Photocatalytic water splitting represents a promising strategy for clean, low-cost, and environmental-friendly production of H2 by utilizing solar energy. There are three crucial steps for the photocatalytic water splitting reaction: solar light harvesting, charge separation and transportation, and the catalytic H2 and O2 evolution reactions. While significant achievement has been made in optimizing the first two steps in the photocatalytic process, much less efforts have been put into improving the efficiency of the third step, which demands the utilization of cocatalysts. To date, cocatalysts based on rare and expensive noble metals are still required for achieving reasonable activity in most semiconductor-based photocatalytic systems, which seriously restricts their large-scale application. Therefore, seeking cheap, earth-abundant and high-performance cocatalysts is indispensable to achieve cost-effective and highly efficient photocatalytic water splitting. This review for the first time summarizes all the developed earth-abundant cocatalysts for photocatalytic H2- and O2-production half reactions as well as overall water splitting. The roles and functional mechanism of the cocatalysts are discussed in detail. Finally, this review is concluded with a summary, and remarks on some challenges and perspectives in this emerging area of research.

Earth-abundant cocatalysts for semiconductor-based photocatalytic water splitting

Transparent conductors as solar energy materials: A panoramic review

http://if-pan.krakow.pl/pjp/pdf/2012/5_1020.pdf

Nanoparticles as drug delivery systems

Importance of the field: Metal oxide nanoparticles, including zinc oxide, are versatile platforms for biomedical applications and therapeutic intervention. There is an urgent need to develop new classes of anticancer agents, and recent studies demonstrate that ZnO nanomaterials hold considerable promise.Areas covered in this review: This review analyzes the biomedical applications of metal oxide and ZnO nanomaterials under development at the experimental, preclinical and clinical levels. A discussion regarding the advantages, approaches and limitations surrounding the use of metal oxide nanoparticles for cancer applications and drug delivery is presented. The scope of this article is focused on ZnO, and other metal oxide nanomaterial systems, and their proposed mechanisms of cytotoxic action, as well as current approaches to improve their targeting and cytotoxicity against cancer cells.What the reader will gain: This review aims to give an overview of ZnO nanomaterials in biomedical applications.Take home...

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Zinc oxide nanoparticles for selective destruction of tumor cells and potential for drug delivery applications.

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

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Hallmarks of mechanochemistry: From nanoparticles to technology

We report the synthesis of nominal 2 and 5 at.% Mn-doped ZnO nanocrystalline particles by a co-precipitation method. Rietveld refinement of x-ray diffraction data revealed that Mn-doped ZnO crystallizes in the monophasic wurtzite structure and the unit cell volume increases with increasing Mn concentration. DC magnetization measurements showed ferromagnetic ordering above room temperature with Hc~150 Oe for nominal 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. A distinct ferromagnetic resonance (FMR) signal was observed in the EPR spectra of the 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. EPR measurements were used to estimate the number of spins participating in ferromagnetic ordering. Of the total Mn present in the 2 at.% Mn ZnO lattice, 25% of the Mn2+ ions were responsible for ferromagnetic ordering, whereas nearly 5% of the Mn2+ ions remained uncoupled (isolated spins). A well resolved EPR spectrum of 5% Mn-doped ZnO samples annealed at 875–1275 K (g = 2.007, A = 80 G, D = 210 G and E = 15 G) confirmed that Mn was substitutionally incorporated into the ZnO lattice as Mn2+. On increasing the temperature of annealing beyond 1075 K an impurity phase emerges in both the 2 and 5 at.% Mn-doped ZnO samples, which has been identified as a variant of (Zn1−XMn(II)X)Mn(III)2O4 with Tc~15 K. Our results indicate that the observed room temperature ferromagnetism in Mn-doped ZnO can be attributed to the substitutional incorporation of Mn at Zn-sites rather than due to the formation of any metastable secondary phases.

https://iopscience.iop.org/article/10.1088/0957-4484/17/5/020/pdf

Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method

In this study we report the synthesis of BiFeO3 nanorods using a sonochemical technique. The nanorods had a diameter of 20–50 nm, a length of 100–500 nm and exhibit aspect ratios in the range of 5–10. However, after doping, the TEM images of Bi0.9Ba0.1Fe0.9Mn0.1O3 and Bi0.9Ca0.1Fe0.9Cr0.1O3 samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO3 nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M–H relationship reported for bulk BiFeO3. The saturation magnetization of these BiFeO3 nanostructures has been found to increase on doping with various metal ions (Ba2+, Ca2+, Mn2+, Cr3+), reaching a maximum value of 1.35 emu g−1 for the Bi0.9Ba0.1Fe0.9Mn0.1O3 nanostructures. However, saturation of electric polarization was observed only in case of the Bi0.9Ca0.1Fe0.9Cr0.1O3 nanostructures.

Effect of doping on the morphology and multiferroic properties of BiFeO3 nanorods

Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wid ...

Room temperature ferromagnetism in pristine MgO thin films

Crystalline nanoparticles of anatase phase nitrogen-doped TiO2 (N–TiO2), boron and nitrogen codoped TiO2 (B–N–TiO2), and undoped TiO2 (TiO2) were synthesized by a facile xerogel method followed by reduction in a glycol medium to forcibly create Ti3+ ions (self-doping) in them (R–N–TiO2, R–B–N–TiO2, and R–TiO2, where R stands for reduced) and studied their photocatalytic activity for hydrogen generation from water. A clear red shift of the absorption edge and stronger absorption in the visible region was observed for both reduced and unreduced N–TiO2 and B–N–TiO2 compared to the other samples. The presence of bonded nitrogen in the N-doped samples was evidenced from their N1s X-ray photoelectron spectra. Photocatalytic activity for hydrogen generation using sunlight-type radiation showed enhanced activity for the reduced and doped samples compared to pristine TiO2. The enhanced photocatalytic activity of the R–N–TiO2 for hydrogen generation is attributed to the enhanced light absorption resulting from the ...

Photochemical Hydrogen Generation Using Nitrogen-Doped TiO2–Pd Nanoparticles: Facile Synthesis and Effect of Ti3+ Incorporation

We report the preparation, characterization, and magnetic properties of highly crystalline colloidal Fe-doped indium oxide nanoparticles. The nanoparticles have been prepared in high yields by simple one-pot thermal decomposition of indium and iron precursors in hexadecylamine and can be easily dispersed in solvents like chloroform and toluene. Detailed X-ray diffraction, microstructure, and Raman studies reveal that the nanoparticles are single phase cubic bixbyite structure without any parasitic secondary phases. DC magnetization studies as a function of temperature and field indicate that nanoparticles are weakly ferromagnetic at room temperature (RT). This observation is further confirmed by the electron paramagnetic resonance spectra of the samples, which show a distinct ferromagnetic resonance signal at RT.

Onattu D. Jayakumar

Papers

Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method

Effect of doping on the morphology and multiferroic properties of BiFeO3 nanorods

Room temperature ferromagnetism in pristine MgO thin films

Photochemical Hydrogen Generation Using Nitrogen-Doped TiO2–Pd Nanoparticles: Facile Synthesis and Effect of Ti3+ Incorporation

Colloidal Fe-Doped Indium Oxide Nanoparticles : Facile Synthesis, Structural, and Magnetic Properties