The drop in capacitance over 1000 cycles was 4%, indicating a sufficiently high FLG stability, allowing us to consider FLG as a prospective material for use in supercapacitors.Graphene nanostructures (GNSs) are among the most promising materials for producing supercapacitors. However, GNSs are still not used in creating supercapacitors due to the impossibility of obtaining large volumes of high-quality material at an acceptable cost. In our previous works, we have shown the possibility of synthesizing large volumes of few-layer graphene  from cyclic biopolymers under conditions of self-propagating high-temperature synthesis (SHS). Using the SHS process makes it possible to synthesize large volumes of FLG without Stone–Wales defects. This work is devoted to the study of the possibility of using FLG synthesized under the conditions of the SHS process in the creation of supercapacitors. It was found that the synthesized FLG makes it possible to obtain better results than using classical materials, namely activated carbon (AC). It was found that the sample based on FLG had a higher specific capacitance of 65 F × g Solving the problem of rapidly growing global energy consumption, combined with the critical issue of climate change, is one of the important challenges for scientists and engineers worldwide, requiring the development of new sustainable and renewable energy sources . Energy Supercapacitors are energy storage devices with high power characteristics, demonstrating a high charge/discharge rate, cycle life, shelf life, a wide operating temperature range, and safety. . GeneralAmong all supercapacitors, one can highlight devices based on aqueous electrolytes, which are both high-power, environmentally friendly, and attractive for mass production ,12,13,142 × g−1) [The concept of adding graphene to supercapacitors was first described in 2008 . The aut2 × g−1) , increasoperties ,32, distoperties ,22,33.The capacitance characteristics of graphene-based supercapacitors depend on key material characteristics such as the specific surface area, pore size distribution, interlayer spacing, heteroatom doping, surface functionalization, and conductivity ,35. MostAccording to the global requirements for sustainable materials, some green technologies have been used to synthesize graphene nanostructures for supercapacitor applications. These approaches aim to minimize toxic chemicals, reduce energy consumption, and utilize renewable resources, making graphene synthesis more environmentally friendly and sustainable. The methods typically use renewable and sustainable carbon sources such as biomass , plants Green-synthesized graphene can be used in supercapacitors by directly using it as an electrode material ,42,43 orHowever, despite all the promise of using GNSs in creating supercapacitors, their practical application has yet to occur. One of the critical reasons for this is the high cost of GNSs, which makes the use of GNSs unprofitable. The high price of GNSs is due to the imperfection of the GNS synthesis methods, which do not allow for the synthesis of large volumes of high-quality material at an acceptable cost. Considering the methods of the synthesis of GNS, two main approaches can be distinguished: “top–down”  and “botIn our previous works, we reported on the possibility of synthesizing large volumes of few-layer graphene (FLG) from cyclic biopolymers under the conditions of the self-propagating high-temperature synthesis (SHS) , free ofThis work is devoted to the study of the possibility of using few-graphene synthesized under the conditions of the SHS process in the creation of supercapacitors.FLG particles synthesized by the SHS method were taken as the basis for the electrode. The initial biopolymer  in a 6 to 4 ratio using a “drunk barrel” type homogenizer  for 15 min (60 rpm). Then, the resulting mixture was placed in a reactor and heated to a temperature of 220 °C . After the completion of the synthesis, the resulting graphene (in the form of a powder) was washed with isopropyl alcohol  and dried in an oven until the weight loss ceased. The yield of graphene was 40 wt. % by weight of the original starch. The procedure for obtaining FLG is described in detail in .To obtain electronic images of the graphene particles, a TESCAN Mira-3M scanning electron microscope (SEM)  and an FEI Tecnai G2 30 S-TWIN transmission electron microscope  were used. To obtain electronic images of graphene particles by the TEM method, FLG was placed in toluene (concentration 0.05 mass. %) and sonicated until a stable suspension was obtained. Then, the resulting suspension was applied to a carbon grid and dried until the complete evaporation of toluene  at 60 °C). The laser diffraction method ) was used to measure the linear dimensions of the particles. For measurement purposes, a suspension of FLG particles in water (0.05 mass %) was prepared by sonication and an ultrasonic bath “Sapphire” .X-ray phase analysis ) was used to measure the number of layers in the FLG. The scanning rate was 1 deg/min.Raman spectroscopy ) was used to measure the quality of the FLG. FLG particles deposited from a toluene suspension (concentration of 0.05 mass %) on a silicon substrate were used for the measurements.The Brunauer–Emmett–Teller (BET) method  was used to measure the specific surface area of the FLG sample. Before measurement, the FLG sample was dried for 2 h at 300 °C under vacuum.®, Merck KGaA, Germany) as a solvent were carefully mixed with ultrasound until a homogeneous mass (slurry) was obtained. Next, a commercially available MF-2012 glassy carbon electrode  was evenly coated with the above suspension using a micropipette (0.7 µL) and then dried at 60 °C for 2 h. The load of electroactive material on each received electrode was 51 µg (0.73 mg × cm−2) (without considering the mass of PVDF). As a reference sample, electrodes were made from commercial activated carbon , specific surface area 740 m2 × g−1) using a similar procedure.The electrodes were prepared according to the following procedure: graphene or carbon powder (22 mg), 2 mg of poly(vinylidene fluoride)  as a binder, and 0.3 mL of N-methyl-2-pyrrolidone  as an auxiliary electrode and a standard silver chloride reference electrode MF-2056 (Ag/AgCl (3 M KCl); BASi, USA). All potentials in the work are given relative to the Ag/AgCl reference electrode.The electrochemical properties of the prepared electrodes were studied on a VSP multichannel potentiostat-galvanostat  in a three-electrode electrochemical cell containing a glassy carbon plate  in distilled water in the range potentials from −1 to 0.8 V. CV measurements were carried out at various scan rates in the range from 5 to 200 mV × s−1.The prepared graphene electrodes were tested as electrodes for supercapacitors using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques in 1 M LiClOsp, F × g−1) was calculated based on the data obtained by the CV and GCD measurements according to Equations (1) and (2), respectively [Q is the accumulated charge in coulombs ; m (g) is the mass of the active substance; ∆t (s) is the discharge time; ∆V (V) is the voltage window; I (A) is the current during discharge.The specific capacitance (Cectively .(1)Csp=−1 in the potential range (a voltage window range) from −1 to 0.8 V. EIS measurements were carried out in the frequency range (100 mHz–100 kHz) with a sinusoidal potential amplitude of 5 mV rms at open circuit potential (OCP). Before the EIS measurements, the electrodes were preliminarily soaked in the electrolyte for 5 min to ensure stability. All parameters were obtained using EC-Lab V11.02 software.GCD was carried out at specific currents from 0.2 to 5 A × gAs can be seen in As can be seen from An X-ray diffraction study was carried out to determine the number of layers in the synthesized FLG sample. The results of the experiment are shown in Based on the position of the 002 peak and its full width at half maximum (FWHM), using the Scherer formula , the cry−1 with the wavy structure of the samples, the presence of a large number of edges, and the multidirectional superposition of the graphene layers on each other. It is essential to note that the FLG samples synthesized under the conditions of the SHS process did not contain Stone–Wales defects. This was shown by us using a chemical technique described in detail in our previous work [As can be seen from ous work .2 × g−1.As can be seen from 4 solution. −1 (Samples made from FLG and activated carbon (AC) were studied by cyclic voltammetry (CV) as model electrodes of supercapacitors in a three-electrode cell in 1 M aqueous LiClOtion. −1 b in the For both scan rates, the samples showed an electrical double-layer capacitance behavior (no pronounced peaks).−1 and 5 mV × s−1, these values were 170 and 64 F × g−1, respectively. It should be noted that despite the fact that the specific surface area of the FLG was much smaller than that of AC , it demonstrated greater efficiency than AC.The specific capacity of the obtained samples was calculated using Equation (1). −1.It can be seen from the presented graphs that for both samples, the values of the current densities became larger with an increasing scan rate. At lower potential scan rates, all samples showed curve shapes close to rectangular (rectangular-like shape), which is typical for double-layer behavior. With an increase in the sweep rate, the shape of the CV curves was distorted (fusiform), which is associated with the resistance of electron transfer. Still, the general shape of the curves remained close to rectangular, which indicates the relatively high-power characteristics of the materials.p)–lg(v) for the FLG and AC. The values of Ip were used at the plateau around 0.0–0.2 V, where the contribution of ohmic polarization did not have a significant effect on the CV shape.b = 0.86), which suggests insignificant limitations of mass transfer in the electrode material. A noticeable contribution of limited mass transfer was observed for the FLG sample only at high values of scan rates .The slope of this dependence enables the estimation of the limiting stage of the process . The slo−1. All samples were characterized by deviations from the linearity of the charge–discharge curves, especially when discharging low potentials, which is probably associated with side irreversible reduction processes. Most likely, there is slow water splitting with the hydrogen evolution. Although the overpotential of the hydrogen evolution reaction at carbon electrodes reached high values, at potentials around −1.0 V vs. Ag/AgCl and at low scan rates/discharge currents, the process may have an impact [The galvanostatic charge/discharge method was used to study the capacitive properties of the obtained graphene samples. n impact ,59.−1 were 265 and 75 F × g−1, respectively. All calculated capacitance values from CV and GCD are presented in The gravimetric capacitances of the electrodes were calculated using Equation (2). The capacitances of the electrodes based on graphene made from FLG and AC at a current of 0.2 A × gThe higher FLG efficiency may be due to a more optimal pore distribution since it is well-known that starting from some value of the surface area, its further increase in surface area does not lead to an increase in capacitance due to limitations of diffusion and electrode penetration into the porous system of the material . AdditioTo better understand the electrochemical properties of the electrodes, the samples were studied by electrochemical impedance spectroscopy (EIS). Spectra in Nyquist coordinates are shown in 4 aqueous solution at a current of 2 A × g−1 for 1000 cycles. The resulting dependence is shown in The stability of electrode materials based on few-layer graphene was tested by the GCD method in 1 M LiClO−1, and after a thousand cycles, it was 138 F × g−1), which indicates a sufficiently high stability of the materials, and allows them to be considered for use in supercapacitors. The decrease in capacity may be associated with irreversible reduction processes (slow water splitting and hydrogen evolution as discussed above), which was confirmed by an increase in the values of the Coulomb efficiency with cycling. It is recommended to use a narrower range of potentials to improve stability.The drop in capacitance for 1000 cycles was 4%  was achieved by the few-layer graphene electrode in an aqueous LiClO4 electrolyte. The achieved capacitance values were 2–4 times higher than the activated carbon-based electrode with a higher surface area. Furthermore, the few-layer graphene electrode maintained its capacitive performance cycling (1000 cycles). Thus, the findings suggest that the few-layer graphene composite could be a promising electrode material for supercapacitors.As a result, few-layer graphene has the optimal structure and particle size distribution and thus achieves higher capacitance values. A high capacitance of 265 F × g


A person’s first language (L1) affects the way they acquire speech in a second language (L2). However, we know relatively little about the role different varieties of the L1 play in the acquisition of L2 speech. This study focuses on German (L1) learners of English (L2) and asks whether the degree to which German speakers distinguish between the two vowels /eː/ and /ɛː/ in their L1 has an impact on how well these individuals identify /æ/ and discriminate between the two English vowels /ɛ/ and /æ/. These two English vowels differ in both vowel quality and duration (/æ/ is longer than /ɛ/). We report on an identification and a discrimination experiment. In the first study, participants heard a sound file and were asked to indicate whether they heard “pen” or “pan” . The stimuli differed from each other in terms of both vowel quality  and duration . In the second study, participants had to signal whether two sound files they were exposed to differed from each other. We modeled the percentage of /æ/  selection , accuracy , and reaction time  by implementing the German Pillai score as a measure of vowel overlap in our analysis. Each participant has an individual Pillai score, which ranges from 0 (= merger of L1 German /eː/ and /ɛː/) to 1 (=maintenance of the contrast between L1 German /eː/ and /ɛː/) and had been established, prior to the perception experiments reported here, in a production study. Although the findings from the discrimination study remain inconclusive, the results from the identification test support the hypothesis that maintaining the vowel contrast in the L1 German leads to a more native-like identification of /æ/ in L2 English. We conclude that sociolinguistic variation in someone’s L1 can affect L2 acquisition. This idea is central to several well-established models of L2 speech, such as the Speech Learning Model SLM, , the Perpen, and /æ/ (TRAP vowel), as in pan. Remember that well-known varieties of English, such as Standard American or Southern British English, distinguish between the two front, unrounded vowels /ɛ/ and /æ/ , as in  /æ/ see . The two /æ/ see .1pen and pan, respectively , pose a possible challenge to L1 German (or Dutch) speakers. The objective of the present paper is to expand previous research by investigating whether some L1 German speakers show fewer difficulties in identifying /æ/ and discriminating /æ/ and /ɛ/ than others. That is, we examine whether the properties of one’s L1 vowel inventory affect the way one deals with the two English vowels /ɛ/ and /æ/. More precisely, we ask whether the presence/absence of the distinction between the two German vowels /eː/-/ɛː/ in a person’s L1 vowel space facilitates the identification of /æ/ and the discrimination of the English contrast between /ɛ/ and /æ/. We do so by examining both binary (identification rate of English /æ/ in the identification and reaction accuracy in the discrimination task) and continuous data (reaction times) in order to get a comprehensive picture and detect potential burdens in the processing of L2 sounds. Before going into detail, however, we consider, more generally, which factors might affect how a person acquires speech in an L2.Since /æ/ is not part of the Standard German vowel inventory, it frequently poses a challenge to learners of English, who may not distinguish between English /ɛ/ and /æ/ and/or rely on a close category they are familiar with from German, such as /ɛ/ or /ɛː/ for vely see .2 Note tvely see . Weber a1.1.In this section, we discuss several factors that can affect the acquisition of speech in an L2. The factors are age and amount of experience (section 1.1.1) and similarities between a person’s L1 and the L2 (section 1.1.2).1.1.1.A first factor is the age at which a person acquires the L2. If the acquisition of the L2 starts later, it is often more difficult to hide a foreign accent, that is, the L1 shapes L2 speech more than if the L2 acquisition begins at an earlier age see . For insA second factor is the amount of experience a person has in the L2. Usually, individuals with more experience in the L2 sound more native-like see . For exaduration difference between the two English vowels and was, so to speak, native-like with respect to the duration contrast. A further finding from Although the two factors age and amount of experience play a crucial role in the acquisition of an L2 in general and with regard to how much the L1 shapes the L2, we see that even highly advanced language users still differ from native speakers. For instance, 1.1.2.A third factor is the degree of similarity between specific phenomena in the L1 and L2. It has been stated that a higher degree of similarity between phenomena in the L1 and L2 typically results in greater L1 influence on the L2 and more difficulties in correctly acquiring the L2 sound see . Bohn an1.1.3.dehnen, [ˈdeːnən], “to stretch”) and /ɛː/  in their L1 has an impact on how well these individuals identify /æ/ and discriminate between the two English front, unrounded vowels /ɛ/  and /æ/ . We therefore intend to expand previous research on how a high degree of similarity between a phenomenon in the L1 and one in the L2 affects L2 speech acquisition in detail, by considering sociophonetic variation across different native speakers of German.To reach an intermediate summary, we can say that whether and to what extent the L1 affects the acquisition of the L2 has been widely examined in the literature, and several factors have been taken into consideration. However, we feel that another factor has been mostly neglected, namely the role of sociolinguistic aspects of an individual’s L1 in the context of L2 speech acquisition. It is the aim of the present paper to investigate this issue. Precisely, we aim at investigating whether the degree to which German native speakers distinguish between the two front, unrounded vowels /eː/  and /ɛː/  are distinct phonemes  and speakers who merge the two vowels (henceforth: /eː/-/ɛː/ mergers). We ask whether these speaker groups identify /æ/ and discriminate the English vowels /ɛ/ and /æ/ differently in speech perception. Assuming that there are two groups, /eː/-/ɛː/ maintainers and /eː/-/ɛː/ mergers, we test the following hypotheses.The identification of English /æ/ and the discrimination of the English /ɛ/−/æ/ contrast is:H0: The same in both groups.H1: More native-like in the group of /eː/-/ɛː/ maintainers.These hypotheses derive from the patterns summarized in 2.2.1.In Experiment I, participants saw two pictures, heard a word, and had to decide which of the two concepts represented in the pictures they had heard.2.1.1.Fifty-one native speakers of German from northern Germany participated in the experiment .All participants were well-educated and had taken English as one of the central school subjects for at least 8 years. That is, all of them had a solid knowledge and command of English. Despite this similarity between our participants, they varied to some extent with regard to their level of English. We grouped our participants into three proficiency groups . Categorizing participants into the three groups was done in the following way. The first author of the paper and a native speaker of English listened to sound files of items, which were recorded in a short production experiment prior to the perception experiments. They examined the pronunciation in terms of nativelikeness, and assigned the participants to the groups “low,” “mid,” and “high.” If the first author and the native speaker of English did not agree, the case was discussed until agreement was reached. Our evaluation of the participants’ level of English is thus based on their pronunciation only. The participants’ level of English was later entered as a control variable into the statistical models.dehnen, [ˈdeːnən], “to stretch”) and 29 items containing /ɛː/  in Standard German. A key element of our work is whether and to what extent our participants distinguish between the German vowels /eː/ and /ɛː/. In order to obtain an objective reflection of this, we relied on the data from the production experiment reported in 2.1.2.pan/pen and paddle/pedal. The four words were spoken and recorded by a 24-year-old male US American from California in a silent room. The four sound files were normalized (70 dB) and subsequently used as the basis for the following manipulations. We created a spectral continuum with 11 steps from an extreme /æ/ (Step 1) to an extreme /ɛ/ (Step 11) based on a Praat script . Hence, the identification task consisted of six distinct blocks . The three blocks relating to one minimal pair always appeared one after the other in the same order . All the pan/pen blocks appeared first, all the paddle/pedal blocks afterwards. Each person was tested on 198 trials . Hence, each of the six blocks contained 33 cases (11 steps of the continuum × 3 times each sound file).The two minimal pairs 2.1.4.The two response variables were the percentage of the selection of the picture representing the /æ/ word (Selection of /æ/) and ReactionTime. We used a binomial logistic regression to examine the first and linear mixed effects models to analyze the second one in R , using tModel fitting proceeded in the following way , Step  were conducted using the emmeans package  in R to 2.1.5.We start presenting the results for Selection of /æ/. The most important results are the two significant interactions GermanPillai × Step and GermanPillai × Duration see , 2. The We see two significant interactions, GermanPillai × Step and GermanPillai × Duration. Let us start with the first one. In In We now turn to the analysis of ReactionTime, where we found a significant interaction of GermanPillai × Duration see , 7.post hoc test revealed further that participants responded faster to Step 2 than to Step 6 , to Step 2 than to Step 7 , and to Step 2 than to Step 8 .In the analysis of ReactionTime, there is a main effect of Step. Participants reacted more quickly to Step 1 than to Step 6. A Tukey Furthermore, we also detected a significant interaction, namely GermanPillai × Duration. In 2.2.In Experiment II, participants heard two sound files and were asked to indicate whether the two were acoustically identical or different.2.2.1.The participants were those from Experiment I.2.2.2.The materials/sound files were those from Experiment I.2.2.3.The experiment was conducted in a silent room. Participants sat about 60 cm in front of a computer screen and wore KOSS R-80 over-ear headphones. We used E-Prime 3 for stimulus presentation. In each trial, participants heard two sound files and indicated via button press, using the left and right arrow on a regular keyboard, whether they believed they were identical or different. We counterbalanced the association of arrow and identical/different across participants. As in Experiment I, both the two minimal pairs and the three vowel duration types appeared in different blocks. The spectral distance between the two sound files of a trial was 3, 2, 1, or 0 steps. That is, for instance, if the first sound file contained Step 3 and the second sound file Step 4, the distance between the two was 1 step. The interstimulus interval (ISI) was 1 s.2.2.4.The two response variables were Accuracy and ReactionTime. We used binomial logistic regression to examine the first and linear mixed effects models to analyze the second one in R, using the lme4 and lmerTest packages. In the analysis of ReactionTime, only correct answers were considered (40% of the answers), following common practice , Duration , LevelOfEnglish , and the three interactions GermanPillai × StepDistance, GermanPillai × Duration, and GermanPillai × LevelOfEnglish in the initial model. The model was reduced step by step and significances were checked using the technique outlined in section 2.1.4. Planned pairwise comparisons were used as outlined in section 2.1.4.2.2.5.We start looking at accuracy. Here, the interaction GermanPillai × StepDistance reached significance see . The stapost hoc test further showed that middle vowels were responded to more accurately than short vowels .In the analysis of Accuracy, we found a main effect of Duration, indicating that short vowels were responded to less accurately than long ones. A Tukey Further, we detected a significant interaction GermanPillai × StepDistance. We see in post hoc test indicated that the response time was longer for middle than for short vowel durations . Second, participants needed more time to respond when the StepDistance between the two sound files of a trial was 1, 2, or 3, in comparison to when it was 0. A Tukey post hoc test showed that the response times were longer for a StepDistance of 1, compared to StepDistances of 2 and 3 . Also, participants responded more slowly for StepDistance 2 than for StepDistance 3 .We now turn to ReactionTime see , 11. The3.The present paper reported on an identification and a discrimination task and aimed at investigating whether the degree of overlap between the vowels /eː/ and /ɛː/ in L1 German affects the way individuals identify the new vowel /æ/ and discriminate between the vowels /ɛ/ and /æ/ in L2 English. We distinguished broadly between /eː/-/ɛː/ maintainers, that is, L1 German speakers who articulate the vowel contrast in their L1, and /eː/-/ɛː/ mergers, that is, L1 German speakers who do not articulate the vowel contrast in their L1.In the identification task, we found that Step 1 was reacted to faster than Step 6 and Step 2 was responded to more quickly than Steps 6, 7, and 8. That is, some of the more extreme steps were easier to process. The significant interaction GermanPillai × Duration for the reaction time data signaled that /eː/-/ɛː/ mergers needed more time to process the difficult intermediate category (middle duration), in comparison to the categories of short and long duration, than /eː/-/ɛː/ maintainers.Moreover, and crucially, we detected two significant interactions, namely GermanPillai × Duration and GermanPillai × Step in the data for the Selection of /æ/. Considering the first interaction, we saw that while /eː/-/ɛː/ maintainers selected English /æ/ slightly more often than /eː/-/ɛː/ mergers for long vowels, /eː/-/ɛː/ mergers picked English /æ/ slightly more frequently than /eː/-/ɛː/ maintainers for short vowels. Importantly, while /eː/-/ɛː/ mergers chose /æ/ for short and long vowels roughly equally often, /eː/-/ɛː/ maintainers selected this vowel more frequently for long than for short vowel durations. This supports H1: /eː/-/ɛː/ maintainers are more native-like in the identification of the new vowel /æ/ than /eː/-/ɛː/ mergers. While both speaker groups assimilate English /ɛ/ to German /ɛ/, the two groups seem to differ with regard to how they treat English /æ/. /eː/-/ɛː/ mergers, who only rely on /ɛ/ in L1 German and do not distinguish between /ɛ/ and /ɛː/, seem to assimilate English /æ/ to German /ɛ/, they fail to make adequate use of the duration parameter. /eː/-/ɛː/ maintainers perform more successfully for the parameter of vowel duration, which might derive from the fact that they are familiar with the distinction between /ɛ/ and /ɛː/ from the L1 German. /eː/-/ɛː/ maintainers either could have assimilated English /æ/ to German /ɛː/ or could have developed the new category /æ/.Interestingly, the second interaction supports H1, too, although /eː/-/ɛː/ maintainers should not necessarily have an advantage when it comes to vowel quality . We observed that /eː/-/ɛː/ maintainers selected English /æ/ more frequently than /eː/-/ɛː/ mergers for Steps 1 to 4. Step 5 shows a slight tendency for this, too. Acoustically speaking, these steps clearly represent English /æ/ and we have thus evidence that /eː/-/ɛː/ maintainers identify this vowel more accurately than /eː/-/ɛː/ mergers. This is further supported by the fact that /eː/-/ɛː/ mergers chose English /æ/ more frequently than /eː/-/ɛː/ maintainers for Steps 7 to 11, which carry the acoustic properties of English /ɛ/. Step 6, which is exactly in the middle of the continuum and can be considered to be neutral, joins for some reason the pattern we found for Steps 7 to 11. Overall, the significant interaction GermanPillai × Step we saw in the analysis of the response variable Selection of /æ/ in the identification task also supports H1: /eː/-/ɛː/ maintainers perform more native-like in the identification of /æ/ than /eː/-/ɛː/ mergers. Remember that we stated above that the results of the significant interaction GermanPillai × Duration could mean that /eː/-/ɛː/ maintainers either assimilated English /æ/ to German /ɛː/ or have developed the new category /æ/. The results of the second interaction, GermanPillai × Step, seem to be more compatible with the interpretation that /eː/-/ɛː/ maintainers have developed the new category /æ/. They outperform /eː/-/ɛː/ mergers not only on the level of vowel duration but also on the spectral level.It is an interesting finding that vowel quality makes such a difference although both /eː/-/ɛː/ maintainers and /eː/-/ɛː/ mergers are familiar with the vowel quality of /ɛ/ but unfamiliar with the vowel quality of /æ/ from their L1 German. A potential explanation might be related to the fact that all of our participants were advanced speakers of English. Possibly, advanced speakers are generally aware of the differences between English /æ/ and German /ɛː/ / /ɛ/ see also . NeverthIn the discrimination study, we found a lower accuracy for the short in comparison to both middle and long vowel durations. That is, more information led to higher response accuracy. The reaction time data revealed that short vowels were responded to more quickly than middle or long vowels. In addition, middle vowels triggered longer reaction times than long vowels. It seems thus that the intermediate category is the hardest one to deal with. Looking at the response times, we further found that participants gave the fastest answers for a StepDistance of 0, followed by StepDistances of 3, 2, and 1. Hence, identical cases posed the smallest challenge to the individuals; beyond that, a greater distance between two sound files of a trial accelerated the reaction.Further, the interaction GermanPillai × StepDistance reached significance in the accuracy data. Despite the significance, the interaction is neglectable. On the one hand, we saw that /eː/-/ɛː/ maintainers responded slightly more accurately than /eː/-/ɛː/ mergers for a StepDistance of 0; on the other hand, /eː/-/ɛː/ mergers answered slightly more correctly for the StepDistances 1 and 2. StepDistance 3 falls, roughly speaking, in the middle. Overall, the discrimination study can only be interpreted to support H0: /eː/-/ɛː/ maintainers and /eː/-/ɛː/ mergers do not differ with regard to the discrimination of the English vowels /ɛ/ and /æ/.We realize that sociophonetic aspects of the L1, in our case the degree of overlap of the two German vowels /eː/ and /ɛː/, affect how language users deal with certain phenomena in the L2. Our results provide a piece of evidence that the concept of the L1 and its function in L2 acquisition is heterogenous. Although there is by now a good amount of research targeting different types of sociolinguistic variation in the L2 itself see , that isFinally, we would like to point out another avenue for future research. As we noted in section 1, varieties of English differ with regard to how the phonological contrast between /æ/ and /ɛ/ is articulatorily and acoustically realized. It goes without saying that it is hard to assign an L2 speaker of English to a specific variety since everyone is exposed to several sources of input, each having its distinct nuances. For instance, one might have had a teacher speaking a variety of US American English at school but later lecturers from the United Kingdom at university. To complicate matters even further, learners can be confronted with yet other varieties of English through the media, in international communities, or during extended stays in English-speaking countries. That being said, and although it would not be a trivial task to find L2 speakers who have been exposed to and used a single variety of English only or at least primarily, disentangling the influence of various Englishes would provide us with even more pieces of the puzzle of how individuals acquire speech in an L2.4.Our findings show that sociophonetic variation within a person’s L1 plays a role in L2 acquisition. Individual variation adds an essential piece to the puzzle of how the L1 determines how language users deal with phenomena in the L2. Here, we showed that the degree to which two vowels are merged in someone’s L1, such as /eː/ and /ɛː/ in German, seems to affect the identification of a new vowel (/æ/) in the L2. We feel that there are promising avenues for future research in this field and hope that this work inspires others to enrich our knowledge on the role of individual variation in the interplay between L1 and L2 speech.The R scripts and the datasets are included in the The studies involving human participants were reviewed and approved by Research Ethics Committee, University of Oldenburg, Germany. The participants provided their written informed consent to participate in this study.MS and JP developed together the research questions against the background of the relevant literature in the field. MS and MF compiled the materials, designed the experiments, collected the data, conducted the statistical analyses, and wrote the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The functionalizationwith a hydrophilic and soft polymer modifies the hydrophobicity ofgraphene and might enhance its biocompatibility. We have characterizedthese hybrid materials by atomic force microscopy (AFM), X-Ray photoelectronspectroscopy (XPS) and Raman spectroscopy and studied their electricalresponse, confirming that the graphene/p-AP/PHEAarchitecture is anchored covalently by the sp3 hybridizationand controlled polymerization reaction on graphene, retaining itssuitable electronic properties. Among all the possibilities, we assessthe proof of concept of this graphene-based hybrid platform as a humiditysensor. An enhanced sensitivity is obtained in comparison with pristinegraphene and related materials. This functional nanoarchitecture andthe two-step strategy open up future potential applications in sensors,biomaterials, or biotechnology fields.The modificationof the surface properties of graphene with polymersprovides a method for expanding its scope into new applications asa hybrid material. Unfortunately, the chemical inertness of graphenehinders the covalent functionalization required to build them up.Developing new strategies to enhance the graphene chemical activityfor efficient and stable functionalization, while preserving its electronicproperties, is a major challenge. We here devise a covalent functionalizationmethod that is clean, reproducible, scalable, and technologicallyrelevant for the synthesis of a large-scale, substrate-supported graphene–polymerhybrid material. In a first step, hydrogen-assisted plasma activationof  Otherwise, PA dissociation hasbeen limited to mono-atomic functionalization,20 but these limitations can be overcome if PA low-vacuumtechniques are used to promote the dissociation of organic moleculesin gas phase that immediately link to the graphene lattice. Thus,PA is a promising strategy for the covalent functionalization of graphene,as we address in this work. In addition, the PA low-vacuum processis fast, clean, cost-effective, and scalable.Graphene, an sp28 It is also a promising polymer with soft and hydrophilic propertiesand high water adsorption capacity,30 one of thekey factors for biocompatible and bioengineering applications. Therefore,we expect this hybrid material to be a great candidate to study themodification of the graphene hydrophobicity and its improvement inthe biocompatible behavior as in other cases where a polymer is combinedwith other materials.28Acrylate polymersare a type of significant vinyl polymers usedin a wide range of industrial products, ranging from contact lensesor bone cement to cosmetics, coatings, adhesives orthopedics, textilesor drug administration. Acrylates in combination with other components form interesting newhybrid materials for bioengineering. PHEA is a polymer broadly usedas a hydrogel for lens, hemotherapy, in bioactive scaffolds, controlledrelease and applications that prove its biocompatible character.p-aminophenol(p-AP) and the carrier H2 gas dissociatein a low-vacuum plasma chamber and the graphene layer is activated,enabling the covalent functionalization of the basal plane with theorganic moiety. We functionalize the substrate-supported graphenewith organic molecules in a low-vacuum clean plasma environment, asan unexplored alternative to the wet chemistry methods5 and UHV8 approaches. This (p-AP) organic molecule incorporates an end-group (phenol)which is intended to be the linker to further anchor more complexmolecules and subsequently obtain a hybrid material. The key advantageof this strategy is the versatility of the method that enables touse specific linker molecules to functionalize graphene on demand.18 Recently, a similar platform has been demonstrated,especially suitable for high-performance bioelectronic devices.31Here, we devise a new versatiletwo-stage functionalization approachto build large-area graphene–polymer hybrid nanoarchitecturesas platforms with potential applications in biotechnology and sensing.In a first stage, the organic linker molecule 32 from the OH group provided bythe p-AP molecule, resulting in a robust and stablegraphene/p-AP/PHEA hybrid functional material. Ourmethod keeps the suitable properties of functionalized graphene, sinceno solvents or high temperatures that could lead to the material degradationare used enhancing, in contrast, the versatility of graphene.36 This approach is highly versatile and opens the door to the combinationof a wide range of linkers and polymers with potential applicationsin several fields.41 For instance, graphene is a material with a large potential in high-performancehumidity sensors, as reported in the literature.44 Therefore,the combination of the graphene sensitivity, the robustness of thecovalent functionalization, and the water absorption capacity of thepolymer make the hybrid platform proposed as a potential candidateto be an efficient humidity sensor. Accordingly, we show in this worka proof of concept of such application.Afterwards, we carry out an in situ surfacepolymerization of 2-hydroxyethylacrylate (HEA) monomer that grows in a controlled and reproduciblemannerp-AP/PHEA architecture is anchoredcovalently, in a stable and robust way, by sp3 hybridizationof graphene bonds and controlled polymerization. Finally, we assessthe sensitivity of our graphene–polymer hybrid platform developedby measuring the surface electrical properties by the four-point probeanalysis after different relative humidity exposures as a proof ofconcept of a humidity sensor. This study describes a new versatileand reproducible route to design functional robust nanoarchitecturesbased on graphene that have shown breakthrough applications in differentfields.The topographic changesin graphene are sequentially characterizedby atomic force microscopy (AFM), and the chemical functionalizationis analyzed by X-ray spectroscopy (XPS) and Raman spectroscopy inboth graphite surfaces and supported graphene samples. We ascertainthat the graphene/22.12.1.145 During functionalization,the chamber pressure is 5.4 × 10–2 mbar, andthe plasma power is 200 W. HOPG purchased from Tip Nano OÚand Si/SiOx wafer-supported CVD graphene purchased from GrapheneaInc. are used as substrates. The p-aminophenol (p-AP) powder precursor is purchased from Sigma-Aldrich (H2NC6H4OH ≥ 98%), and H2 is used as a gas carrier. The second stage of functionalizationand the final step to build up the hybrid material is carried outin an oven with a constant nitrogen flow. The monomer and initiator,2-hydroxyethyl acrylate (HEA)  and 2,2-azobis(isobutyronitrile)(AIBN), the reactants used to carry out in situ free-radical (FR)polymerization on the surface, are purchased and used as receivedfrom Sigma-Aldrich.Thefirst stage of covalent graphene functionalization is carried outby using an ASTEX AX 4500 electron cyclotron resonance (ECR) plasma-assistedequipment. A comprehensive description of the plasma system can befound elsewhere.2.1.2Room-temperatureAFM measurements for topographical analysis are performed with twocommercial equipment: (a) Nanoscope IIIa from Veeco (United States):Dynamic operation mode is selected, and silicon cantilevers (Bruker)with a nominal radius of curvature of 8 nm and nominal constant forceof 1–5 N/m are used. (b) Instrument and software from NanotecElectrónica S.L: Dynamic operation mode is employed, excitingthe tip at its resonance frequency (∼75 kHz) to acquire topographicinformation of the samples. The structure of our graphene films isaddressed by Raman spectroscopy using a confocal Raman microscope(S&I Monovista CRS+). Raman spectra have been obtained using a532 nm excitation laser, a 100× objective lens (NA = 0.9), andan incident laser power of 6 mW. The chemical nature of the hybridmaterial is determined by XPS. XPS measurements are carried out underUHV conditions using a PHOIBOS 100 1D delay line detector electron/ionanalyzer, monochromatic Al Kα anode (1486.6 eV), and pass energyof 30 eV.2.1.3–6 mbar). The 94 ± 3% RH data were acquired after2 h of continuous exposure to a humidity-saturated environment usinga wet paper in an airtight Petri dish . The room RH (27 ± 3%) correspondsto the laboratory ambient conditions. Measurements correspond to I–V curves in a four-point probesystem JANDEL RMS2 Universal Probe with continuous current (from 0.1to 10 μA). We apply the standard equation R□ = 4.53·ΔV/I for sheet resistance (R□) calculations (ΔV being the change in voltagemeasured between the inner probes and I the currentapplied between the outer probes).The water vapor absorption ability onto a sample surfacebecauseof the polymer presence allows using the hybrid material as a humiditysensor that is assessed at 0% relative humidity (RH), room RH (27± 3%), and top RH (94 ± 3%). The 0% RH data were acquiredafter the samples were placed 2 h in a vacuum environment (102.2p-aminophenol (p-AP) and the 2-hydroxyethyl acrylate (HEA) in situ polymerizationon the surface.The build-up strategy includestwo main stages: the linker attachment consisting of a covalent functionalizationwith the organic molecule 2.2.1p-AP precursor powder isevaporated into the chamber at 100 °C during 10 min, while thegraphene or HOPG samples are at room temperature. After the p-AP gas pressure is stabilized, we introduce the H2 gas carrier and switch on the plasma during 30 s . The plasma activationdissociates atomic H and the organic precursor in radicals, as depictedin 3 soft hybridization of the basal plane.47 Note that this ECR plasma produces around 5–10% atomic H.This process enables the attachment of the p-AP organicradicals previously activated by plasma. In this way, a high densityof functionalization can be achieved, controlling time and dose . One plausible reaction path is theplasma-assisted dehydrogenation48 or dissociation49 of the amino group in plasma, leaving behindaromatic groups with hydroxide moieties that anchor to the buckledgraphene lattice, as pointed out by our XPS results below. We alsotested the attachment of the molecule by carrying out an ethanol washand taking AFM images before and after the process. We observe thatthe molecule remains intact . As a result, the phenol end-groupbecomes the linking moiety to anchor more complex molecules.2.2.22 flow in order to perform a slow andcontrolled polymerization based on previous kinetic studies reportedin the bibliography.32 We are interested in a slow polymerizationrate to obtain a low surface coverage. In this work, two in situ polymerizationsare carried out where one sample aims to have the lowest amount ofpolymer on the surface (L-PHEA) and the other intends to achieve higherpolymer coverage on graphene (H-PHEA). For L-PHEA, the reaction timeis 30 min, while for H-PHEA, it is 1 h, and in addition, the polymerizationprocess was repeated once.p-AP linkermolecule anchored on the graphene surface. Similar processes havebeen studied by the radical polymerization of acrylate monomers, suchas poly(hydroxyethyl methacrylate), PHEMA, or poly(butyl methacrylate),PBMA, to obtain nanocomposites based on the reaction of the monomerwith nanosilica or by the addition of graphene oxide (GO).52 This reaction is selective and requires the presence of oxygen-containinggroups in order to accomplish the attachment to the acrylate and,therefore, can be a marker of the presence of free −OH groupsin the linked p-AP. The resulting graphene–polymersamples are washed using ethanol to remove the possible physisorbedmonomer and polymer . The final anchoring of the monomer to thelinker molecule covalently bonded on the graphene surface is depictedin x substrates.The process of anchoring the firstmonomer unit to our functionalized graphene surface proceeds as follows.Initially, as the temperature increases, the initiator (AIBN) fragmentsinto primary radicals by the cleavage of weak bonds. These radicalsfind a monomer molecule to react with their double bond and startthe reaction. During polymerization, several monomer molecules areadded from the cleaved double bond, thus forming macroradical chainsattached to this first monomer represented in 33.1p-AP/L-PHEA)and another with a higher polymer coverage (HOPG/p-AP/H-PHEA). Two types of samples were polymerized in situ with HEA, one witha low amount of polymer on the surface . For the HOPG/p-AP sample, this peak iswider and shifted to slightly higher values because of the surfaceroughening and the p-AP molecules. The rougheningas well as the different morphology allows us to confirm the incorporationof p-AP molecules onto the surface. p-AP/L-PHEA) and highest (HOPG/p-AP/H-PHEA) polymer coverage on graphene, respectively.The wide images in p-AP/L-PHEA, a surface coverage close to 20% and a surface densityof about 350 structures/μm2 are observed. A highdensity of features, with heights between 0.3 nm and 4.6 nm is found,a majority of them being of globular morphology with an average heightaround 1.2 nm. These changes confirm that polymerization has takenplace and that it is stable as the samples were measured after beingwashed with water. Finally, for the HOPG/p-AP/H-PHEAsample, the large image in p-AP molecule through the hydroxyl group, and then fromthere the polymer grows. Larger aggregates represent a larger polymerchain. In addition to the domains observed as aggregates in 3.2p-AP-graphite and PHEA-p-AP-graphitearchitecture. p-AP functionalization (HOPG/p-AP), and HOPG samples after the two polymerization processes(HOPG/p-AP/L-PHEA and HOPG/p-AP/H-PHEA).The C 1s core level . We also check that the main sp2 component remainsalmost unchanged, confirming that no damage was induced in the sampleby plasma-assisted processing. After the polymerization, new contributionsappear at 285.2 and 286.0 eV, which are ascribed to C–OH andC=O, respectively, from the hydroxyls and carboxylic groupsfrom PHEA. Finally, relative to the last C 1s spectrum of p-AP/H-PHEA sample reveals the increment of polymer conversionon the graphite surface with the enhancement of the contributionsat 285.2, 286.0, and 286.8 eV, assigned to the oxygen bonds, C–OH,C=O, and O–C=O respectively, from the hydroxylsand carboxylic groups from the PHEA structure.58 This signalenhancement is a direct consequence of the increase in the polymercoverage, in good agreement with the previous morphology seen in The chemical nature of the hybrid functional material has beencharacterized by XPS. Freshly cleaved HOPG is used as a referencesubstrate to study the chemical variations induced in the consecutivestages, the 52 The next spectrumcorresponds to the p-AP covalent functionalized sample,HOPG/p-AP, where, in addition to the adsorbed species,a new component at 532.8 eV appears. We ascribe this new componentto the OH groups of the p-AP molecule, confirmingits presence.60 We also see the increase of adsorbed species,which is easy to explain considering the plasma activation of theHOPG surface and exposure to ambient air before the XPS analysis.This activation enhances the adsorption of molecules as the samplesurface is not completely saturated during the covalent functionalizationexperiment. This intentioned saturation control allows us to maintainthe proper electronic properties of graphene, as we see below . Regardingthe functionalized surface after the polymerization reaction, as expectedfor a PHEA coverage, there are multiple components in the O 1s peak:531.6, 532.8, and 533.7 eV, assigned to the carbonyl (C=O),hydroxyl (OH), and ester (O–C=O) species, respectively.61 Two similar spectra are observedin both L-PHEA and H-PHEA polymerizations, with the only differencein the intensity of each characteristic contribution being largerafter H-PHEA polymerization, as expected. We also observe a smallremaining contribution due to the adsorbed species at 529.9 eV thatmay be a slight surface oxidation due to the existence of steps, defects,grain boundaries or exposed atomic sites after repeated surface washings.For the pristine sample, the spectrumpresents two small componentsthat can be assigned to the environmental adsorbed species as a consequenceof the exfoliation in air.3.3Figures S1 and S2 in the SupportingInformation). The analyses confirm, overall, that the functionalizationprocess takes place similarly on graphene as remarkable differencesin the final morphology of the samples or in the chemical mechanisminvolved are not observed. We conclude that the synthesis of a polymer/graphenehybrid functional material successfully works, which opens the doorto its application in devices.The study from HOPG has allowed us todevelop, characterize and validate the efficiency of a two-stage graphenefunctionalization process based on a linker and functional moleculeattachment on the surface to obtain a graphene–polymer hybridplatform. However, from the large-scale application point of view,the relevant next step consists of the transfer of this protocol toa graphene sample. In this scenario, the substrate morphology andthe structure of functionalized graphene samples have been sequentiallycharacterized by AFM and Raman spectroscopy in every step of the process(see R□) of thelayer by means of a four-point probe analysis at room temperature. R□ variation of the samples, extractedfrom the analysis of the slope of the corresponding I–V curves performed at several points ofthe samples under room conditions . Theinitial pristine graphene layer exhibits an average sheet resistancevalue of 0.55 kΩ after the cleaning procedure that we applyto our samples, 2 h at 340 °C, in a high vacuum ,being a standard result due to the high quality of the material. Thisresistance value increases to 1.05 kΩ on average after the functionalizationwith p-AP, as expected, considering the induced sp3 hybridization of the graphene lattice. As mentioned above,the functionalization density, and thus the hybridization degree,obviously depends on the plasma-assisted processing time, 30 s, asthis parameter determines the precursor dose. The processing timeused is selected after studying its influence on the electrical propertiesand the structure of graphene as a balance between the functionalizationdensity desired and the reduction of conductivity allowed for theintended application . After the polymerization step, the sheetresistance increases, up to 1.35 kΩ, as seen in the last pointof I–V curves measured on each sample. Finally, 64 A similar behavior is observed when p-AP is covalentlybonded to graphene, G/p-AP in red, which does showa small increase in resistivity as the humidity increases, in agreementwith previous reports on this effect as a function of graphene doping65 and band gap opening.66One of the main challenges ofcovalent graphene functionalization is to retain suitable electricalproperties of the graphene layer after processing. In order to studythe changes in the conductivity of graphene throughout the differentstages, we have measured systematically before and after each stagethe sheet resistance  shows that the 2D peak position is around 2682 cm–1 pointing out toward n-doping.68 The water absorption is known to induce p-doping in graphene, aswater molecules behave as electron acceptors69 when directly into contact with the graphenesurface. As the Raman 2D peak of the functionalized samples is inthe same position as that of pristine graphene in Figure S2d in our samples, the water-induced charge transferdecreases the graphene n-doping, increasing its resistivity.However, when the polymer is anchored to the surface,the sensitivityof this graphene-based hybrid platform, in blue, becomes outstanding.This is related to the hydrophilic character of the polymer and itsability to absorb water into its structure.p-AP exhibit a low interactionwith the dynamic humidity change in the environment (red and greenlines). However, a remarkable improvement in the detection performanceof the G/p-AP/L-PHEA material is observed due tothe natural adsorption and release of water molecules on the polymer(blue line). From a quantitative point of view, the resistance variationsor sensitivity, SR, exceed 29% (R□ (94%RH) = 1.57 kΩ, R□ (0%RH) = 1.21 kΩ, from SR in Table S1). Table S1 compiles a performance comparison ofthis work with a number of resistive humidity sensors reported inthe literature70 that confirms the high sensitivityof the hybrid material to the humidity conditions. It is thus demonstratedthat chemical modification by poly-2-hydroxyethyl acrylate on thesurface is a feasible way to improve the sensitivity of graphene tohumidity.Regarding the reproducibility and sensitivity of the materialsas a sensing platform, 4p-AP). This unexploredphysical protocol is clean, reproducible, easily scalable, and cost-effective.The second stage consists of in situ radical polymerization on thefunctionalized graphene surface, leading to a PHEA/graphene hybridmaterial. This strategy is highly versatile and opens the door forthe design of a wide range of graphene–polymer or biopolymerhybrid platforms for biosensing devices. AFM, XPS, Raman, and four-pointprobe sheet resistance analyses confirm that the graphene/p-AP/PHEA architecture is covalently anchored by sp3 hybridization of graphene, retaining suitable electronicproperties after the polymerization process. We have successfullytested the hybrid material as a resistive humidity sensor since thehydrophilic PHEA polymer modifies the hydrophobicity of graphene,finding an outstanding sensitivity to humidity variations, SR = 29%, competing with previous sensors basedon graphene, graphene oxide, reduced graphene oxide, or polymer-functionalizedgraphene. In addition, this proposed graphene–polymer hybridfunctional material leads the way for further biotechnological applicationsthat will be studied in future research projects in order to expandits field of potential applications.In summary,we present a novel route to synthesize a polymer/graphenehybrid functional material that consists of a two-stage process. Inthe first stage, a low-vacuum hydrogen-assisted plasma activationprocess produces a stable and covalent graphene-functionalized platformwith a small linker molecule (


The results show that the sensor provides direct electrical readout from temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which results in better sensitivity and wide-range temperature sensing. In addition, monolayer graphene is almost no temperature sensitivity. And the few-layer graphene temperature sensitivity, lower than that of the multilayer graphene cavity structure (3.50%/°C), is 1.07%/°C. This work demonstrates that piezoresistive in suspended graphene membranes can effectively enhance the sensitivity and widen the temperature sensor range in NEMS temperature sensors.The substrate impurities scattering will lead to unstable temperature-sensitive behavior and poor linearity in graphene temperature sensors. And this can be weakened by suspending the graphene structure. Herein, we report a graphene temperature sensing structure, with suspended graphene membranes fabricated on the cavity and non-cavity SiO For example, the preparation of suspended graphene on Si/SiOsitivity . Bolotinsitivity . Jian-Hasitivity  revealedsitivity . Howeversitivity . That isIn this work, a cavity graphene structure a on a si2 surface. And the graphene will seal the gas in the cavity, which is led by excellent air tightness and van der Waals forces between graphene and SiO2. The gas pressure in the cavity increases as the temperature rises, leading to the gas pressure difference as shown in As shown in 5 Pa is the initial air pressure at the two sides of the cavity. The gas pressure formula is given as follows [The pressure strain of multilayer graphene with PMMA was simulated using COMSOL Multiphysics 5.5. In the simulation of air pressure in the cavity, we assume that gases are in standard atmospheric pressure. And the  follows :(1)T1p1=5 Pa. The size of the cavity is 1.5 mm × 1.5 mm × 50 μm, and the volume of the gas in the cavity is 1.12 × 10−12 m3. The range of gas pressure values in the cavity is converted to Newtonian mechanical units of 0.2 N–9.6 N. The atmospheric pressure on the suspended graphene is 0.2 N, and the pressure difference on the suspended graphene from the previous analysis is 0 N−9.4 N. The experimental conditions were chosen to remain within the expected tearing limits of the graphene membrane. It can be seen from SEM images that the maximum stretch of the graphene film reaches about 20% [Under the temperature sensing range of 25 °C–120 °C, the pressure range of suspended graphene is 0–3.84 × 10bout 20% ,34,35.2 = 500 nm, Young’s modulus E = 1.6 GPa, Poisson’s ratio γ = 0.22. The simulation results are shown in The PMMA layer in the device designed in this work protects the graphene. PMMA covering the graphene should be unavoidable, which is contrary to the argument. Therefore, the PMMA layer was considered in the simulation. The detailed parameter settings in the simulation are as follows. The thickness of suspended graphene film t = 10 nm, Young’s modulus E = 1 TPa, Poisson’s ratio γ = 0.16, The thickness of PMMA tIf a pressure difference is present between the inside and the outside of the cavity compare c, the grIgnoring the substrate impurity scattering and the thermal resistance effect of graphene. The piezoresistive simulation shows that the device resistance will increase with rising temperature. Piezoresistive effects, substrate scattering effects, and thermal resistance effects all contribute to the output resistance of the sensor. In this work, piezoelectric effect simulations are performed to theoretically verify the role of strain and resistance of graphene. Therefore, the effect of other factors on the resistance is not considered in the simulation. Moreover, the thermal resistance effect of graphene is not the core of the sensor in this article. On the contrary, the thermal resistance effect of graphene is an effect that the paper hopes to eliminate. The substrate scattering effect of silicon substrates on graphene has a significant impact on the performance of the monolayer sensors in this work. However, there is no complete theoretical system for the research results on the scattering effect of silicon substrates on graphene . TherefoThe CVD graphene on copper foil used in the device preparation process is transferred to the target substrate by wetting transfer technology. The PMMA is a protective layer for graphene during the wet transfer process. In addition, PMMA, a sacrificial layer in the wet transfer process, is not removed and continues to protect graphene during the temperature sensing process. The detailed: (a) Removal of residual organic matter from the back side of graphene copper foil using a glue remover. (b) The PMMA solution was spin-coated on the front side of the copper-based graphene and cured on a hot plate at less than 60 °C. (c) The cured copper-based graphene is put into the configured copper sulfate solution to etch the copper base. (d) After all the copper corroded, the graphene film with PMMA is first fished into deionized water with silicon wafers and left to stand for a few minutes. The graphene film with PMMA is then transferred to the target substrate and treated with natural dry. In this work, we prepared monolayer, few-layer, and multilayer graphene for temperature sensing, respectively. Different layers of graphene are used for the preparation of devices.2 film on a silicon substrate. This CVD graphene on copper foil was gotten by wet etching. And the wet etching allows the transfer of graphene from the copper foil to the target substrate. This graphene on copper foil was purchased from Sixcarbon Tech Shenzhen. The thickness of the Si layer is 500 μm, the thickness of the SiO2 layer is 300 nm, and the Si/SiO2 substrate is from Shenzhen Rigorous Technology. The wafer is a heavily-doped monocrystalline silicon. The details of the fabrication shown in 2 substrate needs to be cleaned by acid cleaning and alkali cleaning to remove organic impurities on the surface of the substrate; Removal of SiO2 from the substrate backside using BOE. It is used for subsequent verification of the conductivity of the bottom electrode and the electrodes on two sides of the graphene. (b) A cavity is etched on the prepared sheet using the photolithography technique and RIE etching method. And the depth of the trench is 50 μm. (c) Au electrodes are sputtered on both sides of the cavity using Magnetron Sputtering equipment. (d) CVD graphene, with PMMA, is transferred onto the substrate by wetting transfer technology [In experiments, graphene membranes made from CVD graphene on copper foil are suspended over cavities etched into a Si/SiOchnology ,37. The Preliminary verification of the conductivity of the sample is required because the graphene may be damaged during the transfer process. The finished samples need to select resistance values in the range of 1 kΩ–10 kΩ for subsequent testing. The device yield by the fabrication process is about 90%. Also, the suspension of graphene on the device needs to be verified. The device designed in this work can also be used as a transistor. When the graphene is not suspended but in contact with the silicon substrate at the bottom of the cavity, then the source/drain and the gate will be conductive. Then verifying the conductivity between the source and drain can be a preliminary verification of whether graphene is suspended or not. Then, the qualified samples need to be wire-bonded. In addition, the sensing structure in our work is monolayer, few-layer, and multilayer graphene. The SEM image and Raman test data of the device are shown in In our work, the graphene temperature sensor provides a direct electrical readout of temperature to strain transduction. The hot plate simulated ambient temperature. And Keithley 2611B is for monitoring current change under different temperatures. The specific measurements are as follows: (1) The temperature sensor is fixed on the hot plate with high-temperature tape; (2) The temperature was set as 25 °C. Then, save the I-V curve data after the device value becomes stable. (3) Increase the temperature of the hot plate to 120 ℃ and save the I-V data after the temperature reaches stability. And the temperature is changed in steps at 5 °C. (4) Export the test data and analyze the sensing property between graphene resistance and temperature. Finally, the testing data changed from I-V to R-V data for the benefit of the analysis.The suspended graphene sensors data in The resistance does not show a regularity with temperature on non-cavity samples in From the data in Finally, the sensitivity and linearity of the sensor were analyzed and calculated. In resistance-based temperature sensors, the initial resistance  and the temperature coefficient of resistance (TCR) are essential parameters for temperature measurement . A higheA linear fit of the tested resistance data with temperature performed by Origin is in In this work, the sensor provides a direct electrical readout of temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which achieves better sensitivity and wide-range temperature sensing. The sensor’s sensitivity is 3.50%/°C, the linearity is 0.98, and the sensing temperature range is 25 °C–120 °C. Compared with conventional thermal resistance graphene temperature sensors, the sensors have orders of magnitude higher sensitivity. Further, the experiments suggest that the graphene layers affect the sensitivity, linearity, sensing range, and other sensor parameters. In the experiments, the monolayer, few-layer, and multilayer graphene sensors have different sensor parameters. This work can provide theoretical and technical support for NEMS temperature sensors.