Search

Due to the favorable properties of two-dimensional materials such as SnS

Self-powered detectors based on triboelectric nanogenerators (TENG) have been considered because of their capability to convert ambient mechanical energy to electrical out-put signal, instead of conventional usage of electrochemical batteries as power sources. In this regard, the self-powered photodetectors have been designed through totally two lay out called passive and active circuit. in former model, impedance matching between the TENG and the resistance of the circuit’s elements is crucial, which is not investigated systematically till now. In this paper, a cost effective novel planar photodetector (PD) based on heterojunction of SnS2 sheets and Cs0.05(FA0.83 MA0.17)0.95Pb(I0.83Br0.17)3 three cationic lead iodide based perovskite (PVK) layer fabricated which powered by graphene oxide (GO) paper and Kapton based contact-separated TENG (CS-TENG). To achieve the high performance of this device, the proper range of the load resistances in the circuit regards to TENG’s characterization has been studied. In the next steps, the integrated self-powered photo-detection system was designed by applying Kapton/FTO and hand/FTO TENG, separately, in the proposed impedance matching circuit. The calculated D* of integrated self-powered SnS2/PVK supplied by tapping the Kapton and hand on FTO is 2.83 × 1010 and 1.10 × 1013 Jones under the 10 mW/cm2 of white light intensity, the investigations determine that for designing significate performance of self-powered PD supplied by TENG, the existence of the load resistance with the well match amount to the utilized TENG is crucial. Our results which can be generalized to other types of passive self-powered sensors, are substantial to both academia and industry concepts.

The performance of a quartz crystal microbalance (QCM) used as a sensor/detector relies on the performance and quality of the film coated onto the quartz crystal sensor. This study focuses on the sensor coating preparation for the detection of glycine. Cellulose nanofibrils (CNFs), natural polymers, were coated on a quartz crystal (QC) surface by a spin-coating method. The prepared CNF-coated QC was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and water contact angle (WCA). The stable and fully covered QCs without further modification were then employed for aqueous glycine detection. Detection with a wide concentration range (3–1000 μg/mL) of glycine was studied. The resonance frequency shifts obtained from the samples during each step of the measurement are presented and discussed. The data show a linear range of detection (R2 = 0.9945) for 6–500 μg/mL of glycine and a limit of detection (LOD) of 8 μg/mL. This study indicates that the CNF-coated QCM has a potential application as a biodetector for glycine detection.

Design and fabrication of highly efficient and low-cost oxygen reduction reaction (ORR) electrocatalysts is of paramount importance for practical applications. Herein, we proposed a cost-effective, metal-free catalyst based on ZIF-8 metal-organic framework nanoparticles/electro-polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) film on the surface of flexible carbon cloth (CC) electrode (ZIF-8/PEDOT/CC) via a two-step procedure. For this purpose, worm-like PEDOT nanostructures were deposited on the surface of carbon fibers using a pulse electro-polymerization technique followed by facile growth of ZIF-8 polyhedra nanoparticles via a chemical bath deposition method. The ORR measurements in O2-saturated KOH electrolyte solution using the modified CC electrode demonstrated that the prepared electrode exhibits remarkable electrocatalytic activity towards ORR with 8 times increase in the cathodic current density compared to bare CC (J = 0.13–1.1 mA/cm2) along with lower overpotential due to the synergetic effects between ZIF-8 nanoparticles as particularly porous nanostructure act as electrolyte reservoirs and highly conductive PEDOT film. The Kouteckey-Levich analysis for the ZIF-8/PEDOT-modified CC electrode revealed that the oxygen reduction reaction proceeds via a nearly four-electron pathway along with superior tolerance to methanol crossover as well as enhanced stability in alkaline solution compared to the gold standard commercial Pt catalyst.

Evaporation is a significant outflow in water bodies and is the only outflow in man-made Chitgar Lake. It is estimated to be more than 2 million cubic meters annually. In order to mitigate this outflow, we investigated different kinds of self-assembled thickness films. They consist of six different combinations of stearyl and cetyl alcohols with additives including jojoba oil, stearic acid, and calcium hydroxide. The study has been done from July to August with two pairs of class A evaporation pans; one pair semi-floated on Chitgar lake water and another one located on the shore. The experimental results showed that a monolayer contained 3:1 stearyl to cetyl alcohols with 60% weight of calcium hydroxide had the best performance and could reduce evaporation up to 50% during its 3 days’ lifetime. The study indicated that the films had no significant side effects on lake water pH, turbidity, and total suspended solids except slight increase in water surface temperature.

Self-powered detectors based on triboelectric nanogenerators (TENG) have been considered because of their capability to convert ambient mechanical energy to electrical out-put signal, instead of conventional usage of electrochemical batteries as power sources. In this regard, the self-powered photodetectors have been designed through totally two lay out called passive and active circuit. in former model, impedance matching between the TENG and the resistance of the circuit's elements is crucial, which is not investigated systematically till now. In this paper, a cost effective novel planar photodetector (PD) based on heterojunction of SnS

Introduction To date, numerous iron-based nanostructures have been designed for cancer therapy applications. Although some of them were promising for clinical applications, few efforts have been made to maximize the therapeutic index of these carriers. Herein, PEGylated silica-coated iron oxide nanoparticles (PS-IONs) were introduced as multipurpose stimuli-responsive co-delivery nanocarriers for a combination of dual-drug chemotherapy and photothermal therapy. Methods Superparamagnetic iron oxide nanoparticles were synthesized via the sonochemical method and coated by a thin layer of silica. The nanostructures were then further modified with a layer of di-carboxylate polyethylene glycol (6 kDa) and carboxylate-methoxy polyethylene glycol (6 kDa) to improve their stability, biocompatibility, and drug loading capability. Doxorubicin (DOX) and cisplatin (CDDP) were loaded on the PS-IONs through the interactions between the drug molecules and polyethylene glycol. Results The PS-IONs demonstrated excellent cellular uptake, cytocompatibility, and hemocompatibility at the practical dosage. Furthermore, in addition to being an appropriate MRI agent, PS-IONs demonstrated superb photothermal property in 0.5 W/cm2 of 808 nm laser irradiation. The release of both drugs was effectively triggered by pH and NIR irradiation. As a result of the intracellular combination chemotherapy and 10 min of safe power laser irradiation, the highest cytotoxicity for iron-based nanocarriers (97.3±0.8%) was achieved. Conclusion The results of this study indicate the great potential of PS-IONs as a multifunctional targeted co-delivery system for cancer theranostic application and the advantage of employing proper combination therapy for cancer eradication.

Despite their potential applications, a limited number of studies for synthesizing vertical MoS2 nanoflakes especially via CVD have been reported so far, which generally involve tedious complex- and/or multi-step growth processes. In this study, direct synthesis of vertical MoS2 nanoflakes grown on the SiO2/Si substrate during a rapid sulfidation process by CVD method has been reported. Material characterization was performed using Raman spectroscopy, XRD and FE-SEM. The XRD results indicated the dominant phase of 2H–MoS2 within the synthesized layers. The characteristic distance between the two dominant peaks of E12g and A1g in the Raman spectra confirms the multi-layered structure for grown nanoflakes. Based on the experimental results, the growth mechanism has been explained considering nucleation and growth of two-dimensional islands, followed by coalescence of these islands. Subsequently, in the final stage, standing nanoflakes grow vertically. The vertical MoS2 nanoflakes film forms n-channel for back-gated FET gas sensor, of which gas sensing performance towards ethanol and methanol vapors have been studied. These structures with an increased number of edge sites presented high and fast responses to ethanol and methanol at 1 and 10 ppm concentrations and showed significant potential and promising application as a gas sensor transistor.

Inorganic hole-transport materials (HTMs) have been frequently applied in perovskite solar cells (PSCs) and are a promising solution to improve the poor stability of PSCs. In this study, we investi...

Two-dimensional semiconductor materials can be combined with conventional silicon-based technology and sort out part of the future challenges in semiconductor technologies due to their novel electrical and optical properties. Here, we exploit the optoelectronics property of the silicon/SnS2 heterojunction and present a new class of backward diodes using a straightforward fabrication method. The results indicate an efficient device with fast photoresponse time (5–10 μs), high photoresponsivity (3740 AW–1), and high quantum efficiency (490%). We discuss device behavior by considering the band-to-band tunneling model and band bending characteristics of the heterostructure. This device structure is fully compatible with the semiconductor industry process and allows direct integration with commercial silicon-based technology for novel applications.

In this research a combinative electron transport layer (ETL) composed of TiO2nanocrystals (NCs) and nanorods (NRs) were prepared and applied in perovskite solar cells (PSCs). TiO2NCs with dominant size of 20 nm were synthesized through a hydrothermal method. TiO2NRs were also grown through another hydrothermal process using P25 TiO2nanoparticles (NPs) as the precursors. The diameter and length of the TiO2NRs were measured about 80 nm and 1–2 μm, respectively. Different combinative pastes including TiO2NCs and NRs were prepared and applied in ETL component of the PSCs. The weight percent (wt%) of the included TiO2NRs in electron transport layer was altered in the range of 0–20%. A conventional structure of FTO/TiO2compact layer/TiO2NCs-NRs mesoporous layer/Perovskite/Spiro-OMeTAD/Au. was utilized for fabrication of PSCs in ambient condition. Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3mixed halides perovskite was also used due to its proper bandgap energy, crystalline quality and longtime stability. The effect of ETL composition i.e. the weight percent of the composing TiO2NRs on the photovoltaic (PV) performance of the cells was investigated. According to the results, the PSC with a combinative ETL including 10 wt% of the TiO2NRs demonstrated a Jsc = 22.95 mA/cm2, Voc = 1.055 V, FF = 0.71 and η = 17.2%. This energy conversion efficiency was increased about 20% compared to that of the PSC with nanocrystalline, NRs-free ETL. The reason was attributed to the optimized electron transport property of the ETL and crystalline quality of the over-grown perovskite layer.

A grid configuration based on the aligned nickel oxide nanowire (NiO NW) for humidity sensing were fabricated through the oxidation of ferromagnetic nickel NWs prepared by a template-assisted electrodeposition process. Their structure and elemental compositions were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray analyses (EDAX). The room-temperature humidity sensing behavior of the NiO NWs was investigated successfully based on DC and AC impedance spectroscopy (IS) method in frequencies range 10 Hz to 2 MHz. The sensors showed excellent humidity sensing characteristics such as a high response of about 66 with rather rapid response-recovery times about 9 and 2 s for 90%RH, and good stability. The equivalent circuits were simulated for impedance responses to humidity in the range of 40–90% RH. According to the results, ionic conduction via NW-NW junctions as well as NW-electrode interfaces in the grid configuration is responsible for sensing behavior.

Here in this research, room temperature ethanol and humidity sensors were prepared based on two dimensional (2D) hybrid nanostructures of tungsten di-sulfide (WS2) nanosheets and graphene oxide nanoribbons (GONRs) as GOWS. The characterization results based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (ESD), Raman spectroscopy and X-ray diffraction (XRD) analysis confirmed the hybrid formations. Ethanol sensing of drop-casted GOWS films on SiO2 substrate indicated increasing in gas response up to 5 and 55 times higher compared to pristine GONRs and WS2 films respectively. The sensing performance of GOWS hybrid nanostructures was investigated in different concentrations of WS2, and the highest response was about 126.5 at 1 ppm of ethanol in 40% relative humidity (R.H.) for WS2/GONRs molar ratio of 10. Flexibility of GOWS was studied on Kapton substrate with bending radius of 1 cm, and the gas response decreased less than 10% after 30th bending cycles. The high response and flexibility of the sensors inspired that GOWS are promising materials for fabrication of wearable gas sensing devices.

The room temperature polar vapor sensing behavior of a graphene-TiS3 heterojunction material and TiS3 nanoribbons is described. The nanoribbons were synthesized via chemical vapor transport (CVT) and their structure was investigated by scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and Fourier transform infrared spectroscopies. The gas sensing performance was assessed by following the changes in their resistivities. Sensing devices were fabricated with gold contacts and with lithographically patterned graphene (Gr) electrodes in a heterojunction Gr-TiS3-Gr. The gold contacted TiS3 device has a rather linear I-V behavior while the Gr-TiS3-Gr heterojunction forms a contact with a higher Schottky barrier (250 meV). The I-V responses of the sensors were recorded at room temperature at a relative humidity of 55% and for different ethanol vapor concentrations (varying from 2 to 20 ppm). The plots indicate an increase in the resistance of Gr-TiS3-Gr due to adsorption of water and ethanol with a relatively high sensing response (~495% at 2 ppm). The results reveal that stable responses to 2 ppm concentrations of ethanol are achieved at room temperature. The response and recovery times are around 8 s and 72 s, respectively. Weaker responses are obtained for methanol and acetone.

In this work, nanostructured composites of Cr2O3-graphene oxide (Cr2O3/GO) with conducting polymers; polyaniline (PANI) and polypyrrole (PPy) with the shape of cauliflower were synthesized via s simple and low cost one-step chronoamperometry method. The structures and morphologies of the resulting ternary nanocomposites were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical capacitive properties of the prepared nanocomposites were evaluated by using cycle voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The as-synthesized Cr2O3/GO/PANI and Cr2O3/GO/PPy composites exhibit a highest specific capacitance of 525 and 495 F g−1 at 5 A g−1 in the three-electrode tests, respectively. Interestingly, Cr2O3/GO/PANI and Cr2O3/GO/PPy composites retain 84 and 80% of their initial capacitance values after 4000 charge-discharge cycles, suggesting good electrochemical stability of the nanocomposite electrodes. The assembled symmetric devices based on Cr2O3/GO/PANI and Cr2O3/GO/PPy composites show a high specific capacitance of 263 and 100 F g−1 at the current density of 5 A g−1, respectively.

We fabricated a high rate capability supercapacitor based on fluorine-doped graphene-carbon nanotubes aerogel network (G-CNT-F). Based on the electrochemical impedance spectroscopy data, the fluorination decreases the charge transfer resistance of graphene sheets, while CNTs act as spacer in the 3D structure. Therefore, both treatments improved the electrochemical properties of the resulted aerogel. Based on the Fourier transform infrared spectroscopy and XPS results, these excellent performances are attributed to semi-ionic bonds between fluorine and carbon. The specific capacitance of the graphene aerogel showed 78% decrease, when discharge current increases from 2 to 40 mA, while the G-CNT and G-CNT-F electrode loses 63.8 and 33.3% of its specific capacitance, respectively. The fabricated symmetric supercapacitor based on G-CNT-F shows energy density as high as 9.9 Wh/kg at the power density of 6000 W/kg in aqueous electrolytes.

Iron‑vanadium oxysulfide (Fe-VO-S) nanostructures with different Fe:VO atomic ratios are synthesized by a facile and low cost electrochemical deposition method. The synthesis of the various samples is confirmed by the physicochemical characterizations such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). For different Fe-VO-S nanostructures, the correlation between the physicochemical and the electrochemical properties is investigated. It is found that the Fe:VO atomic ratio has an important effect on the structure and size of the resulted particles. Also, the morphology of Fe-VO-S nanostructures has a remarkable influence on the electrochemical performance of the prepared samples. In addition, ternary Fe-VO-S nanostructures show better electrochemical performances compared to binary VO-S, in terms of high specific capacitance value and good cycling stability, because of the combined contributions from both of Fe and VO elements in the ternary nanostructures. Especially, the as-prepared Fe-VO-S nanostructure with Fe:VO molar ratio of 2:1 shows the highest specific capacitance value of 217 F g−1 at a current density of 3 A g−1 and also exhibits good cycling stability with 92% capacitance retention at a current density of 5 A g−1 after 4000 cycles. In addition, the Fe-VO-S nanostructure with the mentioned molar ratio of Fe:VO can be successfully applied to assemble a symmetric supercapacitor device and achieves good capacitive performances with a high specific capacitance (117 F g−1 at 3 A g−1), excellent energy density (9.3 Wh kg−1 at 2200 W kg−1) and power density (7200 W kg−1 at 1.2 Wh kg−1).

Three-dimensional reduced graphene oxide (3D-rGO) structures decorated with CuO particles (GCu) are synthesized through a simple and scalable method for detection of hydrogen sulfide (H2S) gas. For characterization and investigation of porous structure various techniques were employed. Decorated 3D structures demonstrated higher sensitivity and selectivity in comparison to pure structure. Optimized structure for sensing was obtained through introducing different amounts of CuO. The GCu heterostructures containing 35 μmol of CuO powder demonstrated reproducible response of about 30% to the concentration of 10 ppm at room temperature, while complete recovery was obtained through heating to 150 °C. Sensing behaviour of the samples to H2S gas was investigated at temperatures in the range of 25–150 °C and in different relative humidity levels from 3 to 80%. We discussed the sensing model based on the adsorption of H2S molecules on the additives, and electron injection to the sample, resulting in the electrical resistance enhancement.

Recent research interest in two-dimensional (2D) materials has led to an emerging new group of materials known as transition metal dichalcogenides (TMDs), which have significant electrical, optical, and transport properties. MoS2 is one of the well-known 2D materials in this group, which is a semiconductor with controllable band gap based on its structure. The hydrothermal process is known as one of the scalable methods to synthesize MoS2 nanostructures. In this study, the gas sensing properties of flower-shaped MoS2 nanoflakes, which were prepared from molybdenum trioxide (MoO3) by a facile hydrothermal method, have been studied. Material characterization was performed using X-ray diffraction, Brunauer–Emmett–Teller surface area measurements, elemental analysis using energy dispersive X-ray spectroscopy, and field-emission scanning electron microscopy. The gas sensing characteristics were evaluated under exposure to various concentrations of xylene and methanol vapors. The results reveal higher sensitivity and shorter response times for methanol at temperatures below 200 °C toward 200 to 400 ppm gas concentrations. The sensing mechanisms for both gases are discussed based on simulation results using density functional theory and charge transfer.

Cu2O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu2O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu2O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu2O electrode to make the measurement possible, which could result in deviation from actual values. Here we introduce a non-aqueous electrolyte based on tetrabutylammonium-tetrafluoroborate in 3-methoxypropionitrile for electrochemical analysis of Cu2O. MS analysis shows reproducible results in terms of dopant density and flat band potential, while the analysis in aqueous (0.5M Na2SO4) electrolyte shows inconsistent, irreproducible results. In the case of IS, the transport resistivity of the layers was evaluated using the new electrolyte and shows a linear trend with thickness, as expected. The proposed non-aqueous electrolyte can potentially be used for the electrochemical analysis of other sensitive semiconductors. Keywords: Mott-Schottky, Metal oxide, Cu2O, Non-aqueous electrolyte, Impedance spectroscopy

Herein, a novel sensing platform based on NiCo layered double hydroxide (LDH) nanosheets/graphene nanoribbons (GNRs) modified glassy carbon electrode is presented for sensitive non-enzymetic determination of glucose. In the first step, nanoflower-like NiCo LDH nanosheets were grown on the surface of ZIF-67 dodecahedron nanocrystals which used as sacrificial template and were further characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD) and FTIR. In the next step, in order to fabricate a mechanically stable modified electrode, the as-prepared nanosheets were mixed with narrow graphene nanoribbons synthesized through longitudinal unzipping of MWCNTs as an effective binder which in one hand increase the mechanical stability of the composite film and on the other hand, enhance the electrical conductivity of the final modified electrode. The catalytic behavior of the NiCo NSs/GNR modified electrode toward the electro-oxidation of glucose was investigated in NaOH alkaline solution by using cyclic voltammetry (CV) and amperometry techniques. As an enzymeless glucose sensor, the proposed sensing platform exhibited fast amperometric responses with high sensitivity (344 μAmM− 1 cm− 2) and low detection limit of 0.6 μM within a wide dynamic linear range from 5 μM to 0.8 mM. Moreover, the electrode also demonstrated excellent selectivity toward glucose in the presence of common interfering species such as AA, DA and UA as well as good long-term stability which makes it an appropriate candidate for further practical applications.

Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless steel (SS) as the substrate. The Fe3+-Zn2+-PANI/GO nanocomposite is characterized using X-ray diffraction as well as Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Also, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are used to study the electrochemical performance of the as-prepared electrode materials. Significantly, the Fe3+-Zn2+-PANI/GO nanocomposite exhibits a specific capacitance of 1140 F g−1 at a current density of 10 A g−1, which is far better than PANI (250 F g−1), PANI/GO (610 F g−1), Fe3+-PANI/GO (744 F g−1), and Zn2+-PANI/GO (964 F g−1). After 4000 cycles, the fabricated Fe3+-Zn2+-PANI/GO/SS electrode shows 85% capacitance retention at a current density of 5 A g−1. The resulting good electrochemical performance is owing to the combination of electrical double layer capacitance of GO and pseudocapacitive characteristic of PANI and transition metal ions, which can effectively increase the specific capacitance value and cycling performance of the prepared nanocomposite.

This paper reports on a novel low-temperature method for preparing curcumin-reduced graphene oxide (Cur-rGO) from graphene oxide (GO) and investigates their cyclic voltammetry (CV) and photoluminescence (PL) properties. GO sheets were synthesized using modified Hummers’ method and then were chemically reduced using polyphenol curcumin into graphene sheets. Atomic force microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy were used to confirm the formation of Cur-rGO and revealed their functionalization with polyphenol curcumin. The electrochemical and optical properties of the Cur-rGO sheets were investigated using CV and PL spectroscopy. According to the PL and CV characterization for the Cur-rGO sheets, charges and resonant energy were transferred from curcumin molecules to the GO sheets’ surfaces. This arises from the bonding of the fluorescence curcumin molecules to the Cur-rGO surfaces, through π–π stacking of their aromatic rings. It should be noted that curcumin molecules act as electron donors, suppressing the fluorescence of the GO sheets while improving their electrochemical activities.

A new ternary nanocomposite based on graphene oxide (GO), polypyrrole (PPy) and vanadium pentoxide (V2O5) is obtained via one-step electrochemical deposition process. Electrochemical deposition of V2O5, PPy and GO on a stainless steel (SS) substrate is conducted from an aqueous solution containing vanadyl acetate, pyrrole and GO to get V2O5/PPy/GO nanocomposite. Characterization of the electrode material is carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The electrochemical performance of the as-prepared nanocomposite is evaluated by different electrochemical methods including cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) in 0.5 M Na2SO4 solution. Remarkably, V2O5/PPy/GO nanocomposite shows a specific capacitance of 750 F g−1 at a current density of 5 A g−1, which is far better than PPy (59.5 F g−1), V2O5/PPy (81.5 F g−1) and PPy/GO (344.5 F g−1). Furthermore, V2O5/PPy/GO maintains 83% of its initial value after 3000 cycles, which demonstrates good electrochemical stability of the electrode during repeated cycling. These results demonstrate that the combination of electrical double layer capacitance of GO and pseudocapacitive behavior of the PPy and V2O5 can effectively increase the specific capacitance and cycling stability of the prepared electrode. Also, a symmetric supercapacitor device assembled by V2O5/PPy/GO nanocomposite yielded a maximum energy density of 27.6 W h kg−1 at a power density of 3600 W kg−1, and a maximum power density of 13680 W kg−1 at an energy density of 22.8 W h kg−1.

TiS2, as a family member of Transition Metal Dichalcogenides (TMDs), shows a unique property of semi-metallic to semiconductor transition when going from bulk to few layered structure. In this paper, an electromechanical resonator based on TiS2 ribbons with semi-metallic characteristic is presented. Electrical readout of the mechanical vibratory response of TiS2 ribbons is measured by employing electrostatic actuation. A typical resonator includes a number of overlapped ribbons with approximate width and thickness of 600 nm and 250 nm respectively along with a suspended length of 5 μm. A typical resonator shows a resonance frequency of around 153 MHz with a quality factor (Q) of about 1000 in air at ambient conditions. Also, the resonance frequency of the introduced resonator increases as the bias potential is increased due to the electrostatic spring-stiffening effect. Moreover, finite element simulation shows that the reported frequency of resonance and extracted electrical parameters are relevant.

In the present study, a 3D porous graphene-carbon nanotube (G-CNT) network is successfully constructed on the surface of glassy carbon electrode (GCE) by electrochemical co-deposition from a concentrated graphene dispersion. The large accessible surface area provided by the interpenetrated graphene backbone in one hand and the enhanced electrical conductivity of the 3D network by incorporating CNTs on the other hand, dramatically improved the electrochemical performance of GCE in determination of Methotrexate (MTX) as an important electroactive drug compound. Under the optimum conditions, the electrode modification led to a significant increase in the anodic peak current (∼25 times) along with a considerable shift in the peak potential (∼111 mV). Voltammetric investigations revealed that the proposed method can determine MTX in a wide dynamic linear range with a low detection limit of 70 nM. Moreover, good sensitivity and high accuracy of the prepared modified electrode in voltammetric detections of MTX, which was further confirmed by UV–vis spectroccopy and HPLC methods, make it very suitable for accurate determinations of MTX in pharmaceutical formulations (commercial tablets) and clinical preparations (blood serum) with excellent recoveries.

Highly sensitive flexible humidity sensors based on graphene quantum dots (GQDs) were developed. The GQDs were prepared using a facile hydrothermal method and characterized considering morphological, structural, and compositional experiments. Then, their humidity sensing properties in correlation with flexibility characteristics were investigated. Good selectivity and response (∼390 for a RH change of 99%), broad detection range (1–100% RH), rather short response and recovery times (12 and 43 s, respectively) as well as flexibility were obtained, demonstrating that the GQD sensors have potential for application in wearable electronics and RH monitoring. Detection of hydrogen (H2) gas by the GQDs confirms the exchange of a proton through adsorbed H+ species in the H2O sensing mechanism. Considering the structure of the sensing material and RT performance, capillary condensation resulting in the formation of a conductive path by water molecules is suggested as the dominant sensing mechanism at high RH.

In this research, electrodeposited Cu2O is introduced as a hole-transport layer (HTL) in inverse perovskite (PVK) solar cells, by which the power conversion efficiency of 2.14% has been achieved. Appropriate energy levels for carriers transferring in ITO/Cu2O/PVK/PCBM/Au cell configuration had been evaluated by Mott-Schottky; however, energy dispersive X-ray spectroscopy indicated some chemical reactions happened between layers. Ambient Kelvin Probe has been used to evaluate the work function of Cu2O and Cu2O deposited by PVK. The dissimilar work function for these two layers provoked some chemical reactions. Based on our results, the probable occurrence of discarded interfacial chemical reactions significantly affects solar cell performance.

The room temperature polar vapor sensing behavior of a graphene-TiS

Inorganic hole-transport materials (HTMs) have been frequently applied in perovskite solar cells (PSCs) and are a promising solution to improve the poor stability of PSCs. In this study, we investigate solution-processed copper indium gallium disulfide (CIGS) nanocrystals (NCs) as a dopant-free inorganic HTM in n-i-p type PSCs. Moreover, Cs

Introduction To date, numerous iron-based nanostructures have been designed for cancer therapy applications. Although some of them were promising for clinical applications, few efforts have been made to maximize the therapeutic index of these carriers. Herein, PEGylated silica-coated iron oxide nanoparticles (PS-IONs) were introduced as multipurpose stimuli-responsive co-delivery nanocarriers for a combination of dual-drug chemotherapy and photothermal therapy. Methods Superparamagnetic iron oxide nanoparticles were synthesized via the sonochemical method and coated by a thin layer of silica. The nanostructures were then further modified with a layer of di-carboxylate polyethylene glycol (6 kDa) and carboxylate-methoxy polyethylene glycol (6 kDa) to improve their stability, biocompatibility, and drug loading capability. Doxorubicin (DOX) and cisplatin (CDDP) were loaded on the PS-IONs through the interactions between the drug molecules and polyethylene glycol. Results The PS-IONs demonstrated excellent cellular uptake, cytocompatibility, and hemocompatibility at the practical dosage. Furthermore, in addition to being an appropriate MRI agent, PS-IONs demonstrated superb photothermal property in 0.5 W/cm2 of 808 nm laser irradiation. The release of both drugs was effectively triggered by pH and NIR irradiation. As a result of the intracellular combination chemotherapy and 10 min of safe power laser irradiation, the highest cytotoxicity for iron-based nanocarriers (97.3±0.8%) was achieved. Conclusion The results of this study indicate the great potential of PS-IONs as a multifunctional targeted co-delivery system for cancer theranostic application and the advantage of employing proper combination therapy for cancer eradication.

The recent status of female students and faculties in physics departments in Iran is presented. Growth in female contributions has occurred mainly at the PhD level. A positive trend toward reducing the gender gap in the field of teaching and university research careers has been observed during recent years. However, the percentage of women in decision-making and management positions in universities is weak, at about 2%.

In the present paper, new H2S gasochromic nanomaterial of mixed silver nickel ammonium phosphomolybdate synthesized by microwave assisted technique is reported. The microwave treatment was performed in the solid phase using urea and ammonium nitrate as the promoter and oxidizer agents. The designed process allows rapid synthesis of large amounts of this product in nanosized particulate morphology. Morphological and structural features of the prepared products were studied in detail. Chemical analyses indicated a stoichiometry of (NH4)0.5Ni0.75AgPMo12O40·4H2O revealing a Keggin-type framework with substitution of silver and nickel cations in its secondary structure. A home-made set-up was used to test gasochromic effect via monitoring light intensity variations passing through the samples based on their color change during exposure to different H2S gas concentrations. Response in coloration was obtained about 12% to 61.8% for concentrations from 8.5 to 100 mg L−1. It is suggested that the presence of Ag and Ni ions (especially silver as counter cations) in the secondary structure of a Keggin ion plays an important role in the coloration effect of the substituted phosphomolybdate compared with the un-substituted one. In fact, color centers can be originated from the interaction of these cations of the phophomolybdate network with thiol functional group of H2S molecules.

Graphene/cobalt nanocomposites are promising materials for theranostic nanomedicine applications, which are defined as the ability to diagnose, provide targeted therapy and monitor the response to the therapy. In this study, the composites were synthesized via chemical method, using graphene oxide as the source material and assembling cobalt nanoparticles of 15nm over the surface of graphene sheets. Various characterization techniques were then employed to reveal the morphology, size and structure of the nanocomposites, such as X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high resolution transmission electron microscopy and ultraviolet visible spectroscopy. Using ion-coupled plasma optical emission spectroscopy, cobalt concentration in the nanocomposites was found to be 80%. In addition, cytotoxicity of graphene/cobalt nanocomposites were evaluated using 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide or MTT assay. MTT viability assay exhibited biocompatibility to L929 mouse fibroblasts cells, under a high dose of 100μg/mL over 24h. Hyperthermia results showed the superior conversion of electromagnetic energy into heat at 350kHz frequency for 0.01 and 0.005g/L of the nanocomposites solution. The measured heat generation and energy transfer results were anticipated by the finite element analysis, conducted for the 3D structure. Magnetic resonance imaging characteristics also showed that negatively charge graphene/cobalt nanocomposites are suitable for T1-weighted imaging.

In this work the plasmonic photocatalytic activity of ZnO/noble metals nanocomposites has been investigated. Ag nanowires and Au nanospheres were prepared and mixed with ZnO in order to prepare the nanocomposites. It was demonstrated that the composites containing the plasmonic Ag nanowires and ZnO nanoparticles showed a significant photocatalytic activity enhancement compared to the pure ZnO in decomposition of methylene blue (MB). By investigation of mechanisms governing the performance of plasmonic photocatalysts, it was found that the photocatalytic activity enhancement can be attributed to the energy transfer from Ag nanowires to the ZnO nanoparticles induced by the surface plasmonic resonance (SPR). Such energy transfer is due to increasing the average path length of the photons in the composite and the SPR-induced local electromagnetic field near the surface of Ag nanowires. This mechanism predicts an enhancement in the concentration of charge carriers at the semiconductor surface by which the photocatalytic activity improves. The results showed that the photocatalytic activity enhancement was depended on the diameter size and concentration of Ag nanowires in the composites. Our studies showed that the composite containing 4.5 wt % of Ag nanowires with mean diameter size of 280 nm exhibited the highest photocatalytic activity enhancement compared to the pure ZnO nanoparticles. Furthermore, ZnO/Au nanospheres composite presented a little enhancement in photocatalytic activity compared to the composites containing Ag nanowires.

The electrical bending instability in charged liquid jets is the phenomenon determining the process of electrospinning. A model of this phenomenon is lacking however, mostly due to the complicated interplay between the viscosity and elasticity of the solution. To investigate the bending instability, we performed electrospinning experiments with a solution of polyethylene oxide in water/ethanol. Using a fast camera and sensitive multimeter, we deduced an experimental dispersion relation describing the helix pitch length as a function of surface charge. To understand this relation, we developed a theoretical model for the instability for a wide range of visco-elastic materials, from conducting to nonconducting. The theoretical dispersion relation shows good agreement with the experimental results. Using the new model, we find that the elastic tension in the visco-elastic threads plays an important role in triggering the instability. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1036–1042

Here in this research, we report on surface engineering of bulk Cu2O photocathode thorough employing nanostructured materials. Nanorods (NRs) of copper oxide with average lengths of 150 nm have been synthesized by anodization of Cu foil in aqueous KOH electrolyte, followed by annealing treatment. Several heating processes were examined to reach pure Cu2O nanostructures and lastly the moderate annealing procedure at 700 °C under Ar gas flow resulted in pure Cu2O nanostructures, confirmed by XRD analysis. Surface modified nanorod/bulk Cu2O electrode was prepared by spin coating of sediments suspension of anodized drop on bulk Cu2O film fabricated through thermal oxidation method, followed by final heating process. Photoelectrochemical analysis indicates that nanorod/bulk Cu2O electrodes have noticeable enhancement in photocurrent, around 76% at −0.6 V and the favorable decrease in interface resistance about 103 Ω in comparison to the bulk Cu2O thermal oxidized electrode. This novel bulk Cu2O electrode with modified nanostructured surface can be a good candidate as the electrode of either photoelectrochemical systems for hydrogen generation or the photocathode of bulk heterojunction photovoltaic cells.

A hierarchical core–shell structure composed of ZnO nanotubes/MnO2 nanosheets was fabricated via a two-step electrochemical deposition procedure on the surface of a 3D graphene network (3DGN) as a free-standing monolithic electrode. In the first step, ZnO nanorod arrays were grown on the surface of a 3DGN followed by electrochemical deposition of MnO2 nanosheets in the next step, which caused the inner parts of initial ZnO nanorods to etch away and resulted in the formation of ZnO nanotubes (ZnO NTs). The highly porous interconnected graphene backbone offers very high conductivity and a large accessible surface area. On the other hand, the formation of ZnO nanotubes can enhance the electrode/electrolyte interface, while the porosity of MnO2 nanosheets is a great matrix for immobilizing biomolecules due to its good biocompatibility. The combination of these properties makes the prepared electrode a promising candidate for constructing biosensing platforms. As a proof of concept, the prepared composite electrode was used for the fabrication of a biosensor by immobilizing glucose oxidase (GOx) as a model enzyme and used for the detection of glucose. Amperometry results revealed very short response times. The obtained high sensitivity (3.9 mA μM−1 cm−2) and low detection limit (10 nM) for glucose exhibit that the proposed electrode provides a favorable platform for bioelectrochemical applications.

A novel AC impedance study on three-dimensional hybrid structures of graphene sheets/MoS2 nanorose (GMS) toward ethanol vapor detection is presented in this work. These defective 3D hybrid porous structures are sensitive to the presence of different gases as a result of charge transfer with gas species, as well as a change in the effective capacitance of the system. The sensing behavior of the samples is investigated throughout time-dependent impedance measurement and electrochemical impedance spectroscopy (EIS). The sensor response is estimated at about 20% to 10 ppm ethanol vapor, with the response and recovery times about 3.2 s and 0.8 s, respectively. Sensing mechanism proposed to describe the EIS impedance spectra involves three different procedures: charge transfer, double layer formation and diffusion process. Moreover, these processes are probed using equivalent circuits modeled by the impedance spectra curves.