Hydrophilic Graphene Oxide Research Articles

Classification of Nanomaterials and the Effect of Graphene Oxide (GO) and Recently Developed Nanoparticles on the Ultrafiltration Membrane and Their Applications: A Review.

The emergence of mixed matrix membranes (MMMs) or nanocomposite membranes embedded with inorganic nanoparticles (NPs) has opened up a possibility for developing different polymeric membranes with improved physicochemical properties, mechanical properties and performance for resolving environmental and energy-effective water purification. This paper presents an overview of the effects of different hydrophilic nanomaterials, including mineral nanomaterials (e.g., silicon dioxide (SiO2) and zeolite), metals oxide (e.g., copper oxide (CuO), zirconium dioxide (ZrO2), zinc oxide (ZnO), antimony tin oxide (ATO), iron (III) oxide (Fe2O3) and tungsten oxide (WOX)), two-dimensional transition (e.g., MXene), metal-organic framework (MOFs), covalent organic frameworks (COFs) and carbon-based nanomaterials (such as carbon nanotubes and graphene oxide (GO)). The influence of these nanoparticles on the surface and structural changes in the membrane is thoroughly discussed, in addition to the performance efficiency and antifouling resistance of the developed membranes. Recently, GO has shown a considerable capacity in wastewater treatment. This is due to its nanometer-sized holes, ultrathin layer and light and sturdy nature. Therefore, we discuss the effect of the addition of hydrophilic GO in neat form or hyper with other nanoparticles on the properties of different polymeric membranes. A hybrid composite of various NPs has a distinctive style and high-quality products can be designed to allow membrane technology to grow and develop. Hybrid composite NPs could be used on a large scale in the future due to their superior mechanical qualities. A summary and future prospects are offered based on the current discoveries in the field of mixed matrix membranes. This review presents the current progress of mixed matrix membranes, the challenges that affect membrane performance and recent applications for wastewater treatment systems.

Surface modification of commercial reverse osmosis membranes using both hydrophilic polymer and graphene oxide to improve desalination efficiency.

Various methods have been applied to modify the surface of reverse osmosis (RO) membranes to modify the membrane performance to enhance the flux, rejection, and resistance to various factors of fouling. Hence, the main objective of the current study is to modify the surface of commercial RO membranes using the synergistic effect of the hydrophilic polymer and graphene oxide (GO). GO nanosheets were firstly synthesized by the modified hummer method, then characterized by FTIR, XRD, and SEM analyses. Then, the polyacrylic acid (PAA) was grafted on the membrane surface for membrane fabrication. Furthermore, effective factors of grafting such as monomer concentration, time, and temperature of polymerization were optimized. After that, different amounts of GO nanosheets were loaded in PAA optimized layer. Then, the effect of GO loading on the RO membrane structure and performance was investigated. The outcomes of membrane characterization demonstrated that modified RO membranes had a smoother surface, more negative surface charge, a little better hydrophilicity, and more thickness. Moreover, the results of PAA and GO optimization were shown that grafting 1.5mM of PAA and loading 0.1wt% of GO nanosheets give the best membrane performance. This membrane (GO 0.1@1.5M PAA/RO) between all modified membranes has the most water flux (37.1L/m2h), the highest NaCl rejection (98%), and the best antifouling efficiency. Ultimately, it was concluded that the grafting of GO@PAA on the surface of a commercial RO membrane is an efficient approach for the enhancement of desalination and antifouling performance of this kind of membrane.

Molecule stratification in 2D heterostructured nanochannels towards enhanced selective permeation

Here, lamellar membranes with hydrophilic/hydrophobic heterostructured nanochannels are constructed by alternately stacking graphene oxide (GO) and reduced graphene oxide (RGO) nanosheets via dual-needle electrostatic atomization. This technology exhibits facile controllability over membrane nanostructure, where the dual-needle device can compel active reactants to contact in confined space. Through subtly designing spraying parameters, GO and RGO nanosheets can be alternately deposited on the substrate to construct heterostructured nanochannels. And we demonstrate that the asymmetric channel wall-molecule interactions can induce molecule stratification for acetonitrile/water mixture, where hydrophilic GO layer exerts strong attraction to acetonitrile, whereas water molecules are pushed to hydrophobic RGO layer. Then, the strong attraction further induces acetonitrile molecules to form orderly aligned aggregates and transfer quickly, while water molecules are randomly distributed and transfer slowly. The pre-determined different transfer rates afford a high acetonitrile permeance of 38.9 L m–2h−1 bar−1 and separation factor of acetonitrile/water up to 4.8, surpassing that of homostructured lamellar membranes. Furthermore, this stratification and hence separation performance can be enhanced by channel length, acetonitrile amount in feed, operation temperature and pressure. The first discovery of molecule stratification in heterostructured nanochannels facilitates the sustainable development of advanced separation membranes.

Facile hydrophilic chitosan and graphene oxide modified sustainable non-woven fabric composite sieve membranes (NWF@Cs/Gx): Antifouling, protein rejection, and oil-water emulsion separation studies

Over the last few decades, antifouling, protein rejection, and oil-water separations have become a challenge to technologists and environmentalists. In view of this, the proposed work reports formulation, characterization of facile hydrophilic chitosan-graphene oxide modified sustainable non-woven fabric-based sieve membranes (NWF@Cs/Gx) along with their application for antifouling, protein rejection, and multigrade oil-water emulsions separation studies. The surface morphology, diameter size of the fibers, and elemental analysis of the same were characterized with high-resolution microscopes (SEM), EDAX, and spectroscopically. The hydrophilicity of these membranes was investigated using contact angle and water uptake studies that exhibited pure water flux up to 165 L.m−2.h−1. These studies further confirmed the multigrade oil/water emulsions separation with 98% efficiency and more than 96% protein (Bovine Serum Albumin) rejection. These studies suggest that the formulated membranes may find application in the field of environmental, biological, and petroleum-based industries.

Amino-functionalized graphene oxide supported in charcoal from the gasification of furniture scraps: From one-pot synthesis to wastewater remediation

Wood from furniture scraps were fed into a gasifier to produce clean energy, and its residual charcoal (FSC) was used as support for the development of an amino-functionalized multilayer graphene oxide (AmGO) composite. The AmGO supported on FSC (AmGO@FSC) and its pristine materials were characterized and then investigated as potential adsorbent of water pollutants. The supporting of AmGO on FSC consists in a two-way solution for environmental remediation, since a waste has been benefited to remove water pollutants. Moreover, supporting process eases the separation of the highly hydrophilic graphene oxide from the liquid medium, which is one of the main challenges in applying these nanomaterials. From equilibrium and kinetic studies, the maximum adsorption capacity at monolayer was 54.35 mg g−1, and equilibrium constant was 0.76 L mg−1, and Langmuir-Freundlich isotherm showed the best fit. Based on these studies, the predicted mechanisms of adsorption are governed by resistance to mass transfer in the bulk and liquid–solid film. Moreover, the molecules of Methylene Blue engaged the active sites of AmGO@FSC through π−π stacking and other weak interactions. Thermodynamic assays evidenced the spontaneity and the physical behavior of the adsorption, whilst the AmGO@FSC could be regenerated after six cycles. Finally, AmGO@FSC showed adsorptive capacity 2 times greater than its precursor material FSC. The great adsorptive capacity, high recoverability and easy separation bestow AmGO@FSC as one profitable adsorbent of textile dyes.

Synthesis and characterization of Graphene Oxide and its reduction with different reducing agents

-The present work reports the simplistic formation of graphene oxide (GO) and reduced graphene oxide (rGO) by oxidizing graphite powder with the 9:1 volume combination of concentrated sulfuric acid/and ortho-phosphoric acid (H2SO4/H3PO4) in the company of KMnO4 as an oxidant. The acid combination solution of H2SO4/H3PO4 produces the improved oxidized hydrophilic GO without any evolution of hazardous gases instead of only H2SO4, which differentiates this procedure from the Hummers’ method. Then, the synthesized GO is diminished to rGO by employing various reducers namely hydrazine hydrate, sodium borohydride and, ascorbic acid through the chemical route. The properties of synthesized materials have been investigated by diverse investigative systems that are X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Raman spectroscopy and, Energy Dispersive X-ray spectroscopy (EDS) which approved its high crystallinity and reduction of GO into rGO. EDS analysis confirms that the carbon to oxygen ratio is higher in rGO prepared by using hydrazine hydrate in comparison to rGO made by using sodium borohydride and ascorbic acid which reveals the good reducing capability of hydrazine hydrate. Hence, it may be concluded that the rGO synthesized by the reduction of GO in the presence of hydrazine hydrate is better as compared to others and it is expected that the synthesized material may be used for various applications.

PVA-Based MMMs for Ethanol Dehydration via Pervaporation: A Comparison Study between Graphene and Graphene Oxide

Two different types of 2D nanosheets, including hydrophobic graphene (GR) and hydrophilic graphene oxide (GO), were filled into poly (vinyl alcohol) (PVA) polymers to prepare mixed matrix membranes (MMMs) for ethanol dehydration via pervaporation. The relationship between the physical/chemical properties of graphene and pervaporation performance of MMMs was investigated by a comparison of GR/PVA and GO/PVA MMMs in microstructure and PV performance. The incorporation of GO nanosheets into PVA reduced PVA crystallinity and enhanced the membrane hydrophilicity, while the incorporation of GR into PVA led to the opposite results. The incorporation of GR/GO into PVA depressed the PVA membrane swelling degree, and the incorporation of GR showed a more obvious depression effect. GR/PVA MMMs showed a much higher separation factor than GO/PVA MMMs, while they exhibited a much lower permeation flux than GO/PVA MMMs and pristine PVA membranes. The huge difference in microstructure and performance between GO/PVA and GR/PVA MMMs was strongly associated with the oxygen-containing groups on graphene lamellae. The higher permeation flux of GO/PVA MMMs was ascribed to the facilitated transport of water molecules induced by oxygen-containing groups and exclusive channels provided by GO lamellae, while the much lower permeation flux and higher separation factor GR/PVA MMMs was resulted from the smaller GR interplanar spacing (0.33 nm) and hydrophobicity as well as barrier effect of GR lamellae on the sorption and diffusion of water molecules. It was presumed that graphene intercalated with an appropriate number of oxygen-containing groups might be a good choice to prepare PVA-based MMMs for ethanol dehydration, which would combine the advantages of GR’s high interlayer diffusion selectivity and GO’s high permeation properties. The investigation might open a door to achieve both of high permeation flux and separation factor of PVA-based MMMs by tuning the microstructure of graphene.

Localizable, Identifiable, and Perceptive Untethered Light-Driven Soft Crawling Robot.

Soft robots based on bionics have attracted extensive attention in recent years. However, most of previous works focused on the motion of robots that were incapable of communication and perception. In this work, an untethered crawling robot is proposed with integration of motion, communication, and location based entirely on a flexible material, which is capable of being utilized as a sensing platform. The hydrophilic graphene oxide film, capable of photothermal conversion, allows the robot to undergo a large deformation stimulated by near-infrared light. Conductive fabric with low resistivity and high mechanical strength, replacing the traditional rigid circuit, is utilized to complete the communication of the robot. The designed communication module allows an electrical signal to be inductively coupled to the soft robot instead of being generated by batteries or through transmission lines. The perception of the robot is demonstrated by covering sensitive materials. Furthermore, the positioning and identification of the robot are verified by an external coil array. The proposed soft crawling robot provides an innovative strategy for the integration of multifunctional robots and shows great potential in bionic devices, intelligent robots, and advanced sensors.

Graphene Oxide versus Carbon Nanofibers in Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Films: Degradation in Simulated Intestinal Environments.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a microbial biodegradable polymer with a broad range of promising industrial applications. The effect of incorporation of low amounts (1% w/w) of carbon nanomaterials (CBNs) such as 1D carbon nanofibers (CNFs) or 2D graphene oxide (GO) nanosheets into the PHBV polymer matrix affects its degradation properties, as it is reported here for the first time. The study was performed in simulated gut conditions using two different media: an acidic aqueous medium (pH 6) and Gifu anaerobic medium. The results of this study showed that the incorporation of low amounts of filamentous 1D hydrophobic CNFs significantly increased the degradability of the hydrophobic PHBV after 3 months in simulated intestinal conditions as confirmed by weight loss (~20.5% w/w in acidic medium) and electron microscopy. We can attribute these results to the fact that the long hydrophobic carbon nanochannels created in the PHBV matrix with the incorporation of the CNFs allowed the degradation medium to penetrate at ultrafast diffusion speed increasing the area exposed to degradation. However, the hydrogen bonds formed between the 2D hydrophilic GO nanosheets and the hydrophobic PHBV polymer chains produced a homogeneous composite structure that exhibits lower degradation (weight loss of ~4.5% w/w after three months in acidic aqueous medium). Moreover, the water molecules present in both degradation media can be linked to the hydroxyl (-OH) and carboxyl (-COOH) groups present on the basal planes and at the edges of the GO nanosheets, reducing their degradation potential.

Fabrication of Janus GO/rGO humidity actuator by one-step electrochemical reduction route

Graphene oxide (GO) is an insulator and should be converted to reduced graphene oxide (rGO) paper structure by reduction to provide electrochemical activity. This work maintains an essential route to fabricate rGO paper. Hence, the first aim of this study is to produce rGO paper by one-step electrochemical reduction of GO paper by the optimization of quality parameters. Humidity actuators produce mechanical feedback if the moisture is exposed to their surface. To provide this kind of response, Janus materials are good nominated due to their asymmetric surface character in terms of hydrophilicity. GO paper can be performed for this application by converting one side to rGO layers. By this approach, hydrophobic rGO and hydrophilic GO sheets of the Janus system are generated, in which moisture flow swells the GO side and causes bending motion of the material through the rGO layer. In this work, Janus GO/rGO paper has been prepared by one-step electrochemical reduction of one side of the GO paper. Characterization of the samples has been carried out using numerous techniques. Humidity actuator experiments have indicated that Janus GO/rGO paper is acting circularly and there is an exponential relationship between relative humidity and circularly-oriented bending angle of the actuator.

Wet chemical development of CuO/GO nanocomposites: its augmented antimicrobial, antioxidant, and anticancerous activity

This study employed a bottom-up technique to synthesize copper oxide (CuO) nanoparticles over hydrophilic graphene oxide (GO) nanosheets. The CuO/GO nanocomposite has been prepared using two selected precursors of copper nitrate and citric acid with an intermittent mixing of GO solutions. The synthesized Nanocomposites were characterized using different biophysical techniques like FT-IR, NMR, FE-SEM, and HR-TEM analyses. FT-IR analyses confirm the nanocomposites’ successful formation, which is evident from the functional groups of C=C, C-O, and Cu-C stretching vibrations. Morphological analyses reveal the depositions of CuO nanoparticles over the planar rough GO sheets, which has been elucidated from the FE-SEM and HR-TEM analyses supported by respective EDAX analyses. The antimicrobial activities have been evident from the surface roughness and damages seen from the FE-SEM analyses. The CuO/GO sheets were tested against Gram-positive (e.g., Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa). It is evident that the intrinsic antibacterial activity of CuO/GO sheets, when combined in equal proportions, elicited a robust antibacterial activity when tested over Gram –ve representative bacteria Escherichia coli. The antioxidant behaviour of synthesized CuO/GO nanocomposite was evaluated by scavenging the free radicals of DPPH and ABTS. Moreover, the cytotoxic activity was also studied against epidermoid carcinoma cell line A-431. A brief mathematical formulation has been proposed in this study to uncover the possibilities of using the nanocomposites as potential drug candidates in theranostic applications in disease treatment and diagnosis. This study would help uncover the electronic properties that play in the nano-scaled system at the material-bio interface, which would aid in designing a sensitive nano-electromechanical device bearing both the therapeutic and diagnostic attributes heralding a new horizon in the health care systems.

A Robust PVDF-Assisted Composite Membrane for Tetracycline Degradation in Emulsion and Oil-Water Separation.

Tetracycline (TC) contamination in water has progressively exacerbated the environmental crisis. It is urgent to develop a feasible method to solve this pollution in water. However, polluted water often contains oil. This paper reported a glass fiber (FG)-assisted polyvinylidene fluoride (PVDF) hybrid membrane with dual functions: high TC degradation efficiency in emulsion and oil-water separation. It can meet the catalytic degradation of tetracycline in complex water. This membrane was decorated by coating the glass fiber with PVDF solution containing hydrophilic graphene oxide hybridized NH2-MIL-101(Fe) particles. Moreover, due to its strong mechanical strength enhanced by the glass fiber, it can be reused as TC degradation catalysts for dozens of times without cracking. Thanks to the hydrophobicity of PVDF and the surface pore size of MOFs, the prepared membrane showed a good oil-water separation performance. Besides, the hydrophilic graphene oxide (GO) and NH2-MIL-101(Fe) improved the membrane’s anti-fouling performance, allowing it to be reused as the separation membrane. Therefore, the outstanding stability and recoverability of the membrane make it as a fantastic candidate material for large-scale removal of TC as well as oil-water separation application.

Robust seawater desalination and sewage purification enabled by the solar-thermal conversion of the Janus-type graphene oxide evaporator

The state-of-the-art structure design of solar-thermal evaporators demonstrating convenient manufacture, high evaporation rate, high energy efficiency and multiple environment evaporation is urgently needed in solar-driven low-energy water purification/harvesting. Herein, a novel Janus-type graphene oxide (GO) evaporator is proposed by chemical crosslinking to form integrated GO hydrogel and sunlight triggered partial reduction of top GO layer. The partially reduced GO (PRGO) nanosheets present an extremely high solar absorbance of 92.97%, leading to an efficient localized solar-thermal conversion. The porous and hydrophilic GO hydrogel facilitates the fast vertical water transport to the top PRGO photothermal layer. Taking advantages of the synergistic effect in the water-energy nexus, the Janus-type solar-thermal evaporator evaporates water with an ultra-high rate of 3.24 kg·m−2·h−1 via 99.98% energy efficiency from 1sun irradiation with a low GO loading of 0.146 wt%. The Janus-type GO evaporator presents robust desalination and purification performances in simulated seawater, sewage and acidic/alkaline water. Furthermore, a portable solar-thermal water purification device equipped with the Janus-type GO evaporator desalts a real seawater far above the drinking water standard with a 99.99% salt rejection rate and removes 90.90% of total carbon in a real sewage, highlighting its potential for high-performance clean water harvesting.

Influence of GO-Ag nano-filler on the antibacterial, antifouling and hydrophilic characteristics of polyvinyl chloride membrane

The integral hydrophobic characteristic of polymers hinders their implementations towards water treatment. In the present work, highly hydrophilic and antifouling polyvinyl chloride membranes were fabricated based on graphene oxide-silver (GO-Ag) nanolayers. The distinctive infiltration approach of polyvinyl chloride resin through the stacked GO-Ag layers results in surface availability of highly hydrophilic graphene oxide nanosheets. Incorporation of different weight percent of GO-Ag to the polyvinyl chloride resin increases the permeability, rejection and antifouling properties of polyvinyl chloride membranes. Water contact angle of pure polyvinyl chloride was found to decrease from 92.5° to 61.4° for GO-Ag based membrane. Water flux and bovine serum albumin rejection of pure polyvinyl chloride membrane were improved from 192 Lm−2 h−1 to 613 Lm−2 h−1 and 81.5% to 92.1% respectively. Besides this, graphene oxide silver based membrane depicts least irreversible fouling 14.3% and highest flux recovery ratio 85.6%. Maintenance of high flux recovery ratio of P/GO-Ag 0.5 wt% membrane after three consecutive cycles of water and bovine serum albumin filtration justify the high durability of membrane. The synthesized GO-Ag nanoadditive showed appreciable antibacterial activity against Escherichia coli. Thermo gravimetric analysis and Differential scanning calorimetry analysis of GO-Ag based membranes proves their high thermal stability as well.

Reinforcing natural rubber by amphiphilic graphene oxide for high-performance catheters

Graphene oxide (GO) has been considered as a promising nanofiller to reinforce water-borne polymer due to its exceptional mechanical properties and good dispersibility in an aqueous solution. However, the re-aggregation of hydrophilic GO sheets in a hydrophobic polymer matrix with the evaporation of water, resulting from remarkable discrepancy of the interfacial energy, remains a significant challenge to achieve the high-performance GO-based polymer nanocomposites. Herein, the amphiphilic graphene oxide (AGO) rather than the conventional GO is applied to enhance the mechanical properties of natural rubber latex (NRL) through simple solution blending. Our results show that the AGO demonstrates not only good dispersibility in the NRL aqueous solution but also strong hydrophobic interaction with the NRL particles. Benefiting from this amphiphilic character, the good dispersibility of AGO in the NRL matrix is realized after the oven-drying process, leading to a simultaneous enhancement in tensile strength (up to 35 MPa) and elongation at break (up to 1100%). In particular, it is found that the NRL tube, a kind of catheter, demonstrates a remarkable improvement in both blasting pressure, blasting volume with just a small amount addition of AGO (as less as 0.1%). This work provides a simple, green, and efficient route to fabricate high-performance polymer latex/graphene nanocomposites.

Graphene oxide membranes tuned by metal-phytic acid coordination complex for butanol dehydration

For two-dimensional (2D) lamellar graphene oxide (GO) membranes, tuning the interlayer distance and enhancing surface hydrophilicity are two efficient strategies to achieve high selectivity and permeation flux for solvent dehydration. Herein, Fe3+-phytic acid (PA) coordination complex was designed as both the intercalator and surface modifier to fabricate hydrophilic GO membranes. Fe3+-PA complexes interacted with the oxygen-containing functional groups of GO nanosheets through non-covalent interactions to fix the interlayer distances to 0.61 nm in 90 wt% n-butanol/water mixture.Moreover, Fe3+-PA complexes enhanced the surface hydrophilicity of GO membranes, which promoted the water sorption ability of the membrane and facilitated the fast water-transport. The pervaporation n-butanol dehydration performance was investigated as a function of Fe3+-PA complex content and feed temperature. GO-PA-Fe3+/PTFE membranes with an optimized PA addition amount of 50 wt% exhibited a separation factor of 1059 and a permeation flux of 10.57 kg/(m2 h) under 80 °C for 90 wt% n-butanol/water mixture. This study provides a novel avenue to fabricating 2D lamellar separation membranes by incorporating multifunctional metal-coordinated complexes.

Comparison of the Toxicity of Pristine Graphene and Graphene Oxide, Using Four Biological Models.

There are numerous applications of graphene in biomedicine and they can be classified into several main areas: delivery systems, sensors, tissue engineering and biological agents. The growing biomedical field of applications of graphene and its derivates raises questions regarding their toxicity. We will demonstrate an analysis of the toxicity of two forms of graphene using four various biological models: zebrafish (Danio rerio) embryo, duckweed (Lemna minor), human HS-5 cells and bacteria (Staphylococcus aureus). The toxicity of pristine graphene (PG) and graphene oxide (GO) was tested at concentrations of 5, 10, 20, 50 and 100 µg/mL. Higher toxicity was noted after administration of high doses of PG and GO in all tested biological models. Hydrophilic GO shows greater toxicity to biological models living in the entire volume of the culture medium (zebrafish, duckweed, S. aureus). PG showed the highest toxicity to adherent cells growing on the bottom of the culture plates—human HS-5 cells. The differences in toxicity between the tested graphene materials result from their physicochemical properties and the model used. Dose-dependent toxicity has been demonstrated with both forms of graphene.

Graphene-Reinforced Zn-Ni Alloy Composite Coating on Iron Substrates by Pulsed Reverse Electrodeposition and Its High Corrosion Resistance.

In this paper, a novel kind of graphene (Gr)-reinforced Zn–Ni alloy composite coating is successfully prepared on an iron substrate by pulsed reverse electrodeposition. Hydrophilic graphene oxide (GO) is directly added to the electrolyte and reduced to Gr during coating. The experimental results reveal that (1) there is an optimal adding amount (about 0.4 g/L) of GO in the electrolyte for achieving the highest mechanical properties and corrosion resistance; (2) the composite coating shows grain refinement and a dense microstructure due to heterogeneous nucleation sites provided from the Gr sheets during electrodeposition; and (3) compared to the regular Zn–Ni coating, the composite coating exhibits many enhancements, including hardness increase by 2.3 times, elastic modulus increase by 39%, and corrosion rate decrease from 37.66 to 1.30 mils/annum. This process has advantages such as being simple, effective, well repeatable, economical, and supporting large-scale production and is expected to be widely applied in electronics, automobiles, marine engineering, and military industries.

Ag-nanocubes/graphene-oxide/Au-nanoparticles composite film with highly dense plasmonic hotspots for surface-enhanced Raman scattering detection of pesticide

Concentration of analyte molecules on or nearby plasmonic nanostructures is crucial for sensitive SERS detection. In this paper, a functional SERS system made of Ag-nanocubes/graphene-oxide/Au-nanoparticles (Ag-NCs/GO/Au-NPs) composite film on a hydrophobic surface is constructed for effective accumulation and thus sensitive detection of target analyte in water. High density of plasmonic hotspots are generated between Au nanoparticles-assembled film and the Ag-NCs/GO hybrid, remarkably improving SERS activity. The hydrophobic surface is used to concentrate the analyte molecules in an aqueous droplet onto the Ag-NCs/GO/Au-NPs film during the droplet drying process. The hydrophilic graphene oxide sheets can adsorb analyte molecules nearby the plasmonic nanoparticles. The corners of Ag nanocubes, and the narrow nanogaps between neighboring palsmonic nanoparticles, could provide high density of hotspots for high SERS activity. Due to the effective accumulation of analyte molecules on/nearby hotspots, sensitive SERS detection of pesticides has been realized. The fabricated SERS platform was employed to successfully detect an aqueous solution of rhodamine 6G with an ultralow concentration (0.5 pM), conforming the high SERS sensitivity. To show the potential for practical application, SERS detection of pesticides such as thiram and thiabendazole in drinking-water was realized with limits of detection (LODs) ~ 0.37 ppb and ~ 8.3 ppb respectively. The functional SERS system may have promising applications in inspection of food safety, monitoring environmental pollutants and so on.

A fully integrated wearable electronic device with breathable and washable properties for long-term health monitoring

The fully integrated wearable electronics have recently found widespread applications in long-term health monitoring, where one major challenge is to develop substrate materials with excellent breathability and washability. In this work, we developed a fully integrated wearable electronic device with breathable and washable properties through a facile and scalable paradigm. We directly mixed hydrophilic graphene oxide with hydrophilic cellulose fibers to ensure that graphene nanosheets uniformly spread all over the paper matrix. Then laser reduction was applied to fabricate a graphene-cellulose temperature sensor (LRG-TS), and thermal reduction to make a graphene-cellulose pressure sensor (TRG-PS), both of which were then connected with a flexible printed circuit board (FPCB) to form a fully integrated wearable electronic device with results readable by a mobile phone through Bluetooth. The excellent breathability, attributed to the unique 3D hierarchical porous structure of the e-paper, lays a solid foundation for long-term monitoring as demonstrated in rabbit skin in vitro. Besides, it can endure long-term soaking in water and multiple washing-drying cycles without compromising structural integrity and functional performance, as shown by sensing of body temperature and human motion. The developed device with these two unparalleled properties holds great promise for versatile wearable electronics applications in personal healthcare monitoring.