Visible light driven photodynamic anticancer activity of graphene oxide/TiO2 hybrid

Graphene oxide/TiO₂ hybrid (GOT) was prepared by using Ti(OC₄H₉)₄ and graphene oxide (GO) as reactants. Superior adsorption and photocatalysis performance under visible radiation were achieved in the presence of the GOT rather than in unmodified TiO₂. GO that no toxicity in vitro acted as electron sink in GOT efficiently enhance the photodynamic activities. Consistent with photocatalytic performance of TiO₂, GOT generated reactive oxygen species after visible light irradiation both in cell free condition and in vitro. No dark cytotoxicity was observed using 0–100 μg/mL GOT during long incubation time. In parallel, following exposure of cells to GOT and irradiation, a marked decrease in mitochondrial membrane potential, cell viability, activities of superoxide dismutase, catalase and glutathione peroxidase, as well as increased malondialdehyde production were observed. Moreover, GOT caused significant elevation in caspase-3 activity, and induced apoptotic death. The results indicated that GOT had excellent photodynamic anticancer activity without dark cytotoxicity.     

CuO/TiO2纳米纤维可见光催化CO2合成甲醇

以介孔SiO_2球为模板、TiCl4为前驱体,采用气相生长法制备了直径为8～10nm的TiO_2纳米纤维,然后采用浸渍法制备了具有异质结结构的CuO/TiO_2纳米纤维,在可见光照射下催化CO_2合成甲醇。通过SEM、TEM、XPS、UV-Vis、XRD、荧光光谱(PL)对催化剂进行了表征。结果表明:TiO_2纳米纤维较锐钛矿TiO_2纳米颗粒和商业TiO_2纳米颗粒(P25)荧光强度明显降低,光生电子-空穴对更加稳定。通过在TiO_2纳米纤维上负载CuO形成异质结结构后,进一步降低了催化剂的荧光强度,也增强了在可见光区的吸收。在300 W氙灯照射5 h进行光催化CO_2合成甲醇实验中,P25负载CuO后,催化合成甲醇产量为676μmol/g-cat,而负载了CuO的TiO_2纳米纤维,甲醇产量达1791μmol/g-cat,较CuO/P25提高了165%。     

负载型TiO2/SiO2光催化降解苯酚的研究

以白炭黑为载体、聚乙烯醇 (PVA) 和 Ti(SO₄)₂ 为原料， 在分散剂存在下直接焙烧制备超细负载型 TiO₂/SiO₂ 光催化剂， 结果表明， 在450 ℃焙烧2 h所制 SO₄^2-/TiO₂-SiO₂（SO₄^2-质量分数3.4%，TiO₂∶SiO₂=1∶6，比表面积54 m²/g）具有最佳光催化效果。光催化苯酚结果显示,在紫外灯下光降解苯酚（＜100 mg/L）符合零级动力学方程，催化活性随pH值的增加而增加，pH=10时表观速率常数[WTBX]k[WTBZ]=0.33 mg/L·min，为苯酚废水处理提供了一条简便易行、成本低廉的方法。同时考察了光催化剂制备因素对催化剂活性的影响。     

Molybdenum doped TiO2 nanocomposite coatings: Visible light driven photocatalytic self-cleaning of mineral substrates

The molybdenum doped TiO₂ nanocomposite layer double hydroxide (LDH) suspensions, Mo:TiO₂-LDHs, were synthesized by a wet impregnation method in order to enhance the pure TiO₂ (water suspension) photocatalytic activity and consequently its self-cleaning efficiency under exposure to visible light. The aim was to produce nanocomposites by a simple, energy saving and cost beneficial synthesis. The mass ratio Mo/Ti was systematically varied (0.03, 0.06, 0.09, 0.12). The obtained nanocomposite Mo:TiO₂-LDH suspensions were first characterized by UV–vis spectroscopy (band-gap energies), Zeta-sizer (particle size distribution and stability) and X-ray diffraction (XRD) (structure) and then applied onto the model mineral substrates, brick and stone. The photocatalytic activity of the obtained coating was determined based on the degradation kinetics of the Rhodamine B (RhB) under artificial visible light irradiation (white LED). The obtained results were compared to the ones of the unmodified TiO₂-LDH suspension. The obtained results also showed that all prepared nanocomposites have good photocatalytic activity, particularly the suspension Mo:TiO₂-LDH with the Mo/Ti 0.03 mass ratio which possesses the best value. In addition, as regards the visible light driven self-cleaning effect, this suspension has proven to be a good protective functional coating for porous mineral substrates (bricks and stones).     

Visible light photocatalytic activity of TiO2/heat‐treated PVC film

BACKGROUND: Semiconductor TiO₂ has been investigated extensively due to its chemical stability, nontoxicity and inexpensiveness. However, the wide band gap of anatase TiO₂ (about 3.2 eV) only allows it to absorb UV light. TiO₂ nanoparticles modified by conditional conjugated polymers show excellent photocatalytic activity under visible light. However, these conjugated polymers are not only expensive, but also difficult to process. Polyvinyl chloride (PVC) was heat‐treated at high temperature to remove HCl and a C?C conjugated chain structure was obtained. When TiO₂ nanoparticles were dispersed into the conjugated polymer film derived from PVC, this composites film exhibited high visible light photocatalytic activity. RESULTS: The photocatalytic activity of TiO₂/heat‐treated PVC (HTPVC) film was investigated by degrading Rhodamine B (RhB) under visible light irradiation. The photodegradation of RhB follows apparent first‐order kinetics. The rate constants of RhB photodegradation in the presence of the TiO₂/HTPVC films with different mass content of TiO₂ are 16–56 and 4–14 times that obtained in the presence of the pure HTPVC and TiO₂/polymethyl methacrylate (PMMA) composite film, respectively. The TiO₂/HTPVC film showed excellent photocatalytic activity and stability after 10 cycles under visible light irradiation. CONCLUSION: TiO₂/HTPVC film exhibits high visible light photocatalytic activity and stability. Copyright © 2012 Society of Chemical Industry     

砂子负载纳米TiO2薄膜光降解有机污染物的研究

从光化学的角度，对砂子负载纳米二氧化钛薄膜，光催化剂降解工业污水中的有机污染物的过程进行分析与研究，探讨了多种因素对光降解的影响。实验显示在紫外光和纳米二氧化钛共同存在下，能对工业污水进行处理，砂子负载纳米二氧化钛进行光催化降解的最佳条件：纳米二氧化钛的质量分数为2％，焙烧温度约300℃，工业污水的pH为6．0～7．0。     

可见光促进TiO2催化合成膦酰亚胺

膦酰亚胺类化合物广泛应用于有机合成、生物医药以及高分子等领域，开发其绿色、高效合成新方法具有重要的科学意义。本文报道了在室温下，可见光促进TiO2催化三苯基膦类化合物和3-芳基-1,4,2二噁唑-5-酮合成膦酰亚胺类化合物，收率最高可达97%。利用1H NMR和13C NMR对产物进行了结构的表征。该反应具有条件温和、绿色和高效等优点。     

Methanol oxidation on Au/TiO2 catalysts

We have investigated the adsorption and reaction of methanol with Au/TiO₂ catalysts using a pulsed flow reactor, DRIFTS and TPD. The TiO₂ (P25) surface adsorbed a full monolayer of methanol, much of it in a dissociative manner, forming methoxy groups associated with the cationic sites, and hydroxyl groups at the anions. The methoxy is relatively stable until 250 °C, at which point decomposition occurs, producing mainly dimethyl ether by a bimolecular surface reaction. As the concentration of methoxy on the surface diminishes, so the mechanism reverts to a de-oxygenation pathway, producing mainly methane and water (at ~330 °C in TPD), but also with some coincident CO and hydrogen. Au catalysts were prepared by the deposition-precipitation method to give Au loadings between 0.5–3 wt %. The effect of low levels of Au on the reactivity is marked. The pathway which gives methane, which is characteristic of titania, remains, but a new feature of the reaction is the evolution of CO₂ and H₂ at lower temperature (a peak is seen in TPD at 220 °C), and the elimination of the DME-producing state. Clearly this is associated with the presence of Au and appears to be due to the production of a formate species on the surface of the Au component. This formate species is mainly involved in the reaction of methanol with the Au/TiO₂ catalysts which results in a combustion pathway being followed, with complete conversion occurring by ~130 °C.     

Effect of nanocrystallite size of TiO2 in Co/TiO2 and Co/TiO2-Ru catalysts on methanation

We studied the effect of crystallite size of nanocrystalline TiO₂ derived from the sol-gel method on the properties of Co/TiO₂ catalysts. First, nanocrystalline TiO₂ supports having different crystallite sizes were prepared via the sol-gel method by varying the water:alkoxide ratios from 4 to 165. Then, they were used as support for the cobalt catalyst. After calcination, the crystallite size of Co₃O₄ was dependent on the size of TiO₂ support. CO hydrogenation under methanation was performed to determine the activity and selectivity of Co/TiO₂ catalysts. It revealed that the catalyst with smaller size of TiO₂ crystallite exhibited higher catalytic activity due to higher Co dispersion without significant change in product selectivity. In addition, the Ru modification on the TiO₂ support was also investigated. The Ru modification resulted in increased activity regardless of the size of TiO₂ crystallite.     

Visible light induced self-cleaning performance of iron-doped TiO2 nanoparticles for surface applications

This study aimed to enhance the visible light photosensitivity of TiO₂ nanoparticles for self-cleaning applications by doping with Fe³⁺. Nanocrystalline undoped and Fe-doped TiO₂ (Ti_1 − xFe_xO₂, x = .01–.04) were synthesized via sol–gel method. The results demonstrated that Fe-doped TiO₂ nanoparticles exhibited visible light sensitivity and self-cleaning properties. An increased Fe concentration resulted in a red shift in the absorption band edge. Fe_0.03-doped TiO₂ with an average particle size of ∼21 nm, a crystallite size of ∼12 nm, and a band gap of ∼2.86 eV showed the highest photocatalytic activity (60% methylene blue degradation) and super-hydrophilicity (water droplet contact angle 9°) under visible light radiation. These findings highlight the potential of Fe-doped TiO₂ nanoparticles as a promising material for self-cleaning applications.     

Parameter effect on photocatalytic degradation of phenol using TiO2-P25/activated carbon (AC)

P25 powder embedded and TiO₂ immobilized on activated carbon (TiO₂-P25/AC) was prepared by P25 powder modified sol-gel and dip-coated method. The photocatalysts were characterized by XRD, BET, SEM and their photocatalytic activities were evaluated through phenol degradation in a fluidized bed photoreactor. The addition of P25 in the photocatalysts could significantly enhance the photocatalytic activity, and the optimum loading of P25 was 3 g L^?1. The operating parameter results indicated that the optimum pH for phenol degradation was 5.2; the effect of air flow rate gave an optimal value of 2 L min^?1; the increasing of UV light intensity led to an increase of degradation efficiency due to more photons absorbed on the surface of the photocatalyst. The kinetics of the phenol degradation fitted well with the Langmuir-Hinshelwood kinetics model. Finally, the photocatalytic ability of TiO₂-P25/AC was reduced only 10% after five cycles for phenol degradation.     

Effects of incorporation of ions into Au/TiO2 catalysts for carbon monoxide oxidation

A number of anions and cations have been incorporated into TiO₂ as support for gold catalysts and also into as-prepared Au/TiO₂ catalysts at levels of 0.4 mol% and 2.5 mol% with respect to the support. The activities of the catalysts for CO oxidation reveal that the at the higher concentration level of the ions, in all cases, a decrease in activity compared with unmodified Au/TiO₂. However, and more interestingly, addition of only 0.4 mol% of the ions to the support, prior to gold addition, in most cases resulted in activity enhancement whilst similar addition to Au/TiO₂ resulted in decrease in activity. Attempts have been made to understand the origin of these effects.     

Ni2P/ZrO2催化剂对苯酚的加氢性能

采用浸渍法及热分解法合成了不同负载量的Ni₂P/ZrO₂催化剂,通过XRD、TEM和氮气吸脱附等多种手段表征其物理化学性质,并通过对苯酚的加氢处理来研究载体对Ni₂P活性的影响。结果表明：Ni₂P分散负载在ZrO₂的表面,ZrO₂载体降低了Ni₂P的粒径,有效防止了Ni₂P的聚集,显著提高了Ni₂P对苯酚加氢脱氧的活性。在相同催化条件下,10%-Ni₂P/ZrO₂呈现出最佳催化活性。以10%-Ni₂P/ZrO₂为代表考察催化反应最优条件,在反应温度300℃、初始氢气压5MPa下反应2h,苯酚转化率达到90.8%,环己烷选择性达到91.7%。     

Degradation of phenol in industrial wastewater over the F–Fe/TiO_2 photocatalysts under visible light illumination

F–Fe/TiO_2 composite photocatalyst was synthesized by a facile one-step hydrothermal method and then characterized by XRD, XPS and UV–Vis DRS. The catalyst of F–Fe/TiO_2 exhibited the highest photodegradation rate for phenol as compared with pure TiO_2, F/TiO_2, Fe/TiO_2, F0.38–Fe0.13–TiO_2 and Fe(III)/F-TiO_2 under visible light irradiation. The simulated conditions of industrial phenolic wastewater including initial phenol concentration,visible light intensity, p H and different anions were investigated in the presence of F–Fe/TiO_2 photocatalyst. In addition, as expected, the F–Fe/TiO_2 photocatalyst displayed excellent stability, showing a potential industrial application for the treatment of phenolic wastewater.     

Improving photocatalytic activity of Cu-loaded TiO2 film using a pulse anodic bias

The application of a small anodic bias can promote the photocatalytic oxidation of formic acid on Cu–TiO₂ film. However, the photocatalytic activity was not stable at higher anodic biases or in the process of repeated use due to the electrochemical oxidation of Cu. A new photocatalytic technology with a pulse anodic bias was proposed to tackle the deficiency of the Cu–TiO₂ film. It was found that the photocatalytic technology could not only overcome the Cu oxidation but also increased the photocatalytic activity of the Cu–TiO₂ film.     

Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light

WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3.     

Preparation and visible light photocatalytic activity of carbon quantum dots/TiO2 nanosheet composites

Carbon quantum dots (C QDs)/TiO₂ nanosheet (TNS) composites were prepared by a simple low temperature process in which TNS were dispersed in C QDs solution, and dried at 60 °C. The C QDs/TNS composites were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy (TEM) and high-resolution TEM. The results indicated that C QDs were well combined with TNS through surface carbon–oxygen groups. The photocatalytic activity was investigated by degradation of rhodamine B under visible light irradiation. The photocatalytic activity of C QDs/TNS composites was significantly enhanced compared with that of C QDs/P25 composites and pure TNS, which indicated that the unique up-converted photoluminescence behavior of C QDs and highly reactive {0 0 1} facets of TNS both played important roles in the enhancement of photocatalytic activity of C QDs/TNS composites.     

PS/B-F掺杂纳米TiO2复合材料的可见光光催化降解研究

用悬浮聚合的方法制备了PS/B-F掺杂纳米Ti O2复合材料,进行了加速光降解实验。运用差热分析和扫描电镜对光降解材料的玻璃化转变温度和表面形态进行了表征。结果表明B-F掺杂纳米Ti O2对PS树脂具有很好的光催化降解效率。     

Imaging of low temperature induced SMSI on Pd/TiO2 catalysts

Pd/TiO₂ catalysts were found to enter an strong metal support interaction (SMSI) state after reduction at temperatures as low as 473 K. This was identified as a significant loss in the CO uptake as monitored by low temperature FTIR. Electron microscopy provides direct evidence of the presence of ordered, reduced titanium oxide layers over palladium (SMSI state) for Pd/TiO₂ catalysts following reduction at temperature 623 K. The crystal phase was identified as Ti₄O₇ and this phase, once formed, was found to be stable even after exposure to atmospheric conditions.     

Catalytic oxidation of hydrogen over Au/TiO2 catalysts

Selective catalytic oxidation of hydrogen in the presence of hydrocarbons was studied in a fixed bed quartz reactor, over 3 wt%Au/TiO₂ and 5 wt%Au/TiO₂ catalysts. This reaction can be utilised in the production of light alkenes via catalytic dehydrogenation, providing in situ heat to the endothermic dehydrogenation reaction and simultaneously removing a fraction of the produced hydrogen. It is important to avoid the non-selective combustion of the hydrocarbons in the mixture. Both 3 wt%Au/TiO₂ and 5 wt%Au/TiO₂ are active for the combustion of hydrogen, but in a gas mixture with propane and oxygen the selectivity is dependent upon the feed ratio of hydrogen and oxygen. At 550 °C, with propane present, no carbon oxides are formed when the H₂:O₂ ratio is four, but at lower ratios some CO₂ and some CO is formed.