高分子材料的氧化机理研究

本文对有机化合物的氧化这一历史悠久的课题中有关氧化机理问题进行了深入的研究。并认为无论是简单的有机分子,还是高分子或者是生物体内进行的氧化,大多是自由基过程,一旦体系中生成自由基,经过自由基链式反应,氧化便可很快地进行下去。

自由基簇射脱除氮氧化物

研究了电晕放电诱导自由基簇射脱除烟气中的NOx(DeNOx过程, NOx为NO和NO2的总称). 首先考察了放电特性, 发现适当调节喷嘴电极中的气体流量和电压可以产生稳定的流光电晕.实验表明, 烟气中NO浓度随电压升高而降低; NO2浓度在低电压条件下与电压值成正比, 但是当电压升高到某一阈值后随电压增长迅速降低.电压升高可提高DeNOx效率, 当电压临近击穿电压时, 效率可达70%. 提出了脱除NOx的机理, 认为放电过程中产生的自由基在NOx脱除过程中起关键作用, 自由基反应把NO和NO2转化为酸类物质.为验证所提出的机理, 采用蒙特卡罗方法计算了相关反应的速率常数和自由基产率, 并在此基础上, 通过化学动力学计算得到了反应器出口NO和NO2的浓度以及NOx脱除效率. NO脱除效率的计算结果在低电压时与实验结果相近, 但在高电压时高于实验值.

磁性污泥生物炭活化过硫酸盐降解罗丹明B

采用微波热解法制备磁性污泥生物炭(MBC),并通过XRD、FT-IR和SEM对其晶体结构、表面官能团及形貌进行表征。以罗丹明B(RhB)为目标污染物,研究MBC活化过硫酸盐(PDS)的性能。结果表明MBC活化PDS能够有效去除水体中RhB,效果优于磁性Fe_(3)O_(4),归功于MBC具有丰富的官能团和发达的孔隙结构。此外,探究催化剂投加量、PDS添加量、温度和pH值对MBC活化PDS降解RhB的影响。MBC活化PDS降解RhB主要通过非自由基过程,其中单线态氧(^(1)O_(2))是主要的反应活性物种。

Catalytic ozonation of phenol and oxalic acid with copper-loaded activated carbon

A novel heterogeneous catalytic ozonation process in water treatment was studied, with a copper-loaded activated carbon （Cu/AC） that was prepared by an incipient wetness impregnation method at low temperature and tested as a catalyst in the ozonation of phenol and oxalic acid. Cu/AC was characterized using XRD, BET and SEM techniques. Compared with ozonation alone, the presence of Cu/AC in the ozonation processes significantly improves the degradation of phenol or oxalic acid. With the introduction of the hydroxyl radical scavenger, i.e., turt-butanol alcohol （t-BuOH）, the degradation efficiency of both phenol and oxalic acid in the Cu/AC catalyzed ozonation process decreases by 22% at 30 min. This indicates that Cu/AC accelerates ozone decomposition into certain concentration of hydroxyl radicals. The amount of Cu（II ） produced during the reaction of Cu/AC-catalyzed ozonation of phenol or oxalic acid is very small, which shows that the two processes are both heterogeneous catalytic ozonation reactions.

Desulfurization Mechanism of Cysteine in Synthesis of Polypeptides

The free-radical-based selective desulfurization of cysteine residue is an efficient protocol to achieve ligations at alanine sites in the synthesis of polypeptide and proteins. In this work, the mechanism of desulfurization process has been studied using the density functional theory methods. According to the calculation results, the desulfurization of the thiol group occurs via a three-steps mechanism： the abstraction of hydrogen atom on the thiol group with the radical initiator VA-044 （2,2＇-azobis[2-（2-imidazolin-2-yl）propane]dihydrochloride）, the removal of S atom under the reductant TCEP （tris（2-carboxyethyl）phosphine）, and the formation of RH molecule （with the regeneration of RS radical）. The second step （desulfurization step） is the rate-determining step, and the adduct t-BuSH facilitates the desulfurization of cysteine via benefiting the formation of the precursor of the desulfurization step.

Synthesis of multifunctional ABC stars with a reduction-labile arm by consecutive ROP, RAFT and ATRP processes

This study aims at versatile synthesis of 3-arm ABC-type （A=poly（c-caprolactone）, PCL; B=poly（N-isopropylacrylamide）, PNIPAM; C=poly（tert-butyl acrylate）, PtBA, or poly（acrylic acid）, PAA） miktoarm star copolymers with a reducible disulfide linkage. Using 2-（（2-（（2-hydroxymethyo-2-（（2-bromo-2-methyl）propionyloxy）methyl）propionyloxy）ethyl）disulfanyl）ethyl 4- cyano-4-（phenylcarbonothioylthio）pentanoate （HBCP） as a heterotrifunctional initiator, consecutive ring-opening polymerization （ROP） of g-caprolactone （CL）, reversible addition-fragmentation chain transfer （RAFT） polymerization of N-isopropy- lacrylamide （NIPAM） and atom transfer radical polymerization （ATRP） of tert-butyl acrylate （tBA） afforded ABC1 star, and followed by a subsequent hydrolysis to give ABC2 star. IH nuclear magnetic resonance （IH NMR） and gel permeation chromatography （GPC） analyses revealed the desired stars and their precursors had well-controlled molecular weight and relatively low polydispersity （PDI≤1. 12）. As confirmed by GPC analysis, the disulfide linkage in ABCI star could be efficiently cleaved upon reductive stimulus, during which the topology was converted from star terpolymer to mixtures of homopolymer （B） and diblock copolymer （AC1）. In addition to acting as nanocarriers for stimuli-triggered drug delivery systems, ABC stars with terminal bromide, dithiobenzoate and hydroxyl functionalities are expected to form other reduction-cleavable multicomponent copolymers such as （BC-graft-A）m and dendritic graft copolymers via postpolymerization modification. Our research affords a straightforward ＂core-first＂ method to construct multifunctional star terpolymers with stimuli-responsive arms and reduction-labile linkage.

Naphthalene decomposition in a DC corona radical shower discharge

The naphthalene decomposition in a corona radical shower discharge (CRS) was investigated, with attention paid to the influences of voltage and initial naphthalene density. The OH emission spectra were investigated so as to know the naphthalene decomposing process. The by-products were analyzed and a decomposing theory in discharge was proposed. The results showed that higher voltage and relative humidity were effective on decomposition. The initial concentration affected the decomposing efficiency of naphthalene. When the initial naphthalene density was 17 mg/m3, the decomposition rate was found to be 70% under 14 kV. The main by-products were carbon dioxide and water. However, a small amount of carbonic oxide, 1,2-ethanediol and acetaldehyde were found due to the incomplete oxidization.

A universal etching-free transfer of MoS2 films for applications in photodetectors

Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction, because the current transfer method inevitably employs a wet chemical etching process. We developed an etching-free transfer method for transferring MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method, the MoS2 films can be transferred from all substrates （silica, mica, strontium titanate, and sapphire） and retains the original sample morphology and quality. This method guarantees a simple transfer process and allows the reuse of growth substrates, without involving any hazardous etchants. The etching-free transfer method is likely to promote broad applications of MoS2 in photodetectors.