Enhanced near band gap edge (NBE) emissions of PVA-ZnO nanoparticles were achieved by employing SiO(2)-Au core/shell nanostructures whereas the defect-level emission (DLE) is greatly suppressed. A maximum enhancement of nearly 400% was observed using SiO(2)-Au for the emission with optical resonance at 554 nm. SiO(2)-Au core/shell nanostructures also show a superior tunability of resonance energy as compared to that of the pure metal nanoparticles. The enhancement of the NBE emission and suppressed DLE is ascribed to the transfer of the energetic electrons excited by surface plasmon from metal nanoparticles to the conduction band of ZnO nanoparticles.
Abstract: To address the limitations of traditional drug delivery, TiO 2 nanotubes (TNTs) are recognized as a promising material for localized drug delivery systems. With regard to the excellent biocompatibility and physicochemical properties, TNTs prepared by a facile electrochemical anodizing process have been used to fabricate new drug-releasing implants for localized drug delivery. This review discusses the development of TNTs applied in localized drug delivery systems, focusing on several approaches to control drug release, including the regulation of the dimensions of TNTs, modification of internal chemical characteristics, adjusting pore openings by biopolymer coatings, and employing polymeric micelles as drug nanocarriers. Furthermore, rational strategies on external conditions-triggered stimuli-responsive drug release for localized drug delivery systems are highlighted. Finally, the review concludes with the recent advances on TNTs for controlled drug delivery and corresponding prospects in the future. Keywords: TiO 2 nanotubes, electrochemical anodization, modification, stimulated drug delivery, drug-releasing implant
Transition metal oxides, used as LIB anodes, typically experience significant capacity fading at high rates and long cycles due to chemical and mechanical degradations upon cycling. In this work, an effective strategy is implemented to mitigate capacity fading of Co3O4 at high rates by use of hollow and mesoporous Co3O4 spheres and graphene sheets in a core–shell geometry. The core–shell structure exhibits a high reversible capacity of 1076 mAh g–1 at a current density of 0.1 A g–1, and excellent rate performance from 0.1 to 5.0 A g–1. The graphene/Co3O4 nanosphere composite electrode also displays an exceptional cyclic stability with an extraordinarily high reversible capacity over 600 mAh g–1 after 500 cycles at a high current density of 1.0 A g–1 without signs of further degradation. The highly conductive graphene nanosheets wrapping up on surfaces and interfaces of metal oxide nanospheres provide conductive pathways for effective charge transfer. The mesoporous features of graphene and hollow metal oxide nanosphere also enable fast diffusion of lithium ions for the charge/discharge process. The highly flexible and mechanically robust graphene nanosheets prevent particle agglomeration and buffer volume expansion of Co3O4 upon cycling. The unique nanostructure of Co3O4 wrapped up with highly flexible and conductive graphene nanosheets represents an effective strategy that may be applied for various metal oxide electrodes to mitigate the mechanical degradation and capacity fading, critical for developing advanced electrochemical energy storage systems with long cycle life and high rate performance.
Amorphous TiO2 (a-TiO2) thin films were conformally coated onto the surface of hydroxyl functionalized multi-walled carbon nanotubes (CNTs) using atomic layer deposition (ALD). The electrochemical characteristics of the a-TiO2/CNT nanocomposites were then determined using cyclic voltammetry and galvanostatic charge/discharge curves. The ultrathin TiO2 ALD films displayed high specific capacity and high rate capability. The specific capacities of the a-TiO2/CNT nanocomposites after 50 and 100 TiO2 ALD cycles at 100 mA/g were 220 mAh/g and 240 mAh/g, respectively. For CNTs coated with 100 TiO2 ALD cycles, 88% of the capacity at 100 mA/g could be maintained at 1 A/g. When the voltage window for the a-TiO2/CNT nanocomposites was extended down to 0.5 V versus Li/Li+, the CNTs coated with 50 and 100 TiO2 ALD cycles exhibited specific capacities at 100 mA/g of 275 mAh/g and 312 mAh/g, respectively. These high capacities are higher than the bulk theoretical values and are attributed to additional interfacial charge storage resulting from the high surface area of the a-TiO2/CNT nanocomposites. Free-standing TiO2-CNT electrodes were also fabricated and displayed excellent capacity and rate capability. These results demonstrate that TiO2 ALD on high surface area CNT substrates can provide high power and high capacity anodes for lithium ion batteries.
Abstract Graphene fibers are fabricated by wet‐spinning an aqueous large‐size and small‐size graphene oxide (GO) dispersion in a rotating Me 3 N(C 16 H 33 )Br or CaCl 2 coagulation bath.
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