rGO Layers Research Articles

Reduced Graphene Oxide/Silica Based Electrode Material: Synthesis and Characterization

<span lang="EN-US">Developing a Reduced Graphene Oxide (rGO) synthesis method based on rice husk as a composite electrode material with silica has garnered particular attention for designing high-quality electrode materials. This research successfully synthesized rGO-Si material from rice husk-derived activated carbon through a one-step thermal reduction process at 200 °C. This method offers a simple, efficient, cost-effective, and environmentally friendly synthesis approach. The resulting samples' morphology, surface composition, crystal structure, surface area, and pore diameter size were characterized using FE-SEM, EDX, XRD, and SAA-BET. EDX characterization results confirmed the predominance of carbon content in the samples. At the same time, the natural emergence of Si without external addition due to thermal reduction at 200 °C was an intriguing initial finding. The spherical crystal structure of silica between the wrinkled rGO layers was confirmed through FE-SEM and XRD analysis. The synergistic effect between Si and rGO significantly increased the sample's surface area, with a value of 34.17 m<sup>2</sup>/g for the rGO sample before thermal reduction, which increased to 121.24 m<sup>2</sup>/g after the thermal reduction process at 200 °C. This process also positively impacted the reduction in pore size of rGO-Si, with a value decreasing from 9.33 nm before thermal reduction to 4.89 nm after the thermal reduction process. The results of this study demonstrate that rGO-Si synthesized from rice husk-derived activated carbon holds great potential as a high-performance electrode material, combining the advantages of thermal reduction, natural Si content, and increased surface area for diverse applications.</span>

Insights into the Hydration Layer of Reduced Graphene Oxides: A Computational Stud.

Reduced graphene oxide (rGO) has emerged as a versatile material with diverse applications, particularly in aqueous environments. Understanding its interactions with water molecules is crucial for various fields, ranging from energy storage to sensing. In this study, we investigate the behavior of graphene and rGO in water, focusing on elucidating their wetting properties and the influence of oxygen-containing functional groups. Through extensive molecular dynamics simulations, we analyze the orientation and electrostatic dipole of water molecules near the rGO interface, revealing a direct correlation between rGO hydrophilicity and oxidation level. Specifically, we observe stronger hydrogen bonding networks near higher coverage rGO monolayers, indicating enhanced hydrophilicity. Furthermore, by studying water confined between rGO layers, we find uniform water transport with lateral self-diffusion coefficients comparable to bulk water, highlighting the potential of rGO membranes in various applications. Our findings provide insights into the atomic-scale interactions governing rGO-water interfaces, paving the way for the rational design of graphene-based materials for application in aqueous environments.

Improvement of the hydrogen evolution reaction and photocatalyst activity of ZiF-8 coated with RGO

The need for sustainable energy production is critical because of the considerable impact on the environment associated with the use of fossil fuels. In this study, we examine the physicochemical properties, photocatalytic performance, and electrochemical hydrogen evaluation of ZiF-8 coated with RGO, which were prepared using the ultrasonication method. All samples were examined with x-ray diffraction and exhibited a cubic phase. With an increase in RGO concentrations, the direct optical bandgap transition experienced a decline from 5.6 to 3.62 eV. As the concentration of RGO increased, a higher quantity of RGO was added resulting in the formation of a single layer of amorphous RGO on the surface. This layer of amorphous RGO played a key role in enhancing the electronic conductivity of the samples. The RGO coating effect on the photocatalytic performance since the efficiency of dye removal increased from 67% to 99% in 120 minutes. ZiF-8 combined with 8% RGO (ZiF-8@8%RGO) has a noticeably smaller arc radius compared to pure ZIF-8 and ZIF-8 with 4% RGO. The pure ZiF-8 is a typical n-type semiconductor. The ZiF-8@8%RGO demonstrated the highest rate of hydrogen evolution. These results suggest the feasibility of using ZiF-8@8%RGO for photoelectrochemical hydrogen generation.

Covalently linked 4-Aminopyridine on reduced graphene oxide for high performance electrochemical supercapacitor electrode material

The portability of electrical devices requires the demanding but essential task of improving supercapacitor energy density while preserving stability. Introducing an amine heterocyclic compound on a reduced graphene oxide (rGO) layer can enhance its capacity for energy storage. Here, we employed Catharanthus roseus flower extract as a green reducing agent to prepare rGO for the first time. A stable covalently linked 4-AP-rGO was produced through combining of 4-Aminopyridine on the rGO layer via nucleophilic substitution reaction process. The synthesized materials were systematically characterized by FT-IR, UV–visible, Raman, powder XRD, XPS, SEM, and TEM. Furthermore, the screen-printed carbon electrode (SPCE) was modified with 4AP-rGO (4AP-rGO/SPCE) to evaluate the electrochemical properties using CV, GCD, and EIS in 1 M H2SO4. The electrochemical performance of the 4AP-rGO/SPCE modified electrode was compared with unfunctionalized rGO. The pseudocapacitive efficacy of the 4AP-rGO was exceptional as evidenced by its high energy density (12.27 × 10−4 Wh kg−1), high power density (350.6 × 10−3 W kg−1), and high specific capacitance of (180.3 × 10−3 F g−1) at 1 A g-1. Over 10,000 cycles at 1 A g-1, it maintained 98.8 % capacitance, exhibiting exceptional cycling stability. The energy density of 4-AP-rGO is 2.1 times higher than that of rGO, indicating that it is a suitable candidate for energy storage applications.

Increasing the efficiency of CIGS solar cells due to the reduced graphene oxide field layer of the back surface

Copper indium gallium selenide solar cells (CIGS-SCs) have gained attention due to their cost-effectiveness and environmentally friendly characteristics, making them a promising option for future electricity generation. The efficiency of CIGS-SCs can be enhanced by adding a back surface field layer (BSFL) under the absorber layer to reduce recombination losses. In this study, the electrical parameters, such as the series resistance, shunt resistance, and ideality factor, are calculated for CIGS-SCs with an advanced design, using the SC capacitance simulator (SCAPS) software. The detailed model used in the simulations considers the material properties and fabrication process of BSFL. By utilizing a reduced graphene oxide (rGO) BSFL, a conversion efficiency of 24% and a significant increase in the fill factor are predicted. This increase is primarily attributed to the ability of the rGO layer to mitigate the recombination of charge carriers and establish a quasi-ohmic contact at the metal-semiconductor interface. At higher temperatures, BSFL can become less effective due to an increased recombination and, in turn, a decreased carrier lifetime. Overall, this study provides valuable insights into the underlying physics of CIGS-SCs with BSFL and highlights the potential for improving their efficiency through advanced design and fabrication techniques.

Influence of reduced graphene oxide layer on sensing characteristics of Co3O4/rGO nanocomposite towards Liquefied Petroleum Gas (LPG)

Liquefied petroleum gas (LPG), a mixture of different hydrocarbons, is a highly inflammable and explosive gas that is harmful to the environment and human health. Thus, it is imperative to fabricate LPG sensors with higher sensitivity, selectivity, stability, and minimal power consumption, functioning at low temperatures. The current study reports on the monitoring and detection of LPG at low functional temperatures using Co3O4-loaded on rGO (rGO-Co) prepared using the hydrothermal method. The microstructural properties of the materials were investigated in detail. The rGO-Co (80 wt%) sensor showed outstanding sensitivity (0.00364 ppm−1) and selectivity toward LPG, as well as a limit of detection of 1 ppm at a temperature of 125 °C. The sensing mechanism showed that an even distribution of Co3O4 throughout the rGO layers, serving as efficient sites for the adsorption and desorption of LPG molecules, was associated with enhanced gas-sensing capabilities. Furthermore, the response to LPG detection was significantly influenced by the combination of the finite spherical nanoparticles with increased pore sizes between them and reduced energy band gaps. Thus, the novel improvement of the sensor towards LPG detection was linked to the ohmic connection formed between rGO and Co3O4 forming a p-p heterojunction at the interface. Additionally, the coupling of Co-O-C bonds validated by high-temperature X-ray diffraction and X-ray photoelectron spectroscopy provided extra active sites from Co3+ for effective LPG adsorption. The sensing mechanism induced by the loading of Co3O4 on the rGO surface was also deliberated.

Janus-structured graphene scaffold for bottom-up lithium deposition: A progressive gradient approach

Graphene-based materials have been explored as hosts for Li metal anodes, but their high interfacial activity and short diffusion distances frequently result in dendrite formation on the surface. Herein, we utilize the adjustable conductivity and Li affinity of graphene oxide (GO) to develop a Janus structure comprising a top GO layer and a bottom reduced graphene oxide (rGO) layer. The progressive conductivity and lithiophilicity gradient structure of GO/rGO enables a bottom-up Li deposition mode, rendering an average Coulombic efficiency of 99.1 % over 350 cycles at 1 mA cm−2 and 1 mAh cm−2. Full cells equipped with a LiFePO4 cathode maintain a capacity retention of 85 % after 350 cycles at 1 C. This innovative approach provides fresh insights into the development of graphene-based hosts, offering significant potential for future Li metal battery applications.

Core-shell like rGO coated Co9S8 hollow dodecahedron for enhanced oxygen evolution reaction

The development of low-cost, high-activity, high-durability non-precious metal OER electrocatalysts is still the most critical bottleneck for the preparation of clean-energy by water splitting. In this thesis, the Co9S8@rGO heterogeneous interface was constructed to optimize the electron transport pathway and enhance the active site to improve the OER activity. The ZIF-67 dodecahedron was used as a template to prepare Co9S8 with a hollow dodecahedron structure using the hydrothermal method and annealing treatment to shorten the charge transport path and increase its specific surface area. Subsequently, a protective shell layer of rGO with good conductivity and stability was wrapped around the Co9S8 catalyst core by the construction of a Co9S8@rGO core-shell heterostructure. It was found that the 30 % Co9S8@rGO core-shell heterostructure not only reduced the overpotential (190 mV at 10 mA cm−2) and tafel slope (66.48 mV dec−1) but also improved the stability compared to Co9S8. The density of states and the Gibbs free energy of HO*, O* and HOO* intermediates of Co9S8@rGO were investigated by first-principles theoretical calculations according to density functional theory (DFT). The DFT calculation results showed that the Gibbs free energy (ΔG30) of Co9S8@rGO core-shell heterostructure was lower than that of Co9S8 in the rate-control step, which leaded to the decrease of overpotential and was beneficial to the OER reaction.

On the charge transport mechanism and the dielectric behavior of Fe-doped SnO2/rGO heterostructure

Graphene Oxide (GO) was associated to Fe-doped SnO2 nanoparticles (NPs) through a simple elaboration method to obtain Fe-doped SnO2/reduced graphene oxide (rGO) nanostructure. The effect of GO content on the structural, morphology, transport and dielectric properties of the SnO2/rGO nanocomposite was deeply investigated. X-ray diffraction (XRD) patterns depict the obtention of SnO2 rutile structure and revealed an effect of the NPs size the rGO layer to layer distance. However, transmission electron microscopy (TEM) exploration shows the formation of rGO nanospheres co-present with Fe-doped SnO2 NPs. The electrical properties of the obtained structure were examined through impedance analysis. The conductivity of the SnO2:Fe/rGO nanocomposite obviously increases with the GO amount. The analysis of the relaxation phenomenon shows an abrupt decrease of the relaxation time upon GO addition. A charge carriers transfer is suggested to occur between Fe-doped SnO2 NPs and rGO for high graphene oxide concentrations. Hydrogen bonds are suggested to be established between these NPs and rGO. The functional groups at the NPs/rGO interface were found to considerably contribute to the dielectric response of the heterostructure. Dielectric losses were also evaluated and are suggested to be particularly affected by the rGO functional groups. The explored electric and dielectric properties present the SnO2:Fe/rGO heterostructure as a potential candidate for supercapacitor and electrical battery electrodes.

Preparation and electrochemical properties of flexible self-supported graphene/silicon/carbon nanotube composite electrode for lithium-ion battery

To meet the demand of flexible devices, it was urgent to develop flexible high-capacity electrodes for lithium-ion batteries (LIBs). Silicon (Si) as an active material would effectively elevate the specific capacity of LIBs, but the drastic volume changes and low intrinsic conductivity seriously affected its electrochemical performance during the charge-discharge process. In this research, a new type of composite was designed using two-dimensional reduced graphene oxide (rGO), one-dimensional carbon nanotubes (CNTs), and silicon nanoparticles (Si NPs) as raw materials. The prepared rGO/Si/CNTs composite had an intricate and intersecting porous network structure inside, with rGO as the substrate, CNTs as a bridge, and Si NPs as the active material. The rGO would provide abundant attachment sites for Si NPs, improve electrode conductivity, and alleviate the volume change of electrode. CNTs can effectively suppress the stacking of rGO layers and generate more voids for the reaction, and also serve as a bridge for electron transfer between rGO layers. Furthermore, the interaction between each other also heightened the flexibility and strength of electrodes. Compared to the other composites, rGO/Si/CNTs=2:2:1 electrodes presented the superior electrochemical performance. When cycled at 200 mA g−1, its discharge capacity was 2217.2 mAh g−1 after 200 cycles. As the current density increasing to 1000 and 5000 mA g−1, the discharge capacity maintained at 1877.2 and 534.8 mAh g−1 for 1000th cycle, and it also demonstrated superior rate performance. Besides, the assembled flexible battery maintained a good current output under various bending conditions, and was expected to be widely used in the flexible wearable energy storage devices.

Tungsten, copper and cobalt-single metal atom oxides embedded CeO2-MnO2-rGO nanorods as electrocatalysts for efficient oxygen evolution reaction

BackgroundAn important aspect of energy conversion and storage technology is primarily based on the electrocatalytic oxygen evolution process (OER). MethodHere, we present the newly designed synthesis of an improved variety of WCuCo-CeO2-MnO2-R-3 nanocomposites, to enhance OER by incorporating the reduced graphene oxide (rGO), and SMAO of W, Cu, and Co with the nanorods of CeO2-MnO2 materials. Interestingly, the higher density of SMAO (W, Cu, and Co), atomic utilization and electron transfer layer of rGO influenced the CeO2-MnO2 nanorods with remarkably superior electrocatalytic OER activity. Significant findingsThis makes WCuCo-CeO2-MnO2-R-3 achieve 10 mA cm-2 with an overpotential of 275 mV and a lower Tafel slop of 64.46 mV dec‑1. The higher number of SMAO (W, Cu, and Co) species close to the catalyst surface served as potential active sites assembly to enhance the OER activity by improving the chemical and electrochemical steps during the OER process. The chronoamperometry test revealed that the WCuCo-CeO2-MnO2-R-3 nanocomposite is not degrade in a 1 M KOH solution for 24 h, and it is stable up to 2000 CV cycles. In order to create very effective catalysts for OER, the DFT theoretical results shed light on the connection between the catalytic characteristics of metal oxide structures and their inherent electronic configuration.

Intelligent process monitoring of smart polymer composites using large area graphene coated fabric sensor.

Herein, we report the development of an online process monitoring system for vacuum-assisted resin transfer molding (VARTM) process using large area graphene coated in-situ fabric sensor. Besides imparting excellent mechanical properties to the final composites, these sensors provide critical information during the composite processing including detecting defects and evaluating processing parameters. The obtained information can be used to create a digital passport of the manufacturing phase to develop a cost-effective production technique and fabricate high-quality composites. The fabric sensor was produced using a scalable dip-coating process by coating 1-, 3- or 5-layers of thermally reduced graphene oxide (rGO) onto glass fabric surface according to the number of dips of the fabrics into GO solution. The electrical resistances from all electrode pairs were simultaneously and continuously recorded during distinct stages of the VARTM process to determine the relative conductance. During the vacuum cycle, the range of relative conductance increased with the number of coated rGO layers, with the 5-layer rGO-coated sensor showing the highest conductance range of 16.9 %. Additionally, it was observed that the 5-layer coated sensor showed a consistent decrease in conductance during the infusion phase due to the fluid flow pressure dominating the resin electrical conductivity.

Janus graphene oxide membrane with rational allocation of functional regions as unidirectional ion valve system

Membrane-based ion sieving is critical to green desalination processes such as sustainable ionic resource extraction. Two-dimensional (2D) graphene oxide (GO) membranes exhibit unique ionic transport properties owning to the supernormal enhancement of channel effects induced by diverse functional regions under nanoconfinement. However, the discrete and random distribution of the hydrophilic/hydrophobic and positively/negatively charged regions restricts the GO membrane to give full play to its potential in selective ions separation. Herein, a novel strategy is proposed to engineer the asymmetric three-tier architecture of a Janus GO membrane with rational allocation of functional regions. The wise series connection of ① surface positively charged hydrophilic layer of PEI, ② intermediate negatively charged hydrophilic layer of GO and ③ bottom hydrophobic porous layer of rGO along the cross-membrane direction established internal gradients of structure, wetting and charge, resulting in reinforced exclusion of retained divalent ions and reduced stagnation of targeted monovalent ions. Based on the continuous anisotropic gradients, the Janus GO membrane was endowed with the unique capability to act as a unidirectional ion valve system, showcasing impressive permeation performance of monovalent ions permeation rate of 0.244 mol m−2 h−1 with monovalent/divalent ions selectivity of 66.1, and remarkable nanofiltration performance of divalent salt rejections of >96.5 % with monovalent/divalent ions separation factor up to 70.9. The implications of this work will revolutionize the regulation and functionalization of 2D nanofluidic channels for selective ions transport, which is highly desirable for a wide range of green desalination applications.

Enhanced Ethanol Gas Sensor Performance through Adsorption Energy Analysis of Gd-Doped LaFeO3 with rGO Coating: A Density Functional Theory Study

LaFeO3 (LFO) is commonly used as a material for gas sensor applications. However, the LFO material in ethanol gas sensor applications can still improve sensitivity and selectivity parameters. Gadolinium (Gd) doping is widely used in gas sensor applications to increase the sensitivity of gas sensors. In addition, reduced graphene oxide (rGO) materials are commonly used in gas sensor applications to increase gas sensors' selectivity, sensitivity, and working temperature. This study analyzed the effect of Gd doping (LGFO) and the addition of an rGO single layer on LFO material (LGFO@rGO) on sensitivity and selectivity based on the adsorption energy of the system with ethanol gas molecules. Density Functional Theory studies were conducted to yield insight into the LGFO or LGFO@rGO – ethanol gas interactions and the sensitivity and selectivity improvement by changing adsorption energy. Based on the analysis, the presence of Gd doping and single-layer rGO could increase the adsorption energy. The addition of the rGO layer showed an escalation of the adsorption energy of about 9.45%, 2.49 eV in the LGFO to -2.75 eV LGFO@rGO. This improved adsorption capacity translates to a higher sensitivity for detecting lower concentrations of ethanol gas. This result shows the potential of LGFO and LGFO@rGO as ethanol gas sensor materials.

Light-driven rGO/Cu2 + 1O tubular nanomotor with active targeted drug delivery for combination treatment of cancer cells.

The unprecedented navigation ability in micro/nanoscale and tailored functionality tunes micro/nanomotors as new target drug delivery systems, openup new horizons for biomedical applications. Herein, we designed a light-driven rGO/Cu2 + 1O tubular nanomotor for active targeting of cancer cells as a drug delivery system. The propulsion performance is greatly enhanced in real cell media (5% glucose cells isotonic solution), attributing to the introduction of oxygen vacancy and reduced graphene oxide (rGO) layer for separating photo-induced electron-hole pairs. The motion speed and direction can be readily modulated. Meanwhile, doxorubicin (DOX) can be loaded quickly on the rGO layer because of π-π bonding effect. The Cu2 + 1O matrix in the tiny robots not only serves as a photocatalyst to generate achemical concentration gradient asthe driving force but also acts as ananomedicine to kill cancer cells as well. The strong propulsion of light-driven rGO/Cu2 + 1O nanomotors coupled with tiny size endow them with active transmembrane transport, assisting DOX and Cu2 + 1O breaking through the barrier of thecell membrane. Compared with non-powered nanocarrier and free DOX, light-propelled rGO/Cu2 + 1O nanomotors exhibit greater transmembrane transport efficiency and significant therapeutic efficacy. This proof-of-concept nanomotor design presents an innovative approach against tumor, enlarging the list of biomedical applications of light-driven micro/nanomotors to the superficial tissue treatment.

In situ oxidation of reduced graphene oxide membranes by peracetic acid for dye desalination

Graphene oxide (GO) membranes with tunable interlayer spacings are of interest for dye removal from salty textile wastewater, and the membranes are often reduced to improve their stability, which inevitably lowers water permeance. Herein, we demonstrate that reduced GO (rGO) membranes can be facilely modified using peracetic acid (PAA) in situ to dramatically enhance water permeance while retaining dye rejection. Specifically, PAA-modified membranes (PrGO) are synthesized by vacuum-filtering hydrazine-reduced rGO nanosheets onto Nylon substrate and then exposing them to PAA solutions. The effects of the rGO layer thickness, PAA content, and PAA exposure time on the membrane chemistry, nanostructures, and salt/dye separation properties are thoroughly examined. For example, the PAA oxidation of a 100 nm-thick rGO membrane for 10 min increases water permeance by 180 %, from 35 to 93 Liter m−2 h−1 bar−1, and decreases Na2SO4 rejection from 10 % to 3.3 % while retaining the rejection of Congo red at ≈99.7 %. The PrGO membranes exhibit stable water permeance and >99 % dye rejection in multi-cycle tests in a crossflow system, surpassing state-of-the-art GO membranes and showcasing their potential for practical applications.

Synthesis of reduced graphene oxide and Nickel oxide/reduced graphene oxide composite materials for supercapacitor applications and their computational investigations

This study outlines the synthesis of reduced graphene oxide (rGO) and Nickel oxide/reduced graphene oxide (NiO/rGO) composite materials without the use of binders. The synthesis method involved microwave-assisted reduction using ascorbic acid (AA) and varying weight ratios of potassium hydroxide (KOH) to convert graphene oxide (GO) to rGO. The research investigates how adjusting the weight ratios of GO and KOH influences the electrical conductivity (EC) properties of the synthesized materials, particularly exploring the impact of KOH addition on the porosity growth in the rGO layers during fabrication. Various analytical techniques, including optical, vibrational, morphological, bonding, and network analysis, were employed to characterize the synthesized materials. The materials were evaluated as potential supercapacitor electrodes using electrochemical techniques such as cyclic voltammetry and A.C. impedance analysis, including Nyquist and Bode plots. The specific capacitance (CS) of rGO and NiO/rGO was determined to be 1400 Fg−1 at a scan rate of 0.005 Vs−1. The synthesis process avoided the use of hazardous reagents. Additionally, density functional theory (DFT) based computational analysis was conducted to support the experimental findings. The study documents the influence of incorporating NiO onto the surface of GO and rGO on the energy gap (Egap) and investigates the density of state (DOS) to understand the effect of MO-rGO interaction. Furthermore, frontier molecular orbital (FMO) contours were examined to analyze excitation qualities, and electron potential was visualized and mapped onto the electron density surface to gain insights into charge dispersion within the structures.

Covalently Linking Reduced Graphene Oxide Facilitated Electrodeposition of MoS2 on Silicon Pyramidal Photocathode To Enhance Hydrogen Evolution.

In recent years, increasing attention has been paid to photoelectrochemical (PEC) hydrogen production owing to the utilization of sustainable solar energy and its promising performance. Silicon-based composites are generally considered ideal materials for PEC hydrogen production. However, slow reaction kinetics and poor stability are still key factors hindering the development of silicon-based photoelectrocatalysts. Herein, we present an n+-p Si pyramidal photocathode assembly method to load reduced graphene oxide (rGO) onto the surface of the n+-p Si pyramid by covalently linking (Si/rGO). rGO is utilized as a conductive layer to reduce the interfacial charge-transfer resistance. Then, MoS2 can be successfully electrodeposited on the surface of Si/rGO to form the Si/rGO/MoS2 composite, which possesses excellent PEC hydrogen evolution performance with a high and stable photocurrent of -41.6 mA cm-2 and a hydrogen evolution rate of about 18.1 μmol min-1 cm-2 under 0 V (vs RHE). The covalently linking rGO layer effectively enhances the transfer of photogenerated carriers between the Si substrate and MoS2. MoS2 provides abundant hydrogen evolution active sites, which accelerate the surface reaction kinetics, as well as a protective layer for the Si pyramidal array structure. This work provides a low-cost, convenient, and efficient way of preparing silicon-based photocathodes.

Synergistic Enhancement Effect of Ag/rGO as SERS Platform for Capture and Trace Detection of Fenvalerate Molecules

Surface-enhanced Raman scattering (SERS) provides an alternative rapid detection method for pesticide residues in food, but fenvalerate possesses poor affinity to the novel metal substrate, thus restricting its analysis. To break this bottleneck, a SERS-active platform with an Ag/rGO composite structure was engineered using a facile method for fenvalerate detection. Ag nanoparticles with a 60 nm diameter can grow evenly on the top and bottom of rGO layers under intense ultrasonic oscillation, and rGO in hybrid material acts as an ideal hotspot holder between the gaps of Ag nanoparticles, not only allowing the interaction area to be enhanced both electromagnetically and chemically but also enabling the capture and enrichment of fenvalerate pesticide molecules into the “hotspot” area to improve detection sensitivity. Ag/rGO composite substrate possesses superior SERS performance with an ultralow detectable concentration of 4-aminothiophenol (10−10 M) and good reproducibility, endowing the material with a better enhancement effect than pure Ag nanoparticles. When used as the SERS substrate for fenvalerate detection, Ag/rGO composite material showed excellent performance in both experiments and theoretical calculation, with the limit of detection (LOD) of fenvalerate being as low as 1.69 × 10−5 mg/kg and a detection model with an R2 of 99.2%, demonstrating its exciting potential as a SERS substrate for pesticides detection.

Using Sandwiched Silicon/Reduced Graphene Oxide Composites with Dual Hybridization for Their Stable Lithium Storage Properties.

Using silicon/reduced graphene oxide (Si/rGO) composites as lithium-ion battery (LIB) anodes can effectively buffer the volumetric expansion and shrinkage of Si. Herein, we designed and prepared Si/rGO-b with a sandwiched structure, formed by a duple combination of ammonia-modified silicon (m-Si) nanoparticles (NP) with graphene oxide (GO). In the first composite process of m-Si and GO, a core-shell structure of primal Si/rGO-b (p-Si/rGO-b) was formed. The amino groups on the m-Si surface can not only hybridize with the GO surface to fix the Si particles, but also form covalent chemical bonds with the remaining carboxyl groups of rGO to enhance the stability of the composite. During the electrochemical reaction, the oxygen on the m-Si surface reacts with lithium ions (Li+) to form Li2O, which is a component of the solid-electrolyte interphase (SEI) and is beneficial to buffering the volume expansion of Si. Then, the p-Si/rGO-b recombines with GO again to finally form a sandwiched structure of Si/rGO-b. Covalent chemical bonds are formed between the rGO layers to tightly fix the p-Si/rGO-b, and the conductive network formed by the reintroduced rGO improves the conductivity of the Si/rGO-b composite. When used as an electrode, the Si/rGO-b composite exhibits excellent cycling performance (operated stably for more than 800 cycles at a high-capacity retention rate of 82.4%) and a superior rate capability (300 mA h/g at 5 A/g). After cycling, tiny cracks formed in some areas of the electrode surface, with an expansion rate of only 27.4%. The duple combination of rGO and the unique sandwiched structure presented here demonstrate great effectiveness in improving the electrochemical performance of alloy-type anodes.