Xiaohong Hu

Nonmetal–metal–semiconductor-promoted P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst with superior photocatalytic activity and stability

Recently, modifying TiO2 to develop visible-light-driven photocatalysts via doping with nonmetal elements, metals and semiconductors has attracted much attention. In this study, a facile and reproducible sol–gel method was utilized for the first time to codope nonmetal (P), metal (Ag) and narrow band gap semiconductors (Ag2O and Ag3PO4) in TiO2 to prepare a P/Ag/Ag2O/Ag3PO4/TiO2 composite photocatalyst for developing a novel visible-light-driven photocatalyst. The crystal structure, morphology and optical properties of P/Ag/Ag2O/Ag3PO4/TiO2 were systemically characterized, and the photocatalytic abilities were evaluated under simulated solar light, in comparison with pure TiO2 and Ag/Ag2O/TiO2 photocatalysts. The results indicated that the P/Ag/Ag2O/Ag3PO4/TiO2 composite photocatalyst exhibited a strong absorption band in the visible light region, a small band gap (about 2.2 eV) and extremely high separation efficiency of photo-excited electron–hole pairs, which could account for its enhanced photocatalytic performance. The degradation ratio of rhodamine B (Rh B) by P/Ag/Ag2O/Ag3PO4/TiO2 reached 97.1% after 60 min under simulated solar light with only 13 mW cm−2 light intensity, while just 26.6% and 66.7% of Rh B were degraded by the as-prepared TiO2 and Ag/Ag2O/TiO2 photocatalysts, respectively. Furthermore, the radical trapping experiments implied that photo-generated holes and O2˙− radicals in the P/Ag/Ag2O/Ag3PO4/TiO2 composite photocatalyst were the major active species for Rh B degradation. Metallic Ag could effectively trap the photo-generated electrons from Ag3PO4 and Ag2O to reduce the possibility of decomposing Ag3PO4 and Ag2O, resulting in an improved stability of the P/Ag/Ag2O/Ag3PO4/TiO2 composite with high photocatalytic ability.

A novel P/Ag/Ag2O/Ag3PO4/TiO2 composite film for water purification and antibacterial application under solar light irradiation

TiO2-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag2O/Ag3PO4/TiO2 composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag2O/Ag3PO4/TiO2 composite films with 3 coating layers, synthesized at 400°C for 2h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag2O/Ag3PO4/TiO2 composite film reached 99.9% after 60min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO2 film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 107CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag2O/Ag3PO4/TiO2 composite films were photo-generated holes and O2- radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag2O/Ag3PO4/TiO2 composite films.

Discriminating the Independent Influence of Cell Adhesion and Spreading Area on Stem Cell Fate Determination Using Micropatterned Surfaces

Adhesion and spreading are essential processes of anchorage dependent cells involved in regulation of cell functions. Cells interact with their extracellular matrix (ECM) resulting in different degree of adhesion and spreading. However, it is not clear whether cell adhesion or cell spreading is more important for cell functions. In this study, 10 types of isotropical micropatterns that were composed of 2 μm microdots were prepared to precisely control the adhesion area and spreading area of human mesenchymal stem cells (MSCs). The respective influence of adhesion and spreading areas on stem cell functions was investigated. Adhesion area showed more significant influences on the focal adhesion formation, binding of myosin to actin fibers, cytoskeletal organization, cellular Young’s modulus, accumulation of YAP/TAZ in nuclei, osteogenic and adipogenic differentiation of MSCs than did the spreading area. The results indicated that adhesion area rather than spreading area played more important roles in regulating cell functions. This study should provide new insight of the influence of cell adhesion and spreading on cell functions and inspire the design of biomaterials to process in an effective manner for manipulation of cell functions.

Wastewater treatment by sonophotocatalysis using PEG modified TiO2 film in a circular Photocatalytic-Ultrasonic system

TiO2 photocatalyst film recently has been utilized as the potential candidate for the wastewater treatment, due to its high stability and low toxicity. In order to further increase the photocatalytic ability and stability, different molecular weight of polyethylene glycol (PEG) were used to modify TiO2 structure to synthesize porous thin film used in the developed Photocatalytic-Ultrasonic system in this work. The results showed that PEG2000 modified TiO2 calcinated under 450°C for 2h exhibited the highest photocatalytic activity, attributed to the smallest crystallite size and optimal particle size. Over 95.0% of rhodamine B (Rh B) was photocatalytically degraded by optimized PEG2000-TiO2 film after 60min of UV irradiation, while only about 50.8% of Rh B was decolored over pure TiO2 film. Furthermore, optimized PEG2000-TiO2 film was used in a circular Photocatalytic-Ultrasonic system, and the obtained synergy (0.6519) of sonophotocatalysis indicated its extremely high efficiency for Rh B degradation. In this Photocatalytic-Ultrasonic system, larger amount of PEG2000-TiO2 coated glass beads, stronger ultrasonic power and longer experimental time could result to higher degradation efficiency of Rh B. In addition, repetitive experiments showed that about 97.2% of Rh B were still degraded in the fifth experiment by sonophotocatalysis using PEG2000-TiO2 film. Therefore, PEG2000-TiO2 film used in Photocatalytic-Ultrasonic system has promising potential for wastewater treatment, due to its excellent photocatalytic activity and high stability.

Strategy of mitigating ammonium-rich waste inhibition on anaerobic digestion by using illuminated bio-zeolite fixed-bed process.

Intermittent illumination combined with bio-zeolite fixed-bed process was utilized to improve the efficiency of anaerobic digestion with ammonium-rich substrate. The batch experiments were carried out at NH4+-N concentration of 2211mg/L under intermittent illumination and dark (as control) conditions, respectively. The illuminated bioreactor achieved higher methane production (287mL/g-DOC) and ATP value (0.38μmol/L) than that under dark condition. Then the bio-zeolite fixed-bed bioreactor (NH4+-N concentration: 3000mg/L) was used to study the additional efficiency on the illuminated ammonium-rich anaerobic digestion process. The result showed that the illuminated fixed-bed bioreactor presented the greatest methane concentration (70%), methane yield (283mL/g-DOC) and quantity of methanogens comparing with no-bed bioreactor. Furthermore, the illuminated fixed-bed bioreactor achieved better performance during 118-day semi-continuous fermentation. The combination of the intermittent illumination and bio-zeolite fixed-bed strategy contributed to the higher efficiency and stability of the ammonium-rich anaerobic digestion process.

Regulation of mesenchymal stem cell functions by micro–nano hybrid patterned surfaces

Micro- and nano-structured substrates have been widely used in the biomedical engineering field. Their precise control of cell morphology makes them promising for investigating various cell behaviors. However, regulation of cell functions using micro-nano hybrid patterns is rarely achieved. Since the cell microenvironment in vivo has complex micro- and nano-structures, it is desirable to use micro-nano hybrid patterns to mimic the microenvironment to control cell morphology and disclose its influence on stem cell differentiation. In this study, poly(vinyl alcohol) (PVA) micro-stripes with different spacings (50 μm, 100 μm and 200 μm) were constructed on polystyrene (PS) nano-grooves to prepare micro-nano hybrid patterns where the direction of the PVA micro-stripes and PS nano-grooves was parallel or orthogonal. Human bone marrow-derived mesenchymal stem cells (hMSCs) cultured on the micro-nano hybrid patterns showed a different cell alignment and elongation dependent on the PVA micro-stripe spacing and orientation of the PS nano-grooves. Comparison of the influence of cell alignment and aspect ratio on differentiation of hMSCs indicated that myogenic differentiation was predominantly regulated by cell alignment and osteogenic differentiation by cell elongation, while adipogenic differentiation was regulated neither by cell alignment nor by cell elongation.