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This paper presents a solvothermal strategy for chemical modification of TiO(2) nanoparticles with carboxylic acids. Solvothermal reaction between the TiO(2) nanoparticles and carboxylic acid molecules in an autoclave at 100 degrees C provides carboxylic acid-modified TiO(2) particles with a modification efficiency much higher than the conventional immersion method. TiO(2) nanoparticles were prepared by hydrolysis of titanium isopropoxide in nitric acid solution; the modified nanoparticles were characterized by powder X-ray diffraction pattern, scanning electron microscopy, absorption and Fourier transform infrared spectra, and thermogravimetric analysis. Results show that the binding form of the modifier molecules on TiO(2) surface is in a bidentate chelating mode, the crystalline phase composition and morphological structure of the preformed TiO(2) nanoparticles are not affected by the solvothermal reaction, and the surface coverage of the modifier molecules can be adjusted by the weight ratio of modifier/TiO(2) during feeding. It is evident that the reaction processes in the solvothermal strategy involve the formation of double hydrogen bondings between carboxylic acid molecule and TiO(2) at the same Ti site and the coordination at solvothermal temperature by dehydration from the hydrogen bondings. The solvothermal strategy for modifying TiO(2) nanoparticles is expected to find potential applications in many fields; for example, our results demonstrate that the photovoltaic performance of the TiO(2) nanoparticles can be improved by the solvothermal modification even with an insulating modifier and controlled by the modifier coverage.

Putative G-quadruplex-forming sequences (PQS) are highly prevalent in human genome; however, the structures and functions of most PQSs in genome are poorly understood. Therefore, selective recognition of certain types of G-quadruplexes (G4s) is important for the study of G4s. A new light up fluorescent probe, BPBC composed of benzimidazole and carbazole moieties was designed and synthesized. BPBC possesses a crescent-shaped π-conjugated planar core that is slightly larger than the dimension of the G-quartet plane in G4s. This structure endows BPBC with excellent selectivity to parallel G4s. BPBC exhibits almost no fluorescence in the aqueous buffer condition, its fluorescence increases approximately 330-1800-fold in the presence of parallel G4s but only about 30-fold in the presence of single/double-stranded (ss/ds) DNA and 30-110-fold in the presence of antiparallel G4s. Binding studies indicate that the highly selective fluorescent response of BPBC arises from end-stack binding model to G-quartet.

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For characterization of polymer-based solar cells with vertically aligned ZnO nanorod arrays (ZnO-NAs) by intensity modulated photocurrent spectroscopy (IMPS), a dynamic IMPS model is developed, where the structure-related charge generation and transport dynamics are considered. The model describes the IMPS responses affected by the phase shift φ n (ω) due to the exciton diffusion property (ω 0 ) and the structurerelated device ideality factor N, the electron diffusion coefficient D e , the exciton dissociation rate S, and the device structure (e.g., nanorod length d and interspacing l). The main expectations of the model are confirmed by the experimental data of the polymer/ZnO-NA cells with d ) 180-650 nm, offering mechanistic information on the structure-related charge generation, charge transport, and device performance. The presence of the φ n (ω) makes IMPS response not spiral into the origin and the phase angle in its Bode plot not tend to 90°; the d-dependent direct diffusion (DD) and diffusion-reflection (DF) transport processes are normally involved in the travel of injected electrons to the collection electrode; the incident photon-to-current conversion efficiency (IPCE) and the transit time (τ D ) for DD transport under the influence of DF process reach their peak values at d ≈ 500 nm, and the φ n (ω) effect on electron transport is affected by ω 0 , D e , and S. Satisfactory fittings of measured IMPS responses to the model further reveal that the d dependence of the IPCE or the photocurrent actually originates from the S value governed by d-dependent exciton generation and dissociation; when changing d, a larger number of electrons for DD transport causes a smaller N or a more remarkable φ n (ω) effect; a longer τ D is accompanied by a larger RC effect of the ZnO electrode. Those results clearly suggest that a highly efficient polymer/ZnO-NA device requires d ≈ 500 nm and l ) 5-10 nm, along with a high interfacial exciton dissociation efficiency.

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Here we describe a highly selective and reversible Hg(2+) sensor, tetra-(thymin-1-yl-acetamido)-phthalocyanine Zn(II) (4T-ZnPc), which combined the optical properties of phthalocyanine (Pc) and the specific interaction of Hg(2+) with thymine (T). The novel phthalocyanine-nucleobase conjugate, 4T-ZnPc, shows a typical ultraviolet-visible absorption spectrum with a split Q-band of monomeric Pc in dimethylformamide (DMF)-water (7:3, v/v) solution, as well as strong fluorescence emission. Upon addition of Hg(2+), the formation of T-Hg-T complex induces aggregation of 4T-ZnPc and results in significant decreases of fluorescence intensity and absorption of the Q-band. Furthermore, the sensor molecules, 4T-ZnPc, show excellent selectivity for Hg(2+), and other ions, such as Pb(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Mn(2+), Mg(2+), Ca(2+), Na(+), and K(+), have almost no effect on the optical properties of 4T-ZnPc. This kind of sensor based on Pc may be expanded to the detection of other targets by substituting thymines with other ligands or groups that possess molecular recognition ability.

The complex pathogenic mechanisms of Alzheimer's disease (AD) include the aggregation of β-amyloid peptides (Aβ) into oligomers or fibrils as well as Aβ-mediated oxidative stress, which require comprehensive treatment. Therefore, the inhibition of Aβ aggregation and free-radical scavenging are essential for the treatment of AD. Nanoparticles (NPs) have been found to influence Aβ aggregation process in vitro. Herein, we report the inhibition effects of molybdenum disulfide (MoS) NPs on Aβ aggregation. Polyvinylpyrrolidone-functionalized MoS NPs were fabricated by a pulsed laser ablation method. We find that MoS NPs exhibit multifunctional effects on Aβ peptides: inhibiting Aβ aggregation, destabilizing Aβ fibrils, alleviating Aβ-induced oxidative stress, as well as Aβ-mediated cell toxicity. Moreover, we show that MoS NPs can block the formation of the Ca channel induced by Aβ fibrils in the cell membrane for the first time. Thus, these observations suggest that MoS NPs have great potential for a multifunctional therapeutic agent against amyloid-related diseases.