UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Multiferroic magnetoelectric composite systems such as ferromagnetic-ferroelectric heterostructures have recently attracted an ever-increasing interest and provoked a great number of research activities, driven by profound physics from coupling between ferroelectric and magnetic orders, as well as potential applications in novel multifunctional devices, such as sensors, transducers, memories, and spintronics. In this Review, we try to summarize what remarkable progress in multiferroic magnetoelectric composite systems has been achieved in most recent few years, with emphasis on thin films; and to describe unsolved issues and new device applications which can be controlled both electrically and magnetically.

Recent Progress in Multiferroic Magnetoelectric Composites: from Bulk to Thin Films

In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

The photocatalytic activity of materials for water splitting is limited by the recombination of photogenerated electron–hole pairs as well as the back-reaction of intermediate species. This review concentrates on the use of electric fields within catalyst particles to mitigate the effects of recombination and back-reaction and to increase photochemical reactivity. Internal electric fields in photocatalysts can arise from ferroelectric phenomena, p–n junctions, polar surface terminations, and polymorph junctions. The manipulation of internal fields through the creation of charged interfaces in hierarchically structured materials is a promising strategy for the design of improved photocatalysts.

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Photocatalysts with internal electric fields

Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

Bismuth ferrite (BiFeO3) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method. The resulting microstructures were characterized using X-ray diffraction, scanning/transmission electron microscopies and Raman spectroscopy. Possible formation mechanism for BiFeO3 microcrystals was proposed. UV−vis spectra showed that the optical properties of the microsized BiFeO3 crystals were strongly related to their shape and size. We further demonstrated the useful photocatalytic activity of these regular-shaped structures as determined by degradation of Congo red under visible-light irradiation (λ > 400 nm). Additionally, magnetic responses were observed to be influenced by the morphology of as-synthesized BiFeO3 products, and the ferroelectric performance of BiFeO3 submicrocube was also studied by piezoelectric force microscopy (PFM). Being a multiferroic semiconductor with suitable narrow band gap (∼2.2 eV) and uniform ...

Controlled Fabrication of BiFeO3 Uniform Microcrystals and Their Magnetic and Photocatalytic Behaviors

Mechanochemically synthesized sub-5 nm sized CuS quantum dots with high visible-light-driven photocatalytic activity

Magnetic tunnel junctions (MTJs) [1, 2] have been used for magnetic memory (usually known as MRAM) and sen-sor applications [3, 4], while they also offer opportunities for novel logic devices, either employed as the spin-logic de-vices [5–7], or combining with complementary metal oxide semiconductor (CMOS) transistors in hybrid MTJ/CMOS logic circuits [8–11]. In such MTJ-based logic devices, the high and low resistance states, corresponding respectively to the antiparallel and parallel magnetic configuration in the MTJ unit, are related to the Boolean 1 or 0, and different logic functions can then be defined. Compared with current CMOS logic devices, the MTJ-based magnetic logic has several significant advantages such as nonvolatile in-puts/outputs, non-destructive readout and the possibility of fast operation and run-time reconfigurability [5–7]. How-ever, the high power consumption associated with the cur-rent-induced magnetization switching in the MTJ unit turns into a major drawback of such magnetic logic devices [11], since the accompanying overheating imposes limitations on the performance optimization of the devices and will be-come more severe with increased integration [12]. Therefore, it is of paramount importance to reduce the energy con-sumption in the switching process before industrial applica-tions of such MTJ-based logic devices. Until recently the idea to make purely electric-field-controlled devices [13] has offered a promising route to this goal, i.e., the electric-field-controlled magnetic logic devices, in which electric fields instead of currents are di-rectly used to induce the magnetization switching during the input process, and thus cause much less Joule heating. As an early example, the concept of a magnetoelectric (ME) XOR logic cell [14] was proposed by exploiting ME switching of exchange bias [15]. In this letter, we present a novel concept of electric-field-controlled ME-logic based on the strain-mediated ME coupling in multiferroic ME composites [16], namely, a strain-mediated ME-logic, which is nonvolatile, low power-consumed and compatible with current semiconductor devices. Two possible designs of such ME-logic devices are introduced, which can either be preset as a NOR, NOT, or NAND gate separately, or be electronically configured to perform the logical NOR, NOT, or NAND function at run-time.

Yuan-Hua Lin

Papers

Controlled Fabrication of BiFeO3 Uniform Microcrystals and Their Magnetic and Photocatalytic Behaviors

Mechanochemically synthesized sub-5 nm sized CuS quantum dots with high visible-light-driven photocatalytic activity

A magnetoelectric logic gate

Voltage-driven hysteretic changes in magnetization in multiferroic Co/BTO composite thin films