•rGO/SnO2 composites improved the sensing response three times larger than rGO.•Microporous substrates were utilized with 350% enhancement of sensing response.•The detection limit based on the ...prepared sensors was calculated to be 15.7ppb.•A nice selectivity to 1ppm NO2 gas among numerous interfering gases was obtained.
Sensitive detection for low-concentration NO2 gas is imperative in the fields of environmental monitoring and human healthcare. In this work, reduced graphene oxide (rGO)/tin oxide (SnO2) nanocomposites were prepared by a simple blending and deposited onto different microporous substrates to explore their sensing performance to NO2 gas, combining with multiple characterization techniques such as SEM, TEM, XRD and XPS. The experimental results revealed an increased sensing response with rising SnO2 concentration ranging from 0 to 10mg/ml. Especially, the sensing response at 10mg/ml attained nearly three times larger than that of pure rGO. Investigation on long-term stability manifested a smaller response attenuation of rGO/SnO2 sensors toward NO2 gas of high concentration regime than that of low one. Besides, the largest sensing response of rGO film to 1ppm NO2 was achieved under 200-μm microporous substrate, which was 350% enhancement of that under flat one. To analyze the dynamic equilibrium of adsorption/desorption process, two kinds of measurement methods were contrastively studied. Additionally, interfering factors including operation temperature and relative humidity were probed as well. The prepared rGO/SnO2 sensors exhibited an excellent selectivity toward NO2 gas as well as a nice detection limit as low as 15.7ppb.
Graphene sponge electrodes doped with atomic boron and nitrogen were employed for electrochemical degradation of antibiotics sulfamethoxazole, trimethoprim, ofloxacin, and erythromycin. The removal ...of antibiotics that displayed strong π-π interactions (i.e., ofloxacin) with reduced graphene oxide (RGO) coating was less limited by the mass transfer and removal efficiencies > 80% were observed for the investigated range of electrolyte flowrates. At the highest applied flowrate (700 LMH), increase in the anodic current significantly worsened the removal of trimethoprim and erythromycin due to the detrimental impact of the evolving gas bubbles. Increase in current at 700 LMH led to a stepwise increase in the removal efficiency of sulfamethoxazole due to its enhanced electrosorption. Electrochemical degradation was achieved via ozone, hydrogen peroxide and hydroxyl radical (•OH). Extraction of the employed graphene sponges confirmed the degradation of the strongly adsorbing antibiotics. Identified electrochemical transformation products of erythromycin confirmed the participation of •OH, through N-demethylation of the dimethylamine group. In real tap water, removal efficiencies were lower for all target antibiotics. Lower electric conductivity of tap water and thus increased thickness of the electric double layer likely limited their interaction with the graphene sponge surface, in addition to the presence of low amounts of organic matter.
Display omitted
•Graphene sponge anode and cathode were used for electrodegradation of antibiotics.•Strong π-π interactions of antibiotics with RGO enable more complete removal.•Extraction of antibiotics from graphene sponges confirmed their electro-degradation.•Elucidation of TPs of erythromycin confirms the participation of OH•.•In tap water, low electric conductivity limits the adsorption and degradation of antibiotics.
Na‐ion Batteries have been considered as promising alternatives to Li‐ion batteries due to the natural abundance of sodium resources. Searching for high‐performance anode materials currently becomes ...a hot topic and also a great challenge for developing Na‐ion batteries. In this work, a novel hybrid anode is synthesized consisting of ultrafine, few‐layered SnS2 anchored on few‐layered reduced graphene oxide (rGO) by a facile solvothermal route. The SnS2/rGO hybrid exhibits a high capacity, ultralong cycle life, and superior rate capability. The hybrid can deliver a high charge capacity of 649 mAh g−1 at 100 mA g−1. At 800 mA g−1 (1.8 C), it can yield an initial charge capacity of 469 mAh g−1, which can be maintained at 89% and 61%, respectively, after 400 and 1000 cycles. The hybrid can also sustain a current density up to 12.8 A g−1 (≈28 C) where the charge process can be completed in only 1.3 min while still delivering a charge capacity of 337 mAh g−1. The fast and stable Na‐storage ability of SnS2/rGO makes it a promising anode for Na‐ion batteries.
A SnS2/rGO hybrid with a plate‐on‐sheet architecture exhibits a high capacity, superior cycling stability and excellent rate capability. The hybrid delivers an initial capacity of 469 mAh g−1 at 800 mA g−1 and keeps at 61% after 1000 cycles. At 12.8 A g−1 (28 C), it still yields a charge capacity of 337 mAh g−1.
As an alternative system of rechargeable lithium ion batteries, sodium ion batteries revitalize researchers’ interest due to the low cost, abundant sodium resources, and similar storage mechanism to ...lithium ion batteries. VS4 has emerged as a promising anode material for SIBs due to low cost and its unique linear chains structure that can offer potential sites for sodium storage. Herein, we present the growth of VS4 on reduced graphene oxide (rGO) as SIBs anode for the first time. The VS4/rGO anode exhibits promising performance in SIBs. It delivers a reversible capacity of 362 mAh g–1 at 100 mA g–1 and a good rate performance. We also investigate the sodium storage behavior of the VS4/rGO. Different than most transition metal sulfides, the VS4/rGO composite experiences a three-step separation mechanism during the sodiation process (VS4 to metallic V and Na2S, then the electrochemical mechanism is akin to Na–S). The VS4/rGO composite proves to be a promising material for rechargeable SIBs.
•N-doped rGO was obtained by gaseous NH3-assisted thermal treatment of rGO.•The electrocatalytic ability of N-doped rGO depends on the type of N-containing groups.•rGO sample treated with NH3 at ...950 °C for 8 h had a high content of quaternary-N.•N-doped rGO_950 showed competitive sensing performances for H2O2 and glucose detection.
This paper presents a method of simple and facile preparation of N-doped reduced graphene oxide (N-rGO), which can be applied as a metal-free electroactive electrode material for the detection of hydrogen peroxide and glucose. Two different N-rGO samples (N-rGO_850 and N-rGO_950) were obtained by gaseous NH3-assisted thermal modification of reduced graphene oxide (rGO) at temperatures of 850 °C and 950 °C for 4 and 8 h, respectively. The structural properties of the samples obtained were characterized by Raman spectroscopy, XPS, and N2 adsorption-desorption techniques. Taken together, these analyses demonstrate that, compared to the N-rGO_850 sample, N-rGO_950 possesses a considerably higher amount of quaternary nitrogen species, higher surface area, and a greater amount of structural imperfections, which contribute to its excellent electrochemical activity in the detection of H2O2 and glucose. The sensor based on N-rGO_950 displays a fast response time (∼ 6 s) to sensitive detection of H2O2, a wide linear range (0.1 – 10.7 mM), a sufficiently low limit of detection (LOD) of 26.0 μM, and a superior sensitivity (305 μA mM−1 cm−2). When the same sensor platform used in glucose detection after GOx immobilization results in LOD of 24.7 μM with a linear range of 0.01 – 3.38 mM and a sensitivity of 60.2 μA mM−1 cm−2. Moreover, the proposed (bio)sensor demonstrates satisfactory selectivity, reproducibility, repeatability, and stability.
Display omitted
Display omitted
•Electrical conductance of reduced graphene oxide-ZnO is increased by adding TiO2.•Higher conductivity is obtained with mesoporous TiO2 than with nanoparticle TiO2.•EIS suggests the ...formation of nanocapacitors on the ZnO surface layers.•The nanocapacitor dielectric is the air-containing pores of the mesoporous TiO2.•The electrode is the TiO2 which becomes conducting under UV irradiation.
Semiconducting nanocomposites were formed from layers of reduced graphene oxide (RGO) and ZnO and nanoparticle or mesoporous forms of TiO2 by dip-coating on fluorine-doped tin oxide (FTO) substrates. The effect of nanoparticle or mesoporous TiO2 on the electrical conductivity was compared. The crystalline phases and microstructures of the nanocomposites were investigated by XRD, DRS-UV, FTIR and FE-SEM, showing the layers to be homogeneous and of consistent thickness, with the TiO2 in the anatase form. The bandgaps and electrical conductivities of the nanocomposites, determined by Tauc plots and electrochemical impedance spectroscopy (EIS), show that under UV irradiation, the nanocomposites containing nanoparticle TiO2 have higher electrical conductivities than those containing mesoporous TiO2. A mechanism is suggested involving the formation of nano-capacitors on the surface of the ZnO layer, the pores in the mesoporous TiO2 acting as the dielectric and the conducting electrodes formed by UV irradiation of the TiO2.
Display omitted
•First study to detect SARS-CoV-2 in unprocessed wastewater using a biosensor.•Biosensor can detect SARS-CoV-2 in real samples with an overall agreement >86.4 %.•Biosensor is more ...sensitive than commercial rapid test in real samples.•Response time of biosensor was measured to be around 240 ms.
Quantitative RT-PCR (qRT-PCR) is the most commonly used diagnostic tool for SARS-CoV-2 detection during the COVID-19 pandemic. Despite its sensitivity and accuracy, qRT-PCR is a time-consuming method that requires expensive laboratories with highly trained personnel. In this work, on-site detection of SARS-CoV-2 in municipal wastewater was investigated for the first time. The wastewater was unprocessed and did not require any prefiltration, prior spiking with virus, or viral concentration in order to be suitable for use with the biosensor. The prototype reported here is a reduced graphene oxide (rGO)-based biosensor for rapid, sensitive and selective detection of SARS-CoV-2. The biosensor achieved a limit of detection (LOD) of 0.5 fg/mL in phosphate-buffered saline (PBS) and exhibited specificity when exposed to various analytes. The response time was measured to be around 240 ms. To further explore the capabilities of the biosensor in real clinical and municipal wastewater samples, three different tests were performed to determine the presence or absence of the virus: (i) qRT-PCR, (ii) a rapid antigen-based commercially available test (COVID-19 Test Strips), and (iii) the biosensor constructed and reported here. Taken together, our results demonstrate that a biosensor that can detect SARS-CoV-2 in clinical samples as well as unfiltered and unprocessed municipal wastewater is feasible.
Display omitted
•Conjugated polymer/rGO composites with high sensitivity to VOCs are created.•Photoirradiation facilitates nucleation and growth of polymer aggregates on rGO.•The composites show ...enhanced charge mobility and interfacial charge interactions.•Composite-based OFET sensors exhibit excellent responsivity to polar VOCs.•Rapid response/recovery behaviors are observed in the OFET sensors.
We have reported a facile approach to fabricate poly(3-hexylthiophene)/reduced graphene oxide (P3HT/rGO) composite films via the photoirradiation of the corresponding composite solutions. The films are applied to organic field-effect transistor (OFET) sensors for the high-performance detection of volatile organic compounds (VOCs). The photoirradiation of the composite solutions and the presence of rGO act synergistically to facilitate the molecular ordering of P3HT. Thus, the P3HT/rGO composite films containing 20 wt% rGO exhibit a maximized charge carrier mobility of ~0.18 cm2 V−1 s−1, which is 6-folds higher than that of pristine P3HT films. The interfacial interactions between rGO and P3HT are enhanced by the favorable π − π and electrostatic interactions following photoirradiation. The OFET sensors based on the P3HT/rGO composites consistently show enhanced sensitivity to polar VOCs (methanol, acetone, ethanol, and isopropyl alcohol) compared to those based on the pristine P3HT, photoirradiated bare P3HT, and pristine P3HT/rGO composites. In particular, the photoirradiated P3HT/rGO-based OFET sensors achieve significantly improved responsivity (~110.6%) to methanol vapors (10 ppm) under rapid on/off pulses of 60 s, compared to those based on pristine P3HT (~6.8%), photoirradiated bare P3HT (~20.8%), and pristine P3HT/rGO (~55.1%) composites. Finally, excellent response and recovery behaviors (e.g., ~15 s and ~42 s, respectively) are also observed.
To improve the photovoltaic performance of the traditional TiO2 photoanode for dye-sensitized solar cells (DSSCs), a series of layered TiO2/rGO composited DSSCs photoanode was assembled by changing ...the morphologies of the TiO2 and introducing reduced graphene oxide (rGO) into different areas of the photoanode films. Firstly, TiO2 nanoflowers (TiO2-NFs), TiO2 nanorods (TiO2-NRs) were prepared employing the hydrothermal method and used as photoanode materials to explore the synergistic effect of TiO2 with different morphologies in layered photoanode. Then, TiO2-NFs/rGO composited photoanode (TNF/rGO) were fabricated to research the mechanism of rGO on improving electron transmission in the layered photoanode. The effect of adding rGO at different parts of the layered photoanode on the performance of DSSCs was also investigated. Attributing to the enhancement of light absorption and charge transfer, a champion power conversion efficiency (η) of 9.21 % (Jsc = 23.36 mA cm−2, Voc = 0.74 V, FF = 0.53) was achieved with the layered TiO2/rGO composited photoanode containing two consecutive layers of TiO2-NFs/rGO and P25/rGO, which exhibited an 82.01 % increase than traditional TiO2 (pure P25) photoanode (η = 5.06 %, Jsc = 12.09 mA cm−2, Voc = 0.73 V, FF = 0.58). It is an effective way to design and fabrication of layered TiO2/rGO composited photoanode to regulate the photovoltaic performance of traditional TiO2 photoanode for DSSCs based on the synergistic effect of its multi-layer structure, TiO2 morphologies and introduction of rGO.
Display omitted
•Layered TiO2/rGO photoanode was constructed by TiO2 with different morphologies and reduced oxide graphene.•The dye loading, light utilization and charge transfer of TiO2 photoanode were improved in layered TiO2/rGO photoanode.•Layered photoanode with rGO exhibits improved electron transfer and smaller charge recombination.•Compared with P25 photoanode, the cell efficiency based on the layered TiO2/rGO composited photoanode increased by 82.01 %.
Nanocomposite of zinc oxide nanorods(ZnONR) and reduced graphene(RGO) oxide has been prepared and characterized by XRD, TEM, UV–vis and spectroflurometric techniques. The nanocomposite material is ...found to be an efficient photocatalyst for degradation methylene blue(MB), methyl orange(MO) and their mixture at room temperature. The electron-hole pair recombination in the prepared material has been decreased as observed from photoluminescence(PL) spectral study. The excitation of both ZnONR and methylene blue occurs during photodegradation and the generated electrons are transferred to the RGO. The oxidation of dyes occurs by path I and path II as a result excitation of MB and ZnONR respectively and these electrons are transfereed to the RGO. The excitation of MB during leads to the photodegradation MO in absence of composite through path I as evidenced by its PL spectra.
