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.
In this review article, we describe a general introduction to GO, its synthesis, reduction and some selected frontier applications. Its low cost and potential for mass production make GO a promising building block for functional hybrid materials.
MicroRNAs (miRNAs) are small non-coding endogenous RNAs (18–24 nucleotides) which regulate gene expression at posttranscriptional level either by degrading the target mRNA (plants) or by blocking the ...protein translation through binding with 3′ UTR of the target mRNA (animals). Though miRNAs are known to play key roles in animal development, miRNAs that are involved in plant developmental timing, cell proliferation, and several other physiological functions need to be investigated. In addition, plant miRNAs have been shown to be involved in various biotic (bacterial and viral pathogenesis) and abiotic stress responses such as oxidative, mineral nutrient deficiency, drought, salinity, temperature, cold (chilling), and other abiotic stress. miRNA expression profiling reveals that miRNAs which are involved in the progression of plant growth and development are differentially expressed during abiotic stress responses. The high-throughout techniques can provide genome-wide identification of stress-associated miRNAs under various abiotic stresses in plants. Various web-based and non-web-based computational tools facilitate in the identification and characterization of biotic/abiotic stress associated miRNAs and their target genes. In the future, miRNA-mediated RNA interference (RNAi) approach might help in developing transgenic crop plants for better crop improvement by conferring resistance against biotic (pathogens) as well as abiotic stress responses.
Carbon nanomaterials have huge potential in the field of energy and environmental applications. However, a wide range of greener and environment friendly synthesis methods utilizing natural, ...renewable, cheaper waste materials has to be developed. This will lead to the reduction of green house gases, exploitation of toxic materials and helps in the development of sustainable technologies. In this review, the details progress made in the last ten years concerning the synthesis of new one dimensional (carbon nanotubes CNT, carbon nanofiber) and two dimensional (graphene) carbon based materials using natural precursors and waste materials is summarized. The aim of this review paper is to provide a comprehensive scientific progress of synthesis of graphene and carbon nanotubes using natural precursor and waste materials for the future perspective. This paper also concludes with a brief discussion on the impact of natural precursor for the graphene and CNTs for environment, its toxicological effects and its future prospects in this rapidly emerging field. Natural precursors and waste carbon containing products are emerging as a new class of materials that have efficiency to produce graphene and CNTs. The various synthesis processes of graphene, CNTs and carbon dots has been reported using several natural hydrocarbon precursors (turpentine oil, eucalyptus oil, palm oil, neem oil, sunflower oil, castor oil, biodiesel, tea-tree extract, honey, milk, sugar, butter, egg etc.). Also, some research groups have used foods wastes (cookie and chocolate), vegetation wastes (woods, leaf, grass, fruit wastes), animal/bird/insect wastes (bone and cow dung, dog feces, chicken feather) and agro waste (sugarcane bagasse) for the synthesis of graphene and CNTs. Research on natural hydrocarbon precursors and wastage materials has increased in recent years as they promise to produce better and high quality of graphene and CNTs in large quantities. The fascinating aspect of this research area is that it guides the use of natural hydrocarbons to explore the possibilities of improving graphene stability and robustness suitable for different type of applications.
Highlights
Various synthetic methods for the synthesis of NiCo
2
O
4
nano-/microstructures in bare, doped, and composite/hybrid forms are reviewed.
Currents status and development prospects of NiCo
2
...O
4
nano-/microstructure-based electrochemical biosensors for bioanalytes such as glucose, urea, and H
2
O
2
, along with condition governing the electrochemical biosensor parameters, are summarized.
Also provide an insight into the key challenges and future perspectives about point-of-care monitoring of bioanalytes using NiCo
2
O
4
nano-/microstructure-based biosensors.
Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo
2
O
4
mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo
2
O
4
materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein. Comparative analysis reveals better electrochemical sensing of bioanalytes by one-dimensional and two-dimensional NiCo
2
O
4
nano-/microstructures than other morphologies. Better biosensing efficiency of NiCo
2
O
4
as compared to corresponding individual metal oxides, viz. NiO and Co
3
O
4
, is attributed to the close intrinsic-state redox couples of Ni
3+
/Ni
2+
(0.58 V/0.49 V) and Co
3+
/Co
2+
(0.53 V/0.51 V). Biosensing performance of NiCo
2
O
4
is also significantly improved by making the composites of NiCo
2
O
4
with conducting carbonaceous materials like graphene, reduced graphene oxide, carbon nanotubes (single and multi-walled), carbon nanofibers; conducting polymers like polypyrrole (PPy), polyaniline (PANI); metal oxides NiO, Co
3
O
4
, SnO
2
, MnO
2
; and metals like Au, Pd, etc. Various factors affecting the morphologies and biosensing parameters of the nano-/micro-structured NiCo
2
O
4
are also highlighted. Finally, some drawbacks and future perspectives related to this promising field are outlined.
The importance of graphene and its derivatives for “clean energy” applications became apparent over the last few years due to their exceptional characteristics, especially regarding electrical, ...thermal and chemical properties. In this review article we examine the recent progress and some of the challenges in the syntheses and modification of graphene-based materials, including energy storage applications as electrodes in Li-ion batteries (LIBs). Various synthesis routes have been used for obtaining graphene using different kinds of carbon sources (graphite, non-graphitic carbon and carbon-containing materials). The most popular processing methods include epitaxial growth, liquid phase chemical/electrochemical exfoliation, mechanical exfoliation, chemical vapor deposition and laser-assisted synthesis. Taking the reduction approach, chemical, thermal, microwave and laser reduction methods have been applied to prepare graphene from graphene oxide/graphite oxide. Recent research has shown that graphene derivatives and hybrids/ nanocomposites using metal oxides/mixed metal oxides and metal sulfides/mixed metal sulphides can have a profound impact on the performance of energy storage devices. Closing the text, we speculate on the future prospects for the application of graphene and its derivatives in energy storage devices. We expect that this review article will help in generating new insights for further development and practical applications of graphene-based materials.
Supercapacitors are energy storage devices with unique characteristics, and together with batteries have generated a significant research effort, with various types of electrode materials having been ...developed over the last few years. Current trends for this application have been gradually shifting towards pseudocapacitive/battery-like materials. When compared to electric double-layer capacitors, pseudocapacitive/battery-type materials have a decisive advantage, since they are usually able to deliver improved energy density. Furthermore, these materials can undergo reversible electrochemical reactions within a very short period of time without compromising their high charge storage capacity. In this article, we systematically survey the current state of the art regarding the fabrication and electrochemical performance of the most promising classes of pseudocapacitive/battery-type electrode materials for supercapacitors. The text covers metal oxides, mixed metal oxides, conducting polymers, and MXenes. Closing the article, some of the outstanding problems for increasing the performance of SCs are discussed, and future research directions are suggested.
Systematic survey on the fabrication and electrochemical performance of the most promising classes of pseudocapacitive/battery-type electrode materials for supercapacitors.
The primary objective for deploying renewable energy in India is to advance economic development, improve energy security, improve access to energy, and mitigate climate change. Sustainable ...development is possible by use of sustainable energy and by ensuring access to affordable, reliable, sustainable, and modern energy for citizens. Strong government support and the increasingly opportune economic situation have pushed India to be one of the top leaders in the world’s most attractive renewable energy markets. The government has designed policies, programs, and a liberal environment to attract foreign investments to ramp up the country in the renewable energy market at a rapid rate. It is anticipated that the renewable energy sector can create a large number of domestic jobs over the following years. This paper aims to present significant achievements, prospects, projections, generation of electricity, as well as challenges and investment and employment opportunities due to the development of renewable energy in India. In this review, we have identified the various obstacles faced by the renewable sector. The recommendations based on the review outcomes will provide useful information for policymakers, innovators, project developers, investors, industries, associated stakeholders and departments, researchers, and scientists.
Laser-based approaches for graphene synthesis, reduction, modification, cutting and micro-patterning have been developed and applied to the fabrication of various electronic devices. These ...laser-based techniques exhibit several advantages over alternative methods: low temperature, shorter reaction times, environmentally friendly, energy saving, catalyst free growth on insulating substrates, high productivity, better reproducibility, scalability, excellent control over experimental parameters. Given the importance of the subject, in the last few years a remarkable increase in the number of scientific articles has occurred in this area. Direct fabrication of graphene patterns for micro-supercapacitors, flexible electrodes, field-effect-transistors, and sensors are some of the examples. Direct laser writing enables local graphene synthesis and fabrication of graphene patterns on graphene oxide films. It can be used to achieve band gap modulation, removal of surface functionalities, conductivity enhancement, exfoliation and porous structure formation. The aim of this review is to collect some of the most relevant research efforts published on this important topic, with emphasis in the articles published in the last few years. After an introduction highlighting the main factors affecting the outcome of laser-materials interactions, devices built using direct laser writing (DLW) on graphene oxide/graphene films and the experimental conditions used for their fabrication are summarized. Some of the expected directions for promising future research in this area are briefly discussed.
Currently, nanomaterials are considered to be the backbone of modern civilization. Especially in the energy sector, nanomaterials (mainly, carbon- and metal oxide/hydroxide-based nanomaterials) have ...contributed significantly. Among the various green approaches for the synthesis of these nanomaterials, the microwave-assisted approach has attracted significant research interest worldwide. In this context, it is noteworthy to mention that because of their enhanced surface area, high conducting nature, and excellent electrical and electrochemical properties, carbon nanomaterials are being extensively utilized as efficient electrode materials for both supercapacitors and secondary batteries. In this review article, we briefly demonstrate the characteristics of microwave-synthesized nanomaterials for next-generation energy storage devices. Starting with the basics of microwave heating, herein, we illustrate the past and present status of microwave chemistry for energy-related applications, and finally present a brief outlook and concluding remarks. We hope that this review article will positively convey new insights for the microwave synthesis of nanomaterials for energy storage applications.
Microwave-assisted synthesis of carbon nanomaterials, metal oxides/hydroxides and their composites for energy storage applications.
Two-dimensional crystals with a wealth of exotic dimensional-dependent properties are promising candidates for next-generation ultrathin and flexible optoelectronic devices. For the first time, we ...demonstrate that few-layered InSe photodetectors, fabricated on both a rigid SiO2/Si substrate and a flexible polyethylene terephthalate (PET) film, are capable of conducting broadband photodetection from the visible to near-infrared region (450–785 nm) with high photoresponsivities of up to 12.3 AW–1 at 450 nm (on SiO2/Si) and 3.9 AW–1 at 633 nm (on PET). These photoresponsivities are superior to those of other recently reported two-dimensional (2D) crystal-based (graphene, MoS2, GaS, and GaSe) photodetectors. The InSe devices fabricated on rigid SiO2/Si substrates possess a response time of ∼50 ms and exhibit long-term stability in photoswitching. These InSe devices can also operate on a flexible substrate with or without bending and reveal comparable performance to those devices on SiO2/Si. With these excellent optoelectronic merits, we envision that the nanoscale InSe layers will not only find applications in flexible optoelectronics but also act as an active component to configure versatile 2D heterostructure devices.
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