Showing papers in "RSC Advances in 2016"
TL;DR: In this paper, the chemistry, types, and synthesis of polyurethanes (PUs) are discussed, with a specific emphasis on their recyclability and recoverability, and information is provided on the environmental friendliness of the PU.
Abstract: Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.
861 citations
TL;DR: The DDEC6 method as mentioned in this paper uses a fixed number of charge partitioning steps with well-defined reference ion charges, and it converges to a unique solution with high probability.
Abstract: Net atomic charges (NACs) are widely used in all chemical sciences to concisely summarize key information about the partitioning of electrons among atoms in materials. The objective of this article is to develop an atomic population analysis method that is suitable to be used as a default method in quantum chemistry programs irrespective of the kind of basis sets employed. To address this challenge, we introduce a new atoms-in-materials method with the following nine properties: (1) exactly one electron distribution is assigned to each atom, (2) core electrons are assigned to the correct host atom, (3) NACs are formally independent of the basis set type because they are functionals of the total electron distribution, (4) the assigned atomic electron distributions give an efficiently converging polyatomic multipole expansion, (5) the assigned NACs usually follow Pauling scale electronegativity trends, (6) NACs for a particular element have good transferability among different conformations that are equivalently bonded, (7) the assigned NACs are chemically consistent with the assigned atomic spin moments, (8) the method has predictably rapid and robust convergence to a unique solution, and (9) the computational cost of charge partitioning scales linearly with increasing system size. We study numerous materials as examples: (a) a series of endohedral C60 complexes, (b) high-pressure compressed sodium chloride crystals with unusual stoichiometries, (c) metal–organic frameworks, (d) large and small molecules, (e) organometallic complexes, (f) various solids, and (g) solid surfaces. Due to non-nuclear attractors, Bader's quantum chemical topology could not assign NACs for some of these materials. We show for the first time that the Iterative Hirshfeld and DDEC3 methods do not always converge to a unique solution independent of the initial guess, and this sometimes causes those methods to assign dramatically different NACs on symmetry-equivalent atoms. By using a fixed number of charge partitioning steps with well-defined reference ion charges, the DDEC6 method avoids this problem by always converging to a unique solution. These characteristics make the DDEC6 method ideally suited for use as a default charge assignment method in quantum chemistry programs.
492 citations
TL;DR: In this paper, the authors have incorporated a general introduction of GO, its synthesis, reduction and some selected frontier applications in a wide range of applications, such as energy generation/storage, optical devices, electronic and photonic devices, drug delivery, clean energy, and chemical/bio sensors.
Abstract: Till now, several innovative methods have been developed for the synthesis of graphene materials including mechanical exfoliation, epitaxial growth by chemical vapor deposition, chemical reduction of graphite oxide, liquid-phase exfoliation, arc discharge of graphite, in situ electron beam irradiation, epitaxial growth on SiC, thermal fusion, laser reduction of polymers sheets and unzipping of carbon nanotubes etc. Generally large scale graphene nanosheets are reliably synthesized utilizing other forms of graphene-based novel materials, including graphene oxide (GO), exfoliated graphite oxide (by thermal and microwave), and reduced graphene oxide. The degree of GO reduction and number of graphene layers are minimized mainly by applying two approaches via chemical or thermal treatments. The promising and excellent properties together with the ease of processability and chemical functionalization makes graphene based materials especially GO, ideal candidates for incorporation into a variety of advanced functional materials. Chemical functionalization of graphene can be easily achieved, by the introduction of various functional groups. These functional groups help to control and manipulate the graphene surfaces and help to tune the properties of the resulting hybrid materials. Importantly, graphene and its derivatives GO, have been explored in a wide range of applications, such as energy generation/storage, optical devices, electronic and photonic devices, drug delivery, clean energy, and chemical/bio sensors. In this review article, we have incorporated a general introduction of GO, its synthesis, reduction and some selected frontier applications.
378 citations
TL;DR: In this article, a review paper on strategies to reduce the carbonaceous deactivation of catalysts for improved DRM efficiency by appropriate catalyst development, operating conditions, and flow reactor designs is presented.
Abstract: Catalytic reforming of methane (CH4) with carbon dioxide (CO2), known as dry reforming of methane (DRM), produces synthesis gas, which is a mixture of hydrogen (H2) and carbon monoxide (CO). CH4 + CO2 → 2CO + 2H2, ΔH° = 247.3 kJ mol−1, ΔG = 61 770–67.32T. The DRM process has gained much attention recently as it reduces greenhouse gases (GHG), CO2 and CH4, in the atmosphere. In addition to reducing GHG, the DRM process produces valuable chemicals (CO + H2), provides a good approach to utilizing biogas and natural gas with a significant amount of CO2, has good capability as a chemical energy transmission system as compared to steam reforming, and finally yields the desired unity H2/CO ratio for Fischer–Tropsch synthesis. The bimetallic Ni-based catalysts supported on Al2O3/TiO2 and promoted with Ce/ZrO2 show remarkable performances in the DRM process. But, carbonaceous deactivation of the catalysts is the major problem faced during this process. Numerous studies have been cited on various aspects of DRM, and some papers are also devoted to reviewing carbonaceous deposition problems and their remedies. However, some lacunae exist, which are highlighted in the present review paper on strategies to reduce the carbonaceous deactivation of catalysts for improved DRM efficiency by appropriate catalyst development, operating conditions, and flow reactor designs. The disposal of spent catalysts falls under the category of hazardous industrial materials and is also required to comply with stringent environmental regulations. Therefore, regeneration and reclamation techniques for spent catalysts have also been discussed.
355 citations
TL;DR: In this article, a review of the literature on reverse water gas shift (rWGS) catalyst types, catalyst mechanisms, and the implications of their use in CO2 conversion processes in the future is presented.
Abstract: Current society is inherently based on liquid hydrocarbon fuel economies and seems to be so for the foreseeable future. Due to the low rates (photocatalysis) and high capital investments (solar-thermo-chemical cycles) of competing technologies, reverse water gas shift (rWGS) catalysis appears as the prominent technology for converting CO2 to CO, which can then be converted via CO hydrogenation to a liquid fuel of choice (diesel, gasoline, and alcohols). This approach has the advantage of high rates, selectivity, and technological readiness, but requires renewable hydrogen generation from direct (photocatalysis) or indirect (electricity and electrolysis) sources. The goal of this review is to examine the literature on rWGS catalyst types, catalyst mechanisms, and the implications of their use CO2 conversion processes in the future.
348 citations
TL;DR: In this article, the DDEC6 method reproduces important chemical, theoretical, and experimental properties across an extremely broad range of material types including small and large molecules, organometallics, nanoclusters, porous solids, nonporous solids and solid surfaces.
Abstract: Net atomic charges (NACs) are widely used throughout the chemical sciences to concisely summarize key information about charge transfer between atoms in materials. The vast majority of NAC definitions proposed to date are unsuitable for describing the wide range of material types encountered across the chemical sciences. In this article, we show the DDEC6 method reproduces important chemical, theoretical, and experimental properties across an extremely broad range of material types including small and large molecules, organometallics, nanoclusters, porous solids, nonporous solids, and solid surfaces. Some important comparisons we make are: (a) correlations between various NAC models and spectroscopically measured core-electron binding energy shifts for Ti-, Fe-, and Mo-containing solids, (b) comparisons between DDEC6 and experimentally extracted NACs for formamide and natrolite, (c) comparisons of accuracy of different NAC methods for reproducing the electrostatic potential surrounding a material across one and multiple system conformations, (d) comparisons between calculated and chemically expected electron transfer trends for atoms in numerous dense solids, solid surfaces, and molecules, (e) an assessment of NAC transferability between three crystal phases of the diisopropylammonium bromide organic ferroelectric, and (f) comparisons between DDEC6 and polarized neutron diffraction atomic spin moments for the Mn12-acetate single-molecule magnet. We find the DDEC6 NACs are ideally suited for constructing flexible force-fields and give reasonable agreement with force-fields commonly used to simulate biomolecules and water. We find the DDEC6 method is more accurate than the DDEC3 method for analyzing a broad range of materials. This broad applicability to periodic and non-periodic materials irrespective of the basis set type makes the DDEC6 method suited for use as a default atomic population analysis method in quantum chemistry programs.
307 citations
TL;DR: In this paper, water soluble carbon quantum dots (wsCQDs) were synthesized from lemon peel waste using a facile and cost effective hydrothermal process and an economic, green and highly sensitive fluorescent probe was designed for the detection of Cr6+ ions with a detection limit of ∼73 nM.
Abstract: In this work, water soluble carbon quantum dots (wsCQDs) were synthesized from lemon peel waste using a facile and cost effective hydrothermal process. As synthesized wsCQDs were 1–3 nm in size with spherical morphology and oxygen rich surface functionalities. These wsCQDs manifest excellent photoluminescence (PL) properties and exhibited quantum yield (QY) ∼14% with high aqueous stability. wsCQDs were further used to design an economic, green and highly sensitive fluorescent probe for the detection of Cr6+ ions with a detection limit of ∼73 nM. This wsCQDs based fluorescent probe could provide a simple, rapid, convenient technique for the sensitive and selective detection of Cr6+ in water purification processes. Further, wsCQDs were immobilized over electrospun TiO2 nanofibers and the photocatalytic activity for such a TiO2–wsCQDs composite was demonstrated using methylene blue (MB) dye as a model pollutant. Photocatalytic activity for the TiO2–wsCQDs composite was found to be ∼2.5 times more than that of TiO2 nanofibers. The synthesis method for wsCQDs could be easily scaled up for gram scale synthesis of carbon quantum dots.
299 citations
TL;DR: In this paper, a review has mainly focused on the physico-chemical properties, adsorption characteristics and mechanism of different polypyrrole-based adsorbents, including PPy/biosorbents and their applications towards the removal of heavy metal ions.
Abstract: Water pollution caused by heavy metal ions is becoming a serious threat to human and aquatic lives day by day. Therefore, the treatment of heavy metal ions is of special concern for environmental scientists and engineers. Historically, various methods, such as physical and chemical precipitation, ion-exchange, reverse osmosis, membrane filtration, electrochemical treatment, solvent extraction, and adsorption, have been widely studied for the removal of these metal ions from aqueous/wastewater. However, over the past few decades, conducting polymer-based adsorbents have received considerable attention owing to their potential applications for different heavy metal ions especially Cr(VI), Zn(II), and Pb(II). Among the various conducting polymers, polypyrrole (PPy) based adsorbents play a major role for the removal of various heavy metal ions due to their ease of synthesis, biocompatibility and redox properties. The current review has mainly focused on the physico-chemical properties, adsorption characteristics and mechanism of different polypyrrole-based adsorbents, including PPy/biosorbents, PPy/Fe3O4 nanocomposites, PPy–polyaniline nanofibers, PPy–graphene nanocomposites, exfoliated PPy-organically modified clay nanocomposites, and hierarchical porous PPy-nanoclusters, as well as their applications towards the removal of heavy metal ions.
299 citations
TL;DR: In this paper, the adverse effects of anode lithium plating on the electrochemical performance of lithium-ion batteries are presented, and various in situ and ex situ techniques for characterizing and detecting anode-lithium plating are summarized.
Abstract: Lithium-ion batteries (LIBs) are attractive candidates as power sources for various applications, such as electric vehicles and large-scale energy storage devices. However, safety and life issues are still great challenges for the practical applications of LIBs. Metallic lithium plating on the negative electrode under critical charging conditions accelerates performance degradation and poses safety hazards for LIBs. Therefore, anode lithium plating in LIBs has recently drawn increased attention. This article reviews the recent research and progress regarding anode lithium plating of LIBs. Firstly, the adverse effects of anode lithium plating on the electrochemical performance of LIBs are presented. Various in situ and ex situ techniques for characterizing and detecting anode lithium plating are then summarized. Also, this review discusses the influencing factors that induce anode lithium plating and approaches to mitigating or preventing anode lithium plating. Finally, remaining challenges and future developments related to anode lithium plating are proposed in the conclusion.
277 citations
TL;DR: A brief overview of nanoparticles used for the immobilization of enzymes is presented in this paper, where the authors provide an overview of what is being studied in relation to nanoparticles for enzymes immobilization, and some discussions about them, aimed at assisting researchers in future studies and reviews.
Abstract: Nanotechnology is an area that has been growing over the years, being possible nowadays to find numerous materials constructed at nanoscale In addition, many applications have been attributed to these “new” materials In this review is presented a brief overview of nanoparticles used for the immobilization of enzymes Considering the extensive universe of immobilization in nanoparticles, some were chosen to be exposed here, such as chitosan, graphene, silica, polymers, magnetic, nanoflowers, among others Advantages, disadvantages and limitations of nanoimmobilization also be discussed Some applications of nanoimmobilized enzymes are presented, like as biodiesel, flavor synthesis ester and biosensors The purpose of this paper is to provide an overview of what is being studied in relation to nanoparticles for enzymes immobilization, and some discussions about them, aimed at assisting researchers in future studies and reviews
254 citations
TL;DR: In this paper, the lattice dynamics and thermodynamic properties of monolayer transition metal dichalcogenides were investigated by first principles calculations, and the obtained phonon frequencies and thermal conductivities agree well with the measurements.
Abstract: Phonons are essential for understanding the thermal properties in monolayer transition metal dichalcogenides. We investigate the lattice dynamics and thermodynamic properties of MoS2, MoSe2, and WS2 by first principles calculations. The obtained phonon frequencies and thermal conductivities agree well with the measurements. Our results show that the thermal conductivity of MoS2 is highest among the three materials due to its low average atomic mass. We also discuss the competition between mass effect, interatomic bonding and anharmonic vibrations in determining the thermal conductivity of WS2. Strong covalent W–S bonding and low anharmonicity in WS2 are found to be crucial in understanding its much higher thermal conductivity compared to MoSe2.
TL;DR: The toxicity towards bacteria increased with a higher dissolution rate, suggesting that the toxic species against bacteria are dissolved silver ions.
Abstract: The influence of silver nanoparticle morphology on the dissolution kinetics in ultrapure water as well as the biological effect on eukaryotic and prokaryotic cells was examined. Silver nanoparticles with different shapes but comparable size and identical surface functionalisation were prepared, i.e. spheres (diameter 40–80 and 120–180 nm; two different samples), platelets (20–60 nm), cubes (140–180 nm), and rods (diameter 80–120 nm, length > 1000 nm). All particles were purified by ultracentrifugation and colloidally stabilized with poly(N-vinyl pyrrolidone) (PVP). Their colloidal dispersion in ultrapure water and cell culture medium was demonstrated by dynamic light scattering. Size, shape, and colloidal stability were analysed by scanning electron microscopy, atomic force microscopy, dynamic light scattering, and differential centrifugal sedimentation. The dissolution in ultrapure water was proportional to the specific surface area of the silver nanoparticles. The averaged release rate for all particle morphologies was 30 ± 13 ng s−1 m−2 in ultrapure water (T = 25 ± 1 °C; pH 4.8; oxygen saturation 93%), i.e. about 10–20 times larger than the release of silver from a macroscopic silver bar (1 oz), possibly due to the presence of surface defects in the nanoparticulate state. All particles were taken up by human mesenchymal stem cells and were cytotoxic in concentrations of >12.5 μg mL−1, but there was no significant influence of the particle shape on the cytotoxicity towards the cells. Contrary to that, the toxicity towards bacteria increased with a higher dissolution rate, suggesting that the toxic species against bacteria are dissolved silver ions.
TL;DR: In this paper, a critical review represents an extensive overview of the synthesis of a variety of g-C3N4 nanostructured materials with a controllable structure, morphology and surface modification for superior electronic properties.
Abstract: Graphitic carbon nitride (g-C3N4) is gaining more and more importance as a photocatalytic material due to its promising electronic band structure and high thermal and chemical stability. Very recently, a variety of nanostructured g-C3N4 photocatalysts with varying shapes, sizes, morphologies and electronic band structures have been reported for application in photocatalytic research. This critical review represents an extensive overview of the synthesis of a variety of g-C3N4 nanostructured materials with a controllable structure, morphology and surface modification for superior electronic properties. This article highlights the design of efficient photocatalysts for the splitting of water into hydrogen gas using solar energy. Finally, in the summary and outlook, this article highlights the ongoing challenges and opportunities of g-C3N4. It is also hoped that this review will stimulate further investigation and will open up new possibilities to develop new hybrid g-C3N4 materials with new and exciting applications.
TL;DR: In this article, BaTiO3 and Bi(Zn2/3Nb1/3)O3 materials were fabricated via solid-state reactions and a pure perovskite pseudocubic structure was obtained for all compositions.
Abstract: Lead-free (1 − x)BaTiO3–xBi(Zn2/3Nb1/3)O3 (x = 0.05–0.20) materials were fabricated via solid-state reactions. A pure perovskite pseudocubic structure is obtained for all compositions. Dielectric measurements reveal an intensified diffusion and relaxor-like characteristics from 5 mol% to 20 mol% Bi(Zn2/3Nb1/3)O3. Weakly coupled relaxor behavior is concluded from the exceptionally high activation energies of ∼0.20–0.22 eV from the Vogel–Fulcher model for x ≥ 0.10, which possibly results in the extremely low dielectric nonlinearity and extra slim polarization–electric field loops. An optimal discharged energy density of 0.79 J cm−3 with a high energy efficiency of 93.5% is achieved at 131 kV cm−1 for x = 0.15, which proves that the BaTiO3–Bi(Zn2/3Nb1/3)O3 material is a promising candidate for high energy storage applications.
TL;DR: A review of carbon nanotubes functionalization can be found in this article, where the authors highlight recent developments in the functionalization of CNTs and their applications and highlight the potential of functionalizing CNT to improve chemical compatibility and dissolution properties.
Abstract: Carbon nanotubes (CNT)s show exceptional one-dimensional π-electron conjugation, mechanical strength, high chemical and thermal stability, which make them very attractive for use in many applications. CNTs intrinsically tend to hold together as ropes and bundles due to van der Waals interactions. The prevention of such behavior has been investigated by testing a variety of surface modification methods. The functionalized CNTs present enhanced properties enabling facile production of novel nanomaterials and nanodevices. The functionalization of CNTs could improve their chemical compatibility and dissolution properties, which would enable both a wider characterization and consequent chemical reactivity. This review aims to provide a brief synopsis of CNT functionalization and highlights recent developments in the functionalization of CNTs and their applications.
TL;DR: In this paper, the optimization of specific parameters and the preparation of polymeric solutions for fabricating specialized nanofibrous non-woven membranes, and surface modification for application in water treatment technology are discussed.
Abstract: In this world of nanotechnology, nanofibrous structures offer specialized features, such as mechanical strength and a large surface area, which makes them attractive for many applications. Their large surface area to volume ratio also makes them highly efficient. Among all the techniques for generating nanofibers, electrospinning is an emerging and efficient process. Additionally, the electrospinning technique allows a uniform pore size, which is considered to be one of the important characteristics of membranes. Therefore, electrospun nanofibrous membranes have been used in water purification applications. Furthermore, the technique is widely utilized for generating membranes for membrane distillation and nanofiltration processes, for the removal of contaminants. However, in this review paper, more emphasis is given to the optimization of specific parameters and the preparation of polymeric solutions for fabricating specialized nanofibrous non-woven membranes, and surface modification for application in water treatment technology. Other issues, such as technology limitations, research challenges, and future perspectives, are also discussed.
TL;DR: A comprehensive review on the synthesis of PANI nanocomposites and their applications as gas sensors and biosensors has been presented in this article, where the synergistic effects between the constituents have made these materials particularly attractive as sensing elements for gases and biological agents.
Abstract: A comprehensive review on the synthesis of PANI nanocomposites and their applications as gas sensors and biosensors has been presented. The multi-functionality of PANI nanocomposites have been extensively exploited in diverse applications with impressive results. The synergistic effects between the constituents have made these materials particularly attractive as sensing elements for gases and biological agents. Not only do PANI nanocomposites allow room temperature sensing of a large number of combustible or toxic gases and pollutants with high selectivity and sensitivity, they also enable immobilization of bioreceptors such as enzymes, antigen–antibodies, and nucleic acids onto their surfaces for detection of an array of biological agents through a combination of biochemical and electrochemical reactions. Efforts are on towards understanding the working mechanism of PANI nanocomposites which will increase their potential fields of applications.
TL;DR: In this article, a review covers all the recent reports in which the properties of generic 3D printable materials have been modified either by adding nanoparticles, fibers, other polymers, or by a chemical reaction for fabrication of composites with enhanced biomaterial, mechanical, electrical, thermal, optical and other properties.
Abstract: 3D printing technology is now frequently employed in many areas of research and development. However, a relatively narrow range of 3D printable materials with a limited spectrum of physico-chemical properties still restricts the true potential of this potentially disruptive technology. There is rapidly increasing interest in the improvement and diversification of properties of generic printing materials via the introduction of fillers with unique properties, and/or by blending materials exhibiting different properties to generate high performance composites. 3D printed composites have already been utilised in a wide range of applications, including biomedical, mechanical, electrical, thermal and optically enhanced products. The increasing popularity of 3D printed composites can be attributed to the ability to fabricate complex geometries, low cost production, and other advantages associated with rapid prototyping. This review covers all the recent reports in which the properties of generic 3D printable materials have been modified either by adding nanoparticles, fibers, other polymers, or by a chemical reaction for fabrication of composites with enhanced biomaterial, mechanical, electrical, thermal, optical and other properties.
TL;DR: In this article, the use of bioremediation for polyvinyl alcohol (PVA) release, which has caused serious pollution problems in the natural environment, has attracted much interest.
Abstract: Poly(vinyl alcohol) (PVA) is a water soluble synthetic polymer, with a backbone composed only of carbon atoms and is biodegradable under both aerobic and anaerobic conditions. This polymer can be prepared by the hydrolysis of polyvinylacetate and is one of the most important synthetic polymers used in commercial, industrial, medical and nutraceutical applications. The environmental issues caused by PVA industrial practice have increased globally. Several methods have been used to treat PVA industrial discharge including in particular physicochemical methods such as electrocoagulation. Nowadays, use of bioremediation for PVA release, which has caused serious pollution problems in the natural environment, has attracted much interest. The bioremediation ability of microorganisms and their PVA degrading enzymes, especially PVA oxidases/hydrolases, has long been perceived. These enzymes as well as symbiotic microorganisms could be an effective means for biodegradation of PVA.
TL;DR: In this article, the authors provide an overview of recent progress in developing Mn4+ doped red phosphors for promising applications in warm white light-emitting diodes.
Abstract: Currently, the major commercial white light-emitting diodes consist of a blue-emitting chip and Y3Al5O12:Ce3+ yellow phosphor. However, the shortage of a red emitting component in the constructed device makes it difficult to realize warm white light with a high color-rendering index and low correlated color temperature. In this mini-review article, we provide an overview of recent progresses in developing Mn4+ doped red phosphors for promising applications in warm white light-emitting diodes. Firstly, the spectroscopic properties of Mn4+ in solids, including electronic and vibronic energy-level structures, crystal-field parameters as well as thermal stability, were briefly discussed. And then the related physical and chemical synthesis strategies were introduced in detail. Afterwards, Mn4+ doped phosphors, such as oxides, fluorides as well as glass ceramic composites, and their impact on improving the photoelectric performance of white light-emitting diodes were summarized. Finally, several challenges and perspectives for exploring novel and high-performance Mn4+ doped red phosphors will be presented.
TL;DR: In this paper, the green reduction of graphene oxide (GO) to graphene is discussed and the characterization of GO and its oxide reduction through the analysis of different spectroscopic and microscopic techniques.
Abstract: Graphene is an ultra-thin material, which has received broad interest in many areas of science and technology because of its unique physical, chemical, mechanical and thermal properties. Synthesis of high quality graphene in an inexpensive and eco-friendly manner is a big challenge. Among various methods, chemical synthesis is considered the best because it is easy, scalable, facile, and inexpensive. Different kinds of chemical reducers have been used to produce graphene sheets. However, some chemicals are toxic, corrosive, and hazardous. For this reason, researchers have been using different environmentally friendly substances (termed green reducers) to produce functional graphene sheets. This paper presents an overview and discussion of the green reduction of graphene oxide (GO) to graphene. It also reviews the characterization of GO and its oxide reduction through the analysis of different spectroscopic and microscopic techniques such as Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy.
TL;DR: In this paper, β-cyclodextrin-chitosan modified walnut shell biochars (β-CCWB) were synthesized as a low-cost adsorbent for the removal of heavy metal Cr(VI) from aqueous solutions.
Abstract: In this work, beta-cyclodextrin–chitosan modified walnut shell biochars (β-CCWB) were synthesized as a low-cost adsorbent for the removal of heavy metal Cr(VI) from aqueous solutions. Batch sorption experiments were carried out to investigate the adsorption characteristic of β-CCWB. The experimental data fitted a pseudo-second order equation and Freundlich isotherm model, and the optimum adsorption of the modified biochar was observed at pH 2.0 with an adsorption capacity of 206 mg g−1. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. The removal efficiency of Cr(VI) by β-CCWB (about 93%) was higher than that by the pristine biochar (about 27%). Characteristic analysis indicated that amino and carboxyl groups were the major functional groups for Cr(VI) sorption, and implied that the electrostatic attraction of Cr(VI) to the positively charged biochar surface, reduction of Cr(VI) to Cr(III) ions and the complexation between Cr(III) ions and β-CCWB functional groups were responsible for Cr(VI) removal mechanism in this research. Furthermore, the environmentally friendly and low-cost β-CCWB could be applied as a potential effective adsorbent to remediate Cr(VI) contamination from aqueous solution.
TL;DR: Overall, pretreatment is the major step in the successful production of valuable products from lignocellulosic biomass and the success in biofuel and chemical production strongly depends on the pretreatment method used.
Abstract: In the past three decades, many studies on the production of biofuels and other chemicals have been conducted using renewable sources such as lignocellulosic biomass. Lignocellulosic biomasses are abundantly available in most countries and furthermore they are carbon neutral. However, the main problem in utilizing lignocellulosic materials lies in the recalcitrance of its bonding. This review provides a comprehensive overview and a brief discussion on producing biofuel and valuable chemicals from lignocellulose biomass. Various aspects of the physical, chemical, thermophysical, thermochemical and biological pretreatment of lignocellulosic materials are discussed in this review. The success in biofuel and chemical production strongly depends on the pretreatment method used. Overall, pretreatment is the major step in the successful production of valuable products from lignocellulosic biomass.
TL;DR: In this article, a hematite (α-Fe2O3) nanoparticles have been synthesized by the sole use of the extract of guava (Psidium guajava) leaves.
Abstract: The use of biological products such as microorganisms, plant extracts or plant biomass is a better alternative to chemical and physical methods for the engineering of metal oxide nanoparticles through an environmentally benign route. Hematite (α-Fe2O3) nanoparticles have acquired significant attention from researchers for being the most stable iron oxide in air under ambient conditions. Further, they are also known for their extensive applications in diverse fields. In the present work, hematite (α-Fe2O3) nanoparticles have been synthesized by the sole use of the extract of guava (Psidium guajava) leaves. The synthesized material has been studied by X-ray diffraction (XRD), UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Vibrating Sample Magnetometry (VSM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques. The average diameter of α-Fe2O3 nanoparticles is observed to be about 34 nm. Absorption studies of the sample from UV to near IR regions show four absorption bands at 347 nm, 543 nm, 652 nm and 849 nm. The photoluminescence (PL) spectrum shows band edge emission at 688 nm. The FTIR spectrum reveals the role of biomolecules present in the extract in capping the nanoparticles. The VSM study shows the weak ferromagnetic nature of the synthesized nanoparticles. The antibacterial activities of the synthesized nanoparticles against Gram-positive and Gram-negative bacteria have been ascertained through an agar-well diffusion method. Further, the nanoparticles show enhancement in thermal conductivity for the base fluids water and ethylene glycol. The bioefficacy and thermal conductivity enhancement exhibited by the as synthesized nanoparticles may lead to their possible applications in environmental and industrial fields.
TL;DR: In this article, the elastic and optical properties as well as the crystal and electronic structures of two-dimensional Ti2CT2 and Ti3C2T2 (T = F, O, and OH) MXene monolayers were investigated.
Abstract: Density functional theory is used to investigate the elastic and optical properties as well as the crystal and electronic structures of two-dimensional Ti2CT2 and Ti3C2T2 (T = F, O, and OH) MXene monolayers. It is found that the elastic stiffness, optical response, crystal structure and the electronic structure show strong dependence on the surface terminated groups often formed with MXene during the etching process. The elastic stiffness maintains only with the surface termination of O atoms, but a large degradation is present in the surface terminations of F and OH atoms. The low adsorption and reflectivity in the range from infrared to ultraviolet rays account for the high transmittance of Ti3C2T2 that has been experimentally observed, and it is predicted that Ti2CT2 will have higher optical transmittance in this range. The calculations also demonstrate the presence of the optical bandgap in Ti2CO2, which renders its potential applications in optical and electronic devices.
TL;DR: In this article, temperature-dependent photoluminescence properties of inorganic perovskite CsPbBr3 nanocrystal (NC) films were studied by using steady-state and time-resolved PL spectroscopy.
Abstract: Temperature-dependent photoluminescence (PL) properties of inorganic perovskite CsPbBr3 nanocrystal (NC) films were studied by using steady-state and time-resolved PL spectroscopy. The closely packed solid films were obtained by dropping NC solution on silicon substrates. It was found that the PL intensities of the NC films, which are dependent on the size of NCs, slightly decreased with increasing temperature to 300 K, while the PL intensities dropped rapidly with increasing temperature above 300 K and were nearly quenched at 360 K. Further the corresponding average PL lifetimes increased significantly with increasing temperature below about 320 K and then significantly became shorter. The PL quenching mechanisms were demonstrated through heating and cooling experiments. The experimental results indicated inorganic perovskite NCs exhibited a thermal PL quenching in the temperature range of 80–300 K and a thermal degradation at temperatures above 300 K. The linewidths, peak energies, and lifetimes of PL emissions for the NC films as a function of temperature were discussed in detail.
TL;DR: The current review focuses on the theoretical background regarding thefunctionalization of magnetic nanoparticles for nano-bio applications and covers all the important aspects regarding the functionalization of magnet nanoparticles.
Abstract: Advances in nanotechnology enable the production of magnetic nanoparticles (MNPs) with specific morphologies and the tailoring of their surfaces in order to manipulate their characteristics to suit specific applications. Magnetic nanoparticles are well-established nanomaterials that offer controlled size, biospecificity, and the ability to be manipulated externally. As a result, these nanoparticles can be explored with respect to a wider range of applications. It is essential to ensure the proper and specific functionalization of magnetic nanoparticles for their successful use in nano-bio applications. The current review focuses on the theoretical background regarding the functionalization of magnetic nanoparticles for nano-bio applications. The review covers all the important aspects regarding the functionalization of magnetic nanoparticles. The ideal requirements for their functionalization for nano-bio applications and the mechanisms behind this are explained. Different materials used in the functionalization of magnetic nanoparticles are classified and discussed in detail. The principle criteria for bioconjugation and different bioconjugation strategies are overviewed. Functionalization strategies for magnetic nanoparticles for specific bioapplications, such as magnetic hyperthermia, magnetic resonance imaging, target drug delivery, bacteria detection, enzyme immobilization, cell labelling, magnetic separation, and DNA enrichment, are highlighted.
TL;DR: In this article, a review of perovskite-based materials for high-temperature solid oxide electrochemical devices is presented and analyzed, where correlations between compositional and structural characteristics and their transport, thermal and stability properties are established.
Abstract: High-temperature proton-conducting materials constitute a unique class of oxide materials, which are able to exhibit protonic conductivity under hydrogen-containing atmospheres. Besides being of great fundamental interest, such oxide systems possess practical significance because they can achieve high protonic conductivity levels. This opens the possibility of using proton-conducting materials as electrolytes for a wide range of intermediate- and high-temperature solid oxide electrochemical devices. Recent advances in the field of solid oxide proton-conducting materials that belong to the class of perovskite-based materials (such as doped BaCeO3, BaZrO3, BaCeO3–BaZrO3, SrCeO3, and LaScO3) and to other classes of materials (such as doped Ba2In2O5, CeO2, and LaNbO4) are presented and analyzed in this review. In order to highlight the most appropriate materials for applications in electrochemical devices, the analysis is devoted to the establishment of correlations between compositional and structural characteristics and their transport, thermal and stability properties.
TL;DR: Both the superiorities and the intrinsic drawbacks of detecting glucose by employing non-precious materials including Ni, Cu, Co, Mn, and Fe are intensively highlighted, followed by a systematic discussion on the important progress harvested for enzymeless glucose sensing.
Abstract: With the booming requirements for diabetes management, food quality control, and bioprocess inspection, monitoring of glucose in various matrices has drawn unprecedented interest of both academic and industrial researchers recently. As a relatively new class of glucose sensors, enzyme-free detection of the target is capable of providing several fascinating characters such as ultra-high sensitivity, excellent stability, and simple fabrication. Considering the rapid expansion of the glucose determination field without using any biological enzymes, here we focus our attention on updating the latest advances in non-enzymatic electrochemical glucose sensors based on non-noble transition metal materials achieved in the past few years. In this minireview, both the superiorities and the intrinsic drawbacks of detecting glucose by employing non-precious materials including Ni, Cu, Co, Mn, and Fe are intensively highlighted, followed by a systematic discussion on the important progress harvested for enzymeless glucose sensing. Finally, the potential opportunities of non-noble transition metal materials in fabricating high-performance enzyme-free glucose sensors are given, and the current challenges for their practical applications are also summarized.
TL;DR: In this paper, the structural and optical properties of the as-prepared NH2-MIL-101(Fe) hexagonal micro-spindles were characterized and the catalytic reaction mechanism was investigated on the basis of in situ Fourier Transform infrared spectroscopy (FTIR) technology.
Abstract: This work focuses on exploring metal–organic frameworks (MOFs) for degradation of gaseous pollutants. We demonstrate that NH2-MIL-101(Fe) hexagonal micro-spindles, as a new photocatalyst, showed an improved performance for degradation of toluene under visible light irradiation. The structural and optical properties of the as-prepared NH2-MIL-101(Fe) hexagonal micro-spindles were characterized. Furthermore, the catalytic reaction mechanism has been investigated on the basis of in situ Fourier Transform infrared spectroscopy (FTIR) technology. Meanwhile, some intermediates (benzoic acid) and the final product (CO2) of the degradation of toluene were also identified.