For the rooting phase, agarized substrate and soil were used with shoots derived from a standard proliferation substrate (4 mg L−1 zeatin) and from the substrate that gave the best results in the proliferation phase (2 mg L−1 zeatin and 0.1 mL L−1 neem oil). In the proliferation phase, the addition of neem oil in the substrates with low zeatin concentration (1 and 2 mg L−1) induced an increase in the number of adventitious shoots and shoots length. On the contrary, the addition of neem oil in the rooting substrates did not positively influence the rooting phase, but positive results especially in terms of root number and length were observed in explants derived from a neem oil-enriched proliferation substrate compared to the control substrate. Therefore, the present study demonstrated for the first time the positive role of neem oil in the proliferation of olive in vitro with low zeatin concentrations.Micropropagation is an in vitro propagation technique, established in the nursery field sector for numerous species, which offers several advantages compared to traditional agamic propagation techniques. In the case of the olive tree, however, despite the advances made through research, it is still little used, due to the recalcitrance to in vitro proliferation and/or rooting of many olive cultivars and the high cost of zeatin, the only cytokinin that makes it possible to achieve a satisfactory proliferation rate in this species. In this context, numerous attempts have been made to identify alternative cytokinin compounds able to improve the proliferation rate of olive tree explants and thus reduce the unitary production cost. In particular, there is a growing interest in the use of natural substances , which, when added to the in vitro cultivation substrates, seem to be able to improve proliferation rates. In the present study, neem oil was added to the propagation substrates  and in the rooting phase for the olive cultivar Moraiolo. In particular, in the proliferation phase, the effect of neem oil (0.1 mL L Olea europaea L.) is an evergreen medium size tree and probably originated from the eastern Mediterranean region of the Middle East (southeastern Anatolian region and south Asia Minor) [Xylella fastidiosa infection forcing farmers to plant new olive groves has significantly increased the demand for high genetic and phytosanitary quality olive plantlets [Olive (a Minor) . The olia Minor) . The wora Minor) . In recelantlets . In thisUsually, olive trees are propagated vegetatively by rooting leafy stems or softwood cuttings, by grafting pieces of the stem (scions) onto seedlings or clonal rootstocks or suckers . In partMicropropagation is used worldwide as an important tool for the large-scale production of clonal plantlets since it has several advantages compared to conventional agamic propagation systems. The main advantages are the high genetic and sanitary quality of the propagated material and the possibility to produce a large number of plants in a small space and in a short time, and this facilitates the plant material exchanges between nurseries . Current® system for olive shoots proliferation. Moreover, attempts have been made to identify alternative cytokinins. Meta-Topolin stimulate cytodieresis, providing appreciable results in controlling hyperhydration and delaying senescence, phenomena that can be encountered during olive tree proliferation [For this reason, particular attention has been paid to the possibility of reducing the use of zeatin. In particular, TIS Plantform™ was tested for olive culture (Canino cultivar) and produced an optimal number of shoots at reduced levels of zeatin . Indeed,feration . Dikegulferation . Moreoveferation . BA  increased the shoot length, the number of nodes, and the fresh and dry weight of shoots of olive cultivar Moraiolo.In addition to hormonal substances, organic nitrogens, organic acids, and natural extracts with species-specific effects, such as water and/or coconut milk, casein hydrosylate, malt extracts, tomato extracts, potato extracts, banana homogenate, yeast extract  algal coAzadirachta indica A. Juss, belonging to the Meliaceae family that originates from the Indian subcontinent [Neem oil is usually prepared from the seed kernels of ontinent  and is wontinent . In partontinent ,30. In pontinent . Additioontinent , the knoIn the Z0 substrate, the viability of explants decreased to zero during the second subculture, while in the Z0 n.o. substrate the viability of explants decreased to zero during the third subculture. Therefore, explants’ growth data for the substrates Z0 and Z0 n.o. were not considered. In all other substrates and during the three subcultures, a satisfactory level of explant viability was recorded. In particular, in the Z4 substrate, a viability value equal to 100% was recorded and this value was not statistically different values from that registered for the Z4 n.o. (98.9%) and Z2 n.o. (98.9%) substrates. On the other hand, the viability values observed in Z1 and Z1 n.o.  were statistically lower.The number of shoots in the Z2 and Z1 substrates was lower than that observed in the Z4 substrate, where, generally, the development of both axillary buds present on the explant’s node was observed.The addition of neem oil caused an increase in the number of shoots produced; indeed, in the Z4 n.o. and Z2 n.o. substrates, the values of more than two shoots were recorded . Therefo−1), the addition of n. o. strongly increased the shoot elongation (from 27.3 to 47.7 mm) (At the lowest concentration of zeatin (1 mg L47.7 mm) . In the 47.7 mm) .The addition of n.o. increased the number of leaves produced by each initial explant in all the substrates. In particular, the highest number of leaves was recorded in Z4 n.o. followed by Z2 n.o. and Z1 n.o .−1).The data on the fresh and dry weights  per explTherefore, the addition of neem oil induced the development of adventitious shoots, a greater: shoots’ length, leaves number, and plant fresh and dry weights.This experiment aimed to investigate whether the addition of neem oil could have a residual effect (for the shoots derived from the Z2 with n.o. (Z2 n.o.) substrate) or a direct effect on the rhizogenic capacity of the shoots when added to the rooting substrate. For shoots from the Z2 n.o. substrate, the highest rooting percentage was recorded in the potting substrate (P) without the addition of n.o., whereas for shoots from the Z4 substrate, the highest rooting percentage was recorded in the black agarized medium without n.o. (b) and with n.o. (b n.o.) and in the potting substrate (p). In general, the lowest rooting values were recorded for shoots from Z4 in the white (w) and white n.o. (w n.o) agarized substrates . The addThe potting substrate with shoots from Z2 n.o. provided the highest percentage of rooting and the highest number of roots produced . In gene−1 increased the number of shoots produced, even at the zeatin concentrations of 2 mg L−1. The obtained results suggest that the addition of n.o. also stimulated the development of adventitious buds present on the two main shoots, since an average number of shoots of more than two was observed. This could be interpreted as the ability of this substance to promote the growth of olive explants in vitro [−1) to the nutritive medium (zeatin concentration 4 mg·L−1) was able to improve the shoot length, the multiplication rate, and fresh and dry weights of the proliferated explants. Neem oil contains at least 100 biologically active compounds: the major constituents are triterpenes known as limonoids, the most important being azadirachtin, while other components include meliantriol, nimbin, nimbidin, nimbinin, nimbolides, fatty acids, and salannin [Olive micropropagation is generally limited due to the strong apical dominance limiting secondary axillary shoot formation ,33. Uninin vitro . Indeed,in vitro  reportedsalannin . Thanks salannin , ZnO nansalannin , and diksalannin .−1). Indeed, the present study shows that, at 2 mg L−1, zeatin in substrates with neem oil results in an explants’ viability similar to the control. In general, the use of zeatin in the proliferation phase promotes a higher number of shoots and nodes, a higher shoot length and number of leaves and, as a consequence, a higher proliferated shoot fresh and dry weights. In another study, coconut water in combination with BAP successfully replaced commercial zeatin in Galega vulgar cultivar [The results on the viability of the explants confirm that zeatin is an indispensable element for olive tree micropropagation, although there is the possibility that it can be used at a lower concentration than the standard  produced better results in terms of root development, given the same rhizogenic treatment and substrate used, compared to those obtained from shoots proliferated in the control substrate (zeatin concentration 4 mg L−1). Regarding the optimization of the rooting phase, the addition of putrescine  in combination with IBA, has been the subject of interest for its root-promoting effect [The addition of n.o. to the different substrates had no positive effect on the rooting parameters. However, the use of shoots deriving from a reduced zeatin concentration (2 mg Lg effect . In our −1), and in the substrate characterized by the presence of neem oil “n.o.” was added in the acronym. The neem oil concentration was chosen on the basis of a precedent experiment [The experiment was carried out in 2020 in the Laboratory of Micropropagation and In Vitro Biotechnology of the Department of Agricultural, Food and Environmental Sciences—University of Perugia, Italy. The experiment conducted on the proliferation phase involved the comparison of eight olive media (OM) Duchefa  Table 3Table 3 speriment .−1), agar (7 g L−1) and buffered to a pH of 5.5. Neem oil concentration was established based on a previous study [−2 s−1. For each treatment, six vessels (replicates) for each one of the three subsequent subcultures were used. At the end of each subculture (45 days), this was allowed to carry out the destructive measurements on the proliferated shoots of three pots and to use the proliferated shoots of the remaining vessels as initial explants for the subsequent subcultures.All substrates were enriched with sucrose (30 g Lus study . In part-viability (%): incidence of green and viable explants;-shoots (n): average number of shoots developed from each initial explant;-shoot length (mm): average length of developed shoots;-nodes (n): average number of nodes developed by each initial explant, reusable for further proliferation subculture (multiplication rate);-leaves (n): average number of leaves;-callus (%): incidence of explants that produced basal callus;-fresh weight (mg): average fresh weight per explant of developed vegetative organs  and callus;-dry weight (mg): average dry weight per explant of the vegetative organs and callus, obtained by keeping the plant material in an oven for three days at 105 °C.The following parameters were measured at the end of each subculture:−1 of zeatin and neem oil (0.1 mL L−1). On the contrary, the initial lowercase letter in the acronym was used for the explants derived from a proliferation substrate (OM) with 4 mg L−1 of zeatin. Moreover, in the rooting substrates characterized by the presence of neem oil, n.o. was added in the acronym.For the rooting experiment, shoots from Z4 and Z2 n.o. proliferation substrates were used. The latter was chosen because, among the substrate with reduced zeatin concentration used in the proliferation experiment was the one that gave the best results. The details of the experimental framework for the rooting experiment are shown in ® (150 mg L−1) added. The potting substrate, instead, consists of a mixture of “Solevivo cactacee (AL.FE srl)” + sand  and moistened with liquid OM/2 (20% in volume)  and sucrose (15 g L−1) in the dark, for 3 days, at room temperature.In particular, OM/2 white is a rooting medium consisting of the OM substrate at half concentration of all components (including sucrose) with agar as gelling agent, while OM/2 black is a rooting medium with the same characteristics of OM/2 white but with Brilliant Black volume) . Regardi-viability (%): incidence of green and viable explants;-rooting (%): incidence of explants that develop roots;-roots (n): average number of roots developed by each explant;-roots length (mm): average length of developed roots;-callus (%): incidence of explants that produced basal callus;All substrates were autoclaved for 20 min at 115 °C. Three pots with ten uninodal explants for each treatment were used and placed in the same growth chamber described for the proliferation experiment. After 45 days, the following parameters were monitored:p = 0.05).The trials were organized according to a completely randomized design and collected data were subjected to analysis of variance (ANOVA). Significant differences were assayed by Duncan’s test (−1 with neem oil (0.1 mL L−1) can be considered the best performing of those with a reduced zeatin concentration. This is particularly interesting due to the high cost that the use of zeatin at the higher concentration (4 mg L−1) implies. Indeed, the cost of the amount of neem oil needed to replace zeatin is about one thousandth of the cost of the latter. The increased shoot length obtained by adding neem oil to the substrates is a quality parameter of great importance in commercial micropropagation. Indeed, obtaining well-developed shoots at the end of the proliferation phase provides material that is certainly more suitable for the rooting phase. On the contrary, small explants (which would be excellent for new proliferation cycles) may provide worst performances during rhizogenesis, or once rooted provide smaller plantlets, with difficulties in the acclimatization phase. The direct neem oil use in the rooting phase does not seem to provide any beneficial effects, while positive effects in terms of rooting percentage and root length were observed in shoots deriving from the neem oil-enriched proliferation substrate.From the present study, it can be concluded that the substrate containing zeatin at 2 mg L


The main cause of this degradation is the decrease in oxide capacitance and increase in threshold voltage with increasing humidity, resulting in a reduction of transconductance and an increase in on-resistance. The results of this study can guide designers in designing compensation circuits to achieve some degree of compensation for the degradation of PA specifications.The specification of power amplifiers (PA) is closely related to humidity variation, and few reports on the humidity properties of PA are available in the literature. Therefore, an experimental study of PA specifications was conducted under different humidity conditions to elucidate the relationship between the degradation of PA specifications and humidity conditions. This paper studies and provides results of the degradation of a PA subjected to different humidity levels. The experimental results show that the S With the rapid expansion in the wireless industry ,2, the pFrom a systems point of view, the system cannot tolerate a drop in PA’s specification, such as gain, bandwidth, etc. . Once thThis paper uses a CMOS Class-A PA to systematically investigate the PA’s specifications degradation under different humidity levels from an experimental point of view. The PA’s specifications degrade as humidity rises. Furthermore, the PA’s degradation mechanism under high humidity conditions is elucidated. This paper aims to help PA designers consider the humidity effect of PA in advance in the design process.2 [dd1, Vdd2, and Vdd3 is 3.3 V. Special attention should be paid to the fact that the chip ground (GND) pad must be connected to the real earth; otherwise, it will cause the test to fail, or the test result will be abnormal.The 0.1–1.2 GHz CMOS broadband PA is a technological achievement result of the national science and technology project. The project requires the design of a broadband PA that can be used in industry-specific networks, and the study of the temperature and humidity characteristics of the PA is required to lay the foundation for future product finalization. Therefore, we conducted the humidity characteristics study with this PA in this context. The PA was processed in Global Foundry 1P6M 180 nm CMOS  with a chip area of 0.414 mm2 , as showAs shown in the circuit diagram of 3 1000 MHG)  (This experiment must be performed in a Solar Climatic Test Cabinet (SCGermany) . UnfortuGermany)  and thenTo study the humidity characteristics of individual transistors, existing on-chip test benches can also fail to provide a humidity measurement environment. Therefore, individual transistors are packaged on a PCB and measured in an environmental test chamber. However, the transistor’s input/output impedance is not the typical 50 Ω of the standard test system. Therefore, measuring a single transistor’s performance under humidity variation is impossible using the standard test environment. Therefore, this paper does not discuss the characteristics of transistors in different humidity environments by directly measuring them.RH), this paper reports the variation of the S21 and output power in the humidity range of 10% to 90% RH only.The R&S HMP4040  was used to provide DC bias, an attenuator  was used to reduce the power at the spectrum analyzer’s input, and the R&S ZVA40  and FSV30  were used to record the experimental output results. Since the humidity range that the environmental test chamber can measure is 10% to 90% Relative Humidity , the S21 of the PA will not be able to meet the demand at this time.21 of PA decreases with the increase of humidity. What is the cause of the degradation of S21 of PA with humidity? Next, this paper will discuss and analyze it in detail. For Class A, the PA operates at bias points gs-M8V = 1.7 V, ds-M8V = 3.3 V, and ds-M8I = 60 mA. Therefore, the PA works in the saturation region.As shown in gW is the gate width, nμ is the carrier mobility, oxC is the gate oxide capacitance per unit area, Lg is the gate length, gsV is the gate voltage, thV is the threshold dsV is drain voltage.In the saturation region, we obtain ,27,28:, the transconductance of the saturation region is ,27,28(4oxC) decreases, and the threshold voltage increases as humidity rises. Therefore, according to Equation (4), it is known that the transconductance will decrease with the increase of humidity. And the transconductance is generally considered to be S21. Therefore, it can be observed that S21 decreases with the rise in humidity.It is already known from the previous discussion that the oxide capacitance  and (6), the expressions of SoxC and the increase in threshold voltage cause the drain current to decrease with increasing humidity. Therefore, the following analysis focuses on the causes of the decrease in output power with increasing humidity.We studied the characteristics of the output power of the power amplifier at 433 MHz, as this is a typical radio frequency for different humidity levels. The humidity characteristics of the output power as shown in k is a constant, and 0R represents the initial value of the resistance. The coefficients α and β are 1.5 and 0.2, respectively.In the following, we will discuss and analyze specifically the causes of the decrease in output power with increasing humidity. The on-resistance is :(7)Ron=RAccording to Equation (7), the on-resistance will increase with an increasing threshold voltage. As known from the discussion in 3.1, it has been demonstrated experimentally and in the literature that the threshold voltage increases with increasing humidity. This means that the on-resistance will increase with increasing humidity. The results of our experimental analysis are the same as in the literature . Therefo21 with humidity, and both are related to quadratic humidity. Only the specific coefficients are different.From Equation (8), the saturation output power  and humidity at 433 MHz is shown in 21 and output power changing with humidity in It should be noted that considering that the curves of S21 and saturated output power with humidity change.According to Equation (9), the maximum PAE is linear with the change of humidity, which is different from the relationship between S21 and output power degrades with the increase of humidity. The main reason for this degradation is that the oxC decreases, and the threshold voltage increases as humidity rises.This paper investigates PA specifications’ characteristics at different humidity levels from an experimental point of view. This paper study and provide results of the degradation by the humidity of only one PA. It is found that the S21, and the output power, was found during the study. This indicates that the specification degradation experiments must be continued at this stage for many PAs to extract sufficient experimental data. This will guide the extraction of common patterns of specification degradation for the prediction of specification degradation and compensation of specification degradation.However, no common pattern for the degradation of the two specifications, S


A new hydrazone-Schiff base (H2L1 and 2) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H2L2 ligands and the complexes [MoO2(L1)(H2O)], [MoO2(L2)(H2O)], [MoO2(L1)(MeOH)]∙MeOH, [MoO2(L1)(EtOH)]∙EtOH, [MoO2(L1)(2-PrOH)]∙2-PrOH, and [MoO2(L1)]n were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum Schiff base complexes were prepared via the reaction of [MoO The solution was refluxed for 3 h and was left at room temperature. After several days, the product was obtained. The product was filtered off and dried in the desiccator. The samples were analyzed after a prolonged period of standing at room temperature:2(L1)(MeOH)]::∙2-PrOH:::Mononuclear complex [MoO [MoO2(acac)2]  was dissolved in acetonitrile, ethanol, or 2-propanol (30 mL), and the H2L2 ligand  was added. The solution was refluxed for 2 h and was left at room temperature. The product was filtered off and dried in the desiccator.Color: yellow, Yield: 76.04%−1 (C=N), 1505 cm−1 (C=C), 1271 cm−1 (C–O), 950 and 896 cm−1 (Mo=O)IR-ATR: 1606 cm2Otheo: 4.03%, H2Oexp: 4.39%, MoO3theo: 32.33%, MoO3exp: 30.55%.TGA: Htheo: 37.77, Cfound: 37.65, Htheo: 2.49, Hfound: 2.36, Ntheo: 9.44, Nfound: 9.17%.EA: C2(L1)]n:Polynuclear complex [MoO [MoO2(acac)2]  was dissolved in acetonitrile (30 mL), and the H2L1 ligand  was added. The solution was refluxed for 2 h, and a product formed during the reaction. The product was filtered off and dried in the desiccator.Color: brown, Yield: 38.30%−1 (C=N), 1513 cm−1 (C=C), 1215 cm−1 (C–O), 829 and 810 cm−1 (Mo=O)IR-ATR: 1602 cm3theo: 33.69%, MoO3exp: 32.67%.TGA: MoOtheo: 39.36, Cfound: 39.21, Htheo: 2.12, Hfound: 2.04, Ntheo: 9.84, Nfound: 9.62%.EA: C2(L1)(MeOH)], [[MoO2(L1)(EtOH)] [MoO2(L1)(2-PrOH)]∙2-PrOH, MoO2(L2)(MeOH)], and [MoO2(L2)(H2O)]. The complexes were heated to 290 °C and left at the corresponding temperature for 1 h. After they had cooled to room temperature, further analyses were performed.Stability tests were performed with mononuclear complexes [MoO2(L1)(MeOH)], [MoO2(L2)(MeOH)], [MoO2(L2)(H2O)], and [MoO2(L1)]n were studied via impedance spectroscopy (IS). Complex impedance was measured over a wide range of frequencies (0.01 Hz to 1 MHz) and temperatures  using an impedance analyzer . The temperature was controlled to ±0.2 °C. The measurements were performed on polycrystalline powder samples pressed into cylindrical pellets with a diameter of 5 mm diameter and a thickness of 1 mm under a uniform load of 2 103 kg using a hydraulic press. For the electrical contact, gold electrodes with a diameter of 3.8 mm were sputtered onto both sides of the pellets using an SC7620 sputter coater from Quorum Technologies . The experimental data were analyzed by electrical equivalent circuit (EEC) modeling using the complex nonlinear least-squares (CNLLSQ) fitting procedure and WinFIT software .The electrical and dielectric properties of the compounds , [MoO2(L2)(H2O)], [MoO2(L1)]n, [MoO2(L1)(MeOH)]·MeOH, [MoO2(L1)(EtOH)]·EtOH, and [MoO2(L1)(2-PrOH)]·(2-PrOH) of suitable quality were selected for the diffraction experiments. Data were collected using a Rigaku XtaLAB Synergy-S diffractometer armed with a Dualflex source  and a HyPix detector. Data were collected via ω-scans at 170 K. Data were processed with the CrysAlis program package  were treated for twinning. The twin law was found to be , while the two twin components were present in the 0.212:0.788 ratio.Single-crystal X-ray diffraction: Single crystals of H package . A summa package . The refg SHELXL . The SHEg SHELXL . Geometrg SHELXL . The str2L1 and 93% for H2L2. DSC analysis gave insight into the ligands’ melting points and purity 2] in different solvents provided dioxidomolybdenum(VI) coordination complexes. When H2L1 reacted with [MoO2(C5H7O2)2] in methanol, ethanol, or 2-propanol, the mononuclear complex of the general formula [MoO2(L1)]∙alcohol was obtained. While standing at room temperature, the solvent molecule spontaneously left the crystal structure for the complexes obtained from methanol and ethanol, and the complexes were analyzed as were the [MoO2(L1)] complexes (2L2 and [MoO2(C5H7O2)2] in methanol resulted in the formation of [MoO2(L2)(MeOH)], but the reactions in ethanol, 2-propanol, and even acetonitrile provided [MoO2(L2)(H2O)]. Upon heating all of the mononuclear compounds, the coordinated solvent molecule loss was recorded in the temperature range of 99–126 °C for [MoO2(L1)(MeOH)], 117–145 °C for [MoO2(L1)(EtOH)], 92–135 °C for [MoO2(L1)(2-PrOH)]∙2-PrOH, 100–160 °C for [MoO2(L2)(MeOH)], and 170–194 °C for [MoO2(L2)(H2O)]. Further losses at 342–488 °C for [MoO2(L1)(MeOH)], 345–454 °C for [MoO2(L1)(EtOH)], 327–444 °C for [MoO2(L1)(2-PrOH)] ∙2-PrOH, 345–460 °C for [MoO2(L2)(MeOH)], and 343–460 °C for [MoO2(L2)(H2O)] were attributed to the decomposition of the complexes’ decomposition. The final residue, a white powder, was analyzed by IR and PXRD and compared to commercially available MoO3. Surprisingly, via the reaction of the H2L1 and [MoO2(C5H7O2)2] in acetonitrile, a brown polynuclear compound [MoO2(L1)]n was obtained. TG analysis of the compound [MoO2(L1)]n resulted in a one-step thermogram, a loss in the range 356–466 °C attributed to the complex’s decomposition, and the formation of MoO3 residue (2(L1or2)]n. Stability tests were also performed by exposing the samples [MoO2(L1)(MeOH)], [MoO2(L1)(EtOH)], , and [MoO2(L2)(H2O)] (in the solid state) to solvent vapors in order to determine whether the coordinated solvent molecule could be replaced by the solvent of the exposed vapors. The samples were exposed to the solvent vapors for 24 h, after which IR spectra of the samples were recorded and compared to the initial sample (MeOH)] as exposed to EtOH vapors since [MoO2(L1)(H2O)] was formed, which was not in accordance with the results obtained from the solvent-based synthesis. The new complex [MoO2(L1)(H2O)] was analyzed by TGA, which confirmed water coordination  and the thermogram was very similar to the one for the complex [MoO2(L2)(H2O)]. Due to heating the sample [MoO2(L1)(MeOH)], water decoordinated the complex in the range of 98–137 °C, and further complex decomposition occurred in the range of 338–451 °C. Once isolated, all of the samples were very stable and remained unchanged, even after a few months.Further reactions of the prepared ligands with the molybdenum starting compound , a new band appeared at ~1017 cm−1 due to the C–OMeOH vibrations in the spectra of the [MoO2(L1)(EtOH)] band at 1042 cm−1, which is characteristic for C–OEtOH vibrations, and in the spectra of [MoO2(L1)(PrOH)]∙2-PrOH band at 943 cm −1, which is characteristic for C–OPrOH vibrations. In the polynuclear complexes [MoO2(L1)]n, polymerization occurred through the terminal O atom, assigned to the bands at 829 and 810 cm−1 in the spectra , [MoO2(L2)(H2O)], [MoO2(L1)]n, [MoO2(L1)(MeOH)]·MeOH, [MoO2(L1)(EtOH)]·EtOH, and [MoO2(L1)(2-PrOH)]·2-PrOH, as described in this work, were elucidated via single-crystal X-ray diffraction (SC-XRD) experiments. Basic crystallographic data and refinement parameters are given in the 2L2 is given in the 2L2 ligand and the complexes [MoO2(L2)(H2O)], [MoO2(L1)]n, [MoO2(L1)(MeOH)]·MeOH, [MoO2(L1)(EtOH)]·EtOH, and [MoO2(L1)(2-PrOH)]·2-PrOH were obtained via the conventional solution synthesis, while the single crystals of [MoO2(L1)(H2O)] were obtained via the solvothermal reaction of the H2L1 ligand, [MoO2(acac)2] in methanol.The molecular and crystal structures of the H2L1 or H2L2) is coordinated in its doubly deprotonated form of the imino tautomer [ONO coordination mode ]n (1)]n, the octahedral environment of each Mo atom is realized through the Mo=O···Mo interaction with the neighboring [MoO2(L1)] unit (cis-dioxomolybdenum(VI) complexes to form polynuclear assemblies in the absence of a suitable donor for the sixth coordination site ·(2-PrOH). The main geometrical features of the Mo(VI) complexes investigated here are comparable with those of Mo(VI) complexes with similar ligands reported in the literature n a, an anc1)] unit b. This iion site . The lonterature ,8,31,32.2(L1)(H2O)] and [MoO2(L2)(H2O)], the coordination entities associate via O–H···O, N–H···O, and C–H···O hydrogen bonds. However, the resulting pattern is more complex in the case of [MoO2(L2)(H2O)], where the O5–H5 moiety is disposable for intermolecular hydrogen bonding, which is not the case in [MoO2(L1)(H2O)] (1)]n relies exclusively on C–H···O interactions since the only good hydrogen-bond donor, O5–H5 is functionally engaged in the intramolecular hydrogen bonding (In the structures of [MoO1)(H2O)] . Crystal bonding . In the  bonding .2(L1or2)(MeOH)], while the ones prepared from acetonitrile provided either a polynuclear compound [MoO2(L1)]n or a mononuclear compound [MoO2(L2)(H2O)], depending on the used ligand. Based on the results of the thermal behavior, [MoO2(L1)(MeOH)], [MoO2(L2)(MeOH)], [MoO2(L2)(H2O)], and [MoO2(L1)]n complexes were heated from 30 to 230 °C, after which they were cooled to 30 °C. The temperature of 230 °C was chosen based on the TG analysis since there is no coordinated solvent molecule left in the crystal structure above this temperature and the obtained compounds are stable up to ~300 °C.For the impedance spectroscopy study, we selected four samples prepared from methanol and acetonitrile. The complexes prepared from methanol provided mononuclear compounds n, is presented in σ′, increases with increasing temperature. As for all other samples, the conductivity is thermally activated and shows semiconducting behavior. Moreover, at high temperatures and low frequencies, the conductivity shows no frequency-dependence , with the so-called plateau corresponding to the DC conductivity ]n was plotted in the complex plane, i.e., with the imaginary part as a function of the real part, Z″ vs. Z′ . The impedance spectrum with the shape of a semicircle was analyzed by the EEC model, and a good overlap was observed, indicating a good agreement between the experimental data (red curve) and the theoretical model. The EEC model used is based on the R-CPE parallel circuit, where R denotes the resistor corresponding to the sample resistance, and the constant phase element, CPE, determines the sample capacitance. From the intersection with the X-axis, resistance is calculated @ each temperature, and for the [MoO2(L1)]n compound @ 200 °C, R is equal to 1.06 × 109 Ω. DC conductivity was calculated to be 2.34 × 10−10 (Ωcm)−1 @ 200 °C. Considering that the sample [MoO2(L1)]n is a polynuclear compound, the in situ IS method confirmed that there was no change during the heating/cooling run, which is consistent with the TG analysis and the observed one-step decomposition.Due to the low conductivity of the samples studied, it is obvious that, at lower temperatures, it is not possible to determine the DC value from the graph visually. In this case, the DC conductivity value was obtained by analyzing the experimental complex impedance spectra via EEC modeling using the CNLL S method. (See 2(L1)]n  vs. 1000/T using the following equation: σDC = ∗σ0eEDC/kBT]n. This is to be expected since this compound is stable and does not contain molecules of coordinated or crystalline solvents that would be lost during heating. The low activation energy (67.2 kJ mol−1) of this type of compound indicates that the polynuclear complex, in which the polymerization was achieved through the terminal oxygen atom, enabled a significant and uninterrupted transfer of charge carriers through this structure.For the studied compound [MoO1)]n see a,b, the 1)]n see c. The ac2(L1)(MeOH)], [MoO2(L2)(MeOH)], and [MoO2(L2)(H2O)], there was a certain change. 2(L1)(MeOH)], the thermogram for which shows a two-step decomposition, as discussed above. As previously stated, the first step corresponded to the release of the coordinated methanol molecule which, according to the TG curve, took place in the range of 100–126 °C.On the other hand, for samples [MoO2(L2)(MeOH)] and [MoO2(L2)(H2O)] showed similar behavior along with non-monotonic changes in conductivity with increase in temperature in the heating cycle, which could be related to structural change/transformation (see 2(L1)]n, show a linear temperature dependence (1000/T) of DC conductivity only in the cooling run. An example of a [MoO2(L1)(MeOH)] compound in a heating/cooling cycle is shown in Structural change associated with the release of a coordinated methanol molecule can be seen in situ in the conductivity spectra, as shown in tion see . These t2(L1)(MeOH)] and [MoO2(L2)(MeOH)] compounds polymerized after heating, which is indicated by a similar value of calculated activation energy, as it was for the [MoO2(L1)]n (67.2 vs 65–66 kJ mol−1). Although the polymerization of the compound [MoO2(L2)(H2O)] was proven, there was a difference in the activation energy from the methanol-coordinated complexes. This observation can be correlated to the stability of such a compound. Based on the TG study, it is obvious that a longer period of time is needed for polymerization in the case of the water-coordinated compound, and as result, this reflects upon the electrical properties and the activation energy as well. Moreover, we should emphasize here the interesting behavior observed for the sample [MoO2(L2)(MeOH)], which showed low activation energy. However, its conductivity was still several orders of magnitude lower compared to similar compounds, where polymerization is expected upon heating, including [MoO2(L1)(MeOH)] and the polymer [MoO2(L1)]n. This effect should be further investigated.According to the results shown in Furthermore, the conductivity isotherms @200 °C in the cooling run for all of the studied compounds are shown in , the following conductivity trend can be seen in the cooling cycle @200 °C: σ ([MoO2(L1)(MeOH)]) > σ ([MoO2(L1)]n) > σ ([MoO2(L2)H2O)] > σ ([MoO2(L2)(MeOH)]). Here, a few comments are in order. First, the compound [MoO2(L2)(H2O)], obtained from the H2L2 ligand, shows significantly lower conductivity in comparison to [MoO2(L1)(MeOH)] and ([MoO2(L1)]n). This fact could be attributed to the type of ligand and the slow release of the coordinated solvent during heating. Accordingly, its activation energy was significantly higher, in the range of 100 kJ mol–1. Second, the structural change (polymerization) after the solvent release during heating for compounds [MoO2(L1)(MeOH)], ([MoO2(L2)(MeOH)], and [MoO2(L2)(H2O)] was indicated by the observed differences in the conductivity spectra in the heating vs. the cooling runs (see 2(L1)(MeOH)] sample polymerized and had higher conductivity in the cooling run as compared to the heating run (see 2(L2)(MeOH)] and [MoO2(L2)(H2O)] compounds (see 2(L2)(H2O)]. Finally, an interesting, but still unexpected, behavior for the compound [MoO2(L2)(MeOH)] should be emphasized. Although the complex showed a low activation energy, its DC conductivity was still several orders of magnitude lower compared to the compounds prepared by reactions with the H2L1 ligand, namely: [MoO2(L1)(MeOH)] and [MoO2(L1)]n. However, the activation energy value (66.0 kJ/mol) for the sample [MoO2(L1)(MeOH)] indicated polymerization, while differences in the conductivity values did not. It should certainly be taken into account the type of H2L2 ligand, and the observed steric influence of the ligand on conductivity transport should not be ruled out in compounds [MoO2(L2)(H2O) and [MoO2(L2)(MeOH)]. As mentioned previously, this behavior needs to be investigated in more detail.Based on Table 3runs see . It can  run see . On the unds see , the rel2(L1)]n, along with [MoO2(L1)(MeOH)], the conductivity of which increased by four orders of magnitude after the heating cycle and structural transformation, turned out to be potential candidates for target application due to the considerably high conductivity that they exhibited for this class of materials. Future research will be directed in that direction, along with the preparation of analogous complexes with different transition metal centers  in order to correlate the obtained electric results.New molybdenum complexes containing hydrazine ligands obtained from 5-nitrobenzaldehyde and 2-hydroxy or 4-hydroxybenzhydrazide were prepared and characterized. Chosen Mo(VI) compounds were investigated by the impedance spectroscopy method. For the first time, impedance spectroscopy was used to follow in situ transformations of mononuclear to polynuclear complexes, supporting the results obtained by heat treatment and thermogravimetric analysis for mononuclear compounds. All of the studied complexes showed an increase in conductivity with temperature; in other words, they behaved as semiconductors. Samples with high conductivity certainly open the possibility for the application of such complexes as semiconductors in various devices. For instance, the sample [MoO


It has been proposed that mechanosensitive Piezo1 channels trigger migraine pain in trigeminal nociceptive neurons, but the mechanosensitivity of satellite glial cells (SGCs) supporting neuronal sensitization has not been tested before. Moreover, tools to monitor previous Piezo1 activation are not available. Therefore, by using live calcium imaging with Fluo-4 AM and labeling with FM1-43 dye, we explored a new strategy to identify Piezo channels’ activity in mouse trigeminal neurons, SGCs, and isolated meninges. The specific Piezo1 agonist Yoda1 induced calcium transients in both neurons and SGCs, suggesting the functional expression of Piezo1 channels in both types of cells. In Piezo1-transfected HEK cells, FM1-43 produced only a transient fluorescent response, whereas co-application with Yoda1 provided higher transient signals and a remarkable long-lasting FM1-43 ‘tail response’. A similar Piezo1-related FM1-43 trapping was observed in neurons and SGCs. The non-specific Piezo channel blocker, Gadolinium, inhibited the transient peak, confirming the involvement of Piezo1 receptors. Finally, FM1-43 labeling demonstrated previous activity in meningeal tissues 3.5 h after Yoda1 washout. Our data indicated that trigeminal neurons and SGCs express functional Piezo channels, and their activation provides sustained labeling with FM1-43. This long-lasting labelling can be used to monitor the ongoing and previous activation of Piezo1 channels in the trigeminal nociceptive system, which is implicated in migraine pain. Despite the high prevalence of migraines in the world’s population ,2,3, itsHowever, to date, there is a lack of methods for the retrospective detection of Piezo1 activity. The styryl FM1-43 dye, traditionally known as the marker of synaptic vesicle recycling, has also been suggested to label cells due to its penetration through mechanosensitive channels ,13, but In this project, we used a combination of functional and morphological tests to develop a method for labelling Piezo1 channel activity in the cells of the trigeminovascular system with FM1-43, and we explored presence of the mechanosensitive channels in SGCs. We report that trigeminal SGCs, along with neurons, can be activated by the specific Piezo1 agonist Yoda1 and that FM1-43 can detect this activation in real time. Moreover, the persistent FM1-43 “tail response” could serve as a specific marker of previous Piezo1 activity that can be used to monitor mechanosensitivity within the trigeminal nociceptive system. n = 9/40 responsive neurons) after application of the Piezo1 specific agonist Yoda1 (5 μM). Notably, the SGCs, like neurons, also responded to Yoda1 by the transient elevation of intracellular calcium (n = 12/27 responsive SGCs), indicating the functional expression of Piezo1 receptors in this specific type of trigeminal glia (p = 0.120).As the functional expression of Piezo1 receptors in SGCs has not been addressed before, we first used trigeminal cultures to explore calcium responses induced by a specific agonist of Piezo1 receptors (Yoda1) in different cell types. Trigeminal culture is heterogeneous and contains both neurons and SGCs interacting with each other within the trigeminal nociceptive system . Numerounal glia C. The hiThus, these data demonstrated the functional expression of mechanosensitive Piezo1 channels in both neurons and relative SGCs.Next, we explored whether the styryl FM1-43 dye can specifically report the activity of Piezo1 channels in trigeminal neurons and SGCs. To this end, we tested whether this dye could internalize after specific activation in the Piezo1-transfected HEK293T cells and remain located inside the cells after agonist washout. n = 25, p < 0.001) with the application of FM1-43 alone. During the application of FM1-43 plus Yoda1, the transient peak increased to 154.7 ± 25.3%  with respect to the previous baseline, which was significantly higher than the application of FM1-43 alone. The tail response, in the case of FM1-43 treatment alone, was at baseline levels, corresponding to 0.9 ± 0.6% . The combination of FM1-43 + Yoda1 produced a much higher and sustained tail response of 22.3 ± 4.7% . These results indicated that Piezo1 activation promotes sustained FM1-43 trapping in the HEK cells expressing this type of mechanosensitive channel.Our next aim was to demonstrate that FM1-43 can provide long-lasting reporting of Piezo1 activation in the trigeminal nociceptive system. Therefore, we used primary mouse trigeminal cultures composed of both neurons and SGCs. 3+. Comparable results were also obtained in SGCs , the application of 2 μM of FM1-43 for 2 min alone did not produce either an essential increase in fluorescence or a ‘tail response’ A,D. Howeresponse A, verify in SGCs D, which n = 74, p < 0.001). Notice that, in this case, the tail response was very small   and a much bigger tail response . The transient peak that was induced by a combination of Yoda1 and FM1-43 decreased by Gd3+ . However, the tail response was not affected  C. In conn = 81) that was lower than treatment with both FM1-43 and Yoda1  after FM1-43, but Yoda1 applied together with FM1-43 produced a valuable tail response . Gd3+ reduced the transient FM1-43 response to 138.7 ± 9.3% , but the tail response after Gd3+ application, like in neurons, stayed stable .In order to address the whole spectrum of meningeal cells, we tested fluorescence changes in a full image of the meninges C. We fouThus, we found that trapping of the specific label for several hours demonstrates the previous activity of Piezo1 channels in the meningeal preparation model. The main novel findings of the current study can be summarized in two main points: (i) satellite glial cells (SGCs), that surround trigeminal neurons and support neuroinflammation and neuronal sensitization, express functional Piezo1 receptors and (ii) FM1-43 can report the previous activity of Piezo1 channels through long-lasting labeling of the key components of the trigeminal nociceptive system implicated in migraines, including neurons and SGCs. Given the high calcium permeability of Piezo1 channels, these findings extend the role of mechanosensitive mechanisms from neurons to glial cells, which, in concert, can react to various mechanical  stimuli by a calcium-dependent mechanism of migraine-related sensitization. Mechanosensitive Piezo1/2 receptors emerged recently as the most sensitive detectors of mechanical stimuli . Piezo1,3+, on FM1-43- plus Yoda1-induced transient fluorescence peaks. Our proposal on the functional involvement of Piezo1-expressing SGCs in trigeminal nociception is consistent with the recent hypothesis that glial cells, apart from their supportive role, also functionally modulate neuronal activity [Here, for the first time, we observed the functional activity of Piezo1 in trigeminal SGCs. This was directly detected by Yoda1-induced calcium transients in this type of glia and further confirmed by the depressant effect of the nonspecific blocker of Piezo1 channels, Gdactivity ,27,28. Tactivity ,19. In oactivity . HoweverIn practical terms, the lasting labeling of living tissues by FM1-43 can be used for the non-invasive monitoring of Piezo1 activity in in vivo conditions. Based on our findings regarding the specific chemical activation of Piezo1 channels, we can hypothesize that Piezo1-activity-dependent labeling could also be induced either by physiological or disease-associated mechanical forces. One of the possible applications for migraine research would be an injection of FM1-43 followed by the triggering of a migraine attack with trinitroglycerin  or optogIn summary, our results demonstrate that the long-lasting labeling of trigeminal cells with FM1-43 supports previous proposals on the use of this dye for cell labelling via mechanosensitive channels . HoweverHEK293T cells cultures were maintained as reported previously ,34 in DuThe Animal House of the university of Eastern Finland provided male and female C57BL/6J mice for this study. In order to test Yoda1 and HOS, the cell culture was prepared from trigeminal ganglia of P10-P13 mice. The FM1-43 labelling experiments were conducted on the cell cultures prepared from P10-P13 and P30 mice. The animals were housed under the following conditions: 12 h dark/light cycle, grouped housing, ad libitum access to food and water and an ambient temperature of 22 °C. All the experimental procedures performed in this study followed the rules of the European Community Council Directive of 22 September 2010 (2010/63/EEC). The Animal Care and Use Committee of the University of Eastern Finland approved all the experimental protocols (license EKS-002-2017).2 before the experiment.The trigeminal cell culture was prepared according to a protocol previously described . In brie2, and 2.1 MgCl2, pH adjusted to 7.4 with NaOH, with an osmolarity of ~320 mOsm/kg. Stock solutions of Yoda1 were prepared in DMSO and stored at −20 °C at 50 mM for a maximum of one month. In order to test the selective activation of Piezo1, 5 μM of Yoda1 was applied. In order to test whether Yoda1 coupled to FM1-43, 2 μM of FM1-43 and 25 μM of Yoda1 were applied. The Gadolinium (Gd3+) stock, a nonselective Piezo1 channel blocker, was prepared in mQ water and stored at −20 °C at 50 mM. It was then applied in the experiment as 100 μM of Gadolinium. In the imaging experiments, we performed constant application of DMSO vehicle solution containing the same concentration of DMSO as the Yoda1 solution. Furthermore, the solutions of chemicals that were not dissolved in DMSO were dissolved in it in order to standardize the experiment.An isotonic basic solution (IBS) was used, containing (in millimolar) 152 NaCl, 5 KCl, 10 HEPES, 10 glucose, 2.6 CaCl3+ (with 1 min IBS + DMSO + Gd3+ before and after). The data was recorded and post-processed using Live Acquisition and Offline Analysis software .In the first experiments to observe the selective activation of Piezo1 channels by Yoda1, HOS, or US, primary trigeminal cells were incubated for 30 min and HEK293T for 20 min in 1× Fluo-4 AM  fluorescent dye at 37 °C. Then, the cells were post-incubated (10 min at 37 °C and 10 min at room temperature) in IBS. Next, the cells were placed in a TILL photonics imaging system , where they were constantly perfused with IBS containing 1:10,000 DMSO (with a flow rate of 3 mL/min). Our perfusion system  allowed the application of various solutions and fast (∼30 ms) exchange between them. The cells were imaged with a 10× objective using an Olympus IX-70  equipped with a CCD camera . In all the experiments, the sampling frequency was set to two frames per second. The excitation wavelength was set to 494 nm for Fluo-4 AM and 480 nm for FM1-43. The following protocols were used: (a) Calcium imaging. Loading with Fluo-4 AM. Solutions applied: 20 s of 5 μM of Yoda1, used as a chemical selective agonist for Piezo1 receptors ; (b) FM12/95% O2) aCSF containing (in mM): 120 NaCl, 3 KCl, 2 CaCl2, 1 MgCl2, 1 NaH2PO4, 25 NaHCO3, and 10 glucose, pH 7.3). Imaging was conducted with an Axio Zoom microscope  at 4× magnification using ZEN 2 software .For the FM1-43 tests in meningeal preparations, we used 5-week-old C57BL/6J male mice. Hemiskulls with preserved meninges were prepared as described previously ,36. Briep < 0.05. Student’s paired and unpaired t-tests and mixed effect analysis with Tuckey post hoc tests were used to detect statistical significance. The raw data supporting the conclusions of this manuscript will be made available by the authors, without undue reservation, to any qualified researcher.Data were analyzed and plotted using GraphPad Prizm  and Origin . The data are presented as mean ± SEM (standard error of mean). Differences were considered statistically significant at In this study, for the first time, we demonstrated the long-lasting intracellular labeling of trigeminal neurons and a specific type of glial cells with the styryl FM1-43 dye, mediated by chemically stimulated mechanosensitive Piezo1 channels. This Piezo1-activity-dependent property of FM1-43, which appears to be non-toxic for living tissues, allows to combine both in vivo and in vitro studies of Piezo1-mediated mechanosensitive nociception in the trigeminovascular system. This discovery could help in the monitoring of both previous and ongoing activity of Piezo1 channels in the trigeminovascular system, the origin site of headaches in migraines.


N = 49) while interacting with scientific stimuli at a museum research exhibit. Results indicated that fathers asked significantly more questions than mothers, and fathers’ questions were more strongly related to children’s scientific discourse. Results are discussed in terms of the importance of adult questions for the development of children’s scientific understanding as well as broadening research to include interlocutors other than mothers.Parents’ questions are an effective strategy for fostering the development of young children’s science understanding and discourse. However, this work has not yet distinguished whether the frequency of questions about scientific content differs between mothers and fathers, despite some evidence from other contexts  showing that fathers ask more questions than mothers. The current study compared fathers’ and mothers’ questions to their four- to six-year-old children ( Children acquire knowledge about their world through interactions with adults such as parents . This mawhy did that happen?), scaffold children’s development (is the light on?), wh-questions invite the child to continue the discussion and oftentimes engage in reasoning. Most studies have examined parental questions during book-reading and toy play . Twenty-two mother–child dyads and 27 father–child dyads participated. Fourteen father–daughter, 13 father–son, 14 mother–daughter and 8 mother–son dyads comprised the sample. Ethnicity information was not collected for individual participants due to museum guidelines, but demographic information from the museum indicates it serves primarily European American families  and father  educational attainment, t(45) = 0.16, p = 0.87. Further, there was no difference between mothers and fathers in STEM-related  or non-STEM-related  occupations, χ2 = 1.36, p = 0.24. This study was approved by both the institution and museum ethics review boards.The sample included 49 English-speaking parent–child dyads recruited at a science museum in a large Northeastern city in the United States. Children  were approximately 5 years, 5 months .Trained research assistants coded each parent utterance for whether it was a wh-question, close-ended question, or statement. Every parent question utterance that was related to the balance scale activity was coded. We excluded any questions that were categorized as off-topic , the definition of which was adapted from Question utterances that were framed with does it work? are you going to put that on?) were coded as close-ended questions.All remaining on-topic questions  was computed. Statements were counted by subtracting the number of questions from the total number of utterances produced. Total utterances were counted using automated analyses within CLAN  or causal process . We coded utterances that made reference to balance, weight, or gravity, which were the scientific mechanisms inherent to the balance scale activity. Procedural utterances were defined as those which did not reference a scientific fact or mechanism; most were references to actions or directives .Parent and child utterances were also coded for references to scientific content. Two categories of coding were used: scientific and procedural, though analyses in this paper focus only on scientific codes. Scientific codes were defined as those that referenced a scientific fact , they proceeded to code independently. Discrepancies in coding decisions were resolved through discussion between research assistants, and when necessary, a third coder was consulted. Coders were blind to study hypotheses and parent gender: transcripts did not mark whether the parent was a mother or father. Question and statement coding reliability averaged 95% (Cohen’s Kappa = 0.90). Scientific content coding reliability averaged 88% with a mean Cohen’s Kappa value of 0.75.time on task, or the number of minutes that dyads engaged with the scale after the experimenter introduced the task.Unlike laboratory studies in which parent–child interactions typically take place during a fixed amount of time, we allowed dyads to engage with the balance scale for an open-ended amount of time. Therefore, we calculated wh-questions, close-ended questions and statements were calculated for each parent using the CLAN program. Rates (utterances per minute) were also calculated to control for differences in time on task.The total numbers of parents’ scientific talk by tallying the number of utterances that received a scientific code. We also identified and tallied utterances that received both a scientific code and a wh-question code, yielding a measure of parents’ scientific wh-questions. Scientific talk variables were also converted into rates (utterances per minute) to control for differences in time on task.The CLAN program calculated scientific code. We chose to collapse children’s scientific questions and statements together because the majority of child scientific utterances were statements  rather than questions .Children’s scientific utterances were calculated as the total number of child utterances that received a First, preliminary analyses examined whether key language variables differed as a function of child age and gender. Next, descriptive statistics for each parent talk variable was reported along with their inter-correlations. Finally, Poisson regression was used to compare mothers’ and fathers’ use of questions and the relation between parental talk and children’s scientific discourse.M = 3 min 52 s; SD = 1 min 40 s), although the range extended from 1 min 14 s to 8 min 50 s. Father–child dyads  interacted with the activity significantly longer than mother–child dyads , t(48) = 2.14, p = 0.03. Because of this difference, data were modeled using Poisson regression with time on task as an offset, which allowed us to model the rate of utterances observed per minute rather than the number of utterances used per participant. This ensured that any effect of parent gender on question use was not due to differences how long the dyad engaged with the activity. Offsets are an appropriate choice when the time period during which particular behaviors occur is not consistent across the sample . No significant correlations emerged and thus we did not consider child gender or age as covariates in subsequent analyses.t(48) = 4.76, p < 0.001. A similar pattern of parents’ question-asking emerged when question variables were considered as rates per minute (right portion of Frequencies per Minute). M = 1.90 questions per minute) was nearly twice the rate of mothers’ (M = 1.15 questions per minute). The rate of close-ended questions did not vary by parent gender, nor did the rate of statements.Poisson regression models examined whether use of wh-questions, close-ended questions, or statements varied between mothers and fathers . Model pN = 2 children were not included in this analysis as their scientific talk was more than three standard deviations above the sample mean. Further inspection revealed that the inflated measures of scientific talk from these children were due to the majority of the time spent counting the elements to be placed on the balance scale. Next, we examined whether wh-questions, close-ended questions, or statements were associated with children’s scientific discourse, and if so, whether parent gender moderated these relations. t = 3.57, p = 0.001), whereas mothers’ questions did not, t = 0.53, p = 0.60  whether there was a difference in children’s likelihood of providing an immediate response to father versus mother wh-questions, and (2) if fathers’ wh-questions contained more scientific content than mothers’ wh-questions.Though not an n = 155 responses) were coded as scientific, 26 percent of children’s total scientific utterances. To determine the likelihood of an immediate child scientific response, we fit a multilevel logistic regression model with adult question as the unit of analysis and participant as a random effect. In the model, we included question type , parent gender, and their interaction term as predictors. Model results indicated a significant main effect for question type, B = 1.43; z = 5.95, p < 0.001. That is, the likelihood of a child scientific response was significantly higher for wh-questions than for close-ended questions, controlling for whether children were interacting with mothers or fathers. The main effect of parent gender was not significant, nor was the interaction term between question type and parent gender, B = −0.39; z = −0.74, p = 0.46. These latter effects suggest that in this sample, both mothers’ and fathers’ wh-questions were equally likely to elicit immediate scientific responses from children.First, to determine the role of child responses, we recoded every parental question (both wh-questions and close-ended questions) to reflect whether it received an immediate response from the child. Immediate responses were defined as a child verbal turn that followed directly from a parental utterance. Of the 937 parent questions, 348 questions received an immediate response from children (37 percent). Of those responses, 45 percent  containing scientific content compared to mothers , B = 0.72; t = 2.02, p = 0.04, . Thus, in addition to using more overall wh-questions, fathers also produced more scientific wh-questions.Second, we considered the possibility that fathers’ wh-questions contained more scientific content than mothers’, therefore prompting more scientific talk from children. To explore this possibility, we compared the number of scientific wh-questions across parent gender , and children were significantly more likely to respond scientifically to a wh-question, as compared to a close-ended question. Why might a higher rate of wh-questions relate to more child scientific talk? Controlled experimental studies offer some clues. Consider the difference between the following two parent utterances taken from our corpus of parent–child conversations. These utterances convey the same content but differ in whether the utterance functions as a question (A) or statement (B).How can we test the scale to see if it is unbalanced?Let us test the scale by putting the same number of weights on both sides.how these questions promote learning. Our data supports this argument: in our sample, close-ended questions (M = 3.10 questions per minute) were two times more frequent than wh-questions (M = 1.57 questions per minute), yet close-ended questions were not related to children’s scientific discourse. Differential relations between wh- and close-ended questions to children’s talk holds important implications for educators and parents regarding how to facilitate children’s engagement in informal, and perhaps formal, scientific contexts. For instance, an adult who asks only a few wh-questions may confer larger benefits for their child’s engagement and learning compared to an adult who asks many close-ended questions.Although other studies point to the importance of parental wh-questions for children’s learning , this isThe second major finding of this study was that fathers asked significantly more wh-questions than mothers. Results were presented in the rate of utterances (per minute) in order to control for differences in the length of time spent engaged in the activity. These results indicate that the density of fathers’ wh-questions was greater than that of mothers’, and this difference was not explained by the fact that fathers spent more time with children on the balance scale activity and therefore had more opportunities to ask questions.This work is both similar to and different from prior work on mother and father conversation in non-scientific settings. For example, our work is consistent with These findings contribute to previous work showing that fathers’ wh-questions during book reading and toy play at home are related to various indices of language and cognitive development between 24- and 36-months . Our stuNot only did fathers ask more wh-questions, but their wh-questions were more strongly associated with children’s scientific discourse. A post-hoc analysis offered one explanation for this finding: fathers’ wh-questions more often referenced scientific concepts, perhaps prompting children to engage in more scientific talk themselves. Of course, both speakers are co-constructing the conversation, and children are likely playing an important role in eliciting fathers’ questions. To that end, an additional explanation we did not explore in this paper is the contribution of children’s own interest and background knowledge of the topic. Children who demonstrate more interest in physical science may be initiating additional questions from parents, leading to extended back-and-forth conversation. Future research should explore the bi-directional associations between children’s science interest and parents’ language input. In addition, we did not explore the relation between scientific close-ended questions and children’s scientific discourse, as theory and empirical data point to open-ended questions as more strongly related to scientific discourse. Future studies may consider how the delivery of scientific information using close-ended questions or statements relate to children’s talk about science.Fathers’ high rate of scientific wh-questions adds to previous findings that fathers tend to challenge children to converse and reason beyond their current ability level . HoweverThough we did not observe that mothers’ wh-questions related to child discourse, we must acknowledge other studies which have e.g., . One posA limitation of this study is that the small sample size precluded us from potentially observing effects of both parent and child gender and their interactions. Although child gender was not significantly related to any parent or child conversational variables, it is possible that a larger sample size would have had the power to detect such effects. Furthermore, parent gender effects should be interpreted with caution due to the small sample size. Future work with larger samples should seek to replicate these findings as additional evidence of differences in maternal and paternal discourse patterns. A second limitation is that the current sample included a relatively small number of mother-son dyads. This was not by choice but reflected a recruitment decision to invite participation from any parent–child dyad visiting the museum who fell into the study age range. The unique and combined effects of parent and child gender are interesting and important and would be well-suited for a more controlled study outside of the museum where both parent and child gender are equally distributed.An interesting direction for future research concerns whether the patterns of conversation around the balance scale—a physical science activity—would replicate in contexts that expose children to other scientific domains. There is evidence from the literature that conversational content varies based on the scientific domain of the activity: dyadic math and engineering talk is more common in science museum exhibits that focus on building, whereas biological science talk occurs frequently in settings such as aquaria and live animal exhibits . Parent–In summary, this study adds to existing evidence that parental wh-questions support children’s participation in science conversations. We extend this work by showing that fathers, on average, asked more questions, which are associated with more scientific discourse from children. Fathers’ strengths can serve as a unique and additive role to mothers in supporting children’s developing conceptions about science.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Boston University IRB. Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.KC and IC-C conceptualized the study design. IC-C, JA, and KL collected and coded the data. KL drafted the manuscript. KC, IC-C, and JA provided critical revisions. All authors contributed to the article and approved the submitted version.This work was funded by NSF Grants #1652224 and #1640816 to KC.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 periodic reflections in frequency were observed in a stack of graphene layers and generally reported as a series of mini photonic bandgaps owing to the multiple interference by the graphene layers. In this research, the Floquet-Bloch theory was employed to obtain the effective refractive index and Bloch impedance for understanding the wave propagation characteristic therein. Interestingly, the periodic reflections were found to occur in the frequency band having drastic variation in complex Bloch impedance and effective refractive index as well, wherein a Floquet-Bloch mode having pure real effective refractive index and extremely low Bloch impedance exists. Experimental studies indicated that the optical sheet conductance of graphite per graphene layer is very close to the theoretically expected value of dynamical conductance of isolated monolayer graphene3. Moreover, for few graphene layers  of a graphene sheet, some potential applications were proposed and implemented; to mention a few, a waveguide-integrated electroabsorption modulator based on monolayer graphene was developed by electrically tuning the Fermi level of the graphene sheet8. The Faraday rotation turning the polarization by several degrees through a single- and multilayered graphene was demonstrated in modest magnetic fields9. By stacking graphene bearing quartz substrate on a ground plane, an optically transparent broadband absorbers operating in millimeter wave region was achieved10. A ultra-broadband absorber made of multilayered graphene metamaterial able to absorb 11. A metamaterial consisting of weakly absorbing alternating graphene layers separated by lossless dielectric was fabricated to serve as a polarization-independent extremely broadband absorber covering almost the entire solar spectrum over a large angular range12. A graphene-based tunable hyperbolic metamaterials was designed for enhanced absorption in far-infrared frequencies13. The tunable propagation properties of 3D Dirac semimetal patterned metamaterial structures was symmetrically investigated in the terahertz regime14. The propagation properties of all-dielectric metamaterials based on a Si asymmetric hybrid block, including the effects of structural parameters, asymmetrical degrees, carrier doping concentrations, and graphene Fermi levels were reported15. Tunable terahertz Dirac-semimetal hybrid plasmonic waveguides was systematically investigated16. Moreover, 3D Dirac semimetal supported tunable TE modes was researched17. Concerning the fabrication technology development, multilayered metamaterial consisting of alternating monolayer graphene oxide/graphene and dielectric layers without a transfer step was successfully developed18.Graphene is believed to be one of the most striking materials with its optical property defined only by the fundamental constants rather than on material parameters. The scattering characteristics of a suspended graphene is determined merely by the fine structure constant associated with quantum electrodynamics21, while the physical insight has to invoke some other approaches for understanding the wave propagation characteristics. For example, The extraction method for determining the effective index and impedance from the scattering parameters of a finite slab of metamaterial normally incident by a plane wave was developed22. The S-parameter retrieval was employed to obtain the effective optical properties including permittivity and permeability of the fabricated zero index medium based on purely dielectric constituents23. The extraction of the effective medium properties (refractive index and impedance) of symmetric and asymmetric nanoparticle arrays with arbitrary geometry was developed and verified with analytical approach in the limitation of electrical small24. The dielectric permittivity tensor of the effective non-local medium with a periodic stack of graphene layers was developed for demonstrating its tunability from elliptic to hyperbolic dispersion with an external gate voltage25.Regarding the scattering characteristics of a 1D metamaterial made of a stratified graphene-dielectric structure, the transfer matrix method was popularly employed to obtain the rigorous solution26. As far as a photonic bandgap is concerned, propagation constant against operating frequency (or wavelength) particularly in the stopband has to be carefully examined. Because an extremely large number of periods (unit cells) are considered here, the dispersion relation of wave propagation in the structure of infinite in extent can help the understanding of physical insight in wave mechanism. Furthermore, the Bloch impedance is essential to the impedance matching problem at the input/output interface considering a finite structure. Specifically, the effective refraction index and Bloch impedance were obtained based on Floquet-Bloch theory (periodic boundary condition). By solving the eigenvalue problem of the transfer matrix of a unit cell, the Bloch impedance and effective refractive index can be determined by the eigenvectors and eigenvalues, respectively. Consequently, the finite periodic structure can be modeled as an equivalent transmission line with effective (average) propagation constant and line (Bloch) impedance. The excellent agreement of the numerical results in the scattering analysis between transfer matrix method and Floquet-Bloch approach allows us to confidently interpret the periodic reflections using the effective refractive index and Bloch impedance. Additionally, the effect of chemical potential on the scattering properties and the equivalent transmission line parameters were also investigated intensively.In this research, we focus on studying the physical mechanism of wave process involved in the so-called a series of mini photonic bandgaps reported in literatureN periods (unit cells) each consisting of a graphene sheet and a x-y plane. Here, the input and output mediums both are set to be Figure 20. Such a building block approach can efficiently calculate the scattering properties through cascade connection (matrix multiplication) of each input-output relation expressed in terms of a 2-by-2 matrix. Consider the multiple parallel dielectric and graphene layers in Fig. 28. At normal incidence, the tangential electric- and magnetic-fields in the uniform dielectric slab propagate along the z-axis with propagation constant x-y plane and perpendicular to each other; for example, V(z) and I(z) satisfy the transmission-line equations written as:A and B are two unknowns to be determined.Transfer matrix (or ABCD-matrix) method has been extensively employed in microwave and optical engineeringA and B can be expressed in terms of A and B into Eqs. (V(z) and I(z) at At the input interface of mentclass2pt{minim6 of this zero thickness graphene sheet are Additionally, consider a graphene sheet placed at the interface, N unit cells can be written as 29:Due to the continuous of tangential electric and magnetic fields at the interface between aforementioned two building blocks, the transfer matrix of the unit cell (period) is written as 20. Moreover, the reflectance and transmittance are determined by normalizing them with the incident power.Additionally, the reflectance (or termed as return loss) is given as:For an infinite periodic structure, the wave propagating characteristics can be understood from the property of its unit cell. By the Floquet-Bloch theory, the input-output relation of a unit cell satisfiesEquation  is an eiFrom Eqs.  and 11)11), we k30e is the electron charge, T is the ambient temperature (assumed to be 300° K throughout this paper).Graphene conductivity \documentN (number of periods). Specifically, their peak positions remain for all the cases with fewer or more periods. Although not shown here, the other reflection peaks in Fig. N. It reveals that those reflectance peaks are due to periodic nature of the structure under consideration.Figure N unit cells is determined by Although multiple branches including non-physical solutions were obtained in the real part of effective refractive index due to multiple-valued problem, there is no ambiguity in determining the imaginary part of effective refractive index and the Bloch impedance. In fact, the reflection coefficient of a finite length metamaterial consisting of Notably, m is ranging from 1 to 4. Because of multiple-valued function of q should be taken into account. However, in this figure only the three branches: the blue solid, dashed and dotted curves individually corresponding to branches of q). However, it creates difficulty in unambiguously determining the correct branch when Figure q coincide with one another. Significantly, the Bloch impedance at Additionally, the Bloch impedance versus normalized angular frequency is also plotted and shown in Fig.  To explain the vanishing imaginary part of m is an integer excluding zero, enabling Equation  is also Additionally, the zero Parameter eV to 0.8 eV with a step of 0.1 eV. Incidentally, we also have evaluated them at In Fig. Returning to Fig. d, the better impedance match and lower reflectance achieved, shown in Fig. It is obvious to see the strength of reflectance peak varies irregularly with the increase in chemical potential. Because the reflectance is determined by e in Eq.  can reveTo explain the obvious reflection in the vicinity of The imaginary part of refractive index  and carry out the scattering analysis. Notably, the structure parameters of the graphene metamaterial remains the same as in Fig. To demonstrate that impedance matching affects the scattering characteristic, we further reduce the wave impedance in the input and output regions from The Floquet-Bloch approach was employed to determine the effective refractive index and Bloch impedance of a metamaterial made of a stratified graphene-dielectric structure. Although multiple branches including non-physical solutions were obtained in the real part of effective refractive index due to multiple-valued problem, there is no ambiguity in determining the imaginary part of effective refractive index and the Bloch impedance. From the numerical results we confirm that FBA can correctly predict the scattering characteristics far beyond the long-wavelength limit.Through this research, we found that the periodic reflections of a stratified graphene-dielectric metamaterial take place around the frequencies of


Based on scanning electron microscopy analyses, the morphology characteristics of AgNPs were shown to be modulated by the laser dwell time and power controllably. Further, p-type doping effects were demonstrated using graphene-field-effect transistor structures whose graphene channels were selectively decorated with AgNPs by the PR process, as validated by the decrease in channel resistance and the shift of the Dirac point voltage. Moreover, the growth of AgNPs was observed to be more active on the graphene channel that was laser-annealed ahead of the PR process, leading to enhancing the efficiency of this approach for altering device characteristics.While graphene shows great potential for diverse device applications, to broaden the scope of graphene-based device applications further, it would be necessary to tune the electronic state of graphene and its resultant electrical properties properly. Surface decoration with metal nanoparticles is one of the efficient doping methods to control the properties of two-dimensional materials. Here, we report the p-type doping effects in single-layer graphene decorated with silver nanoparticles (AgNPs) that were formed area-selectively by the facile one-step photoreduction (PR) process based on focused-laser irradiation. During the PR process, AgNPs were reduced on graphene in AgNO Since gR method ,36. ThisR method ,36,37,38In this work, utilizing the facile one-step focused-laser-assisted PR process, p-type doping effects were achieved in graphene where AgNPs were synthesized area-selectively on its surface. It was shown that the morphology characteristics of AgNPs on graphene were adjustable by tuning the laser processing parameters. Adopting graphene-based field-effect-transistor (GFET) devices, we demonstrated that the electronic state and electrical characteristics of graphene could be modified properly by AgNP-decoration-driven p-type doping. In addition, it was also observed that focused-laser-assisted annealing on graphene in water, prior to the PR process, made the AgNP growth kinetics more active, resulting in a more significant alteration of the device characteristics.2/B-doped Si substrates (resistivity: 0.001–0.005 ohm∙cm) with PMMA (polymethyl methacrylate). Laser illumination was applied to single-layer GFs submerged in 0.1 M AgNO3 solution . Under the laser illumination, free-electron-hole pairs were generated by laser-assisted photoexcitation, and then Ag ions were reduced to Ag in the form of particles on the graphene surface by accepting the free electrons, releasing oxygen gas molecules [(1)(2)(3)(4)As described schematically in olecules . Then, tolecules ,41,42,43olecules :(1)Grap2 on the GF in AgNO3 solution at a laser power . The AgNP growth could be roughly localized down to the spot area of the laser beam (2). The morphology of the AgNPs was observed in detail using SEM equipped with a field-emission gun as an electron source.  and analyzed by the ImageJ software. EDS  was also conducted for elemental analyses on the surface of AgNPs-decorated graphene using the field-emission electron source of the SEM operated at an accelerating voltage of 15 keV.Both the focused-laser irradiation for the PR process and Raman spectroscopy experiments were carried out in the ambient conditions on a confocal Raman spectrometer system  equipped with objective lenses and a continuous-wave laser source of wavelength 532 nm. During the focused-laser irradiation, the laser beam diameter and raster step size were ~5 μm and ~3 μm, respectively, and the ser beam . Raman s2 plasma, metallization, etc. Top metal electrodes of Cr/Au (thickness: ~5 nm/~50 nm) were deposited onto the patterned graphene films by e-beam evaporation. Then, all the devices were annealed at 350 °C for 15 min while the processing pressure was kept at ~100 mTorr using Ar gas whose flow rate was ~0.5 sccm (standard cubic centimeters per minute) in a rapid thermal annealing system. The GFET devices were back-gated across the 285 nm-thick SiO2 layers using the heavily p-doped Si substrates as the bottom electrodes during device characterization with a semiconductor device parameter analyzer  at room temperature and vacuum pressure of ~3 × 10−6 Torr in a vacuum probe station equipped with a turbo pump system. To explore the interactive effects of AgNPs on the electronic and electrical properties of graphene as well as the device characteristics of the GFETs, the device measurements were carried out before and after the selective synthesis of AgNPs via the PR process on the microscale graphene channels (GCs).GFET devices were built through a series of conventional fabrication processes including photolithography, reactive ion etching with O2. Herein, To investigate how the laser processing parameters affected the growth of the AgNPs, a series of PR experiments were carried out varying the lsewhere . Then, tectronic  of graphectronic , opto-electronic , sensorsectronic , as wellectronic .2 at a To investigate how the properties of graphene were affected by the Ag decoration, GFET characterization was carried out at room temperature in conjunction with the PR experiments. Considering that the surface morphology deformation and coalescence of AgNPs are known to occur via surface diffusion actively above 200 °C, the structure of the AgNPs/GC and the GFET performance were expected to be stable under ordinary operational conditions ,50,51. TFurther, SEM was also performed on the AgNPs/GCs of dev1 and dev2 to evaluate the morphology of AgNP in more detail and understand their influence on the device characteristics. te trend . From thAs shown in In addition, the x are ~4.60 eV and ~4.90 eV, respectively, and hence, the transfer of electrons from graphene to the SiOx/Si substrate possibly contribute to the p-type doping effects [These p-type doping effects could be due to the possible transfer of charge carriers such as free electrons from the graphene to the AgNPs (or free holes in the opposite direction) and the resultant lowering of the Fermi energy level in the graphene. Previously, the n-type doping effects in graphene have been reported based on several AgNPs/graphene heterostructures created in different ways from that used in this work ,26,29,33 effects ,56,57. R effects .2/V‧s to ~832.9 cm2/V‧s (~30.7% decrease), while for dev2, ~1236.1 cm2/V‧s to ~777.9 cm2/V‧s (~37.1%). The hole carrier concentration (As plotted in he AgNPs .3 solution by the PR process in the same selective area. The GFET visualized in 2.Moreover, we also tried a two-step process to prepare a AgNPs/GC where the first step was to apply focused-laser irradiation selectively onto a GC in water, excluding any PR-related chemical reaction, while the second step was, as previously performed, to grow AgNPs on the GC in AgNOAs summarized in ectively ,33,44,45ectively ,29,33,34nditions . Probabl13 cm−2 after the two-step process, which was higher than ~8.33 × 1012 cm−2 of dev1 after the one-step process and even ~9.80 × 1012 cm−2 of dev2. These results represent that the more active AgNP growth upon the two-step process brought about stronger p-type doping effects on the graphene and, accordingly, more significant modulation of the GFET characteristics.The tunable characteristics of the GFETs under the two-step process were investigated by measuring the es, etc. ,60. Then2/V‧s and ~606.7 cm2/V‧s for the as-fabricated and AgNP-decorated GCs, respectively. Although the amount of AgNPs grown on the GC of dev3 was quite a lot larger than that of dev1 in terms of Moreover, the  devices ,61,62,63In summary, we demonstrated that a single-layer graphene surface can be decorated area-selectively with AgNPs using the facile one-step focused-laser-assisted PR method and investigated in detail how the formation and growth of AgNPs was affected by the laser-processing parameters. Then, we validated that, based on the GFET device characterization, the selective AgNP decoration on the microscale GFET channel controllably led to p-type doping effects in the graphene. Moreover, we showed that the GFET characteristics could be modulated more substantially with no significant degradation in the carrier mobility in the graphene by carrying out an additional pre-annealing process with a focused-laser beam in advance of the PR process. Therefore, our approach is of relevance to widening the applicability of low-dimensional heterostructures into next-generation electronics and optoelectronics.


The proposed approach for directly growing graphene on silicon is highly scalable and compatible with present nano/micro-fabrication systems, thus promoting the application of graphene in microelectronic fields.Direct integration of monolayer graphene on a silicon (Si) substrate is realized by a simple thermal annealing process, involving a top copper (Cu) layer as the catalyst and an inserted polymethylmethacrylate (PMMA) as the carbon source. After spin-coating the PMMA carbon source on the Si substrate, the Cu catalyst was deposited on PMMA/Si by electron beam evaporation. After that, graphene was directly synthesized on Si by decomposition and dehydrogenation of PMMA and the catalyzation effect of Cu under a simple thermal annealing process. Furthermore, under an optimized growth condition, monolayer graphene directly formed on the Si substrate was demonstrated. Utilizing the as-grown graphene/Si heterojunction, near-infrared photodetectors with high detectivity (∼1.1 × 10 Direct integration of monolayer graphene on a silicon (Si) substrate is realized by a simple thermal annealing process, involving a top copper (Cu) layer as the catalyst and an inserted polymethylmethacrylate (PMMA) as the carbon source. Previous works showed that the pre-formation of Si carbide during the PMMA decomposition process weakens the nucleation and growth of graphene.13,14 Although solid source molecular-beam epitaxy or CVD without a metallic catalyst may also provide possibilities, only graphitic films have been accomplished.15–17Owing to its excellent mechanical and electrical properties, graphene has been a focus of research since it was first demonstrated by mechanical exfoliation from graphite in 2004.−1) and detectivity (∼1.1 × 1010 cm Hz1/2 W−1) when illuminated with a 1550 nm light.In this work, we report a practical and straightforward technology to directly synthesize graphene on Si substrates. The key idea of this approach is to form a uniform PMMA on Si, followed by depositing a Cu layer on the PMMA as the catalyst. Notably, the PMMA appears to have a dual-role: (i) as the carbon source to synthesize graphene film; (ii) as the barrier to prevent Cu diffusing into Si substrate. We should stress that Cu atom residuals are still found in silicon after graphene synthesis although the fraction is meager. According to the optimized growth condition, the highest annealing temperature should not exceed 900 °C, aiming to prevent the wetting and evaporation of Cu layer and the annealing time is shortened to be 13 min. Finally, high-performance near-infrared photodetectors are directly fabricated by utilizing the as-grown graphene/Si heterojunctions. Electrical measurement results show that the as-grown graphene/Si heterojunction has a typical current rectification behavior, indicating a Schottky barrier between graphene and Si. Moreover, the graphene/Si based near-infrared photodetector with outstanding photovoltaic conversion capability exhibits high-performances in responsivity 2S2O8 aqueous solution, graphene is exposed on the Si substrate.via a semiconductor parameter analyzer (B1500A and Keithley 4200).The growth condition for high-quality graphene is optimized by tuning the annealing temperature, growth time, and gas atmosphere. For materials characterizations, the layer number, quality, and uniformity of the as-grown graphene were evaluated by Raman scattering (HORIBA Jobin Yvon HR800), atomic force microscopy  measurement and transmission electron microscope ; the element distribution along the depth of the as-grown graphene was analyzed by secondary ion mass spectrometry ; the surface chemical composition of as-grown graphene was revealed by X-ray photoelectron spectroscopy ; the crystalline quality and microstructure of the as-grown graphene were accessed by scanning tunneling microscope  in the constant current mode; electrical properties of graphene/Si based devices were investigated 3.3.1−1, 1580 cm−1, and 2700 cm−1 are found, which are known as the characteristic peaks of graphene,8,9i.e., D-peak, G-peak and 2D-peak, respectively. The calculated peak intensity ratio, ID/IG, of graphene synthesized at a temperature of 810 °C is about 1, implying the presence of defects.18 As the growth temperature increases, the intensity of D-peak gradually attenuates, suggesting an improved crystalline quality. Notably, no appreciable D-peak is observed at 900 °C. Therefore, the optimized temperature for graphene growth is 900 °C. In addition to the annealing temperature, the annealing time is also regarded as an important factor for obtaining graphene with high-quality.19 With an annealing time of 4 min, a distinct D-band is observed, as shown in 14 therefore, complete PMMA decomposition and graphene formation should need sufficient annealing temperature and time. Once the annealing time is over 13 min, the graphene quality will not be further improved. The growth condition was further optimized by changing the Ar : H2 flow rate ratio (sccm), as shown in 2 flow rate ratio is increased from 50 : 10 to 50 : 1, the intensity of D-peak for graphene decreases rapidly, indicating an improved crystalline quality. When the H2 flow is reduced to 1 sccm, the D-band completely disappears.3.220 A conformal PMMA coating layer on the desired substrate has been demonstrated as a vital step for synthesizing high-quality graphene, which can be attributed to the intimate relationship between the layer number of graphene and the carbon distribution in PMMA.21,22 In order to verify the uniformity of PMMA spin-coated on Si, AFM measurement was performed. As shown in 2. The surface roughness has no significant change after exposing graphene which is formed under the above optimized condition , as demonstrated in In our experiment, water-solvable PMMA was selected because of its capability of forming large-area uniform film with tunable thickness on various substrates by spin-coating.9 From the Lorentzian fitting curve of 2D-peak  by utilizing copper-assisted chemical vapor deposition, without any post-transfer process for optical transmittance and transport properties measurements. To further investigate the layer number, the optical transmittance of as-grown graphene on glass is characterized and the result is presented in 25 the layer number of as-grown graphene can be estimated to be only one atom layer, which is consistent with HR-TEM and Raman results. Moreover, the inset of I2D/IG is in a range of 2–2.5, conforming the graphene grown on Si substrate by the presented method is homogenous and uniform.2 V−1 s−1, and the electron mobility is in the range of 1200–1400 cm2 V−1 s−1, are shown in 9,18,26IDS always increases linearly with VDS. Therefore, the contact type between electrode (Ti/Au) and graphene is ohmic. Notably, IDS decreases monotonously with the increase of VG swapping from −20 to 0 V, implying a slight p-doping in the as-synthesized graphene.27Good transport properties, especially the carrier mobility, of graphene determines its potentials for the applications in high-performance electronic devices. In order to investigate the electrical transport ability of the graphene grown by our proposed method, graphene-based field effect transistors (GFETs) with a back gate were fabricated and characterized. 3.428 In terms of high-performance optoelectronic devices, graphene has attracted significant attentions due to its superior electronic and optical properties. For our proposed method, the significant advantage is directly integrating the as-grown graphene/Si heterojunction into a Schottky junction-based photodetector, because the average Schottky barriers of graphene/silicon junctions are estimated to be 0.45–0.47 eV.10 The performances of graphene/Si photodetectors are assessed by measuring the current passing through the Schottky heterojunction at dark and light illumination conditions, as shown in 29,30 When illuminated by a 1550 nm light, the reversed current is significantly enhanced.31 To investigate more details, a magnification of the I–V characteristic is processed and shown in 10tr) and fall time (tf) are estimated to be only 250 μs. Moreover, the detectivity and responsivity are calculated to be as high as ∼1.1 × 1010 cm Hz1/2 W−1 and ∼50 mA W−1, respectively, suggesting great potentials in logic and photoelectric circuits.Photodetectors have exhibited enormous potentials in optical communications, biomedical imaging, and motion detection.4.via tuning the growth conditions. To investigate the optoelectronic properties, Schottky junction based photodetectors are directly constructed by utilizing the as-grown graphene/Si. Optoelectronic results indicate that the as-grown graphene/Si based photodetector exhibits a distinct photovoltaic behavior, with high responsivity and detectivity of ∼50 mA W−1 and ∼1.1 × 1010 cm Hz1/2 W−1, respectively. Our study may pave the way for synthesizing graphene on arbitrary substrate in a highly scalable way, thus promoting applications of graphene in microelectronic and optoelectronic fields.In summary, we describe a simple and convenient approach to directly synthesize graphene on single-crystalline silicon substrate. The quality of synthesized graphene is optimized The authors declare that they have no conflict of interest.