, BDS and Al2O3 can be calculated by:V is the volume of lossy material, and On the whole, as the frequency increases, the intensity of the electric field first increases and then decreases as the frequency increases in the graphene layer. As for the BDS layer, the change trend is opposite and firstly decreases and then increases. This is because that the incident wave excites carriers to oscillate along the 2O3 layer play an important role in absorption. The absorption contribution rate of each part is shown in 2O3 layer, which is consistent with the absolute electric field distributions in 2O3 layer in the THz frequency range. Due to the symmetry of the structure, the TM polarization is the same as the TE polarization.In order to understand how the energy is located at the resonance frequency, the electric field distribution in the y-z plane is simulated to reveal where absorption mainly occurs. In summary, a tunable hybrid graphene-BDS broadband THz absorber is designed and studied. Due to the combination of advantages of graphene and BDS, the structure can achieve a high absorption exceeding 90% over a broad wavelength range of 6.64 THz. By adjusting the Fermi energy level of graphene and BDS, the absorption peaks and bandwidth can be dynamically tuned without reconstructing the structure. Besides, the absorber is insensitive to incident angles, yielding a high absorption over 90% at a large incident angle of 60° and 70° for TE and TM modes, respectively. Owing to its excellent performance, the proposed absorber has great potential in miniaturized ultra-broadband THz devices and microsystems.


Nature-based recreation in urban areas is essential for the well-being of citizens. Park green space (PGS) is a necessary urban infrastructure and a critical step of urban planning and policy-making. The existing research on PGS only focuses on service allocation problems existing in the current urban development, ignoring changes in residential communities accessibility. This research provides new ideas to evaluate PGS. Based on parks and residential communities’ data, we adopt an improved Gaussian-based two-step floating catchment area (2SFCA) method to evaluate PGS accessibility in Ningbo (China) and its matching with different levels of residential areas. We present a case study in Ningbo, and discuss its implications for PGS management. This study contains two elements: (a) Compare the current and initial PGS accessibility of each community to accurately identify the communities with PGS vacancies. (b) Analyze and discuss the association between community accessibility and residential house prices. Compare the PGS coverage ratios of communities at different levels to determine the equity of PGS planning in Ningbo. We found that the level of PGS allocation in the central area of Ningbo is high. Obviously, high-value clusters are formed in Sanjiangkou, Zhenhai New Town, Southern and Eastern Yinzhou. The accessibility level in the middle area of Yinzhou is low, and there are super high accessibility residential communities in the outer city area. There is an exact period of green space vacancy in the middle and the outer area. The residential areas with ultra-high accessibility did not configure PGS services at the beginning of their construction. There is no noticeable difference in PGS accessibility of residential communities of different levels at present, but 149 low- and middle-income residential communities lack green space service when the construction was completed. High-end residential communities have priority on enjoying park green space services. Our study suggests that PGS accessibility should be studied temporally and spatially for each residential community. The Ningbo government should strengthen the balanced construction of green space in parks and guarantee green space services for low-end residential communities to improve green space equity. Half of the world’s population lives in cities, and the urban population’s rapid growth places higher demands on infrastructure . The disSince the 1980s, green space research has increased, mainly using green space rate and green area to reflect the overall green service level. However, there is not enough consideration at the micro-level. In 1998, Chinese scholars first proposed landscape accessibility, which became the main content of green space research . ResearcResearch on PGS equity is usually based on spatial accessibility. Euclidean distance or road network analysis in geographic information systems (GIS) is often used to examine the shortest distance to the nearest green space. However, people may choose other green spaces over the nearest one because of social preferences and PGS size. Accordingly, the gravity model is employed to address this issue. Radke and Mu first proposed a two-step floating catchment area (2SFCA) approach to measure spatial accessibility that takes into account interactions . Luo furResearch on the equity of green spaces has focused on spatial equity and social equity. Spatial equity focuses on differences in the spatial distribution and quality of green spaces. The research found significant differences in the number of users for parks of different sizes . RigolonIn these previous studies, we found a hidden problem. The accessibility evaluation in the green space equity study focused on PGS’s service level at the present stage but neglected the PGS matching with the residential community in its development . The conBeing an economic, political, and cultural center in the Yangtze River Delta China and currently experiencing unprecedented growth and expansion, Ningbo is selected for analysis in this study. Moreover, this city has experienced a tremendous green space loss, similar to many other cities in China. Therefore, we select Ningbo as the research area to enrich the local green space service research cases in China. On the research scale, Chinese studies are mostly evaluated on the sub-districts scale . The evaChina’s research is mostly concentrated in first-tier cities, such as Beijing , ShanghaBecause of its openness and publicity, PGS has become the primary way for Chinese residents to obtain green space services. Take PGS as the service supply source, and use the park level and green space area to reflect the supply capacity. According to the “2014 Ningbo Ecological Green Space System Special Plan”, map the distribution of parks in the study area a, Includhttps://nb.anjuke.com/), “Lianjiawang” (https://nb.lianjia.com/), and “Ningbo Housing Management Bureau,” 2225 residential communities in the study area were collected. The main information includes location, number of households, average price, and year of construction. According to the “Ningbo statistical yearbook 2019”, the average population per household is 2.50. Based on this, calculate the total population of each residential community. Furthermore match the location of it on the map  method. In recent years, 2SFCA has gradually become the mainstream because of its rich expansion forms for different cities. Radke and Mu first proposed 2SFCA, and then the extension of the distance attenuation function was introduced . The priThe extended form of the 2SFCA method has not been adjusted according to the research content in the current study. With the aim in mind, in this paper, we present an improved Gaussian-based 2SFCA for PGS. Add a time limit to the 2SFCA: when the park is built later than the community, it will not be counted in the service radius. Through this restriction, PGS accessibility in the present and at the beginning of the construction is calculated. By comparing the PGS accessibility at different time points, identify people with green space service vacancies. The specific process is as follows:d0  for each park green space j to form a spatial scope. For the community population k distributed in the spatial scope, we use Gaussian equation to give weight. The weighted population is summed to get all the potential users of the green space j, and then the green space is divided by the potential users to get the supply-demand ratio jR.First of all, we set a space distance threshold kC is the number of community population in the spatial scope of green space j; kjd is the spatial distance from the center of the community to the center of green space j; jS is the capacity of green space, where the area of park green space reflects the supply capacity of the park. G is the Gaussian equation, see Equation (2):i, given a spatial distance threshold d0  to form another spatial scope, The supply-demand ratio of each green area l, lR is weighted by the Gaussian equation, and then the weighted weekly supply-demand ratio is summed to obtain the park green space accessibility of each residential community iA, the size of iA can be understood as the threshold per capita green space in each district in the area:In the second step, for each residential community lR represents the supply-demand ratio of green space l within the spatial function threshold of residential community i, lT represents the opening year of green space l, and iT represents the construction year of residential community i. The description of other indicators is the same as above. The accessibility value can be understood as the per capita green area after a unique weighting process. With this formula, we can find out some communities. These communities were not served by parks and green spaces at the time they were first built. We call them unserved communities.In the formula: d0 according to the PGS type, and there are six residential communities in the spatial scope of the PGS. For each of them, the spatial distance from the PGS can be measured, and then the corresponding Gaussian equation can be established according to Equation (2), respectively. The PGS area and the number of people represented by each community are also known, so the corresponding supply and demand ratios can be derived from Equation (1). In d0 is set to 2500 m depending on the residents’ travel speed. According to Equation (3), the PGS accessibility of the residential community is obtained by accumulating the supply ratio to demand for each community.The accessibility calculation result is a spatial latitude value. To make the results easy to understand and analyze, we use house prices to represent the socio-economic attributes of residents. We obtain the prices of houses in the residential neighborhoods within the study area and then match them with the accessibility. According to the average housing price, the residential communities are divided into six levels: first, second, third, fourth, fifth, and unit communities. Respond to the disparity in residents′ access to green space services by counting the number of unserved communities in different classes of neighborhoods. The ratio of green space coverage in Ningbo is based on the greening requirements of the city. Compare the current differences in urban green space coverage.Cr is the coverage ratio of park green space. Ni is the number of i-level communities within 500 m of the park green space. Siis the total number of In Equation (4), At present, the accessibility of PGs in Ningbo is high, but there is imbalance among regions. The Sanjiang area has high-value clusters. Zhenhai New Town, Yinzhou Southern Business District, and Eastern New Town maintain a high level. Meanwhile, there are ultra-high accessibility residential areas in the outer area . SanjianThere are few parks in Zhenhai District. However, two high-value gathering areas are evident. High-access residential communities are mainly distributed near the Ningbo Botanical Garden and Zhenhai Green Axis Sports Park. Because this is the central area in the Zhenhai region. Ningbo Botanical Garden exceeds 10 hectares, which is significantly improving the service level of PGS in surrounding areas. Surprisingly, some residential communities in the outer area of the city have extremely high PGS accessibility. Combined with the population density map, we find that the super high accessibility residential areas in the city’s outer area are its low population density. There is pretty good PGS scattered around them. Taking Beilun ultra-high accessibility level residential areas as an example, the region’s total population is only. There are seven community parks within its radius of 2.5 km, including Xinmo Park, Meixu Park, Ningbobang Park, and Dadongjiang park. The total green area is more than 20 hectares.To further study urban parks and residential communities’ spatial and temporal distribution, Ningbo city is divided into three parts: the inner area, middle area, and the outer area . We count the year that each residential community was built and compare the time that parks were built. Due to the lack of construction years in some communities, 1514 communities have been counted. Equation (3) is used to calculate PGS accessibility when it has just been constructed . By compThere are 45 parks in the inner area. The parks were generally built earlier, with the average year of 1997. The number of parks built before 2000 exceeded 20. Early completion of PGS met the needs of residents. The number of communities without service is the smallest; the percentage is only 2.07%. Simultaneously, the number of residential communities in the inner ring has slowed down, and the entire area’s living space is becoming saturated. The residential communities in the inner ring area have been well supplied with infrastructure throughout the city′s development, and residents of this area enjoy some of the best PGS services in Ningbo. The middle area has the most unserved communities with a percentage of 18.61% . Over thThe outer area is a typical urban-rural junction, with 57 unserviced communities mainly located in Zhenhai, Beilun, and the west of Haishu. There is a significant PGS vacancy in this area, with nearly one-third of communities not having a corresponding PGS at the time they were built . Based oSuch a result is not found in previous surveys, but it is an element that cannot be ignored. Although the current service level is good, we found that the planning and construction process of green spaces in Ningbo has not been timely in meeting residents’ green space needs in the middle and outer area. There is a shortcoming in evaluating the service level of PGS: it ignores the sequence of residents enjoying green space services. Through the space-time matching evaluation of residential communities and PGS in the central area of Ningbo, we can accurately identify the green space vacant area and the residential community with service vacancy, which provides a more accurate judgment for future targeted solutions.In 1998, China implemented the housing commercialization reform. Taking 1998 as the starting year and counting the commercial housing built after that, the socio-economic status of buyers is reflected through house prices. Excluding the houses before 1998 and the houses whose construction year is not available, a total of 1334 commercial communities are counted. According to the average housing price, the residential communities are divided into six levels: first, second, third, fourth, fifth, and unit communities. The higher the group, the lower the income level of the residents of the residential areas. Calculate the average accessibility of each group of residential communities .The results show that: (1) The average accessibility of the unit communities is the highest. At present, the average accessibility of different levels of residential communities in the central urban area of Ningbo is similar, and there is no evident gentrification of PGS. The construction years of the unit communities were all before 1998. They were planned and constructed by the government and distributed in the old city of the Sanjiang area, so they have good green space services. (2) In terms of the average accessibility at the beginning of construction, the unit communities are the highest, followed by the first-level residential communities, and the fifth-level residential communities are the lowest. High-income groups have the smallest difference in PGS accessibility between the two stages, and green facilities can be matched in time. (3) In terms of the number of unserviced communities at the beginning of construction, there is no unserviceable situation in the first and second-level residential communities. Main unserviced communities are concentrated in low—income communities such as the third and fourth levels. High-end residential PGS services have a good match, and they have a priority on enjoying PGS services. There are extensive green space service vacancies in low- and middle-end residential communities. The financial capacity of residents directly affects the level of green space services they receive. Lower-income residents may not have immediate access to PGS when they move into a neighborhood. There are significant social inequalities in the planning process of green spaces in Ningbo.We compared the spatial distribution of different residential communities’ levels and the density of the parks . RegardiIn general, there is a temporal and spatial misalignment in the planning process of Ningbo Greenland, which leads to PGS inequities. There is a period of obvious green space service vacancies in the middle and low-end communities, and high-income communities have priority in enjoying park services. At the same time, the first-level and fifth-level communities have the lowest percentage of seeing gardens in 500 m.The first-level communities have natural and superior green space conditions, while the fifth-level communities have much lower percentages than the second, third, and fourth-level communities. It shows that the lowest-income communities have the lowest level of green space coverage, which is unfair. The unit community maintains a relatively high level in terms of accessibility and the ratio of 500 m garden communities. Planners should formulate reasonable greening policies according to the needs of different types of communities to avoid the waste of PGs resources.The study of PGS in central Ningbo shows that the residential accessibility in the inner ring is higher than that of the middle and outer rings, and that residents in affluent communities benefit more from the green accessibility than those in low—and middle-income communities. This difference is partly attributed to the spatial reconstruction of the green infrastructure in Ningbo. Urban development in the inner ring basically covers all parts of facilities such as medical care, education, and green space. Traffic problems have been alleviated after the opening of urban inner ring viaducts and expressways. Therefore, the urban PGS service level in the inner ring region is the highest. Along with industrial suburbanization, Ningbo takes tertiary industry as the key point of urban development. The development key of the town gradually shifts. The construction of green infrastructure starts, and good green infrastructure in the central area contributes to better accessibility. In the Master Plan of Ningbo city (2006–2020), it is clearly pointed out that the Sanjiang Area need to form a commercial center with dual-core spatial structure and the eastern region should create an ecological leisure axis based on water and green space along the river. In this case, the configuration of urban parks in Sanjiangkou and Eastern New Town is far better than the suburban fringe area.Our results are similar to those of previous studies, which found that compared with disadvantaged communities, more affluent communities are more likely to acquire green space ,52. In tManagers and planners should be sensitive to the inequalities in urban PGS. The attribute of PGS is not only reflected in the quality and spatial distribution. Besides, the urgency of different social groups′ demands for green space in parks is also an important indicator of green planning. To ensure equal opportunities, PGS services should be provided to the social groups living in the middle- and low-end communities. The spatio-temporal inequality of PGS accessibility in Ningbo can help municipalities and planners determine where further efforts should be made to improve green space equity. The time and space mismatch between housing prices and park green space accessibility help to inspire greening strategies. Planning should provide funds for green space around low-income communities in suburban areas to meet the needs of residents for green infrastructure. We are marking residential areas where green spaces have been vacant in the past in the hope that they will be taken seriously by planners. Meanwhile, in the Special Plan for Ningbo Ecological Green space System, it is proposed that the service radius of park green space 500 m reaches over 90%. As shown in This work provides comparative study on the individual accessibility of residential communities so that the method can more accurately evaluate the rationality of urban green space planning. We hope to objectively evaluate the fairness of PGS in this way. Meanwhile, we offer a new object of study for future research. That is to study the micro-perceptions of people in unserved communities. Residents′ perceptions of green space vacancies may not be very sensitive, so our future research will be to investigate residents′ satisfaction with PGS. We would like to know the maximum amount of time residents have allowed PGS vacancies. Setting a maximum threshold for vacancy periods in the future plan can alleviate residents′ frustration with the problem. Although we improve the methods and provide ideas, there are still some limitations. First of all, housing prices are used to reflect the economic conditions of residents without considering relevant factors, including external environmental information such as location, environment, and traffic. In future work, these factors can be combined to reflect changes in socio-economic conditions. Secondly, the green space service level measurement based on the Gaussian-based 2SFCA method takes the spatial distance as the reference, without considering the barrier function of traffic trunk lines, and considering that green accessibility of the Ningbo community may be affected by specific environmental factors, such as the distance to the central business district. It needs to be defined as a control variable in future studies. Thirdly, as for the population of residential areas, there is a certain vacancy rate of houses in the residential areas, so there is a deviation between the population data and the actual situation. We use park green space data, urban block green space and so on are not included in the study. In the future, based on information technology and social software to obtain spatial population data, we should further study the fairness of green space.Based on the data of PGS and residential communities, this paper adopts an improved Gaussian-based 2FCA method to calculate the accessibility of PGS in Ningbo. We integrate the year of construction and housing price information to evaluate the equity of PGS in Ningbo. The results show that the accessibility of PGs in Ningbo is good, but there are still regional differences. The middle part of Yinzhou is an obvious low value area, and there are high accessibility communities in the outer ring. By comparing the initial and current accessibility, we found that 181 residential communities with PGS service vacancies. There are significant spatial differences with initial PGS accessibility in the middle and outer Rings. The current high accessibility communities in outer ring lack PGS service at the beginning of their construction. Unserved communities are concentrated in low-end and mid-range neighborhoods. High-end communities have absolute priority access to the park green space service sequence. The highest end and lowest end communities have the lowest percentage of garden visits at 500 m. The most expensive communities have a very privileged natural environment inside and they don′t need PGS services. While the lowest end of communities have the lowest level of green area coverage, which is unfair.In the past, Chinese residents generally paid more attention to educational resources, commercial facilities, and transportation facilities. With the improvement of living standards, they care more about their health and PGS facilities have also attracted more and more attention. The evaluation of PGS accessibility based on spatial distribution cannot accurately identify communities with green space vacancies, which will impact future in-depth research. Government planning could lead to 5–10 years of residents not getting PGS services. This is unacceptable for a family. Therefore, it is very necessary to identify these groups, because they may dominate the future urban green space planning. That is why we do this research. Our research has identified these groups and demonstrated that social inequality is the main cause. In the future, planners may not be able to avoid this phenomenon. Therefore, future research will focus on the perception of green space among residents of unserved communities. Based on the discussion and conclusion of our study, we put forward the following relevant policy suggestions to the future planning: (a) Adjust the allocation of resources according to the needs of the population, focus on vulnerable areas, and add new PGS. We suggest to create a new comprehensive park in middle area of Yinzhou to meet the recreational needs of a large population. (b) The amount of green space within different communities varies, thus planners should implement appropriate greening strategies for different type communities. (c) Gaining awareness to the green space vacancy in the process of planning, the people without park green space service can provide meaningful ideas for the future planning.


The air gap thus decreases leading to increase in the tunneling current across the junction. The gap however is independent of temperature fluctuations as both patches expand or contract by near equal amounts. Humidity sensor action demonstrates an unassisted reversible resistance reduction Rmax/Rmin ~105 when the device is exposed to 20–90 RH% at a standby DC power consumption of ~0.4 pW. The observed resistance change when subject to a temperature sweep of 25–60 ° C @24% RH was ~0.0025% of the full device output range.We present the design, fabrication and response of a humidity sensor based on electrical tunneling through temperature-stabilized nanometer gaps. The sensor consists of two stacked metal electrodes separated by ~2.5 nm of vertical air gap. Upper and lower electrodes rest on separate 1.5 μm thick polyimide patches with nearly identical thermal expansion but different gas absorption characteristics. When exposed to a humidity change, the patch under the bottom electrode swells but the patch under the top electrode does not, as it is covered with a water-vapor diffusion barrier ~8 nm of Al Kharaz and Jones were one of the first to report optical methods of humidity measurement6. First introduced by Wohltjen in 1984, SAW sensors were widely used as hygrometers, where shift in resonant frequencies was a direct indication of mass of adsorbed water vapor7. The two most common type of hygrometer devices are resistive and capacitive type.Humidity sensors can be realized using various technologies8. These devices are used in approximately 75% of applications3. In these devices, the dielectric properties of a hygroscopic layer  change when exposed to humidity. This change may also be accompanied by swelling of the hygroscopic layer. Micro-cantilevers have also been used as capacitive type humidity sensors. In these devices, a thin polyimide film is patterned on the cantilever and when exposed to humidity, the polymer film tends to expand thereby exerting mechanical stress on the cantilever causing it to bend9. Capacitive humidity sensors display linear operation and can accurately measure from 0–100% relative humidity with an output range typically ~30% of the default capacitance. These devices consume very little electrical power and are relatively cheap to fabricate3.Capacitive humidity sensors are the most common realizations of microfabricated hygrometers2O310, conductive polymers such as PVA with graphitized carbon11 and polyelectrolytes12 have been used as functional materials for resistive humidity sensors. In contrast to capacitive devices, resistive humidity sensors are highly nonlinear and capable of providing several orders of magnitude change in resistance. An advantage of resistive RH sensors is their interchangeability, typically within ±2% RH. Operating temperatures of resistive sensors ranges from −40 °C to 100 °C; however these devices have significant temperature dependencies. For example, a typical temperature coefficient for a resistive RH sensor is −1% RH / °C.Resistive humidity sensors are also extensively used. In these devices the resistance of the sensing material changes when exposed to humidity. Ceramics such as AlIn this work we present a new type of microfabricated humidity sensor that is able to provide large output range and a low temperature dependence. The device utilizes the expansion of a polymer that swells when exposed to humidity as in the capacitive device, but it produces a resistive output that measures the polymer expansion through tunneling current across a humidity dependent, thermally stabilized nanogap. The tunneling current changes many orders of magnitude providing similar output as the resistive type device with a low temperature dependence. Table In the first part of the article, we focus on the fabrication and electrical characterization of the device. The second part of the paper will describe the device response to change in ambient RH% and temperature response of the device. The third part of the article deals with relevant analysis of the current conduction across the nanogap and a mathematical model describing current flow as well as an equivalent electrical circuit. This section also includes a discussion of the sorption kinetics of the device and analysis of the absorption-desorption phenomenon.16. Similar to other devices built by Mastrangelo et al.19, these can be used as low-power and highly sensitive tunneling hygrometers for IoT applications. In this article, we show the working of a new type of tunneling hygrometer. The device consists of a pair of upper and lower electrodes, separated by an air-gap of ~2.5 nm as shown in Fig. Nanogap electrodes (electrodes separated by a gap of a few nanometers), have been previously used for highly sensitive bio-sensor applications20. Figure 21 hence the device resistance goes asA(T) and B are fitting parameters. In the simple configuration shown in Fig. Δ is also affected by the thermal expansion of the polyimide, which makes the coefficient A and the resistance of the device strongly dependent of the ambient temperature.The upper electrode rests at a fixed height. The bottom electrode rests on top of a hygroscopic polymer, polyimide that swells when humidity is absorbed; thus reducing the gap between the two electrodes. The swelling of the polyimide with humidity is linear corresponding to its humidity coefficient of expansion or CHE, which is 60–75 ppm/% RH2O3 diffusion barrier whereas that under the lower electrode is exposed to ambient atmosphere.To eliminate this strong temperature dependence we utilize the differential device arrangement as shown in the schematic of Fig. We thus achieve nanogap temperature stabilization by using cancelation of a common mode thermal expansion of both patches and humidity signal extraction by differential response to humidity between the two patches. Since both the top and bottom electrodes are standing on near identical polyimide patches, any increase in ambient temperature would lead to both the patches expanding almost equally. This ensures that in the event of temperature fluctuation, the nanogap distance between the top and bottom electrode will remain unchanged and the electrical response will be negligible in comparison to sensor response.I-V characteristics of the device after fabrication of the device. The junction I-V characteristics are typical of very low current on account of very low electron tunneling across an air-gap of ~2.5 nm. The average DC resistance of the junction is measured to be ~271 GΩ. This shows an extremely low leakage current under low biasing conditions.The simplified fabrication process is shown in Fig. 2O3 acts as a diffusion barrier and prevents the polyimide patch under the upper electrode from absorbing water molecules22. This differential swelling of the polyimide patches results in the inter-electrode distance to reduce below 2.5 nm. Therefore, after absorption of water vapor molecules, the tunneling distance for the conduction electrons reduces. Since tunneling current exhibits exponential dependence on tunneling distance, increase in humidity levels lead to an exponential increase in tunneling current. In other words, junction resistance decreases exponentially when exposed to increased humidity levels.After the device is fabricated, the upper and lower electrodes are separated by an air-gap of ~ 2.5 nm. Therefore current flow across the nanogap junction involves conducting electrons tunneling through 2.5 nm of air-gap. However, when the device is exposed to an increase in humidity, only the un-protected patch of polyimide which is beneath the lower electrode absorbs water-vapor molecules and swells. This is because the AlI-V plots, the increasing RH% leads to an increase in magnitude of current flow for the same voltage bias. Figure 3/%RH with an average standard deviation of 6.16 × 10−3 which corresponds to an equivalent noise current of ~34.93 fA. The limit of detection of the device that is defined as three times the noise floor is calculated to be 3 ppb. However, the authors would like to clarify that the calculated limit of detection of the device is based on a linear sensitivity approximation of a non-linear device23. Further device characterization and calibration is required to accurately quantify the sensor parameters. Figure Figure 9. Essentially, temperature compensation can be achieved using passive and active methods. In passive temperature compensation, passive electrical elements such as resistors are employed to compensate pre-determined fluctuations in sensor readout due to temperature changes. Active temperature compensation involves an active temperature feedback to the transducer’s signal processing circuit in order to compensate for the temperature drift. However, all these methods require external power that limit their application in power-scarce environments25. Recently, Rinaldi26 and Mastrangelo27 used self-levelling beams in order to achieve temperature compensation in micromachined sensors. In our proposed tunneling hygrometer, we achieve passive temperature compensation without consuming any external power by using a non-differential polymer expansion design when exposed to temperature fluctuations. As shown in Fig. 2O3, absorbs the molecules and expands, but the protected polymer patch does not. Therefore, air-gap between the electrodes reduces and tunneling current flow between them increases. However, when the device is subjected to an increase in temperature, due to near identical thermal mass and negligible thickness of the Al2O3 layer in comparison with the platform, both polyimide patches expand equally. This ensures that the air-gap between the electrodes remains almost constant.Researchers have always tried to neutralize the undesired temperature response of polymer based sensorsFigure 28. Figure The current conduction through the nanogap junction is considered to be electron tunneling. Essentially, current flow across the air-gap is possible only when conduction electrons tunnel between the metal electrodes. As explained above, when the device is exposed to an increasing RH%, the gap between the electrodes reduce. Tunneling current exponentially depends on the distance through which the electrons have to tunnel through. Therefore, exposure to rising levels of humidity leads to an exponential reduction of junction resistance. The air-gap between the upper and lower electrode can then be considered as a function of RH% and coefficient of hygroscopic expansion of polyimide. The current conduction can be modelled by using the generalized Simmons’ expression for electron tunneling current densityIT = current across the air-gap as a function of applied voltage and relative humidity of the testing chamber, V = Biasing voltage across device, Cg = Relative humidity of the testing chamber, β is a fitting parameter proportional to the coefficient of hygroscopic expansion for polyimide, tp = thickness of polyimide platform, Φa is the mean barrier potential of the air-gap, ds = original air-gap, m = effective mass of tunneling electrons, ħ = reduced Planck’s constant, q = charge of electron and GSO is a conductance fitting factor proportional to the overlap area and having units of S.For intermediate voltages, current flowing through the nanogap junction can be written as:I-V plots of the device after being exposed to varying levels of relative humidity curve fitted with Eq. β to be ~2.78 ppm/RH% and GSO to vary from 5.2 × 10−4 Ω−1 for the I-V curve corresponding to 24 RH% to ~10 Ω−1 for the I-V curve corresponding to 83 RH%. The root-mean-square-error of the curve-fitting plots shown in Fig. Figure 29. Fick’s law of diffusion has been extensively used to describe the diffusion process and to experimentally determine diffusion constant of various substances. The desorption process ideally consists of excess water molecules in the polyimide desorbing back into the atmosphere into water-vapor molecules. This typically is characteristic of a simple first-order desorption process where the absorbed gas-molecule on the surface of the solid simply desorbs back into its gaseous form. The kinetic process is mathematically described by the Polanyi-Wigner equation and is used as the theoretical basis for thermal desorption spectroscopy process30. Figure Since sensor dynamics is heavily dependent on the diffusion of water vapor molecules into the polyimide patch causing expansion of the polymer, the dynamic response of the absorption cycle of the sensor can therefore by mathematically described using a modified version of Fick’s second law2 on a 4-inch Si wafer. Polyimide was then diluted by dissolving uncured HD4104 polyimide (purchased from HD Microsystems) in N-Methyl-2-pyrrolidone (NMP) solvent in the ratio of 1:0.5 (wt/wt). This mixture was then dissolved by using a stirring it with a magnetic stirrer at 300 rpm for 2 hours to ensure perfect mixing of the polyimide and the NMP solvent. This mixture was then spin-coated on the sample at 2000 rpm following the standard procedures for polyimide processing. For curing the polyimide, the sample was kept in a nitrogenized environment oven for three hours at a temperature of 300 °C. This procedure resulted in polyimide thickness of ~1.5 μm. Following this, we sputtered 200 nm of Al on the sample at 50 W and used it as a hard-mask to pattern the underlying polyimide. O2 plasma dry etching for 10 minutes at 100 W was sufficient to remove the unwanted polyimide from the sample. Next, the remnant Al was stripped off by using commercially available aluminum etchant. Following this, we sputtered ~100 nm of Cr at 50 W on the sample and lithographically patterned it to define the lower electrodes. After this, we deposited about 2.5 μm of PECVD α-Si on the sample to form the sacrificial bridging supports for the upper electrode. This was followed by thermal ALD of ~8 nm Al2O3 and its lithographic patterning using BOE. Then, we sputtered ~2.5 nm of α-Si on the sample at 50 W to pattern the sacrificial spacer layer to define the thickness of the eventual nanogap between the electrodes. We next deposited ~1 μm of Al on the sample and patterned it to form the upper electrode. Finally, we sacrificially etched away the α-Si using XeF2. A total of 1200 minutes of etching was required to completely etch away the sacrificial Si and release the upper electrode.The fabrication process started by growing ~1 μm of thermal SiOHigh resolution SEM imaging was done at an accelerating voltage of 15.0 kV by the FEI Nova NanoSEM to visually inspect the fabricated device. I-V characteristics of the device were measured using the Keithley 4200A-SCS Semiconductor Parameter Analyzer. Tunneling current measurements were performed in a dark room, where the device under test was placed on a probe-station kept inside an electrically shielded enclosure to ensure low-noise and high fidelity electrical signals. The enclosure had feedthroughs for providing electrical connections to the probe-station. An inlet from a commercially available humidifier with restricted flow was used to control and maintain the humidity levels in the enclosure. An Arduino powered BME280 chip was placed inside the chamber for serial monitoring of the relative humidity levels.We presented the design, fabrication, electrical characterization and working of a temperature compensated tunneling humidity sensor. Sensor response shows a completely reversible reduction of junction resistance of ~five orders of magnitude with a standby DC power consumption of ~0.4 pW when the device is exposed to an increasing RH% of ~ 20–90 RH%. Passive temperature compensation was also achieved using a non-differential swelling design for the polymer patches. Temperature response showed a reduction of ~2.5 times when the device was exposed to a temperature sweep of 25 °C – 60 °C, which is 0.0025% of the maximum sensor output when exposed to rising levels of humidity. A mathematical model and equivalent electrical circuit was also presented to accurately describe the current conduction mechanism responsible for sensor action. Finally, sensor response dynamics was also investigated and established sorption analytical models were used to describe the time dependent sensor action.


Nitrogen and phosphorus dual-doped multilayer graphene (NPG) was prepared by arc discharge process.NPG exhibits good rate capability and stable cycling performance in both lithium and potassium ion batteries.Full carbon-based lithium/potassium ion capacitors are assembled and show excellent electrochemical performance.The online version of this article (10.1007/s40820-019-0260-6) contains supplementary material, which is available to authorized users. 6‖active carbon (AC) LICs and NPG‖KPF6‖AC PICs are assembled and show excellent electrochemical performance, with competitive energy and power densities. This work provides a route for the large-scale production of dual-doped graphene as a universal anode material for high-performance alkali ion batteries and capacitors.Lithium/potassium ion capacitors (LICs/PICs) have been proposed to bridge the performance gap between high-energy batteries and high-power capacitors. However, their development is hindered by the choice, electrochemical performance, and preparation technique of the battery-type anode materials. Herein, a nitrogen and phosphorus dual-doped multilayer graphene (NPG) material is designed and synthesized through an arc discharge process, using low-cost graphite and solid nitrogen and phosphorus sources. When employed as the anode material, NPG exhibits high capacity, remarkable rate capability, and stable cycling performance in both lithium and potassium ion batteries. This excellent electrochemical performance is ascribed to the synergistic effect of nitrogen and phosphorus doping, which enhances the electrochemical conductivity, provides a higher number of ion storage sites, and leads to increased interlayer spacing. Full carbon-based NPG‖LiPFThe online version of this article (10.1007/s40820-019-0260-6) contains supplementary material, which is available to authorized users. Nevertheless, the production costs of LIBs show an increasing trend, due to the limited availability of lithium sources . Recentlcouple − .931 V [2−1) and poor rate performance cannot meet the increasingly high energy and power density demands of lithium ion capacitors (LICs) [Graphite is currently commercialized as an anode material for LIBs. However, its low theoretical specific capacity (372 mAh gs (LICs) . Graphens (LICs) . Recentls (LICs) , 7. For s (LICs) . The incs (LICs) . Moreoves (LICs) . Thus, d3 or another atmosphere. The rigorous reaction conditions and toxic reactants greatly limit the practical applications of this approach [π–π interactions, irreversible stacking of graphene invariably occurs in the direct thermal annealing process [Heteroatom-doped graphene is usually synthesized through post-thermal treatment and direct synthesis. In the case of post-treatment methods, graphene or graphene oxide has to be obtained first, followed by treatment in NHapproach , 12. Due process , 14. The2 atmosphere, with (NH4)3PO4 as the source of nitrogen and phosphorus. The large-scale NPG nanosheets are composed of 2–6 graphene layers, with P and N concentrations of about 1.3 and 3.2 at.%, respectively. Owing to its remarkable structure and uniform heteroatom doping, NPG displays an extraordinary electrochemical performance as an anode material for LIBs. The enhanced lithium storage properties of NPG are attributed to the synergistic effect of the nitrogen and phosphorus dopants. When employed as anode for PIBs, NPG also shows high capacity, good rate capability, and stable cycling performance. Moreover, full carbon-based LICs and PICs are assembled using the as-prepared NPG as anode and active carbon (AC) as cathode. Both LICs and PICs exhibit a high voltage window, high energy density, and remarkable power density, demonstrating their potential applications. This work introduces a facile arc discharge approach to prepare graphene doped with different heteroatoms, with promising potential as an anode material. In addition, the present work may provide a new route to design high-performance electrode materials for not only Li/K ion batteries or capacitors, but also other energy storage systems.Herein, a one-step arc discharge method is employed to obtain dual N, P heteroatom co-doped graphene (NPG) under He and H4)3PO4 powders were then loaded into the cavity of the graphite rod as the raw materials, and the resulting rod was used as the cathode. At the same time, a pure graphite rod served as the anode. The cathode and anode were placed in a vacuum chamber pumped to below 1 Pa. The arc discharge process was carried out in a water-cooled stainless-steel chamber under a steady current of 120 A and a voltage of 15 V. Hydrogen and helium were introduced into the pre-vacuumed chamber as working atmospheres at a volume ratio of 1:3; both gases had 99.99% purity. NPG was obtained after cooling the cavity to room temperature. For comparison, N-doped graphene (NG) was obtained by introducing NH3 into the reactant gas in the absence of (NH4)3PO4, while P-doped graphene (PG) was obtained by introducing the same number of moles of phosphate instead of (NH4)3PO4. Pure graphene was obtained under the same conditions, without (NH4)3PO4. Graphene sheets were exfoliated by arc discharge in a buffer gas mixture of H2 (10 kPa) and He (90 kPa).The NPG material was prepared by a one-step arc discharge method. In a typical procedure, graphite powders were first compressed into a rod, and an opening was drilled in the center of the rod. (NHX-ray diffraction (XRD) patterns were obtained with a Siemens D500 diffractometer, to investigate the crystal structure of the samples. The surface morphologies and detailed microstructures were analyzed by scanning electron microscopy  and transmission electron microscopy . The Raman spectra were obtained using a LabRAM HR800 confocal microscopic spectrometer with a laser excitation wavelength of 532 nm. The surface elemental composition and bonding configuration were determined by X-ray photoelectron spectroscopy . Thermogravimetric analysis (TGA) was carried out with a Netzsch STA 449C thermal analyzer.N-methylpyrrolidinone solution. The mixtures were mixed evenly, coated onto copper foil substrates and dried at 110 °C for 24 h in a vacuum oven; the cells were then assembled in an argon-filled glove box. The mass loading of the active material was about 1 mg cm−2. The electrolytes used for LIBs and PIBs were 1 M LiPF6 and 1 M KPF6, respectively, in ethylene carbonate/diethyl carbonate . Polypropylene film and lithium foil were used as the separator and counter electrode, respectively, for LIBs. A glass microfiber filter film and potassium foil were used as the separator and counter electrode, respectively, for PIBs. Charge/discharge tests were performed in the 0.01–3.0 V voltage window at various current densities, using a Neware battery tester. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements of the electrodes were carried out on a Bio-Liogic VMP3 workstation. The CV measurements were conducted with a sweep rate of 0.1 mV s−1 in the range of 0.01–3.0 V. The frequency range of the EIS tests was set to 0.01–100 kHz, with a 5 mV amplitude.The electrochemical performances were tested using CR2032 coin-type cells. The electrode materials were prepared by mixing the active material, Super P conductive additive, and the polyvinylidene fluoride binder at 8:1:1 weight ratio in the −1 over five cycles, with a final lithiation at 1.0 V. LICs and PICs were then assembled with AC as the cathode and activated NPG as the anode in cathode/anode mass ratios of 1:1, 2:1, 4:1, 6:1, and 8:1.Before assembling the LICs and PICs, the NPG half-cells were tested by lithiation at 0.02 V followed by delithiation at 3.0 V and 100 mA gC, mAh g−1) of both half and full cells were derived from galvanostatic charge/discharge (GCD) curves according to Eq. I is the discharge current, t is the discharge time, and m is the mass of AC. The energy density  and power density  of the LIC and PIC systems were calculated from the GCD curves according to Eqs. V(t) is the potential of the device and m is the total mass of NPG and AC.The specific capacities C, mAh g− of both entclass1pt{minima4)3PO4, which was used as both nitrogen and phosphorus source. Due to the enormous cooling gradient under the arc discharge process, the nitrogen and phosphorus atoms could be isolated from (NH4)3PO4 and rapidly doped into the graphene structure. In the case of the NG and PG samples, nitrogen and phosphorus atoms were generated from NH3 and pure red phosphorus, respectively. Defect sites would be generated during the doping process, via the adsorption of dissociated oxygen atoms on the surface of graphene.The synthetic strategy for the preparation of NPG is schematically illustrated in Fig. The arc discharge exfoliation protocol is a fast and straightforward route to achieve mass production of doped graphene. The output depends on the size of the graphite rod and the reaction time. In this work, 1.0 g NPG Fig. a was preθ = 26.1° indicates a highly organized crystal structure, such as that of standard graphene [−1 can be assigned to the D, G, and 2D bands, respectively. The G band is ascribed to the zone center Eg2 mode related to phonon vibrations in sp2 carbon materials [IG/ID) corresponds to the amount of defects in graphene [IG/ID intensity ratios of the G, NG, PG, and NPG products are 2.26, 2.32, 2.38, and 2.31, respectively. The defects present in pristine graphene can be doped or replaced with nitrogen and phosphorus, resulting in little changes in the IG/ID ratio. Moreover, the IG/I2D ratio can be used to determine the number of graphene layers, with smaller IG/I2D values denoting fewer layers [IG/I2D intensity ratios of the four products are calculated to be ~ 0.75, suggesting that the obtained graphene sheets are mainly composed of 2–6 layers [s, O 1s, P 2p, and N 1s signals, respectively, indicating the successful P and N doping in graphene. The analysis shows that the amounts of nitrogen and phosphorus doped into graphene are 3.2 and 1.3 at.%, respectively. High-resolution C 1s, N 1s, and P 2p XPS spectra of NPG were also collected to gain further insight into the nitrogen and phosphorus doping. The peaks located at 284.6, 285.8, and 287.3 eV in Fig. S3 can be attributed to C–C, C–P, and C=N groups [s, N 1s, and P 2p XPS spectra of NG and PG are shown in Figs. S4, S5, respectively. The spectra of NG, PG, and G are identical in all respects, except for the presence of nitrogen and phosphorus in NG and PG. The amount of nitrogen and phosphorus doped into NG and PG, as estimated by the elemental analysis of the XPS data, are 3.31 and 1.18 at.%, respectively.The XRD analysis was used to characterize the crystal structure of NPG, NG, PG, and graphene sheets, as shown in Fig. graphene . Moreoveaterials . The D bgraphene . The intr layers . As show6 layers , which iN groups , 23, resN groups . The preN groups . For com−1, as shown in Fig. −1 in the voltage range from 0.01 to 3 V, measured in the 20th, 50th, 100th, 200th, and 500th cycle. In the first cycle, the NPG electrode delivers a lithiation capacity of 1383 mAh g−1 and a charge capacity 859 mAh g−1 at a current density of 100 mA g−1. The irreversible capacity is due to the SEI formation and to the irreversible lithium storage, in agreement with the CV results. For comparison, NG shows initial discharge and charge capacities of 982 and 636 mAh g−1, respectively, while the values obtained for PG are 913 and 576 mAh g−1, respectively , which are much lower than those of NPG. This suggests that co-doping with heteroatoms could provide a higher number of lithium ion storage sites and an improved capacity. In addition, the profiles largely maintain their shape with increasing number of discharge–charge cycles, demonstrating a good structural stability. Figure −1. A reversible discharge capacity of 758 mAh g−1 is obtained even at a high current density of 2000 mA g−1, denoting a high rate performance. A potential plateau is observed at under 0.5 V, which can enhance the working voltage of the full cell. Figure −1 at current densities of 100 and 2000 mA g−1, respectively, which is higher than those of undoped G, NG, and PG, respectively. Owing to the similar morphology and structure of NPG, G, NG, and PG, the enhancement of the reversible electrochemical performance observed for NPG should be attributed to the N and P doping. Furthermore, all samples exhibit a small capacity loss at each current density  and a nearly 100% recovery of discharge and charge capacities when the rate is restored to 100 mA g−1, demonstrating a remarkable rate capability. Moreover, the stable capacity of NPG obtained at each current rate is also higher than that of the G, NG, and PG samples. The enhanced capacity of NPG is ascribed to the synergistic effect of phosphorus and nitrogen co-doping in graphene. The capacity enhancement is closely related to the doping content of nitrogen or phosphorus. As shown in Fig. S7, the NPG sample displays not only an enhanced capacity upon doping with nitrogen and phosphorus, but also a further increase in capacity due to the synergistic effect of N and P co-doping. Figure −1. A reversible capacity of 798 mAh g−1 is achieved in the initial cycles. After 1000 cycles, NPG retains a capacity of 787 mAh g−1, corresponding to a retention of 98.6% and a fading of 0.0014% per cycle. Moreover, NPG displays a stable coulombic efficiency of ~ 100% during the whole cycling process, with the exception of the initial cycles. For comparison, Fig. S6 shows that the discharge capacities of G, PG, and NG are about 280, 570, and 627 mAh g−1, respectively, at the same current density, confirming that heteroatom doping can improve the capacity of graphene. The AC impedance of NPG before and after cycling is shown in Fig. To investigate the electrochemical performance, CV tests were carried out at a scan rate of 0.1 mV s+/K and Li+/Li couples, the irreversible peak is located at 0.6 V. In addition, the CV curves retain a similar shape in the second and third cycle, indicating a highly reversible potassium ion storage behavior in the NPG sample. Galvanostatic charge–discharge tests were carried out to further investigate the electrochemical performance of NPG in PIBs. As shown in Fig. −1, respectively. The large irreversible capacity is due to the formation of the SEI layer and the irreversible potassium ion storage on defect and edge sites of the NPG. Considering that the atomic radius of potassium ions (1.38 Å) is larger than that of lithium ions (0.76 Å), NPG provides a lower number of ion storage sites, leading to more potassium ions irreversibly binding to the defect and edge sites of NPG; thus, NPG shows a lower capacity and initial coulombic efficiency. A coulombic efficiency of 98% is obtained for the NPG electrode during cycling, except for the first cycle, indicating the high reversibility of the intercalation/extraction process of potassium ions. Moreover, the rate capability of the NPG sample is shown in Fig. −1 are 387, 324, 280, 247, and 194 mAh g−1, respectively. When the current density is switched back to 200 mA g−1, the discharge capacity returns to 270 mAh g−1, highlighting an outstanding rate capability . At the same time, the discharge–charge profiles maintain similar shapes at various current densities, confirming the good rate performance and structural stability. The NPG electrode also exhibits a remarkable cycling stability, as shown in Fig. −1 is achieved at the current density of 500 mA g−1. The capacity shows a slow decrease in the first 50 cycles, followed by a gradual increase due to the activation process during cycling. A discharge capacity of 242 mAh g−1 is obtained after 500 cycles. NPG also shows a stable coulombic efficiency of ~ 100%, except for the initial cycles. This indicates that potassium ions could be reversibly stored in NPG, which thus represents a promising anode material for PIBs [Potassium ion batteries have attracted considerable attention, due to their low cost and potential application in large-scale energy storage systems. Thus, the potassium storage behavior of NPG was also investigated by CV. As shown in Fig. for PIBs .Fig. 5a The high reversible capacity, rate performance, and cycling ability of NPG as the anode material for both LIBs and PIBs can be attributed to the intrinsic properties of graphene and the synergistic effect of N and P doping. First, the arc discharge method could produce high-quality and few-layer graphene nanosheets. The small thickness could provide shorter diffusion paths for lithium/potassium ions, and the large surface area enhances the contact between active materials and electrolyte. Second, doping with nitrogen atoms introduces active sites in graphene, providing additional storage sites for lithium/potassium ions , 31. At v)  at a given potential (V) can be determined from the diffusion-controlled and surface capacitive contributions  on the basis of the following equation: i(V) = k1v + k2v1/2 [k1 and k2 constants. The typical profile in Fig. −1 to a maximum value of 72.8% at 1 mV s−1  Fig. a. The cu+ k2v1/2 –28. The s−1 Fig. c. Simila −1 Fig. f. This fsite//AC , AC//sodsite//AC , graphitsite//AC , TiO2/rexide//AC , peanut  [2Ti3O7 , LiNi0.5.3O2//AC , nitroge.3O2//AC , and TiO−1 and outstanding cyclability over 1000 cycles at the current density of 1000 mA g−1. Moreover, NPG also shows remarkable electrochemical performance as the anode material for PIBs. A capacity of 194 mAh g−1 is obtained at the current density of 1000 mA g−1. Even at a high current density of 500 mA g−1, NPG exhibits a high reversible capacity along with a stable cycling performance after 500 cycles. In addition, full carbon-based NPG‖LiPF6‖AC LICs and NPG‖KPF6‖AC PICs show capacities of 98 and 56 mAh g−1 at 1 A g−1, respectively. Maximum energy densities of 195 and 104.4 Wh kg−1 and power densities of 14,983.7 and 14,976 W kg−1 can be achieved for the LICs and PICs, respectively, demonstrating the potential applications of NPG anodes. Thus, the arc discharge method is an effective way to prepare graphene doped with various heteroatoms, which can be used as promising electrode materials for high-performance energy storage systems. Moreover, multiple doping represents a smart option to improve the electrochemical performance of electrode materials, including not only graphene, but also other carbon-based materials.An anode material based on nitrogen and phosphorus dual-doped graphene has been successfully designed and synthesized via a one-step arc discharge method. NPG can be employed as a universal anode material for lithium ion and potassium ion batteries. As anode for LIBs, NPG displays a high specific capacity of 889 mAh gSupplementary material 1 (PDF 859 kb)Below is the link to the electronic supplementary material.


Patient-centric care entails optimising healthcare provision to patients based on their perspective and opinion. It involves appropriate treatment at a reasonable cost and a focus on patient characteristics in the decision-making process to make it more personally useful. The optimisation of medicines in the older population is a challenge due to physiological changes, comorbidity, and polypharmacy. Furthermore, patient-centric care is difficult to achieve due to the high proportion of patients with dementia and frailty. Decision support concerning the appropriateness of indication, formulation, dose, administration, co-prescribing, and length of treatment to older patients is frequently in demand. In the current study, we aimed to review clinical questions concerning administration and dosage to older patients of relevance to patient-centric care. We analysed questions concerning medicines to patients 65 years or older in the database of the network of Norwegian drug information centres from 2010 to 2020. The analysis included the distribution of drugs, diseases, and recurring topics among the questions. Through a Boolean search that combined the indexed categories of “older” and “administration and dosage”, we retrieved 84 question-answer pairs. Questions about psychotropic and cardiovascular drugs in relation to therapy, adverse drug reactions, and pharmacokinetics dominated, and more than 60% of the questions came from physicians. Topics relevant to patient-centric pharmacotherapy were drug withdrawal (10 questions), drug formulation (8 questions), drug initiation (8 questions), and switching drugs (5 questions). One question concerned drug withdrawal and switching, and one question drug formulation and switching. Answers provided decision support regarding appropriate formulations of drugs to patients with dementia who chew capsules or tablets, the use of parenteral administration in patients who refuse to take oral formulations, and the pharmacokinetics of transdermal or rectal drug administration. The results highlight the importance of including pharmacological factors in the assessment of the acceptability and appropriateness of oral and parenteral medicine to older patients. Patient-centric care entails optimising healthcare provision to patients based on their personal perspective and opinion ,2. In a The optimisation of medicines in the older population is a challenge due to physiological changes, comorbidity, and polypharmacy. Appropriate indication, formulation, dose, administration, co-prescribing, and length of treatment are frequent clinical issues. Patient-centric pharmaceutical drug product design, formulation, and optimisation for the older population is of current interest . HoweverNorwegian drug information centres provide decision support for drug-related questions from health care professionals in four health regions serving the total Norwegian population. In a previous study, we found frequent questions concerning psychopharmacology and cardiovascular pharmacology concerning older patients . In the Regional Medicines Information and Pharmacovigilance Centres (RELIS) is a Norwegian network of drug information centres providing decision support for health care professionals  in four health regions. The centres are associated with clinical pharmacology units in regional university hospitals, and pharmacists and physicians with expertise in searching and critically evaluating literature constitute the staff in the centres . RELIS pWe performed a Boolean search combining the category “older” with the category “administration & dosage” in the period 1 January 2010–30 September 2020. Q/As from all types of healthcare occupations and workplaces were included, since patient-centric care involves communication with, and observation of, patients in general practice, pharmacies, nursing homes, and hospitals . The WHODescriptive statistical analyses were performed with SPSS version 26 . Percentages were not rounded up to 100 in either text or tables. Notice that the same question can include several drugs, indexed categories, descriptive categories, and diseases. Several drugs in a question can belong to the same main ATC group (ATC 1st level). ICD-11 can also include symptoms, and some questions concern the use of drugs in relation to procedures such as surgery or diagnostic measures.The database contained 51,867 Q/As by the end of September 2020, and RELIS handled 3305 questions in 2019. In the study period, the size of the RELIS database increased from 19,785 to 51,867 Q/As. Two Q/As were excluded from the 86 Q/As retrieved by the Boolean search. In one Q/A, the patient was younger than 65 years, and in the other Q/A the category “older” was indexed when the appropriate category was “adverse drug reaction”. The final 84 Q/As were relatively evenly distributed (4–11 per year) over the study period, with the exception of a peak of 18 questions in 2015.Fifty-four questions (64%) came from physicians and 25 (30%) from pharmacists. Three questions (4%) came from nurses, one (1%) from a dentist, and one (1%) from a patient relative. The four major workplaces were general practice (GP) and pharmacies, with 24 questions (29%) each; nursing homes with 18 questions (21%); and hospitals with 14 questions (17%). Sixty-three questions (75%) were patient-related, and 21 (25%) were general. Among the patient-related questions, 35 questions (54%) concerned women, 13 questions (21%) concerned men, and in 16 questions (25%) gender was unknown. Regarding age, 18 (29%) of the 63 patient-related questions concerned patients in their eighties, 9 questions (14%) concerned patients in their seventies, 8 questions (13%) concerned patients in their nineties, and 5 questions (8%) concerned patients in their late sixties (≥65 years). In 23 (37%) patient-related questions, age was unknown. Three of the general questions (14%) concerned patients older than 80 years, and one question (5%) concerned a patient older than 95 years. In 17 general questions (81%), age was not described. The eighty-four questions concerned 129 brand drug names that involved 82 chemical or generic substances (ATC 5th level). The two most frequent generic substances were acetylsalicylic acid (6 questions) and metoprolol (5 questions). According to the WHO ATC system, the four most frequent ATC groups (ATC 1st level) were N (nervous system) with 53 counts, B (blood and blood-forming organs) with 24 counts, A  with 18 counts, and C (cardiovascular system) with 14 counts. The 84 questions concerned 104 diseases and three procedures . According to WHO ICD-11, the questions covered 13 codes, of which the majority concerned mental, behavioural, or neurodevelopmental disorders (24 questions), diseases of the circulatory system (20 questions), diseases of the digestive system (11 questions), and diseases of the genitourinary system (11 questions). See The 84 Q/As were indexed 90 times across eight categories , such asIn this descriptive study, we aimed to review clinical questions concerning the administration and dosage of medicines to older patients of relevance to patient-centric care. The search in the RELIS database showed that questions about psychotropic and cardiovascular drugs in relation to therapy, adverse drug reactions, and pharmacokinetics dominated. More than 60% of the questions came from physicians. Our results are in accordance with a previous study on questions concerning older patients in the same database from the period 2010–2015 ,21,22. WWe do not know to what degree the distribution of drugs in the questions is influenced by factors such as the availability of authorised product information, professional handbooks, other drug information sources or the size of the portfolio of drug products. Although the pharmacokinetic information on the formulations in the summaries of product characteristics (SmPCs) is quite comprehensive, physicians still infrequently use this source . FurtherAdverse drug reactions, treatment, and pharmacokinetics are frequent reasons for questions to drug information centres ,23,24. TOur examples reflect the problem with eating disturbances and drug intake among patients with dementia. Eating habits such as chewing or sucking without trying to eat is associated with mild to moderate dementia, while swallowing disturbance becomes critical in severe disease according to an observational study of 200 patients with Alzheimer’s disease . Our exaDysphagia is common in the elderly  and is aThe long-term use of prescribed and over-the-counter effervescent formulations is reported to be frequent among older people according to a study from the UK . A possiThe perception that the absorption and bioavailability of transdermal and rectal formulations are limited in older patients could potentially reduce the use of alternative routes of administration. Transdermal formulations are particularly useful for the administration of analgesic drugs to patients with dysphagia, and the formulations are now available in several strengths to allow titration of dose. RELIS have received questions about cutting patches to allow titration, but we warn against this practice. A case reported in 2013 to the Institute for Safe Medication Practices (ISMP) described a physician who instructed staff from a hospice health care agency to cut a 50 mcg/h fentanyl transdermal system patch in half and apply it to a patient to deliver a 25 mcg/h dose . A conseRELIS receive frequent questions concerning the switching of psychotropic drugs. In a commentary from 2016 we described several risk factors associated with this therapeutic intervention. Our experience is that physicians and other health care professionals are unaware of withdrawal reactions to old drugs, early-onset ADRs to new drugs, and that they lack knowledge about the role of active metabolites and interactions during switching . The queWhen interventions of treatment and care are carried out despite the resistance of the patient and/or against the patient’s will or knowledge, this is termed as coerced treatment and care. . A studyLength of prophylactic treatment in older patients is also a relevant ethical and clinical question. In our study, this issue concerned osteoporosis and dementia, among other diseases. A problem is that there are no clear age limits, and many of the drugs are proposed to be effective in old age. Thus, we receive numerous questions from physicians who want to discuss problems that the recommendations and clinical guidelines cannot answer. The example with intermittent use of acetylsalicylic acid where the physician was advised to weigh cardiovascular risk and strength of indication against acceptability on behalf of the patient, show that RELIS are aware of the principles of patient-centric care. The individual assessment of a patient and including the patient perspective is of importance in our work.The material in this study is naturalistic and descriptive, with a risk of biased interpretation. The great number of topics presented excludes a thorough discussion of each. Notice that the answers to the questions are related to the year they were provided. Furthermore, questions to RELIS are spontaneous, and do not necessarily represent drug problems perceived by the general population of health care professionals. However, in comparison to spontaneous ADR reports, a question to RELIS is in the context of clinical decision support, and as such a more deliberate action on behalf of a health care professional with a motivation to provide the best possible treatment of their patients.The examples from the recurring topics focused on pharmacological factors associated with different formulations and administration of generic substances. However, the RELIS database is searchable for brand names, and health care professionals often submit questions about choice or differences between brands. We are aware of potential differences between brands as well as generic copies, but RELIS are independent of the pharmaceutical industry and we usually avoid favouring any specific trademarks in our answers. The examples also raise several ethical issues, and RELIS use a disclaimer on all written answers to state that they are based on the available literature and other resources, and health care professionals have sole responsibility for using the content of the answers in their treatment of patients. Our credibility among health care professionals relies on the fact that they can safely ask us all sorts of drug-related questions knowing that RELIS have no control function with regard to their professional practice. If we receive questions from patients or relatives, we usually motivate them to discuss the questions with their treating physician. Accordingly, RELIS do not interfere in the physician–patient relationship.Although the problems presented are known in patient-centric care, a review of our database could be useful to find relevant topics for drug information activities for clinicians and patients. In particular, this is because the topics concern everyday, real-world problems not sufficiently described in recommendations and guidelines. Our selection of questions concerning the administration and dosage of medicines in older patients could be used to propose topics relevant to patient-centric medicine design. Furthermore, relevant stakeholders, including the pharmaceutical industry, should be aware of the specific drug information needs with regard to rational use in a patient population with specific challenges.Our review of the database of the Norwegian drug information centres highlights the importance of assessing pharmacological factors in decision support concerning the acceptability and appropriateness of oral and parenteral medicine in older patients. Drugs and diseases of priority include those concerning the nervous system, blood and blood-forming organs, the digestive system, and the cardiovascular system. Through examples, we have described practical solutions to drug-related problems. The practical solutions involve several principles of importance for patient-centric care and involve scenarios that could motivate patient-centric medicine design. Given the current focus on new design of medicine, our present topics with examples could generate hypotheses to be tested in clinical settings in future studies.


Sarcoidosis is a multisystem granulomatous disorder of unknown aetiology. Cutaneous involvement occurs in up to 30% of patients and skin findings are often the initial presenting symptom. The facial atrophic form of sarcoidosis without associated ulceration in adolescents has rarely been described in the literature. We report a case of 13-year-old male patient with a facial atrophic sarcoidosis who was successfully treated with the combination of prednisone and hydroxychloroquine. Sarcoidosis is a common systemic, noncaseating granulomatous disease of unknown aetiology. Cutaneous sarcoidosis, the “great imitator”, can baffle clinicians because of its diverse manifestations and its ability to resemble both common and rare cutaneous diseases. Morphologically, plaques and papules are the most commonly observed cutaneous lesions.A 13-year-old man presented with a 2-year history of multiple depressed skin lesions on his face. The lesions initially presented as asymptomatic erythematous patches which had gradually developed depressed centres over time. There was no history of trauma, ulceration, fever, cough, breathlessness, sensory loss, or intralesional steroid used to treat the lesions. Before presenting to our hospital, he had been diagnosed as lupus vulgaris in another hospital and had been given antituberculous therapy for 6 months. However, the skin lesions had gradually progressed during treatment. On physical examination, multiple erythematous plaques with a slightly atrophic appearance were seen on the patient's face A and B. Cutaneous sarcoidosis with atrophic-appearing lesions is uncommon and has primarily been reported in association with ulcerative lesions, mostly on the lower legs of young and middle-aged people.In conclusion, we diagnosed and curatively treated a patient with cutaneous atrophic sarcoidosis. In such patients, the long-course combination therapy with prednisone and hydroxychloroquine may achieve the clinical cure.10.13039/501100003139CAMS Innovation Fund for Medical Sciences (CIFMS-2017-I2M-1-017).Xiaomei Zhu: Approval of the final version of the manuscript; elaboration and writing of the manuscript; obtaining, analysis, and interpretation of the data; effective participation in research orientation; critical review of the literature; critical review of the manuscript.Jianfang Sun: Approval of the final version of the manuscript; critical review of the literature; critical review of the manuscript.None declared.


Affinity biosensors based on graphene field-effect transistor (GFET) or resistor designs require the utilization of graphene’s exceptional electrical properties. Therefore, it is critical when designing these sensors, that the electrical properties of graphene are maintained throughout the functionalization process. To that end, non-covalent functionalization may be preferred over covalent modification. Drop-cast 1,5-diaminonaphthalene (DAN) was investigated as a quick and simple method for the non-covalent amine functionalization of carbon-based surfaces such as graphene, for use in biosensor development. In this work, multiple graphene surfaces were functionalized with DAN via a drop-cast method, leading to amine moieties, available for subsequent attachment to receptor molecules. Successful modification of graphene with DAN via a drop-cast method was confirmed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and real-time resistance measurements. Successful attachment of receptor molecules also confirmed using the aforementioned techniques. Furthermore, an investigation into the effect of sequential wash steps which are required in biosensor manufacture, on the presence of the DAN layer, confirmed that the functional layer was not removed, even after multiple solvent exposures. Drop-cast DAN is thus, a viable fast and robust method for the amine functionalization of graphene surfaces for use in biosensor development. Graphene possesses exceptional electrical properties ,2 such a2 carbon bonds in the aromatic lattice and the subsequent introduction of sp3 bonds at these reaction sites, reducing the aromaticity of the graphene lattice and therefore affecting the properties of the graphene as electrical mobility is reduced −3/−4 in 1 × PBS (pH 7.4), at a scan rate of 50 mV/s. An increase in peak current is observed after DAN functionalization ,  Figure a in 5 mMlization a. This sTo ensure that the measured peak current changes were due to the presence of DAN on the graphene surface and not due to solvent interference, a control sample was measured using ethanol only in the place of DAN (using the same drop-cast method). A cyclic voltammogram for the ethanol only control can be seen in −1 can vary across the surface of the graphene device before modification, however, its intensity ratio to the G peak (ID/IG) is generally seen to increase after modification with DAN . The full width half maximum (FWHM) of the “D” peak broadens from ~34 cm−1 to ~190 cm−1 after surface modification. This broadening of the peak suggests that it contains a component from the C-N band at 1247 cm−1, from the DAN, as further evidenced by its asymmetric shape. The intensity ratio of the “2D” peak (~2678 cm−1) to the G peak changes dramatically following DAN modification, from 2D/IGI ~2.5 for unmodified graphene to ~0.3 following modification. This change in peak ratio is consistent with the addition of aromatic carbon-containing molecules to monolayer graphene surfaces [Raman spectroscopy was used to monitor the effects of surface modification of monolayer graphene with drop-cast DAN. Extended Raman scans were taken using a Renishaw inVia Raman system  with a 532 nm laser. Before surface modification, typical Raman spectra of graphene devices were obtained. Representative point spectra are shown in surfaces ,37.−1 and 2600 cm−1, in a grid pattern. Peak analysis based on previous reports [2 is typically p-doped [2) might be intrinsic or n-doped [2 substrate, The positions of the G and 2D peaks can be used to indicate doping and strain in graphene. Raman spectra were obtained, centered at 1600 cm reports ,38,39 wa p-doped , under a n-doped . A shift n-doped . Before 2/Si substrates, graphene with surface modification (DAN) and graphene with surface modification followed by attachment of an antibody (DAN + Ab), using a Kratos Axis Supra XPS system  using an Al Kα monochromatic X-ray source with an emission current of 15 mA at 20 eV pass energy. A minimum of three scan locations per sample were used to ensure the spectra were representative of the surface. 2 layer along with organic contaminants on the graphene surface (C-O/C=O) [2), corresponding to an atomic concentration of approximately 2.2%. Following the application of the antibody (and after standard wash steps), a further increase in the N 1s signal is evident (10.9 at. %), along with an attenuation of the Si 2s/2p and O 1s substrate signals, consistent with surface antibody coverage. The atomic concentrations for the samples are summarized in Functionalization with amine moieties should further allow for attachment of receptor molecules in affinity biosensors, e.g., antibody molecules. To that end, non-covalent functionalization of graphene with drop-cast DAN has been used for attachment of an antibody , providing evidence of its viability as a functional layer. X-ray photoelectron spectroscopy (XPS) measurements were performed, on unmodified graphene (before surface modification with DAN (blank graphene)) on SiOC-O/C=O) . Followi2/sp3 C-C contribution above the predominantly sp2 graphene blank , relaxation occurred over 5.5 h, this relaxation time occurs after any exposure of the graphene to solution and it is not a DAN specific effect. Long relaxation times occur with solution on bare graphene, e.g., 2/Si substrates [Real-time resistance data, bstrates ,46 and t2)) steps are also shown in 2. The I–V linear sweep measurements were therefore performed on dry samples. The ∆R/R0 for DAN functionalized resistor devices was + 0.078 ± 0.039 (SD of N = 13), and the ∆R/R0 for the ethanol only control resistor devices was −0.069 ± 0.043 (SD of N = 13), individual measurements can be found in 2 substrates [2/Si substrates). DAN is diluted in 70% ethanol, which has a slight p-doping effect; however, the final resistances increased above bare graphene (dry intrinsic resistance), meaning these changes in resistance are due to the likely electron donation from DAN and not due to solvent effects.As there is a resistance change after surface modification  which could affect device-to-device performance issues. Amorphous carbon made and deposited on the graphene during the growth process (CVD), residues left by fabrication chemicals or residual polymer left behind from the graphene transfer process [R/R0 of DAN functionalized graphene resistor devices. Whether the contaminants e.g., aromatic resist components, are electron acceptors or donors can affect doping of the graphene, and as the level of contamination varies with each manufacturing step, the level of doping will, therefore, show variation between batches but also between devices in the same batch.Variation in the final ∆ process  can all  process . Causes  process . The pre process  and can Exposure of the functionalization layer to multiple solvents is inevitable during affinity biosensor development, it is, therefore, essential to check the ability of the drop-cast DAN to withstand these multiple solvent exposures. The strength of the π-π stacking between the graphene surface and the aromatic molecules of the functionalization layer e.g., DAN can make the surface stacking quite stable against rinsing or other solution processing . An inveThe wash step investigation consisted of an initial ethanol wash to remove residual DAN from the surface , followed by 1, 2, or 3 DI water washes, to simulate further standard biosensor process steps. XPS analysis indicates that the DAN layer is not affected or removed by sequential wash steps. This is shown in 3 carbon, C-O and C=O bonds [2/Si substrate [After peak fitting, several additional peaks were found in the unmodified graphene sample at ~284.76, ~285.67, and ~286.27 eV, =O bonds . These bubstrate ,55. Afteubstrate . Followiubstrate ,57.−1, 1598 cm−1, and 2692 cm−1, respectively. After each successive DI water wash, the peaks red shift slightly until, after 3 DI water washes, the D-peak, G-peak, and 2D-peaks reach 1358 cm−1, 1603 cm−1, and 2700 cm−1, respectively. These shifts are consistent with graphene being p-doped with water [ID/IG), at ~1350 cm−1 and 1580 cm−1 respectively, are consistently around 0.2. Also, the I2D/IG ratio decreases from approximately 2 to approximately 0.55 for the modified samples, which is consistent for all wash steps. Both XPS and Raman results from subsequent wash steps of drop-cast DAN modified graphene demonstrate that the functionalized surface is robust for use in a biosensor process sequence after multiple solvent exposures.Raman spectra were also obtained following subsequent wash steps. Drop-cast DAN as a robust and facile method to amine functionalize carbon surfaces has been demonstrated. The addition of a functional layer containing amine groups allows for further bio-functionalization with specific receptors, using common crosslinking chemistries such as carbodiimide EDC-NHS, for the development of affinity biosensors. Real-time resistance measurements, cyclic voltammetry, XPS, and Raman analysis showed successful modification of graphene surfaces with DAN. As the purpose of surface modification with DAN was to provide amine moieties for further bio-functionalization with receptor molecules, the successful attachment of an antibody molecule was also confirmed, further demonstrating the viability of drop-cast DAN as a surface functionalization strategy. The robustness of the DAN and subsequently crosslinked antibody to withstand multiple washes was also demonstrated, with the presence of the DAN layer and successful antibody attachment confirmed via XPS, Raman spectroscopy, cyclic voltammetry, and real-time resistance measurements. The viability of drop-cast DAN as a surface functionalization method, providing available amine moieties was demonstrated with the resultant attachment shown to withstand multiple wash steps, therefore, providing a quick and simple route to prototype for biosensor development.