一种新的光催化氧化体系用于化学需氧量的测定研究

基于KMnO₄能获得光生电子从而提高半导体光催化氧化能力的原理,建立了一种用纳米ZnO-KMnO₄协同体系光催化测定化学需氧量(COD)的新方法,探讨了催化氧化测定COD的机理,考察了测定COD的最佳反应条件.COD值浓度在1.5～10mg/L范围内与信号呈良好的线性关系,检测限为0.5mg/L.用本方法测定实际水样,结果和标准高锰酸盐指数法(COD_Mn法)相符.     

TiO2/石墨烯复合材料的光生电荷分离调控与光催化产氢性能研究

半导体光生电荷分离是光催化过程中的关键步骤之一,其效率极大地影响了最终光催化性能.将TiO₂纳米片与石墨烯复合,能够促进TiO₂中光生电子和空穴的分离,从而提高其光催化活性.为了研究光生电荷的分离对TiO₂/石墨烯复合材料光催化性能的影响,通过调控TiO₂纳米片的尺寸来调节TiO₂/石墨烯复合材料中光生电荷分离的能力,然后研究其对TiO₂/石墨烯复合材料光催化性能的影响.合成了一系列不同厚度的TiO₂纳米片,将其与石墨烯复合,并通过光沉积负载Pt纳米颗粒作为助催化剂,用于光催化产氢.实验结果显示,随着TiO₂纳米片厚度减小,其与石墨烯形成的复合结构的光催化性能显著提高.这主要是由于TiO₂纳米片厚度减小时,光生电子沿厚度方向穿过TiO₂纳米片迁移到石墨烯的距离缩短,从而减少了光生电子在迁移过程中与空穴的复合;同时TiO₂纳米片厚度减小使其比表面积增大,使得TiO₂/石墨烯界面面积增大,从而使石墨烯更好地分离出TiO₂中的光生电子,有更多的光生电子到达石墨烯参与催化反应,提高TiO₂/石墨烯复合材料的光催化性能.此研究表明通过控制TiO₂纳米片的尺寸来调控TiO₂/石墨烯复合材料中光生电子和空穴的分离,是显著提高其光催化性能的有效途径.     

三维网状Dy3+:YVO4/TiO2复合纤维的制备及光催化产氢性能

以电纺TiO₂纳米纤维为基质, 柠檬酸为软模板, 采用一步水热法制备了具有三维立体网状结构的稀土Dy ³⁺掺杂YVO₄/TiO₂复合纤维. 通过X射线衍射、 扫描电子显微镜、 X射线光电子能谱、 N₂吸附-脱附、 紫外-可见漫反射光谱及荧光光谱等手段对材料的组成、 表面形貌和性能进行表征, 以光分解水产氢实验考察其光催化活性. 结果表明, Dy ³⁺∶YVO₄纳米枝与TiO₂纳米纤维相互交联构筑的纳米纤维网具有大比表面积, 可提供更多活性位点, 改善了多相光催化反应的传递过程; 稀土Dy ³⁺掺杂的YVO₄与TiO₂复合形成异质结相互促进, 在拓宽光谱响应范围、 提高太阳光利用率的同时使光生电子-空穴对得到较好分离, 从而提高了样品的光催化活性. 模拟太阳光照射下, Dy ³⁺∶YVO₄/TiO₂复合纤维光催化产氢速率达到8.63 mmol· h ^-1·g ^-1, 是纯TiO₂纳米纤维的10倍.     

1D/2D TiO2/ZnIn2S4S型异质结光催化剂及其高效制氢性能

通过半导体催化剂利用太阳能分解水制氢被认为是解决人类面临的环境问题和能源危机的有效途径.在众多的半导体光催化剂中,TiO₂由于其良好的光化学稳定性、无毒性、丰富的形貌以及低廉的价格,在光催化制氢领域备受关注.然而TiO₂的内在缺陷,如较宽的带隙、较窄的光响应范围,光生电子空穴对的快速复合,极大限制了其太阳能制氢效率.构建异质结结构被认为是解决以上问题的一个有效方法,通过将TiO₂与另一个半导体复合可以提升催化剂对太阳光的吸收范围,也可降低光生电子空穴对的复合速率.但构建一个成功的异质结结构不仅要满足上述的要求,还需要保留异质结催化剂体系中光生电子和空穴的氧化还原能力.研究表明,S型异质结是将两个具有合适能带结构的半导体进行耦合,由于费米能级的差异,两个半导体间将发生电子转移,从而引起能带弯曲并形成内建电场.光照条件下,具有较弱还原能力的光生电子在内建电场和能带弯曲的作用下与较弱氧化能力的光生空穴复合,实现异质结催化剂体系中各个半导体内部光生载流子有效分离的目标,同时保留了异质结催化剂体系中较强氧化能力和较强还原能力的光生电子和空穴,进而实现光催化活性的提高.本文采用水热合成方法,将具有更强还原能力和可见光响应特性的半导体(ZnIn₂S₄)原位生长在TiO₂纳米纤维表面,构建了1D/2DTiO₂/ZnIn₂S₄S型异质结光催化剂.最优比例的TiO₂/ZnIn₂S₄复合材料表现出优越的光催化制氢活性(6.03mmol/h/g),分别是纯TiO₂和纯ZnIn₂S₄制氢活性的3.7倍和2倍.TiO₂/ZnIn₂S₄复合材料光催化活性的提高可以归因于紧密的异质结界面、光生载流子的有效分离、丰富的反应活性位点以及增强的光吸收能力.通过原位XPS和DFT计算研究了异质结内部光生电子的转移机制.结果表明,在光照条件下电子由TiO₂向ZnIn₂S₄迁移,遵循了S型异质结内部电子的转移机制,实现了TiO₂和ZnIn₂S₄内部光生载流子的有效分离,同时保留了具有较强还原能力的ZnIn₂S₄价带电子和较强氧化能力的TiO₂导带空穴,从而显著提升光催化制氢效率.综上,本文制备的TiO₂/ZnIn₂S₄S型异质结光催化剂很好地克服了TiO₂在光催化制氢领域所面临的诸多障碍,为设计和制备高效异质结光催化剂提供了新的思路.     

流动态甲醇气相光催化降解的机制研究

在253.7 nm紫外光作用下, 研究纳米TiO₂光催化氧化流动态甲醇的机制, 结果表明, 甲醇的光催化降解不受水汽的影响, 只受氧气含量的影响. 在不含氧气的情况下, 即使有足量的水汽, 甲醇都不会有明显的降解. TiO₂受光诱导生成空穴-电子对后, 空穴直接氧化甲醇, 生成的甲醇正离子在氧气作用下进一步被氧化, 形成各种氧化产物. 甲醇氧化过程是多通道反应, 宏观表现为准一级反应. 空气和氧气条件下甲醇的总降解速率常数分别为9.78×10^－3和1.79×10^－2 s^－1.     

超氧化物歧化酶对TiO2光催化损伤DNA的影响

以小牛胸腺DNA为对象, 在超氧化物歧化酶(superoxide dismutase, SOD)存在下, 研究了纳米二氧化钛(TiO₂)光催化对DNA损伤特性及SOD对TiO₂光催化损伤DNA的影响. 采用凝胶电泳和高效液相色谱(HPLC)分析法, 探讨了DNA的损伤程度. 运用生物标准样8-羟基脱氧鸟苷(8-hydroxy-2 -deoxyguanosine, 8-OHdG)为内标物并通过高效液相色谱-电喷雾离子化串联质谱联用技术(HPLC-ESI-MS/MS)对DNA损伤产物进行了跟踪分析, 采用过氧化物酶催化分光光度法及顺磁共振技术(ESR)跟踪测定TiO₂光催化DNA损伤过程中H₂O₂和氧化物种的变化, 探讨了DNA氧化损伤机理. 结果表明, 在实验条件下紫外光照(UV, λ＝200～275 nm), Dark/TiO₂和UV/TiO₂体系中, DNA氧化损伤程度为UV/TiO₂＞UV＞Dark/TiO₂. 光催化260 min DNA损伤99%, 反应动力学常数K＝7.82×10^－3 min^－1. 抗氧化剂SOD具有清除光催化体系中超氧自由基( )的能力, 可以抑制DNA的损伤, 反应动力学常数K＝2.27×10^－3 min^－1. 8-OHdG为DNA损伤中鸟嘌呤氧化的特异产物, UV及光催化体系对DNA损伤主要涉及 及羟基自由基(•OH)历程, 光催化体系对DNA损伤伴随有深度氧化(矿化)过程, 实验条件下12 h DNA矿化75.06%.     

花状CeO2/TiO2异质结的构筑及光催化性能

采用溶剂热法制备了三维花状CeO₂/TiO₂异质结光催化剂,然后以甲基橙(MO)为模拟有机污染物,在氙灯照射下考察了其光催化活性。结果表明,花状结构由纳米片和纳米颗粒复合而成,纳米片上均匀地附着CeO₂颗粒。Ce/Ti的物质的量之比(n_Ce/n_Ti)和溶剂热时间影响异质结的光催化性能,当n_Ce/n_Ti=0.1、溶剂热时间为6 h时,CeO₂/TiO₂的光催化活性达到最佳,氙灯照射50 min的降解率达95%,光催化活性优于纯TiO₂,这主要是CeO₂和TiO₂形成了异质结,有利于光生电子和空穴的分离。     

NiO/TiO2异质结构纳米管阵列膜对不锈钢的光生阴极保护及其储能性能

本工作通过修饰TiO₂制备半导体复合膜,提高其光吸收和光电化学性能,以期应用于光生阴极保护。先采用阳极氧化法在Ti表面制备TiO₂纳米管阵列膜,再应用水热处理法在膜表面沉积NiO纳米颗粒,形成具有异质结构纳米管复合膜。利用扫描电子显微镜、X-射线衍射、X-射线光电子能谱、紫外-可见吸收光谱、光致发光谱和光电化学技术对制备的纳米膜进行表征。结果表明,与纯TiO₂纳米管膜比较,NiO/TiO₂纳米管复合膜的光吸收扩展到可见光区。白光照射下,其在0.5 mol·L^?1 KOH和1 mol·L^?1 CH3OH混合液中的光电流密度达到176μA·cm^?2,是纯TiO₂纳米管膜的2倍。复合膜具有良好的光生阴极保护作用,与0.5 mol·L^?1 NaCl溶液中的403不锈钢耦连后,可使其电极电位下降440 mV,在光照2.5 h再转为暗态后,因具有电荷储存能力还可继续提供约15.5 h的阴极保护效应。     

FeNi层状双氢氧化物/TiO2复合光催化剂的制备及其制氢性能

层状双氢氧化物(LDH)的光生电子-空穴对易复合,虽然纳米薄片的结构促进了载流子分离,但其光催化效率仍然较低。我们利用LDH薄片结构的优势,将FeNi LDH和TiO₂通过静电自组装复合,设计制备出新型高效的FeNi LDH/TiO₂复合光催化材料,评价了其光催化分解水产氢性能。对其结构、光催化性能和光电化学等进行了详细表征。结果表明,FeNi LDH的高比表面积、复合物的异质结结构都有利于光生电荷的转移。光催化产氢结果表明,FeNi LDH/TiO₂复合材料的产氢速率(22.6mmol·g^-1·h^-1)分别比纯TiO₂(0.1 mmol·g^-1·h^-1)和FeNi LDH(0.05 mmol·g^-1·h^-1)提高了226和452倍,表明了异质结在提高LDH光催化效率方面的重要作用。     

CeO2/TiO2复合纳米纤维的制备及光催化性能研究

采用静电纺丝技术和水热合成法制备了CeO₂/TiO₂复合纳米纤维. 利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电镜(SEM)、透射电镜(TEM)和比表面积测定(BET)等分析测试手段对样品的形貌及结构进行了表征, 并以罗丹明B的脱色降解为模式反应, 考察了样品的光催化性能. 结果表明: CeO₂纳米粒子均匀地生长在TiO₂纳米纤维表面, 形成了异质结构的CeO₂/TiO₂复合纳米纤维光催化材料. 通过改变碱源, 可以得到不同形貌的CeO₂. CeO₂的存在增加了TiO₂纳米纤维的比表面积, 有效地实现TiO₂光生电子和空穴的分离, 增强了体系的量子效率, 与纯TiO₂纳米纤维相比光催化活性明显提高. 初步探讨了异质结的形成机理.     

纳米TiO2膜用于光催化氧化测定化学需氧量的研究

A photocatalytic oxidation method for determination of chemical oxygen demand （COD） using nano-TiO2 film, based on the use of a nano-TiO2-Ce（SO4）2 system and electrochemical detection, was proposed. The technique was originated from the direct determination of the Ce（Ⅲ） concentration change resulting from photocatalytic oxidation of organic compounds. Ce（Ⅲ）, which was produced by photocatalytic reduction of Ce（SO4）2, could be measured at a multi-walled carbon nanotubes （MWNT） chemically modified electrode （CME）. The COD values by this method were calculated from the differential pulse voltammetry （DPV） current of Ce（Ⅲ） at the CME. Under the optimal operation conditions, the detection limit of 0.5 mg·L^-1 COD with the linear range of 1-600 mg·L^-1 was achieved. This method was also applied to determination of various COD of ground water and wastewater samples. The resuits were in good agreement with those from the conventional COD methods, i.e., permanganate and dichromate ones.     

Preparation of photocatalytic nano-ZnO/TiO2 film and application for determination of chemical oxygen demand

A composite nano-ZnO/TiO₂ film as photocatalyst was fabricated with vacuum vaporized and sol-gel methods. The nano-ZnO/TiO₂ film improved the separate efficiency of the charge and extended the range of spectrum, which showed a higher efficiency of photocatalytic than the pure nano-TiO₂ and nano-ZnO film. The photocatalytic mechanism of nano-ZnO/TiO₂ film was discussed, too. A new method for determination of low chemical oxidation demand (COD) value in ground water based on nano-ZnO/TiO₂ film using the photocatalytic oxidation technology was founded. This method was originated from the direct determination of the Mn(VII) concentration change resulting from photocatalytic oxidation of organic compounds on the nano-ZnO/TiO₂ film, and the COD values were calculated from the absorbance of Mn(VII). Under the optimal operation conditions, the detection limit of 0.1 mg l⁻¹, COD values with the linear range of 0.3-10.0 mg l⁻¹ were achieved. The results were in good agreement with those from the conventional COD methods.     

Study on photocatalytic oxidation for determination of the low chemical oxygen demand using a nano-TiO2-Ce(SO4)2 coexisted system

A new photocatalytic system, nano-TiO₂-Ce(SO₄)₂ coexisted system, which can be used to determine the low chemical oxygen demand (COD) is described. Nano-TiO₂ powders is used as photocatalyst in this system. The measuring method is based on direct determination of the concentration change of Ce(IV) resulting from photocatalytic oxidation of organic compounds. The mechanism of the photocatalytic oxidation for COD determination was discussed and the optimum experimental conditions were investigated. Under the optimum conditions, a good calibration graph for COD values between 1.0 and 12 mg l⁻¹ was obtained and the LOD value was achieved as low as 0.4 mg l⁻¹. When determining the real samples, the results were in good agreement with those from the conventional methods.     

H2O2-鲁米诺-荧光素钠-K2CO3高灵敏化学发光法测定二氧化碳

在碱性介质中, CO₃^2－对H₂O₂氧化鲁米诺化学发光反应具有重要作用, 荧光素钠对该反应具有很强的增敏作用. 据此, 建立了化学发光法测定二氧化碳的新方法. 方法的线性范围为1.0×10^－10～5.0×10^－6 mol•L^－1 CO₃^2－, 检出限为 1.2×10^－11 mol•L^－1 CO₃^2－ (相当于5.3×10^－10 g•L^－1 CO₂). 该方法用于室内外空气中二氧化碳含量的测定, 相对标准偏差1.8%～2.1% (n＝11), 加标实验回收率97.6%～101.4%. 论文还探讨了反应的发光机理, 发光反应很可能是由溶液中的CO₃^2－与H₂O₂作用而产生的活性自由基引发, 荧光素钠对发光的增敏作用为化学能量转移过程.     

Determination of chemical oxygen demand values by a photocatalytic oxidation method using nano-TiO2 film on quartz

A COD measurement by a photocatalytic oxidation method using nano-TiO₂ film was investigated. K₂Cr₂O₇ was added into the solution to enhance the efficiency of photocatalytic degradation, and simultaneously K₂Cr₂O₇ was reduced to Cr(III) by photogenerated electrons, which were adsorbed on the surface of TiO₂. The measuring principle was based on direct determination of Cr(III) concentration which was proportional to the COD value. Under the optimized experiment condition, the application range was 20-500 mg l⁻¹, and the detection limit was 20 mg l⁻¹. The immobilization of photocatalyst on the supports could not only solve the problem of low recovery of the catalyst and hard separation from the solution, but also overcome its shortcoming of poor stability. Applied this method to the determination of real samples, it was found to be rapid and environmentally friendly. Additionally, the method proposed above for determination of COD was in excellent correspondence with values obtained by using the conventional method.     

基于多层酶/纳米金固定甲胎蛋白免疫传感器的研究

>利用自组装技术和静电吸附作用, 将甲胎蛋白抗体(anti-AFP)固定在多层辣根过氧化物酶/纳米金及L-半胱胺酸修饰的金电极表面, 制备出用于检测甲胎蛋白抗原(AFP)的无试剂型免疫传感器. 通过交流阻抗技术、循环伏安法和计时电流法考察了电极的电化学特性, 并对该免疫传感器的作用机理及性能进行了详细的研究. 用计时电流法测得AFP的线性范围为1.0～10.0和10～200 ng•mL^－1, 检出限为0.5 ng•mL^－1. 实验结果表明, 该方法提高了抗体的固定量, 增强了传感器的灵敏度和稳定性, 且该传感器响应迅速、选择性好, 血清中常见抗原不干扰测定. 将其用于临床血清检验, 与放射免疫测定法(RIA)的符合率为86.7%.     

高效液相色谱化学发光法检测牛奶中残留四环素类化合物的研究

基于四环素类抗生素药物中的四环素(TC)、土霉素(OTC)、金霉素(CTC)和多西环素(DC)能够强烈增敏通过恒电流电解方法在线电生BrO^－和鲁米诺之间产生的化学发光, 提出了一种高效液相色谱(HPLC)化学发光(CL)法检测4种四环素类抗生素药物的新方法. 以Nucleosil RP-C₁₈ (250 mm×4.6 mm, i.d., 5 μm, pore size, 100 Å)为色谱柱, 0.05 mol• L^－1磷酸二氢钾(pH 2.5)-乙腈(30∶70, V∶V)为流动相, 流速1.2 mL/min, 柱温25 ℃, 同时分离检测四种抗生素的总时间为11 min. 研究并优化了流动相、电生试剂化学发光检测的条件. 四种抗生素的检出限为0.002～0.008 μg•mL^－1 (3σ), 对0.01 μg•mL^－1的四种抗生素测定的相对标准偏差为2.0%～3.6% (n＝11). 该方法已成功应用于牛奶中残留四环素类抗生素含量的分析.     

载铂Sr(Zr1－xYx)O3－δ-TiO2异质结光催化剂模拟太阳光催化产氢

利用光化学还原法制备载铂Sr(Zr_1－xY_x)O_3－δ-TiO₂ (Pt-SZYT)异质结光催化剂, 采用XRD, SEM, UV-Vis, PL对催化剂的形貌及性能进行表征. 以工业有机污染物草酸为电子给体, 模拟太阳光下光催化产氢为探针, 评价了催化剂的活性. 研究了载铂量、草酸浓度对催化剂产氢活性的影响, 并探讨了Pt-SZYT催化剂产氢活性与光致发光(PL)性能的关系, 以及催化剂的连续使用效果. 结果表明: 模拟太阳光条件下, Pt-SZYT催化剂具有良好稳定的光催化产氢活性, 催化剂的最佳载铂量为0.90 wt%. PL分析表明Pt-SZYT的光催化产氢活性越高, 其荧光强度越弱. 草酸50 mmol•L^－1, 催化剂用量1.0 g•L^－1时, 催化剂(w＝0.90%) Pt-SZYT-70的平均产氢速率为1.68 mmol•h^－1.     

Voltammetric determination of trace doxorubicin at a nano-titania/nafion composite film modified electrode in the presence of cetyltrimethylammonium bromide

A sensitive electrochemical method was developed for the determination of doxorubicin at a glassy carbon electrode (GCE) modified with a nano-titania (nano-TiO₂)/nafion composite film. Nano-TiO₂ was dispersed into nafion to give a homogeneous suspension. After solvent evaporation, a uniform film of nano-TiO₂/nafion composite was obtained on the GCE surface. The nano-TiO₂/nafion composite film modified GCE exhibited excellent electrochemical behavior toward the reduction of doxorubicin. Compared to the reduction of doxorubicin at the bare GCE, the reduction current of doxorubicin at the nano-TiO₂/nafion composite film modified GCE was greatly enhanced. Based on this, a novel voltammetric method was applied to the determination of doxorubicin. The experimental parameters that influence the reduction current of doxorubicin, were optimized. Under optimal conditions, a linear response of doxorubicin was obtained in the range from 5.0?×?10^?9 to 2.0?×?10^?6 mol L^?1 (R?=?0.998) and with a limit of detection (LOD) of 1.0?×?10^?9 mol L^?1(S/N?=?3). The RSD of the measurement is 4.7%, and the RSD of the inter-electrode is of 5.1% which indicate the reproducibility of this method. The current response decreased only by around 3.8% of its initial response after 2 weeks exposing the electrode in air. The procedure was applied to assay doxorubicin in human plasma samples with the recoveries of 94.9–104.4%.     

Study on Determination of Chemical Oxygen Demand in Water with Ion Chromatography

A new method for determining chemical oxygen demand （COD） value in water using ion chromatography coupled with nano TiO2-K2S2O8 co-existing system was described. The photocatalytic oxidation system and nano TiO2-K2S2O8 co-existing system could degrade the organic compounds in water. All sulfur-containing species in the reactive solution were eventually transformed to sulfate which could be determined by conductivity detector in ion chromatography. The change of conductivity of sulfate was proportional to COD value. The optimal experimental conditions and the mechanism of the detection were discussed. The application range was 10.0-300.0 mg·L^-1 and the lowest limit of detection was 3.5 mg·L^-1. It was considered that the value obtained could be reliably correlated with the COD value obtained using the conventional methods.