微纳米分子系统研究领域的最新进展--IEEE NEMS 2013国际会议综述

2013年4月7日至10日，第八届IEEE国际纳米/微米工程及分子系统大会(IEEE-NEMS 2013)在中国苏州市召开[1-2]，来自世界各地的360多位专家、学者齐聚一堂，就微纳研究领域的微/纳米制造和计量、微/纳米传感器、执行器和系统、纳米医学、微/纳流体、生物芯片、纳米材料、碳纳米管、石墨烯器件、微纳传热器件、能量采集器等多个方向展开了学术讨论和交流，充分展示了国内外在以上研究领域的最新研究成果、热点和动态，并对其发展趋势进行了分析。NEMS 2013国际会议的成功举办表明，以微/纳米分子系统等为代表的研究领域已成为高科技的重要代表，并极大地影响着世界的发展和人类生活。     

Photoluminescence and X-ray luminescence of Pb0.30Cd0.70I2 solid solutions. Comparative study

The nature and relative contributions (RCs) of various radiative recombination processes to the photoluminescence (PL) spectra for bulk nanostructured Pb_0.30Cd_0.70I₂ solid solutions have been established at different temperatures. The analysis indicates that the PL is caused by free, bound and self-trapped excitons as well as by donor-acceptor pairs emission with the participation of shallow and deep acceptor centers. It was shown that X-ray luminescence (XRL) spectra are also determined by these recombination processes. However, their RC and the temperature evolution are considerably different. Besides, XRL spectra contain an intense long-wavelength band associated with the emission of many LO-phonons. It was shown that the deep luminescence surface states, associated with the self-trapped excitons and deep intrinsic defects, mainly determine the intensity of XRL spectra both at 80 K and room temperature. The results obtained open the way to the optimization of the scintillator properties of the investigated materials.     

Carbonaceous-TiO2 nanomaterials for photocatalytic degradation of pollutants: A review

Semiconductor photocatalysis is one of most appealing and attractive technologies, which has been directly utilized to harvest solar energy for energy and environmental applications. Titanium dioxide (TiO₂) has been proved to be leading semiconductor photocatalyst for the degradation of pollutants. However, it suffers from low photocatalytic activity under visible light activation because of its intrinsic wide band gap. Various strategies have been developed to enhance TiO₂ efficiency in the visible light region. Among them TiO₂ modification with carbonaceous nanomaterials is very effective route for excellent photocatalytic activity. This critical review aims to present recent progress in the design and synthesis of carbonaceous-TiO₂ photocatalysts, covering carbon doping, activated carbon, fullerenes, carbon nanotubes and graphene. Moreover, proposed mechanisms of enhancement, effect of synthesis routes, demonstrations of performance and applications reported in literature are reviewed. Ongoing challenges and possible new directions are outlined.     

Two-dimensional nanomaterials for photocatalytic water disinfection: recent progress and future challenges

Photocatalysis has received ever-growing attention as a promising alternative to traditional water treatment technologies for waterborne biohazard inactivation. Due to unique optical, electronic, physicochemical properties and feasibility of functional architecture assembly, two-dimensional (2D) nanomaterials have become important in developing novel photocatalysts. This review summarizes the recent progress in configuring nanostructures with 2D materials as building blocks for photocatalytic water disinfection. In this review, five categories of 2D nanomaterials, that is, graphene, graphitic carbon nitride, 2D metal oxides and metallates, metal oxyhalides and transition metal dichalcogenides, for photocatalytic pathogen inactivation are introduced. First, the synthesis process, nanostructure engineering and disinfection performance of 2D-based photocatalysts are reviewed in categories. In the following section, the bacteria destruction mechanism based on the generation and roles of reactive species (RSs) is presented. Moreover, the effects of the chemical characteristics of the water matrix on photocatalytic bactericidal performance are discussed. Finally, the challenges regarding the development and application of 2D-based photocatalysts for highly efficient water sterilization are highlighted. © 2018 Society of Chemical Industry     

One‐Pot Synthesis of Dealloyed AuNi Nanodendrite as a Bifunctional Electrocatalyst for Oxygen Reduction and Borohydride Oxidation Reaction

A novel one‐pot approach for synthesizing the dealloyed nanomaterials at room temperature is introduced for the first time. In such a synthetic strategy, applying modulated potentials effectively simplifies the traditional dealloying route, which usually requires additional corrosion process to dissolve nonprecious metals. The dealloyed AuNi nanodendrites (AuNi NDs) with tunable composition and uniformly elemental distribution are well developed by the one‐pot strategy. Impressively, the as‐synthesized AuNi NDs exhibit a higher electrochemically active area and definite improvements in electrocatalytic activity for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) compared to the commercial Pt/C. In particular, the AuNi NDs are 81 mV more positive in half‐wave potential and about 3.1 times higher in specific activity (at 0.85 V) for the ORR than Pt/C, together with excellent stability and methanol tolerance. The superior BOR activity is highly promising compared to the previously reported catalysts. The unique nanodendritic structure with Au‐rich surface and bimetallic electronic effect is the main factor to greatly enhance the bifunctional catalytic performance for the AuNi NDs. Furthermore, such a newly developed facile method is of great significance because it is one of the first examples to effectively engineer dealloyed bimetallic nanostructures via the practical and low‐cost route for electrocatalytic applications.     

Antibiotic-Free Antibacterial Strategies Enabled by Nanomaterials: Progress and Perspectives

Bacterial infection is one of the top ten leading causes of death globally and the worst killer in low-income countries. The overuse of antibiotics leads to ever-increasing antibiotic resistance, posing a severe threat to human health. Recent advances in nanotechnology provide new opportunities to address the challenges in bacterial infection by killing germs without using antibiotics. Antibiotic-free antibacterial strategies enabled by advanced nanomaterials are presented. Nanomaterials are classified on the basis of their mode of action: nanomaterials with intrinsic or light-mediated bactericidal properties and others that serve as vehicles for the delivery of natural antibacterial compounds. Specific attention is given to antibacterial mechanisms and the structure–performance relationship. Practical antibacterial applications employing these antibiotic-free strategies are also introduced. Current challenges in this field and future perspectives are presented to stimulate new technologies and their translation to fight against bacterial infection.     

Zwitterionic‐Coated “Stealth” Nanoparticles for Biomedical Applications: Recent Advances in Countering Biomolecular Corona Formation and Uptake by the Mononuclear Phagocyte System

Nanoparticles represent highly promising platforms for the development of imaging and therapeutic agents, including those that can either be detected via more than one imaging technique (multi‐modal imaging agents) or used for both diagnosis and therapy (theranostics). A major obstacle to their medical application and translation to the clinic, however, is the fact that many accumulate in the liver and spleen as a result of opsonization and scavenging by the mononuclear phagocyte system. This focused review summarizes recent efforts to develop zwitterionic‐coatings to counter this issue and render nanoparticles more biocompatible. Such coatings have been found to greatly reduce the rate and/or extent of non‐specific adsorption of proteins and lipids to the nanoparticle surface, thereby inhibiting production of the “biomolecular corona” that is proposed to be a universal feature of nanoparticles within a biological environment. Additionally, in vivo studies have demonstrated that larger‐sized nanoparticles with a zwitterionic coating have extended circulatory lifetimes, while those with hydrodynamic diameters of ≤5 nm exhibit small‐molecule‐like pharmacokinetics, remaining sufficiently small to pass through the fenestrae and slit pores during glomerular filtration within the kidneys, and enabling efficient excretion via the urine. The larger particles represent ideal candidates for use as blood pool imaging agents, whilst the small ones provide a highly promising platform for the future development of theranostics with reduced side effect profiles and superior dose delivery and image contrast capabilities.     

Au/NaYF4 : Yb,Er Binary Superparticles: Synthesis and Optical Properties

Colloidal superparticles (SPs) are nanoparticle (NP) assemblies in the form of colloidal particles. Assembling nanoscopic objects into mesoscopic or macroscopic composite architectures allows for the bottom-up fabrication of functional nanomaterials. In this study, a method for single-step self-assembly synthesis of Au/NaYF₄ : Yb,Er SPs was developed using oil-in-water (O/W) microemulsions to simultaneously encapsulate gold nanoparticles (AuNPs) and NaYF₄ : Yb,Er upconversion nanoparticles (UCNPs) via evaporation at room temperature. The synthesized Au/NaYF₄ : Yb,Er SPs possess good dispersibility and stability. When the number of AuNPs added is increased, the SPs exhibit decreased upconversion luminescence, which can be ascribed to the Förster resonance energy transfer (FRET) from the NaYF₄ : Yb,Er UCNPs to the AuNPs. Time-resolved measurements of the green emission further confirm the existence of a new decay route corresponding to the FRET process. Our research provides a facile and versatile strategy for the synthesis of novel multifunctional nanocomposites with tunable upconversion luminescence properties, which can be of great significance in biological applications.