Structural Evolution of Hydrothermally Derived Reduced Graphene Oxide

Evaluation of reduced graphene oxide from cotton waste as an efficient phenol adsorbent in aqueous media

The elimination of organic substances, such as phenol, in conventional and biological processes, has been considered a challenge for the petroleum industry. In this work, reduced graphene oxide (rGO), obtained from cellulosic biomass (CB-rGO), as cotton waste, was employed as a phenol adsorbent in an aqueous solution simulating refinery effluent. The CB-rGO was characterized using HRTEM, Raman, XRD, FTIR, BET, and zeta analysis. The behavior of variables such as pH, contact time, temperature, CB-rGO mass, and adsorbate concentration on the characteristics of the adsorption process were continuously investigated. These parameters of the adsorption process were evaluated across a range of adsorbent concentrations from 100 to 300 mg/L, pH in the range of 2-11, adsorbent mass 5-25 mg, contact time of 0-180 min, and temperature of 20-60 °C. The adsorption isotherm data were better described by the Freundlich equation compared to the Langmuir and Sips models, despite the small difference in R2 values. Mechanism diffusion was analyzed using the Boyd model and confirmed to be the rate-limiting step in the adsorption process. The endothermic nature of this CB-rGO adsorption process with phenol was confirmed by verifying the thermodynamic data. This successful removal of phenol from synthetic effluents highlights the promising potential of this adsorbent obtained from an industrial residue and being an ecologically more sustainable alternative compared to the synthesis of other materials identified to remove this contaminant.

'Donor-acceptor', 'interpenetrating polymer network' and 'electrostatic self-assembly' work in tandem to achieve extraordinary specific shielding effectiveness

The exploration of 'electrostatic self-assembly' on solid surfaces has garnered significant interest across various fields. With the sophistication of gadgets, managing electromagnetic interference (EMI) from stray signals, especially in stealth applications, necessitates materials that can absorb microwaves. A promising approach involves integrating lightweight self-healing polymeric materials. This study employs electrostatic self-assembly to design a carbon nanotube structure on an interpenetrating polymer network (IPN) made of PVDF and bismaleimide (BMI)-grafted dopamine hydrochloride, enhancing mechanical integrity through well-formed IPNs. Graphene oxide (GO) is introduced before IPN formation to facilitate an 'acceptor-donor' interaction via the Diels-Alder adduct between BMI and GO, which binds with multi-walled carbon nanotubes (MWCNTs). MWCNTs, modified with PQ7 or PDDA for a positive charge, self-assemble onto the IPN-GO construct, creating a lightweight and chemically stable structure capable of absorbing electromagnetic radiation. The 21 μm thick construct exhibits enhanced microwave absorption within the X-band (8.2-12.4 GHz), with a specific shielding effectiveness of 8637 dB cm2 g-1 and a green index (gs ≈ 1.41). The construct is coated with self-healable polyetherimide (PEI) containing exchangeable disulfide bonds to address maintenance challenges, providing heat-triggered self-healing properties. These innovative structures offer solutions for 5G and IoT applications where lightweight, durable, and multifunctional properties are essential for effectively shielding electronic devices from stray signals.

Modulation of Interlayer Nanochannels via the Moderate Heat Treatment of Graphene Oxide Membranes

In response to the phenomenon of interlayer transport channel swelling caused by the hydration of oxygen-containing functional groups on the GO membrane surface, a moderate heat treatment method was employed to controllably reduce the graphene oxide (GO) membrane and prepare a reduced GO composite nanofiltration membrane (mixed cellulose membrane (MCE)/ethylenediamine (EDA)/reduced GO-X (RGO-X)). The associations of different heat treatment temperatures with the hydrophilicity, interlayer structure, permeability and dye/salt rejection properties of GO membranes were systematically explored. The results indicated that the oxygen-containing groups of the GO membrane were partially eliminated after heat treatment, and the hydrophilicity was weakened. This effectively weakened the hydration between the GO membrane and the water molecules and inhibited the swelling of the oxidized graphene membrane. In the dye desalination test, the MCE/EDA/RGO membrane exhibited an ultra-high rejection rate of over 97% for methylene blue (MB) dye molecules. In addition, heat treatment increased the structural defects of the GO membrane and promoted the fast passage of water molecules via the membrane. In pure water flux testing, the water flux of the membrane remained above 46.58 Lm-2h-1bar-1, while the salt rejection rate was relatively low.

Comparative performance analysis of mussel-inspired polydopamine, polynorepinephrine, and poly-α-methyl norepinephrine in electrochemical biosensors

Polydopamine (PDA) has garnered significant interest for applications in biosensors, drug delivery, and tissue engineering. However, similar polycatecholamines like polynorepinephrine (PNE) with additional hydroxyl groups and poly-α-methylnorepinephrine (PAMN) with additional hydroxyl and methyl groups remain unexplored in the biosensing domain. This research introduces three innovative biosensing platforms composed of ternary nanocomposite based on reduced graphene oxide (RGO), gold nanoparticles (Au NPs), and three sister polycatecholamine compounds (PDA, PNE, and PAMN). The study compares and evaluates the performance of the three biosensing systems for the ultrasensitive detection of Mycobacterium tuberculosis (MTB). The formation of the nanocomposites was meticulously examined through UV-Visible, Raman, XRD, and FT-IR studies with FE-SEM and HR-TEM analysis. Cyclic voltammetry and differential pulse voltammetry measurements were also performed to determine the electrochemical characteristics of the modified electrodes. Electrochemical biosensing experiments reveal that the RGO-PDA-Au, RGO-PNE-Au, and RGO-PAMN-Au-based biosensors detected target DNA up to a broad detection range of 0.1 × 10-8 to 0.1 × 10-18 M, with a low detection limit (LOD) of 0.1 × 10-18, 0.1 × 10-16, and 0.1 × 10-17 M, respectively. The bioelectrodes were proved to be highly selective with excellent sensitivities of 3.62 × 10-4 mA M-1 (PDA), 7.08 × 10-4 mA M-1 (PNE), and 6.03 × 10-4 mA M-1 (PAMN). This study pioneers the exploration of two novel mussel-inspired polycatecholamines in biosensors, opening avenues for functional nanocoatings that could drive further advancements in this field.

Dual-potential ratiometric electrochemiluminescence based on single emitter and single coreactant for the sensitive detection of carcinoembryonic antigen

Dual-potential ratiometric electrochemiluminescence (ECL) is in favor of resistance to environmental interference. However, two kinds of emitters or coreactants, and a wide scan potential range (>2 V) are mandatory. This work developed a new dual-potential ratiometric ECL sensor for detection of carcinoembryonic antigen (CEA) using single emitter (luminol) and single coreactant (H2O2) with a mild potential range from -0.1 to 0.6 V. Luminol could produce a strong cathodic ECL (Ec) induced by hydroxyl radicals (HO‧) from the reduction of H2O2, and a relatively weak anodic ECL (Ea). After the ferrocene modified CEA aptamer (Apt-Fc) was attached, Fc could promote Ea by catalyzing the oxidation of H2O2, and reduce Ec by consuming HO‧. With the cycling amplification of the exonuclease I, CEA could substantially reduce the amount of Apt-Fc, resulting in the decrease of Ea and the rise of Ec. So, the ratio of Ec to Ea (Ec/Ea) was used as the detection signal, realizing the sensitive determination of CEA from 0.1 pg mL-1 to 10 ng mL-1 with a LOD of 41.85 fg mL-1 (S/N = 3). The developed sensor demonstrated excellent specificity, stability and reproducibility, with satisfactory results in practical detection.

Preparation of nanocellulose/reduced graphene oxide matrix loaded with cuprous oxide nanoparticles for efficient catalytic reduction of 4-nitrophenol

The paper reports on the preparation of cellulose nanocrystals/reduced graphene oxide matrix loaded with cuprous oxide nanoparticles (CNC/rGO-Cu2O) through a simple solvothermal method and its application for 4-nitrophenol reduction to 4-aminophenol using sodium borohydride. The CNC/rGO-Cu2O nanocomposite was formed chemically by first mixing CNC and graphene oxide (GO) followed by complexation of the negatively charged functional groups of CNC/GO with Cu2+ ions and subsequent heating at 100°C. This resulted in the simultaneous reduction of GO to rGO and the formation of Cu2O nanoparticles. The as-elaborated nanocomposite was firstly characterized using different techniques such as atomic force microscopy, scanning electron microscopy, transmission electron microscopy, UV-Vis spectrophotometry, Raman spectroscopy and x-ray photoelectron spectroscopy. Then, it was successfully applied for efficient catalytic reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride: the reduction was completed in about 6 min. After eight times use, the catalyst still maintained good catalytic performance. Compared to CNC/rGO, rGO/Cu2O and free Cu2O nanoparticles, the CNC/rGO-Cu2O nanocomposite exhibits higher catalytic activity even at lower copper loading.

Scaly MoS2/rGO Composite as an Anode Material for High-Performance Potassium-Ion Battery

Potassium-ion batteries (PIBs) have been widely studied owing to the abundant reserves, widespread distribution, and easy extraction of potassium (K) resources. Molybdenum disulfide (MoS2) has received a great deal of attention as a key anode material for PIBs owing to its two-dimensional diffusion channels for K+ ions. However, due to its poor electronic conductivity and the huge influence of embedded K+ ions (with a large ionic radius of 3.6 Å) on MoS2 layer, MoS2 anodes exhibit a poor rate performance and easily collapsed structure. To address these issues, the common strategies are enlarging the interlayer spacing to reduce the mechanical strain and increasing the electronic conductivity by adding conductive agents. However, simultaneous implementation of the above strategies by simple methods is currently still a challenge. Herein, MoS2 anodes on reduced graphene oxide (MoS2/rGO) composite were prepared using one-step hydrothermal methods. Owing to the presence of rGO in the synthesis process, MoS2 possesses a unique scaled structure with large layer spacing, and the intrinsic conductivity of MoS2 is proved. As a result, MoS2/rGO composite anodes exhibit a larger rate performance and better cycle stability than that of anodes based on pure MoS2, and the direct mixtures of MoS2 and graphene oxide (MoS2-GO). This work suggests that the composite material of MoS2/rGO has infinite possibilities as a high-quality anode material for PIBs.

Dual-Defect Engineering Strategy Enables High-Durability Rechargeable Magnesium-Metal Batteries

Rechargeable magnesium-metal batteries (RMMBs) are promising next-generation secondary batteries; however, their development is inhibited by the low capacity and short cycle lifespan of cathodes. Although various strategies have been devised to enhance the Mg2+ migration kinetics and structural stability of cathodes, they fail to improve electronic conductivity, rendering the cathodes incompatible with magnesium-metal anodes. Herein, we propose a dual-defect engineering strategy, namely, the incorporation of Mg2+ pre-intercalation defect (P-Mgd) and oxygen defect (Od), to simultaneously improve the Mg2+ migration kinetics, structural stability, and electronic conductivity of the cathodes of RMMBs. Using lamellar V2O5·nH2O as a demo cathode material, we prepare a cathode comprising Mg0.07V2O5·1.4H2O nanobelts composited with reduced graphene oxide (MVOH/rGO) with P-Mgd and Od. The Od enlarges interlayer spacing, accelerates Mg2+ migration kinetics, and prevents structural collapse, while the P-Mgd stabilizes the lamellar structure and increases electronic conductivity. Consequently, the MVOH/rGO cathode exhibits a high capacity of 197 mAh g-1, and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g-1, capable of powering a light-emitting diode. The proposed dual-defect engineering strategy provides new insights into developing high-durability, high-capacity cathodes, advancing the practical application of RMMBs, and other new secondary batteries.

Recycled gold-reduced graphene oxide nanocomposite for efficient adsorption and photocatalytic degradation of crystal violet

In this study, gold-reduced graphene oxide (Au@rGO) nanocomposite has been synthesized by repurposing electronic waste and dry batteries. This innovative approach involved utilizing the graphite rod from dry batteries to produce reduced graphene oxide (rGO), which was subsequently modified through the incorporation of gold nanoparticles obtained from recycled electronic waste. This methodology marks a significant breakthrough in electronic waste recycling, presenting a cost-effective and sustainable means of creating novel nanocomposites for applications in photocatalysis and adsorption, particularly in the removal of crystal violet (CV) from aqueous media. The synthesized Au@rGO nanocomposite was characterized using X-ray diffraction, scanning electron microscopy, energy dispersed X-ray, and N2 adsorption/desorption. Parameters that affect the adsorption and photocatalytic degradation of CV dye have been studied in detail. The optimal conditions for CV adsorption and photocatalytic degradation were pH of 10, equilibrium time of 30 min, CV concentration of 10 mg/L and adsorbent dosage of 40 mg. Furthermore, the isotherm and kinetics of CV removal were also studied. The removal of CV dye using adsorption and photocatalytic degradation techniques reached 95% and 99%, respectively. Consequently, the results showed that photocatalytic degradation of CV dye onto the mesoporous Au@rGO nanocomposite is more proper way than the adsorption technique for removing the CV dye from aqueous media. The designed photocatalyst has high efficiency and it can be reused and activated several times so it can be used in real water treatment applications.

An electrochemical AChE-based biosensor for organophosphate pesticides using a modified CuNWs/rGO nanocomposite on a screen-printed carbon electrode

An enzymatic electrochemical biosensor was built for the indirect detection of organophosphates (OPs), based on acetylcholinesterase inhibition. The biosensor was fabricated for enhanced performance on a screen-printed carbon electrode (SPCE), modified with copper nanowires (CuNWs) composited with reduced graphene oxide (rGO). The oxidation current was measured using the cyclic voltammogram (CV) method, as generated by the enzymatic interaction between acetylcholinesterase (AChE) and its substrate, acetylthiocholine (ATCh). The biosensing response is the reduction in signal caused by the inhibition of acetylcholinesterase in the presence of an organophosphate inhibitor. Benchmarking shows that the CuNWs/rGO nanocomposite enhanced the signal current considerably and decreased the oxidation potential for electrochemical detection of the OP chlorpyrifos, exhibiting a wide linear detection rangefrom 10 µg/L-200 µg/L, with a limit of detection of 3.1 µg/L and limit of quantification of 12.5 µg/L. This sensor is useful for the analysis of chlorpyrifosin drinking water and orange juice, with high recovery rates and no interference effects.

Nanoarchitectonics of MXene Derived TiO2 /Graphene with Vertical Alignment for Achieving the Enhanced Supercapacitor Performance

Structural engineering and hybridization of heterogeneous 2D materials can be effective for advanced supercapacitor. Furthermore, architectural design of electrodes particularly with vertical construction of structurally anisotropic graphene nanosheets, can significantly enhance the electrochemical performance. Herein, MXene-derived TiO2 nanocomposites hybridized with vertical graphene is synthesized via CO2 laser irradiation on MXene/graphene oxide nanocomposite film. Instantaneous photon energy by laser irradiation enables the formation of vertical graphene structures on nanocomposite films, presenting the controlled anisotropy in free-standing film. This vertical structure enables improved supercapacitor performance by forming an open structure, increasing the electrolyte-electrode interface, and creating efficient electron transport path. In addition, the effective oxidation of MXene nanosheets by instantaneous photon energy leads to the formation of rutile TiO2 . TiO2 nanoparticles directly generated on graphene enables the effective current path, which compensates for the low conductivity of TiO2 and enables the functioning of an effective supercapacitor by utilizing its pseudocapacitive properties. The resulting film exhibits excellent specific areal capacitance of 662.9 mF cm-2 at a current density of 5 mA cm-2 . The film also shows superb cyclic stability during 40 000 repeating cycles, maintaining high capacitance. Also, the pseudocapacitive redox reaction kinetics is evaluated, showing fast redox kinetics with potential for high-performance supercapacitor applications.

Effects of graphene oxide and reduced graphene oxide nanomaterials on porcine endothelial progenitor cells

Graphene oxide (GO) and reduced graphene oxide (rGO) have been widely used in the field of tissue regeneration and various biomedical applications. In order to use these nanomaterials in organisms, it is imperative to possess an understanding of their impact on different cell types. Due to the potential of these nanomaterials to enter the bloodstream, interact with the endothelium and accumulate within diverse tissues, it is highly relevant to probe them when in contact with the cellular components of the vascular system. Endothelial progenitor cells (EPCs), involved in blood vessel formation, have great potential for tissue engineering and offer great advantages to study the possible angiogenic effects of biomaterials. Vascular endothelial growth factor (VEGF) induces angiogenesis and regulates vascular permeability, mainly activating VEGFR2 on endothelial cells. The effects of GO and two types of reduced GO, obtained after vacuum-assisted thermal treatment for 15 min (rGO15) and 30 min (rGO30), on porcine endothelial progenitor cells (EPCs) functionality were assessed by analyzing the nanomaterial intracellular uptake, reactive oxygen species (ROS) production and VEGFR2 expression by EPCs. The results evidence that short annealing (15 and 30 minutes) at 200 °C of GO resulted in the mitigation of both the increased ROS production and decline in VEGFR2 expression of EPCs upon GO exposure. Interestingly, after 72 hours of exposure to rGO30, VEGFR2 was higher than in the control culture, suggesting an early angiogenic potential of rGO30. The present work reveals that discrete variations in the reduction of GO may significantly affect the response of porcine endothelial progenitor cells.

One-Step Synthesis of Fragment-Reduced Graphene Oxide as an Electrode Material for Supercapacitors

We herein report for the first time a simple environmentally friendly hydrothermal method for one-step synthesis of fragment-reduced graphene oxide (FrGO) under mild conditions without the addition of reducing agents, and we applied it as an electrode material for a supercapacitor. The characterization results show that the introduction of Al2O3 as a spacer and HCl as an etchant results in a macroporous/mesoporous structure, increases the fragmentation of the FrGO microtopography, shortens the electron/ion transport path, and increases the contact between the electrode material and the electrolyte. Compared to the traditional hydrothermal reduced graphene materials, FrGO shows a larger specific capacitance. The results indicate that suitable hydrothermal temperature and time can effectively promote the retention of more oxygen-containing functional groups on the graphene surface. The first-principles density functional theory (DFT) calculation results show that the electrostatic potential in carbonyl group graphene is more negative, favored by the H+ adsorption, and provides the system with a pseudocapacitive effect. Under optimized conditions, FrGO (1:4, 180 °C, 3 h) exhibits 417 F/g at 1 A/g with an outstanding capacitance retention of 78.51% at 50 A/g and exhibits remarkable stability over 20 000 charge/discharge cycles. The proposed FrGO-based synthesis method can be used to guide the development of electrode materials for various supercapacitor devices.

Low-Cost Perovskite Solar Cell Fabricated using the Expanded Graphite Back Contact and Electronically Conducting Activated Carbon as the Hole Transporting Material

Although perovskite solar cells (PSCs) have reached a record high conversion efficiency of 25.7%, the materials used to fabricate them invoke costly hole-transporting materials, such as spiro-OMeTAD, and expensive gold back contacts. The cost of fabrication of a solar cell or any other practical device is an important issue in their practical applications. In this study, we describe the fabrication of a low-cost, mesoscopic PSC, eliminating the use of expensive p-type semiconductors and substituting them with electronically conducting activated carbon, and the gold back contact with expanded graphite. The activated carbon hole transporting material was derived from readily available coconut shells and the expanded graphite from graphite attached to rock pieces of graphite vein banks. We drastically reduced the overall cell fabrication cost using these low-cost materials and added commercial value to discarded graphite and coconut shells. Under ambient conditions, our PSC gives a conversion efficiency of 8.60 ± 0.10 % at 1.5 AM simulated sunlight. We have identified the lower fill factor as the limiting factor for the low conversion efficiency. We believe that the lower cost of the materials used and the deceptively simple powder pressing method would compensate for the relatively lower conversion efficiency in its practical application.

Enhancing Cementitious Composites with Functionalized Graphene Oxide-Based Materials: Surface Chemistry and Mechanisms

Graphene oxide-based materials (GOBMs) have been widely explored as nano-reinforcements in cementitious composites due to their unique properties. Oxygen-containing functional groups in GOBMs are crucial for enhancing the microstructure of cementitious composites. A better comprehension of their surface chemistry and mechanisms is required to advance the potential applications in cementitious composites of functionalized GOBMs. However, the mechanism by which the oxygen-containing functional groups enhance the response of cementitious composites is still unclear, and controlling the surface chemistry of GOBMs is currently constrained. This review aims to investigate the reactions and mechanisms for functionalized GOBMs as additives incorporated in cement composites. A variety of GOBMs, including graphene oxide (GO), hydroxylated graphene (HO-G), edge-carboxylated graphene (ECG), edge-oxidized graphene oxide (EOGO), reduced graphene oxide (rGO), and GO/silane composite, are discussed with regard to their oxygen functional groups and interactions with the cement microstructure. This review provides insight into the potential benefits of using GOBMs as nano-reinforcements in cementitious composites. A better understanding of the surface chemistry and mechanisms of GOBMs will enable the development of more effective functionalization strategies and open up new possibilities for the design of high-performance cementitious composites.

Universal Strategy for Reversing Aging and Defects in Graphene Oxide for Highly Conductive Graphene Aerogels

The production of highly stable, defect-free, and electrically conducting 3D graphene structures from graphene oxide precursors is challenging. This is because graphene oxide is a metastable material whose structure and chemistry evolve due to aging. Aging changes the relative composition of oxygen functional groups attached to the graphene oxide and negatively impacts the fabrication and properties of reduced graphene oxide. Here, we report a universal strategy to reverse the aging of graphene oxide precursors using oxygen plasma treatment. This treatment decreases the size of graphene oxide flakes and restores negative zeta potential and suspension stability in water, enabling the fabrication of compact and mechanically stable graphene aerogels using hydrothermal synthesis. Moreover, we employ high-temperature annealing to remove oxygen-containing functionalities and repair the lattice defects in reduced graphene oxide. This method allows obtaining highly electrically conducting graphene aerogels with electrical conductivity of 390 S/m and low defect density. The role of carboxyl, hydroxyl, epoxide, and ketonic oxygen species is thoroughly investigated using X-ray photoelectron and Raman spectroscopies. Our study provides unique insight into the chemical transformations occurring during the aging and thermal reduction of graphene oxide from room temperature up to 2700 °C.

An Overview of Recycling Wastes into Graphene Derivatives Using Microwave Synthesis; Trends and Prospects

It is no secret that graphene, a two-dimensional single-layered carbon atom crystal lattice, has drawn tremendous attention due to its distinct electronic, surface, mechanical, and optoelectronic properties. Graphene also has opened up new possibilities for future systems and devices due to its distinct structure and characteristics which has increased its demand in a variety of applications. However, scaling up graphene production is still a difficult, daunting, and challenging task. Although there is a vast body of literature reported on the synthesis of graphene through conventional and eco-friendly methods, viable processes for mass graphene production are still lacking. This review focuses on the variety of unwanted waste materials, such as biowastes, coal, and industrial wastes, for producing graphene and its potential derivatives. Among the synthetic routes, the main emphasis relies on microwave-assisted production of graphene derivatives. In addition, a detailed analysis of the characterization of graphene-based materials is presented. This paper also highlights the current advances and applications through the recycling of waste-derived graphene materials using microwave-assisted technology. In the end, it would alleviate the current challenges and forecast the specific direction of waste-derived graphene future prospects and developments.

Interfacing reduced graphene oxide with an adipose-derived extracellular matrix as a regulating milieu for neural tissue engineering

Enthralling evidence of the potential of graphene-based materials for neural tissue engineering is motivating the development of scaffolds using various structures related to graphene such as graphene oxide (GO) or its reduced form. Here, we investigated a strategy based on reduced graphene oxide (rGO) combined with a decellularized extracellular matrix from adipose tissue (adECM), which is still unexplored for neural repair and regeneration. Scaffolds containing up to 50 wt% rGO relative to adECM were prepared by thermally induced phase separation assisted by carbodiimide (EDC) crosslinking. Using partially reduced GO enables fine-tuning of the structural interaction between rGO and adECM. As the concentration of rGO increased, non-covalent bonding gradually prevailed over EDC-induced covalent conjugation with the adECM. Edge-to-edge aggregation of rGO favours adECM to act as a biomolecular physical crosslinker to rGO, leading to the softening of the scaffolds. The unique biochemistry of adECM allows neural stem cells to adhere and grow. Importantly, high rGO concentrations directly control cell fate by inducing the differentiation of both NE-4C cells and embryonic neural progenitor cells into neurons. Furthermore, primary astrocyte fate is also modulated as increasing rGO boosts the expression of reactivity markers while unaltering the expression of scar-forming ones.

Chitosan/graphene oxide hybrid hydrogel electrode with porous network boosting ultrahigh energy density flexible supercapacitor

To overcome the low energy density and poor conductivity of conventional electrode materials for building supercapacitor, herein, a hybrid hydrogel prepared from compositing bio-based chitosan with holey graphene oxide by microwave-assisted hydrothermal is proposed. This binary hydrogel is endowed with heteroatomic functional groups and conductive porous network by chemical pretreatments, where amides and carboxyl groups are introduced during the acylation modification of chitosan to enable it soluble in water for sufficient reaction, while the oxidation etching for graphene oxide in the defect area by H₂O₂ facilitates in-plane nanopores network to provide abundant active surface and short ion diffusion pathway. Benefited from the high conductivity and flexibility, this hydrogel present promising performance when used as additive-free electrode in a three-electrode, with a high specific capacitance of 377 F/g at 5 A/g. The rich nitrogen and oxygen groups on surface of the hydrogel contribute to high capacitance directly, while the in-plane nanopores and hierarchically porous network benefit to promote their wettability, accelerate the charge transfer and enhance their charge storage ability. When the hydrogel composite is adopted into a flexible solid-state supercapacitor employing lignin hydrogel electrolyte, it unfolds a specific capacitance of 210 F/g at 0.5 A/g, with an ultrahigh energy density of 31 Wh/kg at the power density of 150 W/kg. The solid-state supercapacitor exhibits promising potential in applications such as signal sensor and portable energy storage.

One-pot hydrothermal preparation of capsule-like nanocomposites of C/Ce-co-doped ZnO supported on graphene to enhance photodegradation

Nanocapsule composites of C/Ce-co-doped ZnO supported on graphene synthesized by a one-pot hydrothermal method with a band gap of 2.72 eV were used to enhance the photodegradation of methylene blue under various conditions.

Efficacy of Graphene-Based Nanocomposite Gels as a Promising Wound Healing Biomaterial

The development of biocompatible nanocomposite hydrogels with effective wound healing/microbicidal properties is needed to bring out their distinguished characteristics in clinical applications. The positive interaction between graphene oxide/reduced graphene oxide (GO/rGO) and hydrogels and aloe vera gel represents a strong strategy for the advancement of therapeutic approaches for wound healing. In this study, the synthesis, characterization, and angiogenic properties of graphene-based nanocomposite gels have been corroborated and substantiated through several in vitro and in vivo assays. In this respect, graphene oxide was synthesized by incorporating a modified Hummer's method and ascertained by Raman spectroscopy. The obtained GO and rGO were uniformly dispersed into the aloe vera gel and hydrogel, respectively, as wound healing materials. These formulations were characterized via in vitro bio-chemical techniques and were found suitable for the appropriate cell viability, attachment, and proliferation. In addition, in vivo experiments were conducted using male Wistar rats. This revealed that the GO/rGO-based gels stimulated wound contraction and re-epithelialization compared to that of the non-treatment group. From the study, it is suggested that GO/rGO-based aloe vera gel can be recommended as a promising candidate for wound healing applications.

Study of Thermal Effect on the Mechanical Properties of Nylon 610 Nanocomposites with Graphite Flakes That Have Undergone Supercritical Water Treatment at Different Temperatures

This study investigates the thermal effect of supercritical water treatment at different temperatures (150, 175, 200 °C) and semi-vacuum state (-0.08 MPa) on graphite flakes which are then incorporated into nylon 610. The treatment is deemed to increase the surface activity of nanofillers through the formation of oxygen-containing functional groups. X-ray diffraction (XRD) analysis indicated that the crystal structure of the flakes remained similar before and after supercritical water treatment. Fourier transform infrared spectroscopy (FTIR) also showed the presence of hydrogen bonding between the flakes and the polymer matrix through the appearance of amide bands. The intensity of the amide peaks is higher for nanocomposites with treated flakes than untreated ones. Furthermore, scanning electron microscopy (SEM) showed that at higher wt%, aggregation will occur, which leads to a weakening in physical properties. The tensile strength of nanocomposites with treated flakes decreased with increasing wt%, while those with untreated flakes increased with increasing wt%. Young's modulus of all the nanocomposites generally increased with increasing wt%. The highest tensile strength obtained is 967.02 kPa, while that of neat nylon 610 is 492.09 kPa. This enhancement in mechanical properties can be attributed to the intact structure of the graphite flakes and the interaction between the flakes and the nylon 610 matrix. A higher temperature of water treatment was discovered to cause higher oxidation levels on surface of the nanofillers but would result in some structural damage. The optimum nylon 610 nanocomposite synthesized was the one that was incorporated with 1.5 wt% graphite flakes treated at 150 °C and -0.08 MPa, as it has the highest tensile strength.

Fabrication and Conductivity of Graphite Nanosheet/Nylon 610 Nanocomposites Using Graphite Nanosheets Treated with Supercritical Water at Different Temperatures

In this study, water at high temperatures (150, 175, 200 °C) and in a vacuum state (−0.1 MPa) was applied to graphite nanosheets to enhance surface activity to promote the formation of oxygen-containing functional groups through supercritical water treatment. Nylon 610 nanocomposites (with treated or untreated nanosheets as nanofillers) were then synthesized using interfacial polymerization. X-ray diffraction (XRD) analysis showed that the water treatment did not alter the crystal structure of the carbon nanosheets. Additionally, Fourier transform infrared spectroscopy (FTIR) analysis showed the presence of amide peaks within the nanocomposites, indicating the presence of hydrogen bonding between the nanosheets and the polymer matrix. The intensity of the amide peaks was higher for nanocomposites combined with treated nanosheets than untreated ones. This hydrogen bonding is beneficial to the conductivity of the nanocomposites. The conductivity of treated nanosheets/nylon nanocomposites generally decreased with increasing wt%, while the conductivity of untreated nanosheets/nylon nanocomposites increased with increasing wt%. The decrementing of conductivity in the treated nanosheets/nylon nanocomposites is due to the agglomeration of the nanosheets within the composite. This is in in line with scanning electron microscopy (SEM) results which showed that at higher wt%, the aggregation condition tended to occur. The highest conductivity obtained is 0.004135 S/m, as compared to the conductivity of neat nylon 610, which is 10−14 S/m. This improvement in electrical properties can be attributed to the intact structure of the nanosheets and the interaction between the nanofillers and the nylon 610 matrix. The optimum nylon 610 nanocomposite synthesized was the one incorporated with 0.5 wt% graphite nanosheets treated at 200 °C and −0.1 MPa, which possess the highest conductivity.

NiFeMn-Layered Double Hydroxides Linked by Graphene as High-Performance Electrocatalysts for Oxygen Evolution Reaction

Currently, precious metal group materials are known as the efficient and widely used oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. The exorbitant prices and scarcity of the precious metals have stimulated scale exploration of alternative non-precious metal catalysts with low-cost and high performance. Layered double hydroxides (LDHs) are a promising precursor to prepare cost-effective and high-performance catalysts because they possess abundant micropores and nitrogen self-doping after pyrolysis, which can accelerate the electron transfer and serve as active sites for efficient OER. Herein, we developed a new highly active NiFeMn-layered double hydroxide (NFM LDH) based electrocatalyst for OER. Through building NFM hydroxide/oxyhydroxide heterojunction and incorporation of conductive graphene, the prepared NFM LDH-based electrocatalyst delivers a low overpotential of 338 mV at current density of 10 mA cm⁻² with a small Tafel slope of 67 mV dec⁻¹, which are superior to those of commercial RuO₂ catalyst for OER. The LDH/OOH heterojunction involves strong interfacial coupling, which modulates the local electronic environment and boosts the kinetics of charge transfer. In addition, the high valence Fe³⁺ and Mn³⁺ species formed after NaOH treatment provide more active sites and promote the Ni²⁺ to higher oxidation states during the O₂ evolution. Moreover, graphene contributes a lot to the reduction of charge transfer resistance. The combining effects have greatly enhanced the catalytic ability for OER, demonstrating that the synthesized NFM LDH/OOH heterojunction with graphene linkage can be practically applied as a high-performance electrocatalyst for oxygen production via water splitting.

Supercapacitance in graphene oxide materials modified with tetrapyrrole dyes: a mechanistic study

The global increase in mobile technology usage has created a need for better energy storage systems. With standard batteries reaching their technological limits, alternate energy storage methods are gaining momentum. In this study, we demonstrate a cheap and efficient way of building from scratch high-performance supercapacitors based on graphene oxide (GO) functionalized with tetrapyrrole derivatives: porphyrins and phthalocyanines. We present supercapacitors with capacitances about 30 times larger than those of the pristine graphene oxide-based counterparts. Experimental characterisation methods including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations revealed correlations between the structural, magnetic, electronic and thermodynamic properties of these materials and their performance as supercapacitors. Electrochemical studies indicate the complex and versatile nature of capacitive effects associated with thin layers of supramolecular composites of graphene oxide. The electrical double layer (EDL) capacitance, cation intercalation and faradaic processes are coupled. Moreover, differences in the electronic interactions between GO and tetrapyrrolic modifiers have a profound effect on the observed capacitance. At the same time, these interactions are sufficiently weak to induce only subtle spectral changes, as well as a small increase of the interlayer distance as determined by XRD measurements. The present work offers a viable strategy for manufacturing high-performance supercapacitive materials that are superior to the state of the art nanocarbon-based supercapacitors using benign electrolytes in terms of capacitance per mass unit and have the potential for application in future green energy storage technologies. Our study provides insight into the multifarious origins of supercapacitance beyond the well-known EDL mechanism.

Graphdiyne Oxide Quantum Dots: The Enhancement of Peroxidase-like Activity and Their Applications in Sensing H2O2 and Cysteine

As one of the typical carbon nanomaterials, graphdiyne (GDY) with unique chemical, physical, and electronic properties has a great potential in various fields. Although it is an important member of carbon nanozymes, the research on its intrinsic enzyme mimetic properties and applications is still limited. Herein, graphdiyne oxide quantum dots (GDYO QDs) have been synthesized through oxidative cleavage, which exhibit enhanced peroxidase-like activity with lower K_m and higher V_max than those of most carbon-based nanozymes. The catalytic mechanism is explored, showing that the enhanced catalytic performance is attributed to the good conjugated structure, large number of oxygen-containing groups, and small-sized nanosheets with few layers. As a kind of peroxidase mimetic, the GDY-based nanozyme has excellent potential in sensing H₂O₂ and biological antioxidants through the colorimetric assay, with a linear range from 5 to 500 μM and detection limit of 1.5 μM for H₂O₂ and a linear range from 0 to 90 μM and detection limit of 0.48 μM for l-cysteine. Our work will be beneficial to develop high-performance artificial enzymes and to understand their mechanism for better applications.

Tunable Switching Behavior of GO-Based Memristors Using Thermal Reduction

This work reports on the fabrication of a novel planar reduced graphene oxide (rGO) memristor (MR) device. For the first time in the literature, the MR tunable resistive switching behavior is controlled by the GO reduction time at a constant temperature. The device is fabricated using standard microfabrication techniques on a flexible cyclic olefin copolymer substrate (COC). Thermal reduction of the GO layer at low temperatures (100 °C) avoids the drawbacks of chemical reduction methods such as toxicity and electrode metal damage during fabrication, while allowing for fine-tuning of the MR’s switching behavior. The device has analog switching characteristics, with a range of different resistance states. By taking advantage of the slow nature of GO thermal annealing, the switching properties of the rGO memristors can be precisely controlled by adjusting the reduction period. At short annealing times (i.e., T < 20 h), the devices switch from high to low resistance states, while at longer annealing times the switching behavior is reversed, with the device switching from low to high resistance states (LRS to HRS). Resistive switching occurs as a result of the diffusion and removal of the oxygen functional groups in the GO film caused by Joule heating induced by the electric current. Complete electrical characterization tests are presented along with wettability and X-ray diffraction (XRD) tests. This work opens a new vision for realizing rGO-based MR devices with tunable switching properties, broadening the application horizon of the device.

Carbon-based low-pressure filtration membrane for the dynamic disruption of bacteria from contaminated water

Carbon-based materials, especially graphene oxide (GO) and carbon dots possessing antibacterial properties, are widely used for various applications. Recently, we reported the antibacterial and antioxidant properties of carbonized nanogels (CNGs) for the treatment of bacterial keratitis, and as a virostatic agent against infectious bronchitis virus. In this work, we demonstrate the use of CNGs/GO nanocomposite (GO@CNGs) membrane for the efficient removal of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria from contaminated water. The GO@CNGs composite membrane with an optimized ratio of GO to CNGs could achieve more than 99% removal efficiency toward E. coli and S. aureus. Various strains of bacteria interact differently with the membrane, and hence the membrane shows different removal rate, which can be optimized by controlling the interaction time through regulating the water flux. The GO@CNGs membrane with an active area of 2.83 cm² achieved > 99% bacterial removal efficiency at a water flux of 400 mL min^-1 m^-2. The dynamic disruption of bacteria by GO@CNGs plays a crucial role in eliminating the bacteria. Rather than filtering out the bacteria, GO@CNGs membrane allows them to pass through it, interact with the bacteria and rupture the bacterial cell membranes. Our GO@CNGs membrane shows great potential as a filter to remove bacteria from contaminated water samples, operating under tap water pressure without any extra power consumption.

Composite Nanoarchitectonics with CoS2 Nanoparticles Embedded in Graphene Sheets for an Anode for Lithium-Ion Batteries

Cobalt sulfides are attractive as intriguing candidates for anodes in Lithium-ion batteries (LIBs) due to their unique chemical and physical properties. In this work, CoS2@rGO (CSG) was synthesized by a hydrothermal method. TEM showed that CoS2 nanoparticles have an average particle size of 40 nm and were uniformly embedded in the surface of rGO. The battery electrode was prepared with this nanocomposite material and the charge and discharge performance was tested. The specific capacity, rate, and cycle stability of the battery were systematically analyzed. In situ XRD was used to study the electrochemical transformation mechanism of the material. The test results shows that the first discharge specific capacity of this nanocomposite reaches 1176.1 mAhg-1, and the specific capacity retention rate is 61.5% after 100 cycles, which was 47.5% higher than that of the pure CoS2 nanomaterial. When the rate changes from 5.0 C to 0.2 C, the charge-discharge specific capacity of the nanocomposite material can almost be restored to the initial capacity. The above results show that the CSG nanocomposites as a lithium-ion battery anode electrode has a high reversible specific capacity, better rate performance, and excellent cycle performance.

Optimizing the Properties of Hybrids Based on Graphene Oxide for Carbon Dioxide Capture

The reduction of CO2 emissions and its elimination from the atmosphere has become one of the major problems worldwide, since CO2 is the main cause of the greenhouse effect and climate change. In recent years, a great number of carbonaceous materials that can be used as CO2 adsorbents have been synthesized. The strategy is usually to synthesize the materials and determine their adsorption capacity without studying previously the factors that influence this capacity. In this work, different properties of the adsorbents are analyzed to study their influence on the CO2 adsorption capacity. For this purpose, 10 adsorbents have been synthesized using different strategies and characterized with X-ray photoelectron spectroscopy, X-ray diffraction, and micro-Raman spectroscopy. The percentage of sp2 carbons, the position of the D + D' peak of the second-order Raman spectrum, the micropore volume, and the grain size of the C sp2 domains have been related to the amount of CO2 adsorbed by the adsorbents. The results confirm a linear relationship between the volume of the micropores and the CO2 uptake and it proves that CO2 retention is favored in those materials that, in addition to having a high volume of micropores, also have low grain size of C.

Soft template-assisted copper-doped sodium dititanate nanosheet/graphene oxide heterostructure for photoreduction of carbon dioxide to liquid fuels

Photoreduction of CO₂ to a high-value product is an interesting approach that not only captures CO₂ but also converts it into other products that can be sold or used in industry. The mechanism for the CO₂ conversion relies strongly on photo-generated electrons that further couple with CO₂ and form active radicals for the reaction. In this research, we synthesized a heterostructure of copper-doped sodium dititanate nanosheets and graphene oxide (CTGN) following a one-step hydrothermal process with assistance from a sodium hydroxide soft template. The role of the template here is to facilitate the formation of the nanosheets, creating the nanosheet–graphene 2D–2D heterostructure. The heterostructure yields excellent charge mobility and a low charge recombination rate, while the nanosheet–graphene interfaces house active radicals and stabilize intermediates. The CTGN exhibits an outstanding photoactivity in the photoreduction of CO₂, producing liquid fuels, including acetone, methanol, ethanol and i-propanol.

The copper-doped sodium dititanate nanosheets/graphene oxide heterostructure (CTGN) was synthesized following a one-step hydrothermal process, exhibiting an outstanding photoactivity in converting CO₂ to acetone, methanol, ethanol and i-propanol.

Review elucidating graphene derivatives (GO/rGO) supported metal sulfides based hybrid nanocomposites for efficient photocatalytic dye degradation

Photocatalysis by utilizing semiconductors for the removal of toxic pollutants has gained tremendous interest for remediation purposes. The organic pollutants usually include; pesticides, dyes and other phenolic compounds. An imperative restraint associated with the photocatalytic effectiveness of the catalyst is the rapid recombination of the light generated electrons and holes. The particle agglomeration and electron-hole recombination hinders the rate of pollutant removal. For decades, researchers have used metal-sulfides efficiently for photocatalytic dye degradation. The recent use of hybrid nanomaterials with the combination of graphene derivatives such as graphene oxide and reduced graphene oxide (GO/rGO)-metal sulfide has gained interest. These composites have displayed an impressive upsurge in the photocatalytic activity of materials. The current review describes the various researches on dye photodegradation by employing (GO/rGO)-metal sulfide, exhibiting a boosted potential for photocatalytic dye degradation. A comprehensive study on (CuS, ZnS and CdS)–GO/rGO hybrid composites have been discussed in detail for effective photocatalytic dye degradation in this review. Astonishingly improved dye degradation rates were observed in all these studies employing such hybrid composites. The several studies described in the review highlighted the varying degradation rates based on diverse research parameters and efficacy of graphene derivatives for enhancement of photocatalytic activity.

Effect of Nitrogen Doping on the Optical Bandgap and Electrical Conductivity of Nitrogen-Doped Reduced Graphene Oxide

Graphene as a material for optoelectronic design applications has been significantly restricted owing to zero bandgap and non-compatible handling procedures compared with regular microelectronic ones. In this work, nitrogen-doped reduced graphene oxide (N-rGO) with tunable optical bandgap and enhanced electrical conductivity was synthesized via a microwave-assisted hydrothermal method. The properties of the synthesized N-rGO were determined using XPS, FTIR and Raman spectroscopy, UV/vis, as well as FESEM techniques. The UV/vis spectroscopic analysis confirmed the narrowness of the optical bandgap from 3.4 to 3.1, 2.5, and 2.2 eV in N-rGO samples, where N-rGO samples were synthesized with a nitrogen doping concentration of 2.80, 4.53, and 5.51 at.%. Besides, an enhanced n-type electrical conductivity in N-rGO was observed in Hall effect measurement. The observed tunable optoelectrical characteristics of N-rGO make it a suitable material for developing future optoelectronic devices at the nanoscale.

Two-Dimensional Organic/Inorganic Hybrid Nanosheet Electrodes for Enhanced Electrical Conductivity toward Stable and High-Performance Sodium-Ion Batteries

To investigate the effect of electrical conductivity on the energy-storage characteristics of anode materials in sodium-ion batteries, covalent organic nanosheets (CONs) are hybridized with highly conductive graphene nanosheets (GNs) via two different optimized synthesis routes, that is, reflux and solvothermal methods. The reflux-synthesized hybrid shows a well-overlapped 2D structure, whereas the solvothermally prepared hybrid forms a segregated phase in which the contact area between the CONs and GNs is reduced. These two hybrids synthesized by facile methods are fully characterized, and the results reveal that their energy-storage properties can be significantly improved by enhancing the electrical conductivity via the formation of a well-overlapped structure between CONs and GNs. The discharge capacity and rate capability of the reflux-synthesized hybrid was considerably larger than that of the bare CONs, highlighting that the improvement in the charge-carrier transport properties can improve the accessibility of Na ions to the surface of the hybrids. This synthetic methodology can be extended to the fabrication of high-performance anodes for Na-ion batteries.

A comparative study between two novel silicone/graphene-based nanostructured surfaces for maritime antifouling

Two novel superhydrophobic nanocomposite series of polydimethylsiloxane (PDMS) enriched with reduced graphene oxide (RGO) and graphene oxide/boehmite nanorods (GO-γ-AlOOH) nanofillers were synthesized as maritime fouling-release (FR) surfaces. Controlling the nanofillers' structures and distribution in the silicone matrix influenced the self-cleaning and antifouling properties. γ-AlOOH nanorods had a single crystallinity with an average diameter of 10-20 nm and < 200 nm length. A hydrothermal method was used to prepare RGO, while the chemical deposition method was used to synthesis GO-γ-AlOOH nanocomposites for use as fouling-release coating materials. For studying the synergetic effects of graphene-based materials on the surface, mechanical, and FR features, these nanofillers were dispersed in the silicone matrix using the solution casting method. The hydrophobicity and antifouling properties of the surface were studied using water contact angle (WCA), scanning electron, and atomic force microscopes (SEM and AFM). Coatings' roughness, superhydrophobicity, and surface mechanical properties all improved for the homogeneity of the dispersion of the nanocomposite. Laboratory assessments were carried out for 30 days using selected microorganisms to determine the antifouling effects of the coating systems. PDMS/GO-γ-AlOOH nanorod composite had better antibacterial activity than PDMS/RGO nanocomposite against different bacterial strains. This is caused by the high surface area and stabilizing effects of the GO-γ-AlOOH hybrid nanofillers. The PDMS/GO-γ-AlOOH nanorod composite (3 wt%) had the lowest biodegradability percentage (1.6%) and the microbial endurability percentages for gram-positive, gram-negative, and fungi were 86.42%, 97.94%, and 85.97%, respectively. A field trial in natural seawater was conducted to confirm the coatings' FR performance based on the screening process and image analysis for 45 days in a tropical area. The most profound superhydrophobic antifouling nanostructured coating was the homogeneity of the GO-γ-AlOOH (3 wt%) dispersion, which had a WCA of 151° and a rough surface.

Microfluidic investigation of the effect of graphene oxide on mechanical properties of cell and actin cytoskeleton networks: experimental and theoretical approaches

Biomechanical and morphological analysis of the cells is a novel approach for monitoring the environmental features, drugs, and toxic compounds’ effects on cells. Graphene oxide (GO) has a broad range of medical applications such as tissue engineering and drug delivery. However, the effects of GO nanosheets on biological systems have not been completely understood. In this study, we focused on the biophysical characteristics of cells and their changes resulting from the effect of GO nanosheets. The biophysical properties of the cell population were characterized as follows: cell stiffness was calculated by atomic force microscopy, cell motility and invasive properties were characterized in the microfluidic chip in which the cells are able to visualize cell migration at a single-cell level. Intracellular actin was stained to establish a quantitative picture of the intracellular cytoskeleton. In addition, to understand the molecular interaction of GO nanosheets and actin filaments, coarse-grained (CG) molecular dynamics (MD) simulations were carried out. Our results showed that GO nanosheets can reduce cell stiffness in MCF7 cells and MDA-MB-231 cell lines and highly inhibited cell migration (39.2%) in MCF-7 and (38.6%) in MDA-MB-231 cell lines through the GO nanosheets-mediated disruption of the intracellular cytoskeleton. In the presence of GO nanosheets, the cell migration of both cell lines, as well as the cell stiffness, significantly decreased. Moreover, after GO nanosheets treatment, the cell actin network dramatically changed. The experimental and theoretical approaches established a quantitative picture of changes in these networks. Our results showed the reduction of the order parameter in actin filaments was 23% in the MCF7 cell line and 20.4% in the MDA-MB-231 cell line. The theoretical studies also showed that the GO nanosheet–actin filaments have stable interaction during MD simulation. Moreover, the 2D free energy plot indicated the GO nanosheet can induce conformational changes in actin filaments. Our findings showed that the GO nanosheets can increase the distance of actin-actin subunits from 3.22 to 3.5 nm and in addition disrupt native contacts between two subunits which lead to separate actin subunits from each other in actin filaments. In this study, the biomechanical characteristics were used to explain the effect of GO nanosheets on cells which presents a novel view of how GO nanosheets can affect the biological properties of cells without cell death. These findings have the potential to be applied in different biomedical applications.

Enhancing Light Absorption and Prolonging Charge Separation in Carbon Quantum Dots via Cl-Doping for Visible-Light-Driven Photocharge-Transfer Reactions

Limited light absorption beyond the UV region and rapid photocarrier recombination are critical impediments for the improved photocatalytic performance of carbon quantum dots (CQDs) under visible-light irradiation. Herein, we demonstrate single-step microwave-assisted syntheses of O-CQDs (typical CQDs terminated by carboxylic and hydroxyl functional groups) from a sucrose precursor and Cl-doped CQDs (Cl-CQDs) from a sucralose precursor in short reaction times and without using obligatory strong acids for Cl doping. The doping of Cl into the CQDs is observed to widen the absorption range and facilitate an enhanced separation of photoexcited charge carriers, which is confirmed by the results of optical absorption, photothermal response, and pump-probe ultrafast transient absorption spectroscopy measurements of the O-CQDs and Cl-CQDs. The photoexcited charge carriers with their longer lifetimes in Cl-CQDs enabled the quick degradation of methylene blue dye, rapid conversion of Ag⁺ ions to metallic Ag nanoparticles on the CQD surfaces, and reduction of GO to a well-dispersed rGO through the photoelectron transfer reactions under visible-light irradiation. The facile Cl doping strategy, hybridization of Ag nanoparticles or rGO to CQDs, and the elevated charge separation mechanism would open up new avenues in designing CQD-based materials for futuristic applications.

Benefits in the Macrophage Response Due to Graphene Oxide Reduction by Thermal Treatment

Graphene and its derivatives are very promising nanomaterials for biomedical applications and are proving to be very useful for the preparation of scaffolds for tissue repair. The response of immune cells to these graphene-based materials (GBM) appears to be critical in promoting regeneration, thus, the study of this response is essential before they are used to prepare any type of scaffold. Another relevant factor is the variability of the GBM surface chemistry, namely the type and quantity of oxygen functional groups, which may have an important effect on cell behavior. The response of RAW-264.7 macrophages to graphene oxide (GO) and two types of reduced GO, rGO15 and rGO30, obtained after vacuum-assisted thermal treatment of 15 and 30 min, respectively, was evaluated by analyzing the uptake of these nanostructures, the intracellular content of reactive oxygen species, and specific markers of the proinflammatory M1 phenotype, such as CD80 expression and secretion of inflammatory cytokines TNF-α and IL-6. Our results demonstrate that GO reduction resulted in a decrease of both oxidative stress and proinflammatory cytokine secretion, significantly improving its biocompatibility and potential for the preparation of 3D scaffolds able of triggering the appropriate immune response for tissue regeneration.

Controlling the structure and photocatalytic properties of three—dimensional aerogels obtained by simultaneous reduction and self-assembly of BiOI/GO aqueous colloidal dispersions

Water pollution affects all living habitats, since it is the most basic element that sustains all life forms and, as an exceptional solvent, it readily makes any compound available for living cells, either nutrients or noxious substances. Elimination of molecular contaminants from water quality is one of the most challenging technical problems that conventional treatments like flocculation and filtration fail short to defeat. Particulate photocatalysts, used to degrade contaminants, have the main drawback of their recovery from the water matrices. The inclusion of photocatalytic nanoparticles (NPs) into a large supporting framework, is presented as an innovative approach aiming to ensure a facile separation from water. To this end, three-dimensional (3D) aerogels with photocatalytic properties were prepared by a simple and scalable method based on the reduction—induced self-assembly of graphene oxide (GO) in the presence of BiOI nanoparticles. With the help of ascorbic acid, as a green reducing agent, partial reduction of GO into reduced graphene oxide (RGO) and self-assembly of both kinds of nanostructures into a porous monolith was achieved. BiOI doped RGO aerogels were further stabilized and morphologically controlled using poly (ethylene glycol) as stabilizer. The photocatalytic performance of these aerogels was evaluated by following the discoloration of methylene blue (MB) solution, under visible light irradiation, showing that structure and dispersion degree of NPs to be fundamental variables. Hence, this methodology is proposed to produce hybrid aerogels with controlled morphology and photocatalytic performance that has the potential to be used in water cleaning procedures.