Microwave-assisted synthesis of highly water-soluble graphene towards electrical DNA sensor

A robust host-guest interaction controlled probe immobilization strategy for the ultrasensitive detection of HBV DNA using hollow HP5-Au/CoS nanobox as biosensing platform

The combination of supramolecular chemistry and nanotechnology has potentially applied in the construction of biosensors, and thus improves the analytical performance and robustness of electron devices. Herein, a new sandwich-type DNA sensor was constructed for ultrasensitive determination of hepatitis B virus (HBV) DNA, a recognized marker for chronic hepatitis B. The water-soluble pillar[5]arene stabilized Pd NPs combined with reduced graphene oxide nanosheet (WP5-Pd/RGO) was synthesized and employed as supporting material for the modification of electrode surface. The probe DNA was immobilized onto the electrode surface through a new strategy based on the host-guest interaction between WP5 and methylene blue labeled DNA (MB-DNA). Moreover, MOF-derived cobalt sulfide nanobox was prepared to anchor the hydroxylatopillar[5]arene stabilized Au NPs (HP5-Au/CoS), which had superior electrocatalytic performance towards H₂O₂ reduction to achieve signal amplification. Under the optimized conditions, the proposed sensor displayed a linear relationship between amperometric currents and the logarithm of tDNA solution from 1 × 10^-15 mol/L to 1 × 10^-9 mol/L, and a low detection limit of 0.32 fmol/L. What's more, the DNA sensor had remarkable behaviors of stability, reproducibility, specificity, and accuracy, which provided a potential and promising prospect for clinical diagnosis and analysis.

Developing Graphene-Based Nanohybrids for Electrochemical Sensing

Graphene-based nanohybrid is considered to be the most promising nanomaterial for electrochemical sensing applications due to the defects created on the graphene oxide layers. These defects provide graphene oxide unique properties, such as excellent conductivity, large specific surface area, and electrocatalytic activity. These unique properties encourage scientists to develop novel graphene-based nanohybrids and improve the sensing efficiency. This review, therefore, addresses this topic by comprehensively discussing the strategies to fabricate novel graphene based nanohybrids with high sensitivity. The combinations of graphene with various nanomaterials, such as metal nanoclusters, metal compound nanoparticles, carbon materials, polymers and peptides, in the direction of electrochemical sensing, were systematically analyzed. Meanwhile, the challenges in the functional design and application of graphene-based nanohybrids were described and the reasonable solutions were proposed.

Modulation of photothermal anisotropy using black phosphorus/rhenium diselenide heterostructures

Manipulating the polarization of an incident beam using two-dimensional materials has become an important research direction towards the development of nano-optical devices. Black phosphorus (BP) and rhenium diselenide (ReSe2) possess excellent in-plane optical anisotropy with optical birefringence in the visible region, which has led to novel applications in polarizing optics and optoelectronics. Herein, the polarization-dependent absorption of BP and ReSe2 and a modulated pump beam is utilized to obtain the photothermal signal from them. The photothermal anisotropy of BP and ReSe2 has been explored using photothermal detection. Then we have defined the photothermal contrast using the ratio of the maximum to the minimum of the photothermal signal. The photothermal contrast of BP and ReSe2 can be obtained accurately by the relationship between the polarization angle of the pump light and the photothermal signal. We demonstrate that a layered BP with different thicknesses can remarkably change the photothermal contrast. In contrast, the photothermal contrast of ReSe2 does not change with the different thicknesses of the samples. Further, the photothermal anisotropies of BP/ReSe2 heterostructures were also explored. The photothermal contrasts of samples were observed to change with different stacking angles indicating that the photothermal anisotropy of heterostructures is dependent on the stacking angle. Our findings provide new prospects for designing novel optical devices based on two-dimensional anisotropic materials, with potential applications in electronics, photonics, and optoelectronics.

Advances in microbial biosynthesis of metal nanoparticles

Metal nanoparticles are garnering considerable attention owing to their high potential for use in various applications in the material, electronics, and energy industries. Recent research efforts have focused on the biosynthesis of metal nanomaterials using microorganisms rather than traditional chemical synthesis methods. Microorganisms have evolved to possess molecular machineries for detoxifying heavy metals, mainly by employing metal-binding proteins and peptides. Biosynthesis of diverse metal nanoparticles has recently been demonstrated using such heavy metal detoxification systems in microorganisms, which provides several advantages over the traditional chemical synthesis methods. First, metal nanoparticles can be synthesized at mild temperatures, such as at room temperature, with less energy input. Second, no toxic chemicals or reagents are needed, and thus the process is environmentally friendly. Third, diverse metal nanoparticles, including those that have never been chemically synthesized, can be biosynthesized. Here, we review the strategies for the biosynthesis of metal nanoparticles using microorganisms, and provide future prospects.

Graphene-based nanoprobes for molecular diagnostics

In recent years, graphene has received widespread attention owing to its extraordinary electrical, chemical, optical, mechanical and structural properties. Lately, considerable interest has been focused on exploring the potential applications of graphene in life sciences, particularly in disease-related molecular diagnostics. In particular, the coupling of functional molecules with graphene as a nanoprobe offers an excellent platform to realize the detection of biomarkers, such as nucleic acids, proteins and other bioactive molecules, with high performance. This article reviews emerging graphene-based nanoprobes in electrical, optical and other assay methods and their application in various strategies of molecular diagnostics. In particular, this review focuses on the construction of graphene-based nanoprobes and their special advantages for the detection of various bioactive molecules. Properties of graphene-based materials and their functionalization are also comprehensively discussed in view of the development of nanoprobes. Finally, future challenges and perspectives of graphene-based nanoprobes are discussed.

Synthesis and Modification of Carbon Nanomaterials utilizing Microwave Heating

Microwave-assisted synthesis and processing represents a growing field in materials research and successfully entered the field of carbon nanomaterials during the last decade. Due to the strong interaction of carbon materials with microwave radiation, fast heating rates and localized heating can be achieved. These features enable the acceleration of reaction processes, as well as the formation of nanostructures with special morphologies. A comprehensive overview is provided here on the possibilities and achievements in the field of carbon-nanomaterial research when using microwave-based heating approaches. This includes the synthesis and processing of carbon nanotubes and fibers, graphene materials, carbon nanoparticles, and capsules, as well as porous carbon materials. Additionally, the principles of microwave-heating, in particular of carbon materials, are introduced and important issues, i.e., safety and reproducibility, are discussed.

The electrochemical synthesis of Pt particles on ZrO2–ERGO modified electrodes with high electrocatalytic performance for methanol oxidation

A schematic representation of methanol oxidation taking place at a Pt/ZrO₂–ERGO electrocatalyst modified electrode.

The graphene/nucleic acid nanobiointerface

In this critical review, we present the recent advances in the design and fabrication of graphene/nucleic acid nanobiointerfaces, as well as the fundamental understanding of their interfacial properties and various nanobiotechnological applications.

Scalable graphene synthesised by plasma-assisted selective reaction on silicon carbide for device applications

Graphene, a two-dimensional material with honeycomb arrays of carbon atoms, has shown outstanding physical properties that make it a promising candidate material for a variety of electronic applications. To date, several issues related to the material synthesis and device fabrication need to be overcome. Despite the fact that large-area graphene films synthesised by chemical vapour deposition (CVD) can be grown with relatively few defects, the required transfer process creates wrinkles and polymer residues that greatly reduce its performance in device applications. Graphene synthesised on silicon carbide (SiC) has shown outstanding mobility and has been successfully used to develop ultra-high frequency transistors; however, this fabrication method is limited due to the use of costly ultra-high vacuum (UHV) equipment that can reach temperatures over 1500 °C. Here, we show a simple and novel approach to synthesise graphene on SiC substrates that greatly reduces the temperature and vacuum requirements and allows the use of equipment commonly used in the semiconductor processing industry. In this work, we used plasma treatment followed by annealing in order to obtain large-scale graphene films from bulk SiC. After exposure to N2 plasma, the annealing process promotes the reaction of nitrogen ions with Si and the simultaneous condensation of C on the surface of SiC. Eventually, a uniform, large-scale, n-type graphene film with remarkable transport behaviour on the SiC wafer is achieved. Furthermore, graphene field effect transistors (FETs) with high carrier mobilities on SiC were also demonstrated in this study.

Herpes simplex virus type-1 attachment inhibition by functionalized graphene oxide

Graphene oxide and its derivatives have lately been the subject of increased attention in the field of bioscience and biotechnology. In this article, we report on the use of graphene oxide (GO) derivatives to inhibit herpes simplex virus type-1 (HSV-1) infections, mimicking the cell surface receptor heparan sulfate, and the GO derivatives compete with the latter in binding HSV-1. The inhibition does not affect cell-to-cell spreading. Media content has a significant effect on the inhibition properties of the nanomaterials. These have no cytotoxic effect, suggesting that this is a promising approach for the development of antiviral surfaces and for diagnostic purposes.

Graphene nanonet for biological sensing applications

We report a simple but efficient method to fabricate versatile graphene nanonet (GNN)-devices. In this method, networks of V2O5 nanowires (NWs) were prepared in specific regions of single-layer graphene, and the graphene layer was selectively etched via a reactive ion etching method using the V2O5 NWs as a shadow mask. The process allowed us to prepare large scale patterns of GNN structures which were comprised of continuous networks of graphene nanoribbons (GNRs) with chemical functional groups on their edges. The GNN can be easily functionalized with biomolecules for fluorescent biochip applications. Furthermore, electrical channels based on GNN exhibited a rather high mobility and low noise compared with other network structures based on nanostructures such as carbon nanotubes, which was attributed to the continuous connection of nanoribbons in GNN structures. As a proof of concept, we built DNA sensors based on GNN channels and demonstrated the selective detection of DNA. Since our method allows us to prepare high-performance networks of GNRs over a large surface area, it should open up various practical biosensing applications.

Visible light photocatalytic degradation of dyes by bismuth oxide-reduced graphene oxide composites prepared via microwave-assisted method

Bi2O3-reduced graphene oxide (RGO) composites were successfully synthesized via microwave-assisted reduction of graphite oxide in Bi2O3 precursor solution using a microwave system. Their morphologies, structures, and photocatalytic performance in the degradation of methylene blue (MB) and methyl orange (MO) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, UV-vis absorption spectroscopy, and electrochemical impedance spectroscopy, respectively. The results show that the RGO addition can enhance the photocatalytic performance of Bi2O3-RGO composites. Bi2O3-RGO composite with 2 wt.% RGO achieves maximum MO and MB degradation rates of 93% and 96% at 240min under visible light irradiation, respectively, much higher than those for the pure Bi2O3 (78% and 76%). The enhanced photocatalytic performance is ascribed to the increased light adsorption and the reduction in electron-hole pair recombination in Bi2O3 with the introduction of RGO.

Label-free electrochemical impedance genosensor based on 1-aminopyrene/graphene hybrids

In this work, we proposed a novel simple protocol for preparing 1-aminopyrene/graphene (ApG) hybrids for fabricating label-free electrochemical impedance genosensor. Graphene, with the structure of a single-atom-thick sheet of sp(2)-bonded carbon atoms, was anchored to 1-aminopyrene (1-Ap) with the pyrenyl group viaπ-stacking interaction. The morphology, conductivity, and interaction of ApG hybrids were characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), UV-visible (UV-vis) and fluorescence spectra. The amino-substituted oligonucleotide probe was conjugated to 1-Ap by the cross-linker glutaraldehyde. The DNA hybridization reaction of oligonucleotide probe with target DNA was monitored by EIS. Under optimum conditions, the proposed biosensor exhibited high sensitivity and a low detection limit for detecting the complementary oligonucleotide. The target oligonucleotide could be quantified in a wide range of 1.0 × 10(-12) to 1.0 × 10(-8) M with good linearity (R = 0.9900) and low detection limit of 4.5 × 10(-13) M (S/N = 3).

Recent advances in microwave initiated synthesis of nanocarbon materials

This Feature Article focuses on the recent advances in synthesis of nanostructured carbon materials using microwave irradiation as the heating source. Although the microwave approach to chemical synthesis is relatively mature in organic synthesis, it is still in the early stage for nanomaterials synthesis, especially nanocarbons. Due to the energy efficient nature of microwave heating, there is a great opportunity to apply microwave irradiation to nanocarbon production, which normally requires high temperature, high vacuum or inert gas protections. Using microwave irradiation will give a green feature to the nanocarbon synthesis, since it offers high efficiency heating and fast carbonization. With our recent discovery, multi-walled carbon nanotubes can be synthesized through the microwave process even in air. Background about nanocarbons and microwave chemistry are introduced, the application of microwaves in synthesis of different types of nanocarbons is discussed and finally, the perspectives in the future research directions of microwave assisted nanocarbon synthesis are deliberated as well.

A graphene nanoribbon network and its biosensing application

Graphene oxide nanoribbons (GONRs) have been prepared by chemically unzipping multiwalled carbon nanotubes (MWCNTs). Thin-film networks of GONRs were fabricated by spray-coating, followed by a chemical or thermal reduction to form reduced graphene oxide nanoribbons (rGONRs). Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations indicate that the thermal reduction in the presence of ethanol vapor effectively restores the graphitic structure of the GONR as compared to chemical reduction with hydrazine vapor. Electrical measurements under a liquid-gate configuration demonstrates that rGONR network field-effect transistors exhibit much higher on/off ratios than a network of microsized reduced graphene oxides (rGOs) or a continuous film of single-layered pristine or chemical vapor deposited (CVD) graphene. Furthermore, we demonstrated the potential applications of rGONR networks for biosensing, specifically, the real-time and sensitive detection of adenosine triphosphate (ATP) molecules.

Gold nano particle decorated graphene core first generation PAMAM dendrimer for label free electrochemical DNA hybridization sensing

A novel first generation (G1) poly(amidoamine) dendrimer (PAMAM) with graphene core (GG1PAMAM) was synthesized for the first time. Single layer of GG1PAMAM was immobilized covalently on mercaptopropionic acid (MPA) monolayer on Au transducer. This allows cost effective and easy deposition of single layer graphene on the Au transducer surface than the advanced vacuum techniques used in the literature. Au nano particles (17.5 nm) then decorated the GG1PAMAM and used for electrochemical DNA hybridization sensing. The sensor discriminates selectively and sensitively the complementary double stranded DNA (dsDNA, hybridized), non-complementary DNA (ssDNA, un-hybridized) and single nucleotide polymorphism (SNP) surfaces. Interactions of the MPA, GG1PAMAM and the Au nano particles were characterized by Ultra Violet (UV), Fourier Transform Infrared (FTIR), Raman spectroscopy (RS), Thermo gravimetric analysis (TGA), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Cyclic Voltmetric (CV), Impedance spectroscopy (IS) and Differntial Pulse Voltammetry (DPV) techniques. The sensor showed linear range 1×10(-6) to 1×10(-12) M with lowest detection limit 1 pM which is 1000 times lower than G1PAMAM without graphene core.

Unidirectional arrays of vertically standing graphenes in reactive plasmas

The possibility for the switch-over of the growth mode from a continuous network to unidirectional arrays of well-separated, self-organized, vertically oriented graphene nanosheets has been demonstrated using a unique, yet simple plasma-based approach. The process enables highly reproducible, catalyst-free synthesis of arrays of graphene nanosheets with reactive open graphitic edges facing upwards. Effective control over the nanosheet length, number density, and the degree of alignment along the electric field direction is achieved by a simple variation of the substrate bias. These results are of interest for environment-friendly fabrication of next-generation nanodevices based on three-dimensional, ordered self-organized nanoarrays of active nanostructures with very large surface areas and aspect ratios, highly reactive edges, and controlled density on the substrate. Our simple and versatile plasma-based approach paves the way for direct integration of such nanoarrays directly into the Si-based nanodevice platform.

Programmable peptide-directed two dimensional arrays of various nanoparticles on graphene sheets

In this research, we report an innovative, chemical strategy for the in situ synthesis and direct two-dimensional (2D) arraying of various nanoparticles (NPs) on graphenes using both programmed-peptides as directing agents and graphenes as pre-formed 2D templates. The peptides were designed for manipulating the enthalpic (coupled interactions) constraint of the global system. Along with the functionalization of graphene for the stable dispersion, peptides directed the growth and array of NPs in a controllable manner. In particular, the sequences of peptides were encoded by the combination of glutamic acid (E), glycine (G), and phenylalanine (F) amino acids as follows: (E-G-F)(3)-G, with E for the interaction with NPs and F and G for the interaction with graphenes. For the entropic (restricted geometry) constraint, graphene was used as a 2D scaffold to tune the size, density, and position of NPs, while maintaining the intrinsic properties for electrochemical applications. The excellent quality of the resultant hybrids was demonstrated by their high electrocatalytic activity in the electrooxidation of methanol. This synergistic combination of peptides and graphenes allowed for a uniform 2D array and spontaneous organization of various NPs (i.e., Pt, Au, Pd, and Ru), which would greatly expand the utility and versatility of this approach for the synthesis and array of the advanced nanomaterials.

Innovative polymer nanocomposite electrolytes: nanoscale manipulation of ion channels by functionalized graphenes

The chemistry and structure of ion channels within the polymer electrolytes are of prime importance for studying the transport properties of electrolytes as well as for developing high-performance electrochemical devices. Despite intensive efforts on the synthesis of polymer electrolytes, few studies have demonstrated enhanced target ion conduction while suppressing unfavorable ion or mass transport because the undesirable transport occurs through an identical pathway. Herein, we report an innovative, chemical strategy for the synthesis of polymer electrolytes whose ion-conducting channels are physically and chemically modulated by the ionic (not electronic) conductive, functionalized graphenes and for a fundamental understanding of ion and mass transport occurring in nanoscale ionic clusters. The functionalized graphenes controlled the state of water by means of nanoscale manipulation of the physical geometry and chemical functionality of ionic channels. Furthermore, the confinement of bound water within the reorganized nanochannels of composite membranes was confirmed by the enhanced proton conductivity at high temperature and the low activation energy for ionic conduction through a Grotthus-type mechanism. The selectively facilitated transport behavior of composite membranes such as high proton conductivity and low methanol crossover was attributed to the confined bound water, resulting in high-performance fuel cells.

Microwave assisted CdSe quantum dot deposition on TiO2 films for dye-sensitized solar cells

CdSe quantum dot (QD ) sensitized TiO(2) films have been fabricated using a one-step microwave assisted chemical bath deposition (MACBD) technique and used as photoanodes for quantum dot sensitized solar cells. This technique allows direct and rapid deposition and a good contact between the CdSe and TiO(2) films. The photovoltaic performances of the cells with CdSe deposited at different times are investigated. The results show that cells based on MACBD deposited TiO(2)/CdSe electrodes achieve a maximum short circuit current density of 12.1 mA cm(-2) and a power conversion efficiency of 1.75% at one Sun (AM 1.5 G, 100 mW cm(-2)), which is comparable with those fabricated using conventional techniques.