Meeting the growing global energy demand is one of the important challenges of the 21st century. Currently over 80% of the world's energy requirements are supplied by the combustion of fossil fuels, which promotes global warming and has deleterious effects on our environment. Moreover, fossil fuels are non-renewable energy and will eventually be exhausted due to the high consumption rate. A new type of alternative energy that is clean, renewable and inexpensive is urgently needed. Several candidates are currently available such as hydraulic power, wind force and nuclear power. Solar energy is particularly attractive because it is essentially clean and inexhaustible. A year's worth of sunlight would provide more than 100 times the energy of the world's entire known fossil fuel reserves. Photocatalysis and photovoltaics are two of the most important routes for the utilization of solar energy. However, environmental protection is also critical to realize a sustainable future, and water pollution is a serious problem of current society. Photocatalysis is also an essential route for the degradation of organic dyes in wastewater. A type of compound with the defined structure of perovskite (ABX3) was observed to play important roles in photocatalysis and photovoltaics. These materials can be used as photocatalysts for water splitting reaction for hydrogen production and photo-degradation of organic dyes in wastewater as well as for photoanodes in dye-sensitized solar cells and light absorbers in perovskite-based solar cells for electricity generation. In this review paper, the recent progress of perovskites for applications in these fields is comprehensively summarized. A description of the basic principles of the water splitting reaction, photo-degradation of organic dyes and solar cells as well as the requirements for efficient photocatalysts is first provided. Then, emphasis is placed on the designation and strategies for perovskite catalysts to improve their photocatalytic activity and/or light adsorption capability. Comments on current and future challenges are also provided. The main purpose of this review paper is to provide a current summary of recent progress in perovskite materials for use in these important areas and to provide some useful guidelines for future development in these hot research areas.

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment.

Development of cost-effective and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of prime importance to emerging renewable energy technologies. Here, we report a simple and effective strategy for enhancing ORR and OER electrocatalytic activity in alkaline solution by introducing A-site cation deficiency in LaFeO3 perovskite; the enhancement effect is more pronounced for the OER than the ORR. Among the A-site cation deficient perovskites studied, La0.95FeO3-δ (L0.95F) demonstrates the highest ORR and OER activity and, hence, the best bifunctionality. The dramatic enhancement is attributed to the creation of surface oxygen vacancies and a small amount of Fe4+ species. This work highlights the importance of tuning cation deficiency in perovskites as an effective strategy for enhancing ORR and OER activity for applications in various oxygen-based energy storage and conversion processes.

Enhancing Electrocatalytic Activity of Perovskite Oxides by Tuning Cation Deficiency for Oxygen Reduction and Evolution Reactions

Globally cancer is a disease which severely effects the human population. There is a constant demand for new therapies to treat and prevent this life-threatening disease. Scientific and research interest is drawing its attention towards naturally-derived compounds as they are considered to have less toxic side effects compared to current treatments such as chemotherapy. The Plant Kingdom produces naturally occurring secondary metabolites which are being investigated for their anticancer activities leading to the development of new clinical drugs. With the success of these compounds that have been developed into staple drugs for cancer treatment new technologies are emerging to develop the area further. New technologies include nanoparticles for nano-medicines which aim to enhance anticancer activities of plant-derived drugs by controlling the release of the compound and investigating new methods for administration. This review discusses the demand for naturally-derived compounds from medicinal plants and their properties which make them targets for potential anticancer treatments.

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Medicinal Plants: Their Use in Anticancer Treatment.

Perovskite-type oxides are a class of compounds with the general formula ABO 3 . They are a very important family of materials and exhibit properties suitable for numerous applications. In this review, the preparation, characterization, and application of selected perovskite oxides such as SrTiO 3 , KTaO 3 , NaTaO 3 , KNbO 3 , and NaNbO 3 in photocatalysis are described. In addition, various strategies for enhancing their photocatalytic activities are discussed, including doping with metals and nonmetals (Cr, Ni, Mn, Pb, Bi, N, Br, S, C, and F), modification with noble metal (Au, Ag, Pt, Pd, Ph, Ru) nanoparticles, and doping with rare earth elements (La). Moreover, the review summarizes the influence of different morphologies and surface properties on the photoactivity of the materials.

Selected perovskite oxides: Characterization, preparation and photocatalytic properties—A review

Background Quercetin, one of the most well-known flavonoids, has been included in human diet for a long history. The use of quercetin has been widely associated with a great number of health benefits, including antioxidant, anti-inflammatory, antiviral and anticancer as well as the function to ease some cardiovascular diseases (i.e., heart disease, hypertension, and high blood cholesterol). However, poor water solubility, chemical instability and low bioavailability of quercetin greatly limit its applications. Utilization of delivery systems can improve its stability, efficacy and bioavailability. Scope and approach In this review, biological activities, chemical stability, metabolism and toxicity of quercetin and different delivery systems for quercetin were discussed. Key findings and conclusions Quercetin digested in human body (e.g., mouth, small intestine, liver, kidneys) undergoes glucuronidation, sulfation or methylation. During the food processing and storage, many factors such as heat, pH, metal ions, could affect the chemical stability (including oxidation and degradation) of quercetin. Utilization of delivery systems including lipid-based carriers, nanoparticles, inclusion complexes, micelles and conjugates-based encapsulation has the potential to improve both the stability and bioavailability and thus health benefits of quercetin. Each delivery system has its unique advantages and shortcomings, and the specific selection should be based on the application domains. Moreover, the exploration of natural food-grade ingredients as main compositions of delivery systems for quercetin might be required in the future.

The biological activities, chemical stability, metabolism and delivery systems of quercetin: A review

Shape evolution of nanostructured LaFeO3 with fascinating morphologies like cubes, rods and spheres was successfully synthesized by a facile and environmentally friendly hydrothermal process. Tuning the morphologies was achieved using different surfactants. The prepared samples were systematically characterized using X-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy for structural, morphological and chemical composition analysis by X-ray photoelectron spectroscopy. The optical properties of prepared samples were studied employing UV-Vis diffusion reflectance analysis. Brunauer–Emmett–Teller measurement reveals a large surface area for all the prepared nanostructures. Most importantly, the visible-light photocatalytic activities of the three LaFeO3 nanostructures were evaluated by photocatalytic decolorization of Rhodamine B in aqueous solution. The enhanced photocatalytic activity of LaFeO3 nanospheres compared to other nanostructures and commercial Degussa P25 TiO2 can be ascribed to high specific surface area, pore size distribution and the smaller particle size. The underlying growth mechanism responsible for the formation of LaFeO3 nanostructures is also discussed. The results from this study illustrate the morphology-dependent photocatalytic performance of LaFeO3.

Shape evolution of perovskite LaFeO3 nanostructures: a systematic investigation of growth mechanism, properties and morphology dependent photocatalytic activities

Controlled synthesis of perovskite LaFeO3 microsphere composed of nanoparticles via self-assembly process and their associated photocatalytic activity

A novel hydrothermal process was used for the preparation of hydroxyapatite (HAp) nanorods on two-dimensional reduced graphene oxides (RGO). The hydrothermal reaction temperature improves the crystallinity of HAp and partially reduces graphene oxide (GO) to RGO. The crystalline structure, chemical composition and morphology of the prepared nanocomposites were characterized by using various analytical techniques. Nanorods of HAp with a diameter and length of ∼32 and 60–85 nm were grown on basal planes and edges of the layered RGO sheets. The estimated specific surface area and pore-size distribution are 120 m2 g−1 and 5.6 nm, respectively. We also report the direct electrochemistry of glucose oxidase (GOx) on 1D HAp-on-2D RGO nanocomposite-modified glassy carbon electrode (GCE) for glucose sensing. The electrocatalytic and electroanalytical applications of the proposed RGO/HAp/GOx-modified GCE were studied by cyclic voltammetry (CV) and amperometry. The increased electron rate constant of 3.50 s−1 was obtained for the modified GCE. The reported biosensor exhibits a superior detection limit and higher sensitivity ca. 0.03 mM and 16.9 μA mM−1 cm−2, respectively, with a wide linear range of 0.1–11.5 mM. The tremendous analytical parameters of the reported sensor surpass those of related modified electrodes and are promising for practical industrial applications.

Enzymatic electrochemical glucose biosensors by mesoporous 1D hydroxyapatite-on-2D reduced graphene oxide

Polyaniline/graphene oxide (PANI-GO) fibrous nanocomposites have been prepared and the electrochemical catalytic activity towards the electro-oxidation of ascorbic acid (AA), Dopamine (DA) and Uric acid (UA) has been investigated. The nanocomposites were synthesized via an in situ chemical polymerization method. The morphology, composition, thermal and electrochemical properties of the resulting nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy, thermo gravimetric analysis and cyclic voltammetry. The catalytic behavior of PANI-GO nanocomposite modified glassy carbon electrode (GCE) towards AA, DA and UA has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV). The PANI-GO/GCE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to the bare GCE. The electrochemical oxidation signal of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 343 mV, 145 mV and 488 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separation in DPV mode are 320 mV, 230 mV and 550 mV. Under the optimized DPV experimental conditions, the peak current of AA, DA and UA give linear response over the range of 25–200 μM (R2 = 0.9955), 2–18 μM (R2 = 0.9932) and 2–18 μM (R2 = 0.9902) with detection limit of 20 μM, 0.5 μM and 0.2 μM at S/N = 3, respectively. The attractive features of PANI-GO provide potential applications in the simultaneous detection of AA, DA and UA. The excellent electrocatalytic behavior of PANI-GO may lead to new applications in electrochemical analysis.

Conducting polyaniline-graphene oxide fibrous nanocomposites: preparation, characterization and simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Single-crystalline novel LaFeO3 dendritic nanostructures are synthesized by a well-controlled, surfactant-assisted facile hydrothermal process. The morphology of the material is investigated by high-resolution transmission and scanning electron microscopy. The crystal nature and chemical composition of LaFeO3 dendritic nanostructures are revealed from the X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Structural characterizations imply the preferential growth along the [121] direction by oriented attachment of LaFeO3 nanoparticles in the diffusion limit, leading to the formation of LaFeO3 dendrites. The microscopic studies confirm the formation of dendrites with a length of 3–4 μm, a branch diameter of 80 nm, and a length of 1–1.5 μm. The possible growth mechanism of the dendritic morphology is discussed from the aspect of diffusion and oriented attachment based on experimental results. Further, the electrochemical measurements performed on LaFeO3 dendritic nanostructures dep...

Novel Synthesis of LaFeO3 Nanostructure Dendrites: A Systematic Investigation of Growth Mechanism, Properties, and Biosensing for Highly Selective Determination of Neurotransmitter Compounds

C. Viswanathan

Papers

Shape evolution of perovskite LaFeO3 nanostructures: a systematic investigation of growth mechanism, properties and morphology dependent photocatalytic activities

Controlled synthesis of perovskite LaFeO3 microsphere composed of nanoparticles via self-assembly process and their associated photocatalytic activity

Enzymatic electrochemical glucose biosensors by mesoporous 1D hydroxyapatite-on-2D reduced graphene oxide

Conducting polyaniline-graphene oxide fibrous nanocomposites: preparation, characterization and simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Novel Synthesis of LaFeO3 Nanostructure Dendrites: A Systematic Investigation of Growth Mechanism, Properties, and Biosensing for Highly Selective Determination of Neurotransmitter Compounds