NIR-Responsive Photocatalytic Activity and Mechanism of NaYF₄:Yb,Tm@TiO₂ Core–Shell Nanoparticles

Core–shell structured nanoparticles for near-infrared (NIR) photocatalysis were synthesized by a two-step wet-chemical route. The core is composed of upconversion luminescence NaYF₄:Yb,Tm prepared by a solvothermal process, and the shell is anatase TiO₂ nanocrystals around NaYF₄ particles formed via a method similar to a Stöber process. Methylene blue compound as a model pollutant was used to investigate the photocatalytic activity of NaYF₄:Yb,Tm@TiO₂ composites under NIR irradiation. To understand the nature of NIR-responsive photocatalysis of NaYF₄:Yb,Tm@TiO₂, we investigated the energy transfer process between NaYF₄:Yb,Tm and TiO₂ and the origin of the degradation of organic pollutants under NIR radiation. Results indicate that the energy transfer route between NaYF₄:Yb,Tm and TiO₂ is an important factor that influences the photocatalytic activity significantly and that the degradation of organic pollutants under NIR irradiation is caused mostly by the oxidation of reactive oxygen species generated in the photocatalytic reaction, rather than by the thermal energy generated by NIR irradiation. The understanding of NIR-responsive photocatalytic mechanism helps to improve the structural design and functionality of this new type of catalytic material

Health assessment of tree trunk by using acoustic-laser technique and sonic tomography

Abstract An innovative tree defect detection scheme, which combines acoustic-laser technique and sonic tomography, is studied. A new sensor distribution can be adopted based on the near-surface response detected by acoustic-laser technique, and a more reliable image of the tree trunk can be observed by sonic tomography. By using such hybrid detection scheme, the near-surface defects (bark detachment, cracks, decay) can be revealed at the early stages of defect development. The accuracy of defect detection during advanced tree risk assessment is therefore highly improved. As a newly developed detection technique for detecting the near-surface defect in tree trunk, the measurement results of acoustic-laser technique in tree trunk are comprehensively discussed, especially toward the detectable depth beneath the tree surface. The experimental results demonstrated that the acoustic-laser technique can identify the presence of near-surface defects in a tree trunk that are normally overlooked by the conventional sonic tomography measurements with random distribution of sensors

A versatile in situ etching-growth strategy for synthesis of yolk–shell structured periodic mesoporous organosilica nanocomposites

This paper describes a versatile in situ etching-growth strategy for the preparation of periodic mesoporous organosilica (PMO) composites with yolk-shell structure, which can generate the void space and construct the outer PMO shells at the same time. The superparamagnetic yolk-shell Fe3O4@PMO composites (YS-Fe3O4@PMO) with radical mesochannels were also synthesized with this unique in situ etching-growth strategy by using Fe3O4@nSiO2 nanoparticles as the initial core. This method provides a general route for the synthesis of yolk-shell structured nanomaterials with different sized void spaces, various chemical composition cores, as well as organic functional PMO shells with radical mesochannels. Moreover, we can also obtain asymmetric or asymmetric hollow Fe3O4@PMO materials with a cubic PMO shell. All the magnetic mesoporous composites possess very high surface areas and large pore volumes (586 m2 g-1 and 0.52 cm3 g-1 for YS-Fe3O4@PMO, 946 m2 g-1 and 0.86 cm3 g-1 for asymmetric hollow Fe3O4@PMO). Gold nanoparticles could be encapsulated and confined in the void space of YS-Fe3O4@PMO composites through an in situ salt impregnation. The resultant YS-Fe3O4@Au@PMO nanomaterials could be used to catalyze the reduction of 4-nitrophenol with an ultrahigh efficiency (k = 0.01197 s-1). The magnetic catalysts could be easily recovered by a magnet and reused for more than 10 cycles with efficiency retained as high as 95%. 2016 The Royal Society of Chemistry.This work was supported by the State Key Basic Research Program of the PRC (2012CB224805, 2013CB934104), the NSF of China (21210004 and U1463206), Shanghai Sci. & Tech. Committee (14JC1400700). We extended our appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the 530 research group Project No. RGP-227.Scopu

Dysbiosis characteristics of gut microbiota in cerebral infarction patients

The aim of this study is to investigate the dysbiosis characteristics of gut microbiota in patients with cerebral infarction (CI) and its clinical implications