Sulfur-functionalized graphene oxide by epoxide ring-opening

Boosting Zinc Hybrid Supercapacitor Performance via Thiol Functionalization of Graphene-Based Cathodes

Zinc hybrid supercapacitors (Zn-HSCs) hold immense potential toward the next-generation energy storage systems, effectively spanning the divide between conventional lithium-ion batteries (LIBs) and supercapacitors. Unfortunately, the energy density of most of Zn-HSCs has not yet rivalled the levels observed in LIBs. The electrochemical performance of aqueous Zn-HSCs can be enhanced through the chemical functionalization of graphene-based cathode materials with thiol moieties as they will be highly suitable for favoring Zn2+ adsorption/desorption. Here, a single-step reaction is employed to synthesize thiol-functionalized reduced graphene oxide (rGOSH), incorporating both oxygen functional groups (OFGs) and thiol functionalities, as demonstrated by X-ray photoelectron spectroscopy (XPS) studies. Electrochemical analysis reveals that rGOSH cathodes exhibit a specific capacitance (540 F g-1) and specific capacity (139 mAh g-1) at 0.1 A g-1 as well as long-term stability, with over 92% capacitance retention after 10 000 cycles, outperforming chemically reduced graphene oxide (CrGO). Notably, rGOSH electrodes displayed an exceptional maximum energy density of 187.6 Wh kg-1 and power density of 48.6 kW kg-1. Overall, this study offers an unprecedented powerful strategy for the design and optimization of cathode materials, paving the way for efficient and sustainable energy storage solutions to meet the increasing demands of modern energy applications.

Hybrid Ascharite/Reduced Graphene Oxide with Polysulfide Adsorption Host for Advanced Lithium-Sulfur Batteries

Balancing the adsorption of lithium-polysulfide intermediates on polar host material surfaces and the effect of their electronic conductivity in the subsequent oxidation and reduction kinetics of electrochemical reactions is necessary and remains a challenge. Herein, we have evaluated the role of polarity and conductivity in preparing a series of ascharite/reduced graphene oxide (RGO) aerogels by dispersing strong polar ascharite nanowires of varying mass into the conductive RGO matrix. When severed as Li-S battery cathodes, the optimized S@ascharite/RGO cathode with a sulfur content of 73.8 wt % demonstrates excellent rate performance and cycle stability accompanied by a high-capacity retention for 500 cycles at 1.0 C. Interesting advantages including the enhanced adsorption ability by the formation of the Mg-S and Li bonds, the continuous and quick electron/ion transportations assembled conductive RGO framework, and the effective deposition of Li2S are combined in the ascharite/RGO aerogel hosts. The electrochemical results further demonstrate that the polarity of ascharite components for the S cathode plays a dominant role in the improvement of electrochemical performance, but the absence of a conductive substrate leads to serious capacity attenuation, especially the rate performance. The balanced design protocol provides a universal method for the synthesis of multiple S hosts for high-performance LSBs.

Insights into Structural Behaviors of Thiolated and Aminated Reduced Graphene Oxide Supports to Understand Their Effect on MOR Efficiency

It is essential to develop novel catalysts with high catalytic activity, strong durability, and good stability for further application in methanol fuel cells. In this work, we present for the first time the effect of the chemical functional groups (thiol and amine) with different electron affinity in reduced graphene oxide supports on the morphology and catalytic activity of platinum nanoparticles for the methanol oxidation reaction. Hydroxyl groups on graphene oxide were initially brominated and then transformed to the desired functional groups. The good dispersion of metal nanoparticles over functionalized carbon substrates (particle size less than 5 nm) with good durability, even at a limited functionalization degree (less than 7%) has been demonstrated by morphological and structural studies. The durability of the catalysts was much improved via strong coordination between the metal and nitrogen or sulfur atoms. Impressively, the catalytic activity of platinum nanoparticles on aminated reduced graphene oxide was found to be much better than that on thiolated graphene oxide despite the weaker affinity between amine and noble metals. These findings support further developing new graphene derivatives with the desired functionalization for electronics and energy applications..

The "How" and "Where" Behind the Functionalization of Graphene Oxide by Thiol-ene "Click" Chemistry

Graphene oxide (GO) is a 2D nanomaterial with unique chemistry due to the combination of sp2 hybridization and oxygen functional groups (OFGs) even in single layer. OFGs play a fundamental role in the chemical functionalization of GO to produce GO-based materials for diverse applications. However, traditional strategies that employ epoxides, alcohols, and carboxylic acids suffer from low control and undesirable side reactions, including by-product formation and GO reduction. Thiol-ene "click" reaction offers a promising and versatile chemical approach for the alkene functionalization (-C=C-) of GO, providing orthogonality, stereoselectivity, regioselectivity, and high yields while reducing by-products. This review examines the chemical functionalization of GO via thiol-ene "click" reactions, providing insights into the underlying reaction mechanisms, including the role of radical or base catalysts in triggering the reaction. We discuss the "how" and "where" the reaction takes place on GO, the strategies to avoid unwanted side reactions, such as GO reduction and by-product formation. We anticipate that multi-functionalization of GO via the alkene groups will enhance GO physicochemical properties while preserving its intrinsic chemistry.

Controlling the spacing of the linked graphene oxide system with dithiol linkers under confinement

2D nanoscale confined systems exhibit behavior that is markedly different from that observed at the macroscale. Confinement can be tuned by controlling the interlayer spacing between confining layers using organic dithiol linkers. Adjusting spacing and selective intercalation have important impacts for catalysis, superconductivity, spin engineering, sodium ion batteries, 2D magnets, optoelectronics, and many other applications. In this study, we report how reaction conditions and organic linkers can be used to create variable, reproducible spacings between graphene oxide to provide confinement systems. We determined the conditions under which the spacing can be variably adjusted by the type of linker used, the concentration of the linker, and the reaction conditions. Employing dithiol linkers of different lengths, such as three (TPDT) and four (QPDT) aromatic rings, we can adjust the spacing between graphene oxide layers under varied reaction conditions. Here, we show that by varying dithiol linker length and using different reaction conditions, we can reproducibly control the spacing between graphene oxide layers from 0.37 nm to over 0.50 nm.

ZIF-67 on Sulfur-Functionalized Graphene Oxide for Lithium-Sulfur Batteries

How to overcome the problem of fast capacity fading and low sulfur utilization is the key to promote the practical applications of lithium-sulfur (Li-S) batteries. Based on the fact that sulfur-functionalized graphene oxide (GO-S) can avoid the loss of sulfur/polysulfides through the strong C-S interaction, and the zeolitic imidazolate framework (ZIF-67) can capture sulfur and catalyze lithium polysulfide (Li₂S_x, 4 ≤ x ≤ 8), the combination of ZIF-S (ZIF-67 after combining with sulfur) with GO-S can be expected to be an excellent electrode material for Li-S batteries due to the synergistic effect. Herein, ZIF-S@GO-S (n) nanocomposites (n = 1, 2, and 3 for the mass ratio of ZIF-67/GO of 4:1, 6:1, and 8:1, respectively) as the cathode materials in Li-S batteries were successfully fabricated, and ZIF-S@GO-S (2) showed better electrochemical performances and cycle stability with a high specific capacity of 1529.5 mA h g^-1 at the initial cycle and 792 mA h g^-1 after 500 cycles at 0.1 C (1 C = 1675 mA h g^-1). The fact that ZIF-S@GO-S (n) can simultaneously improve the conductivity and utilization of S (C-S···S₈ and C-S···S_xLi₂) and the conversion kinetics of Li₂S_x (4 ≤ x ≤ 8) provides a new avenue for designing and fabricating promising cathodes for high-performance Li-S batteries.

Recent trends in covalent functionalization of 2D materials

Covalent functionalization of the surface is more crucial in 2D materials than in conventional bulk materials because of their atomic thinness, large surface-to-volume ratio, and uniform surface chemical potential. Because...

Preparation of graphene/copper composites with a thiophenol molecular junction for thermal conduction application

An electron thermal conduction route is constructed between graphene and Cu using a thiophenol molecular junction.

Functional groups in graphene oxide

Graphene oxide consists of diverse surface chemistry which allows tethering GO with additional functionalities and tuning its intrinsic properties. This review summarizes recently advanced methods to covalently modify GO for specific applications.

Sulfur Functionalization via Epoxide Ring Opening on a Reduced Graphene Oxide Surface to Form Metal (II) Organo-bis-[1,2]-oxathiin

The epoxide ring-opening reaction in graphene oxide (GO) by nucleophiles is a very fascinating and advanced methodology to develop novel functional material. Herewith, we report an advanced strategy for opening the epoxide ring on the rGO surface via easily an available nucleophile (Na₂S), which is further functionalized with O atom to obtain four-membered rings (FMRs). The Cd coordination with the S atom puts extra stress on the FMR leading to the C-C bond cleavage of the four-membered heteroatomic rings on the rGO surface. This strategic approach leads to the fabrication of an innovative metal (II) organo-bis-[1,2]-oxathiin (MOBOT) chemical moiety (M = Cd, Zn). The MOBOT compound further shows enhanced H₂ generation activity and hence is promising as a potential photocatalyst for solar hydrogen generation. This compound might also be a potential candidate for optoelectronic applications.

High Li-Ion Conductivity Artificial Interface Enabled by Li-Grafted Graphene Oxide for Stable Li Metal Pouch Cell

The fragile electrolyte/Li interface is responsible for the long-lasting consumption of Li resources and fast failure of Li metal batteries. The polymer artificial interface with high mechanical flexibility is a promising candidate to maintain the stability of the electrolyte/Li interface; however, sluggish Li-ion transportation of the conventional polymer interface hinders the application. In this work, Li-functionalized graphene oxide (GO-ADP-Li₃), which is synthesized by covalent grafting of adenosine 5'-diphosphate lithium on GO nanosheets, is used as a functional additive to improve the Li-ion conductivity of the polymer artificial interface based on PVDF-HFP/LiTFSI. The enhanced Li-ion conductivity is contributed by accelerated Li-ion hopping at the surface between polymer chains and functionalized GO as well as the reduced crystallization degree of PVDF-HFP by this novel additive. The use of this modified polymer as an artificial interface on Li foil enables highly reversible Li stripping/plating and a high capacity retention of 78.4% after 150 cycles for a 0.2 A h Li metal pouch cell (Li/NCM811, strictly following practical conditions). This Li-grafted strategy on GO sheets provides an alternative for designing a compatible electrolyte/Li interface for practical Li metal batteries.

Functionalization of Graphene Oxide with Porphyrins: Synthetic Routes and Biological Applications

Among the available carbon nanomaterials, graphene oxide (GO) has been widely studied because of the possibility of anchoring different chemical species for a large number of applications, including those requiring water-compatible systems. This Review summarizes the state-of-the-art of synthetic routes used to functionalize GO, such as those involving multiple covalent and non-covalent bonds to organic molecules, functionalization with nanoparticles and doping. As a recent development in this field, special focus is given to the formation of nanocomposites comprising GO and porphyrins, and their characterization through spectroscopic techniques (such as UV-Vis, fluorescence, Raman spectroscopy), among others. The potential of such hybrid systems in targeted biological applications is also discussed, namely for cancer therapies relying on photodynamic and photothermal therapies and for the inhibition of telomerase enzyme. Lastly, some promising alternative materials to GO are presented to overcome current challenges of GO-based research and to inspire future research directions in this field.

Metal-free bifunctional graphene oxide-based carbocatalysts toward reforming biomass from glucose to 5-hydroxymethylfurfural

Graphene oxide (GO) and its derivatives are promising metal-free heterogeneous catalysts due to their high surface area and rich chemical properties. We developed a bifunctional boron-doped sulfonated graphene oxide (BS-GO) and demonstrated its excellent catalytic conversion of glucose to 5-hydroxymethylfurfural (HMF) in a one-pot reaction. BS-GO afforded a high HMF yield of 36.0% from glucose without the use of additives or strong acids. Furthermore, the origin of the catalytic active sites of BS-GO was investigated, unveiling the unique bifunctional catalytic mechanism; it was revealed that two disjunct moieties, boronic acid and phenylsulfonic acid, in a single nanosheet of BS-GO catalyst have a bifunctional effect resulting in excellent catalytic production of HMF. This study suggests the potential of BS-GO as a green and sustainable carbocatalyst for reforming biomass to produce value-added chemicals. We anticipate that the unique structural design presented in this study will provide a guide to afford viable carbocatalysts for diverse organic reactions.

Easily Processable, Highly Transparent and Conducting Thiol-Functionalized Reduced Graphene Oxides Langmuir-Blodgett Films

We report synthesis and fabrication of highly thionated reduced graphene oxide and its Langmuir-Blodgett (LB) film without an LB trough. As the synthesized product, mercapto reduced graphene oxide (mRGO) contains high thiol content estimated from XPS, corresponding to a surface coverage of 1.3 SH/nm². The mRGO LB film shows two electronic transport properties, following Efros-Shklovskii variable-range hopping (VRH) and Mott VRH at low and high temperature, respectively. Optical and band gap of the LB film was estimated from Tauc plot and semi-logarithmic-scale plot of sheet resistance versus temperature to be 0.6 and 0.1 eV, respectively. Additionally, the sheet resistance of the mRGO LB film depends on the quantity of the thiol functional group with the same transmittance at 550 nm (500 kΩ for mRGO, 1.3 MΩ for tRGO with 92% transmittance).

Lerf-Klinowski-type models of graphene oxide and reduced graphene oxide are robust in analyzing non-covalent functionalization with porphyrins

Graphene-based nanohybrids are good candidates for various applications. However, graphene exhibits some unwanted features such as low solubility in an aqueous solution or tendency to aggregate, limiting its potential applications. On the contrary, its derivatives, such as graphene oxide (GO) and reduced graphene oxide (RGO), have excellent properties and can be easily produced in large quantities. GO/RGO nanohybrids with porphyrins were shown to possess great potential in the field of photocatalytic hydrogen production, pollutant photodegradation, optical sensing, or drug delivery. Despite the rapid progress in experimental research on the porphyrin-graphene hybrids some fundamental questions about the structures and the interaction between components in these systems still remain open. In this work, we combine detailed experimental and theoretical studies to investigate the nature of the interaction between the GO/RGO and two metal-free porphyrins 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) and 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (TPPH)]. The two porphyrins form stable nanohybrids with GO/RGO support, although both porphyrins exhibited a slightly higher affinity to RGO. We validated finite, Lerf-Klinowski-type (Lerf et al. in J Phys Chem B 102:4477, 1998) structural models of GO ([Formula: see text]) and RGO ([Formula: see text]) and successfully used them in ab initio absorption spectra simulations to track back the origin of experimentally observed spectral features. We also investigated the nature of low-lying excited states with high-level wavefunction-based methods and shown that states' density becomes denser upon nanohybrid formation. The studied nanohybrids are non-emissive, and our study suggests that this is due to excited states that gain significant charge-transfer character. The presented efficient simulation protocol may ease the properties screening of new GO/RGO-nanohybrids.

Edge-Functionalized Nanographenes

Nanographenes (NGs) have recently emerged as new carbon materials. Their nanoscale size results in a size-dependent quantum confinement effect, opening the band gap by a few eV. This energy gap allows NGs to be applied as optical materials. This property has attracted researchers across multiple scientific fields. The photophysical properties of NGs can be manipulated by introducing organic groups onto their basal planes and/or into their edges. In addition, the integration of organic functional groups into NGs results in NG-based hybrid materials. These features make the post-synthetic modification of NGs an active research area. As obtainable information on chemically functionalized NGs is limited owing to their nonstoichiometry and structural uncertainty, their structural characterization requires a combination of multiple spectroscopic methods. Therefore, information on the characterization procedures of recently published chemically functionalized NGs is of value for advancing the field of NG-based hybrid materials. The present review focuses on the structural characterization of chemically functionalized NGs. It is hoped that this review will help to advance this field.

Magnetic solid-phase extraction for speciation of mercury based on thiol and thioether-functionalized magnetic covalent organic frameworks nanocomposite synthesized at room temperature

A simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method for extraction and determination of trace mercury species, including inorganic mercury (IHg), monomethylmercury (MeHg) and ethylmercury (EtHg), was developed. The MSPE adsorbent, urchin-like thiol and thioether-functionalized magnetic covalent organic frameworks (Fe₃O₄@COF-S-SH), was synthesized by coating covalent organic frameworks (COFs) on the surface of Fe₃O₄ nanoparticles at room temperature and then easily grafting 1,2-Ethanedithiol on the COFs. The as-prepared Fe₃O₄@COF-S-SH has strong adsorption capacity for IHg, MeHg and EtHg, with excellent static adsorption capacity: 571, 559 and 564 mg g^-1, respectively. The parameters influencing the extraction and enrichment had been optimized, including pH, adsorption and desorption time, composition and amount of the eluent, co-existing ions and dissolved organic materials etc. Under the optimized condition, the limit of detection (3δ) of the proposed method were 0.96, 0.17 and 0.47 ng L^-1 for IHg, MeHg and EtHg, and the developed method has high actual enrichment factors of 370, 395, 365-fold for IHg, MeHg and EtHg based on 200 mL samples, respectively. The high accuracy and reproducibility has been proved by the spiked recoveries (96.0‒108 %) in real water samples and determination of the certified reference material. Both the adsorption and desorption process can be completed within 5 min. The proposed method with simple operation, short pre-concentration time and high sensitivity has been successfully applied to mercury speciation at trace levels in the samples with complicated matrices, including underground water, surface water, sea water and fish samples.

Three-Dimensional Binary-Conductive-Network Silver Nanowires@Thiolated Graphene Foam-Based Room-Temperature Self-Healable Strain Sensor for Human Motion Detection

A lot of attention has recently been focused on wearable strain sensors because of their promising applications in the rising areas of human motion detection, health monitoring, and smart human-machine interaction. However, the design and fabrication of self-healable strain sensors with superior overall properties including stretchability, sensitivity, response ability, stability, and durability is still a huge challenge. Herein, we report an innovative self-healable strain sensor with exceptional overall performance constructed with three-dimensional binary-conductive-network silver nanowire-coated thiolated graphene foam (AgNWs@TGF) and room-temperature self-healing functionalized polyurethane (FPU) elastomer. Taking advantage of the good ductility and continuity of the AgNWs@TGF binary structure and the excellent resilience of the FPU, the strain sensor exhibits good stretchability (up to 60% strain), high sensitivity [gauge factor (GF) of 11.8 at 60% strain and detection limit of 0.1% strain], fast response ability (response/recovery time of 40/84 ms), and exceptional durability for 800 cycles of fatigue test. Besides, the highly flexible polydimethylsiloxane chains, strong intermolecular hydrogen bonding, and dynamic exchange reaction of aromatic disulfides ensure the sensor excellent recovery property of electrical conductivity, and the GF of sensor after self-healed only increases slightly. More importantly, the sensor is successfully applied for detecting a variety of human motions including pulse beats, voice recognitions, various joint movements, and handwriting. The method for preparing room-temperature self-healable strain sensor is facile, scalable, and cost-effective. The finds provide a new perspective on fabricating new-generation high-performance and functional strain sensors for health monitoring, wearable electronics, and intelligent robots.

State of the art: synthesis and characterization of functionalized graphene nanomaterials

Nanomaterials play nowadays a preponderant role in the field of materials science due to the wide range of applications and synergy with other fields of knowledge. Recently, carbonaceous nanomaterials, most notably bi-dimensional graphene (2D graphene), have been highlighted by their application in several areas: electronics, chemistry, medicine, energy and the environment. The search for new materials has led many researchers to develop new routes of synthesis and the expansion of the current means of production, by the anchoring of other nanomaterials on graphene surface, or by modifications of its hexagon sp2 structure, through the doping of heteroatoms. By adding functional groups to the graphene surface, it is possible to increase its affinity with other materials, such as polymers, magnetic nanoparticles and clays, leading to the formation of new nanocomposites. Several covalent and non-covalent functionalization processes, their advantages and disadvantages with respect to their interactions with other chemical species, are discussed in this review. The characterization of these materials is a sensitive topic, since the insertion of functional groups over the graphene basal plane causes changes in its morphology and the so-called chemistry of surface. In this sense, beyond the classical techniques, such as x-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), Raman Spectroscopy and Transmission Electron Microscopy (TEM), modern characterization techniques of graphene-based nanomaterials are discussed, focusing on those more indicated according to the proposed modifications. A significant attention was driven to environmental applications of functionalized graphenes, specifically in the removal of pollutants from wastewaters.

Controlled Assembly of Cu/Co-Oxide Beaded Nanoclusters on Thiolated Graphene Oxide Nanosheets for High-Performance Oxygen Evolution Catalysts

The use of water splitting modules is highly desired for the sustainable production of H₂ as a future energy carrier. However, the sluggish kinetics and demand of high anodic potential are the bottlenecks for half-the cell oxygen evolution reaction (OER), which severely hamper the overall conversion efficiency. Although transition metal oxides based electrocatalysts have been envisioned as cost-effective and potential contenders for this quest, nevertheless, their low conductivity, instability, and limited number of active sites are among the common impediments that need to be addressed to eventually enhance their inherent catalytic potential for enhanced OER activity. Herein, the controlled assembly of transition metal oxides, that is, Cu@CuO_x nanoclusters (NCs, ≈2 nm) and Co@CoO_x beaded nanoclusters (BNCs, ≈2 nm), on thiol-functionalized graphene oxide (G-SH) nanosheets is reported to form novel and highly efficient electrocatalysts for OER. The thiol (-SH) functionality was incorporated by selective epoxidation on the surface of graphene oxide (GO) to achieve chemically exfoliated nanosheets to enhance its conductivity and trapping ability for metal oxides in nanoscale dimensions (≈2 nm). During the electrocatalytic reaction, overpotentials of 290 mV and 310 mV are required to achieve a current density of 10 mA cm^-2 for BNCs and NCs, respectively, and the catalysts exhibit tremendous long-term stability (≈50 h) in purified alkaline medium (1 m KOH) with no dissolution in the electrolyte. Moreover, the smaller Tafel slopes (54 mV/dec for BNCs and 66 mV/dec for NCs), and a Faradic efficiency of approximately 96 % indicate not only the selectivity but also the tailored heterogeneous electrons transfer (HET) rate, which is required for fast electrode kinetics. It is anticipated that such ultrasmall metal oxide nanoclusters and their controlled assembly on a conducting surface (G-SH) may offer high electrochemical accessibility and a plethora of active sites owing to the drastic decrease in dimensions and thus can synergistically ameliorate the challenging OER process.

Theranostic Nanoplatforms of Thiolated Reduced Graphene Oxide Nanosheets and Gold Nanoparticles

In this study, graphene oxide (GO) and reduced-thiolated GO (rGOSH) were used as 2D substrate to fabricate nanocomposites with nanoparticles of gold nanospheres (AuNS) or nanorods (AuNR), via in situ reduction of the metal salt precursor and seed-mediated growth processes. The plasmonic sensing capability of the gold-decorated nanosheets were scrutinized by UV-visible (UV-VIS) spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analyses (TGA), and atomic force microscopy (AFM) were performed in order to prove the actual reduction that occurred concomitantly with the thiolation of GO, the increase in the hydrophobic character as well as the size, and preferential gathering of the gold nanoparticles onto the nanosheet substrates, respectively. Moreover, the theoretical electronic and infrared absorption (UV-VIS and IR) spectra were calculated within a time-dependent approach of density functional theory (DFT). Eventually, in vitro cellular experiments on human neuroblastoma cells (SH-SY5Y line) were carried out in order to evaluate the nanotoxicity of the nanocomposites by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium reduction (MTT) colorimetric assay. Results pointed out the promising potential of these hybrids as plasmonic theranostic platforms with different hydrophilic or hydrophobic features as well as cytotoxic effects against cancer cells.

Aerogel doped by sulfur-functionalized graphene oxide with convenient separability for efficient patulin removal from apple juice

Patulin (PAT) contaminant causes severe food safety issue throughout apple industry. Although adsorption is the feasible approach to remove PAT, the limited adsorption capacity and separation difficulty of most adsorbent is the major drawback that remains to be overcome. Here GO-SH doped aerogel was prepared and used for removal PAT from apple juice. The intrinsic porous of the aerogel and abundant active sites including -COOH, -NH₂ and -SH offered the PAT adsorption capacity of 24.75 μg/mg that superior to most reported adsorbents. Furthermore, it could reduce 89 ± 1.23% PAT in real apple juice without juice quality deterioration and cytotoxicity. Importantly, the aerogel with good mechanical strength and structure stability could endure the complex juice solution so that there was no any residue after convenient separation of the aerogel, which proved that the proposed aerogel was a promising adsorbent to be applied to apple juice industry for PAT removal.

Chemically Functionalized Two-Dimensional Carbon Materials

Nanographenes (NGs), also known as graphene quantum dots, have recently been developed as nanoscale graphene fragments. These nanocarbon species can be excited with UV light and emit light from the UV-to-visible region. This photoemission has received great attraction across multiple scientific fields. NGs can be produced by cutting off carbon sources or fusing small organic molecules to grow graphitic structures. Furthermore, the organic synthesis of NGs has been intensely studied. Recently, the number of research papers on postsynthetic modification of NGs has gradually increased. Installed organic groups can tune the properties of NGs and provide new functionalities, opening the door for the development of sophisticated carbon-based functional materials. This review sheds light on recent progress in the postsynthetic modification of NGs and provides a brief summary of their production methods.

Concise, Single-Step Synthesis of Sulfur-Enriched Graphene: Immobilization of Molecular Clusters and Battery Applications

The concise synthesis of sulfur-enriched graphene for battery applications is reported. The direct treatment of graphene oxide (GO) with the commercially available Lawesson's reagent produced sulfur-enriched-reduced GO (S-rGO). Various techniques, such as X-ray photoelectron spectroscopy (XPS), confirmed the occurrence of both sulfur functionalization and GO reduction. Also fabricated was a nanohybrid material by using S-rGO with polyoxometalate (POM) as a cathode-active material for a rechargeable battery. Transmission electron microscopy (TEM) revealed that POM clusters were individually immobilized on the S-rGO surface. This battery, based on a POM/S-rGO complex, exhibited greater cycling stability for the charge-discharge process than a battery with nanohybrid materials positioned between the POM and nonenriched rGO. These results demonstrate that the use of sulfur-containing groups on a graphene surface can be extended to applications such as the catalysis of electrochemical reactions and electrodes in other battery systems.

L-cysteine reduced/functionalized graphene oxide application as a smart/control release nanocarrier of sustainable cerium ions for epoxy coating anti-corrosion properties improvement

One of the main limitations for large scale mass production of reduced graphene oxide is the application of some toxic and hazardous reducing agents such as hydrazine and borohydride. In this study, the effectiveness of the l-Cys (HSCH₂CH(NH₂)CO₂H) molecules, as a green amino acid in the GO reduction, as well as its active corrosion inhibition capacity were explored. The l-Cys/GO nanosheets were then modified by trivalent-cerium ions to obtain a nanocarrier with excellent controlled release activity. The electrochemical impedance spectroscopy (EIS) and polarization tests were used to measure the smart corrosion inhibition activity of the cerium modified l-Cys/GO nanocarrier in the saline solution and epoxy coating. The results showed that the cerium ions adsorption on the l-Cys/GO nanosheets obeyed a Langmuir isotherm model. The l-Cys/GO sample showed cerium ions adsorption capacity about 66% higher than the unmodified GO nanosheets. Furthermore, the EIS tests results revealed that in the presence of cerium modified l-Cys/GO nanocarriers the improvement in the corrosion resistance of bare steel in the solution phase and coated sample was about 7.5 times (after 24 h) and 950 times (after 40 days) higher than the blank saline solution and the pure epoxy sample, respectively.

rGO/GO Nanosheets in Tribology: From the State of the Art to the Future Prospective

In the last few decades, in the lubricant industry, the request for new performing additives has been becoming imperative. In this scenario, control at the nanoscale can be the key factor for the improvement of more efficient nanolubricants. Herein, after a discussion about the nanoparticles’ four main lubrication mechanisms, considerable attention is devoted to the usage of reduced graphene oxide/graphene oxide (rGO/GO) nanosheets in tribology. Moreover, graphene surface functionalization is reviewed, also including unexplored results in the field of lubrication. As far as the literature is concerned, it can be postulated that rGO/GO nanosheets can reduce wear and friction. Wear reduction is obtained by deposition and film formation, while friction reduction is related more to the shear and lamination of the sheets on the contacting surfaces. Nevertheless, the two phenomena are interrelated and work in sync. In this context, it is of high importance to form a homogenous suspension for a continuous nanosheet supply after deposition and shearing. The focus of this review was placed on the main issues still to be overcome, e.g., the literature results in rationalization; dispersion stability enhancement; and finding the optimum concentration in the delicate balance of different components. Possible solutions for their efficient overcoming are eventually reported.

A Flexible Method for Covalent Double Functionalization of Graphene Oxide

A method for the double functionalization of graphene oxide (GO) under mild alkaline conditions has been developed. Two functional groups were covalently linked to GO in two steps: the first group was attached by an epoxide ring-opening reaction and the second, bearing an amine function, was covalently conjugated to benzoquinone attached to the GO. The doubly functionalized GO was characterized by several techniques, confirming the sequential covalent modification of the GO surface with two different functional groups. This method is straightforward and the reaction conditions are mild, allowing preservation of the structure and properties of GO. This strategy could be exploited to prepare multifunctional GO conjugates with potential applications in many fields ranging from materials science to biomedicine.

Simultaneous Improvement on Strength, Modulus, and Elongation of Carbon Nanotube Films Functionalized by Hyperbranched Polymers

Carbon nanotube (CNT) buckypapers, or films, have the potential for wide applications because of their unique properties. Neat buckypapers or pristine CNT (PCNT) films have relatively large elongation but low strength and low modulus due to the weak interaction between CNTs. Chemical modifications of PCNT films can significantly strengthen the interaction between CNTs, resulting in high strength and high modulus but usually accompanied by low elongation. Here, we report the functionalization of pristine CNT films by thiol-ended hyperbranched polymers (THBP-n) via a thiol-ene click reaction that can introduce simultaneous improvements on the strength, modulus, and elongation to the PCNT film by 689, 812, and 32.4%, respectively. The high thiol content of THBP-n enables the formation of a network with a high degree of cross-linking between carbon nanotubes, which provides high-efficiency load transfer that increases the tensile strength and modulus of the resulting films and at the same time a compressible hyperbranched structure that allows for deformation and slip between CNTs and consequently improved elongation. The main factors affecting the mechanical performance of the functionalized CNT film are also investigated.

The encapsulation of metal nanoparticles within porous liquids

Herein, we report the first successful encapsulation of metal nanoparticles within a Type I porous liquid. We found that the presence of thiol groups was critical to both the encapsulation and the stabilisation of the metal nanoparticles.

Highly efficient and cost-effective removal of patulin from apple juice by surface engineering of diatomite with sulfur-functionalized graphene oxide

Patulin (PAT) contamination of apple juice leads to a serious food safety issue. Developing an excellent adsorbent to efficiently remove PAT is more desirable. Herein, a cost-effective and efficient adsorbent (GO-SH/diatomite) with abundant active sites was successfully fabricated via surface engineering of diatomite with sulfur-functionalized graphene oxide (GO-SH) nanosheets, which exhibited excellent selective adsorption capacity toward PAT. The adsorption behavior, adsorption mechanism, stability and cytotoxicity were investigated by systematic studies. The adsorption results showed that its maximum adsorption capacity was 10.68 μg/mg. Moreover, attributed to the specific interaction between PAT and thiol group, more than 90% of PAT was removed from apple juice without any juice quality deterioration. Importantly, the risk of food safety issue of apple juice caused by residual GO-SH/diatomite was negligible due to the properties of easy removal and excellent biocompatibility, which guaranteed its potential application in apple juice industry for PAT removal.

Synthesis of nanogate structure in GO-ZnS sandwich material

Graphite Oxide (multi-layer) composite with other materials has a huge application in various field of science, due to its excellent and unique properties. Even though from past decade, immense research has been done by materials scientists in this field, but the chemistry is still not yet satisfactory. Here, in this work, through the discovery of Nanogate structure, we have reported for the first time the experimental results that enlightened the clear chemistry between the GO and ZnS which is further supported by the DFT calculations. This novel synthesis method led to the discovery of nanogate structure sandwiched between the GO layers. The nanogate formation also shows enhanced properties for various applications like photocatalytic activities, etc. Due to the nanogate formation, there might be a possibility of enormous generation of electrons on excitation of the composite materials, which can be a boom for various applications like photocatalysis, water splitting, solar cell, etc.

Thiolated Graphene@Polyester Fabric-Based Multilayer Piezoresistive Pressure Sensors for Detecting Human Motion

In the past several years, wearable pressure sensors have engendered a new surge of interest worldwide because of their important applications in the areas of health monitoring, electronic skin, and smart robots. However, it has been a great challenge to simultaneously achieve a wide pressure-sensing range and high sensitivity for the sensors until now. Herein, we proposed an innovative strategy to construct multilayer-structure piezoresistive pressure sensors with an in situ generated thiolated graphene@polyester (GSH@PET) fabric via the one-pot method. Taking advantage of the spacing among the rough fabric layers and the highly conductive GSH, the sensor realized not only a wide pressure range (0-200 kPa), but also high sensitivity (8.36 and 0.028 kPa^-1 in the ranges of 0-8 and 30-200 kPa, respectively). After 500 loading-unloading cycles, the sensor still kept high sensitivity and a stable response, exhibiting great potential in long-term practical applications. Importantly, the piezoresistive pressure sensor was successfully applied to accurately detect different human behaviors including pulse, body motion, and voice recognition. Additionally, the sensing network integrated by the sensors also realized mapping and identifying spatial pressure distribution. Our method to construct the wide-range and high-sensitivity piezoresistive pressure sensor is facile, cost-effective, and available for mass production. The findings provide a new direction to fabricate the new-generation high-performance sensors for healthcare, interactive wearable devices, electronic skin, and smart robots.

Functionalization of graphene: does the organic chemistry matter?

Reactions applying amidation- or esterification-type processes and diazonium salts chemistry constitute the most commonly applied synthetic approaches for the modification of graphene-family materials. This work presents a critical assessment of the amidation and esterification methodologies reported in the recent literature, as well as a discussion of the reactions that apply diazonium salts. Common misunderstandings from the reported covalent functionalization methods are discussed, and a direct link between the reaction mechanisms and the basic principles of organic chemistry is taken into special consideration.

Mussel-inspired construction of thermo-responsive double-hydrophilic diblock copolymers-decorated reduced graphene oxide as effective catalyst supports for highly dispersed superfine Pd nanoparticles

Well-dispersed ultrafine palladium nanoparticles supported by reduced graphene oxide functionalized with catechol-terminated thermo-responsive block copolymer (PdNPs@BPrGO) were successfully constructed for highly efficient heterogeneous catalytic reduction. We first synthesized a novel temperature-responsive episulfide-containing double-hydrophilic diblock copolymer, poly(poly(ethylene glycol) methyl ether methacrylate-co-2,3-epithiopropyl methacrylate)-block-poly(N-isopropylacrylamide) (P(PEGMA-co-ETMA)-b-PNIPAM), through a reversible addition-fragmentation chain transfer (RAFT) polymerization utilizing a chain-transfer agent with a catechol unit as the end group. The obtained block copolymers can be facilely anchored to the surface of GO via mussel-inspired chemistry. The PdNPs were loaded on GO decorated with block copolymer brushes (BPrGO) as a support via the in situ reduction of palladium precursors with the episulfide ligands of the block copolymer as a stabilizer. The resulting PdNPs@BPrGO nanohybrid catalyst had good water dispersibility and stability. Furthermore, a low dosage of PdNPs@BPrGO catalyst exhibited excellent catalytic performance in the reduction of methylene blue and nitrophenols. The performance was attributed to the ability of PdNPs@BPrGO to facilitate the diffusion of reactants compared to PdNPs@GO without polymer modification. PdNPs@BPrGO also possessed an interesting temperature-responsive catalytic property due to the reversible "coil-to-globule" phase transition behaviour of PNIPAM blocks onto the surface of catalyst. The PdNPs@BPrGO catalyst was successfully recovered and reused five times without any detectible loss in catalytic activity, demonstrating its great potential in a wide range of industrial catalytic applications.

Impact of sequential surface-modification of graphene oxide on ice nucleation

Base-washed graphene-oxide which has been sequentially-modified by thiol-epoxy chemistry, results in materials with ice-nucleation activity. The role of hydro-philic/phobic grafts and polymers was evaluated with the most potent functioning at just 0.25 wt%. These 2-D hybrid materials may find use in cryopreservation and fundamental studies on ice formation.

Chemistry of Graphene Derivatives: Synthesis, Applications, and Perspectives

The chemistry of graphene and its derivatives is one of the hottest topics of current material science research. The derivatisation of graphene is based on various approaches, and to date functionalization with halogens, hydrogen, various functional groups containing oxygen, sulfur, nitrogen, phosphorus, boron, and several other elements have been reported. Most of these functionalizations are based on sp³ hybridization of carbon atoms in the graphene skeleton, which means the formation of out-of-plane covalent bonds. Several elements were also reported for substitutional modification of graphene, where the carbon atoms are substituted with atoms like nitrogen, boron, and several others. From tens of functional groups, for only two of them were reported full functionalization of graphene skeleton and formation of its stoichiometric counterparts, fluorographene and hydrogenated graphene. The functionalization of graphene is crucial for most of its applications including energy storage and conversion devices, electronic and optic applications, composites, and many others.