Strategies in boosting photosensitization for biomedical applications

Science China Chemistry -     

聚苯硫醚熔体的压致凝固行为

采用施加压力的方法将聚苯硫醚熔体凝固,凝固后获得的聚苯硫醚样品经过降温和卸压后在常温常压下回收. X射线衍射和差示扫描量热分析表明:约20 ms时间的快速压缩过程可以抑制熔体结晶,制备出非晶态聚苯硫醚块材,样品的表面及中心都是非晶态.非晶态聚苯硫醚的玻璃化转变温度和晶化温度分别为318和362 K.常压下的退火实验表明,非晶态聚苯硫醚在425 K等温结晶的产物为正交相晶型.压致凝固法中熔体的凝固不是靠温度变化,而是靠压力变化,样品表面和内部处在一致的温度下同时受压凝固,避免了热传导对非晶尺寸的影响,因此非常有利于获得结构均匀的大尺寸非晶态材料.     

Theoretical studies of photovoltaic properties of five new silol dithiophene based D2-A-D1-A-D2 donors

Organic solar cell of silol dithiophene based D₂-A-D₁-A-D₂/PC₇₁BM (D: donor part; A: acceptor part; 1 and 2 denote different units) possesses promising power conversion efficiency. Researchers have studied D₂-A-D₁-A-D₂ molecules carefully, including the effects of the different number of terminal thiophenes, the different central moiety (D₁), and the length of the alkyl chain. However, there are few investigations, especially theoretical studies, on the influences of different A (acceptor) units on the properties of D₂-A-D₁-A-D₂ molecule. In the present work, we have designed and modeled five new D₂-A-D₁-A-D₂ (D₂ = bithiophene and D₁ = silol dithiophene) donors by changing A units (A = diketopyrrolopyrrole, naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole, 5-fluoro-2,1,3-benzoselenadiazole, benzobisthiadiazole, and thiazolo[5,4-d]thiazole). We have applied density functional theory (DFT) and time-dependent DFT to predict their ground-state electronic structures and the UV–vis spectra, and the open circuit voltages (Vocs) of organic solar cells of D₂-A-D₁-A-D₂/PC₇₁BM. Based on the calculated results, we find that bithiophene thiazolo[5,4-d]thiazole siloldithiophene (BTTS) (D₂ = bithiophene, A = thiazolo[5,4-d]thiazole, D₁ = silol dithiophene) possesses the highest lowest unoccupied molecular orbital (−2.60 eV) and the lowest highest occupied molecular orbital (−5.33 eV) energies, and the strongest absorption in the visible region. Besides, the solar cell of BTTS/PC₇₁BM has the highest Voc of 1.02 V. These results indicate that it may be a promising donor. In contrast, bithiophene benzobisthiadiazole siloldithiophene (BBBS) (A = benzobisthiadiazole) has low absorption strength in the visible region, which indicates that it may not be a suitable donor material.     

Magnetic retrievable Ag/AgBr/ZnFe2O4 photocatalyst for efficient removal of organic pollutant under visible light

In the present work, a visible-light-driven Ag/AgBr/ZnFe₂O₄ photocatalyst has been successfully synthesized via a deposition–precipitation and photoreduction method. The crystal structure, chemical composition, morphology and optical properties of the as-prepared nanocomposites were characterized by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscope, UV–vis diffuse reflectance spectroscopy and photoluminescence. The photocatalytic activities of the Ag/AgBr/ZnFe₂O₄ nanocomposites were evaluated through the photodegradation of gaseous toluene and methyl orange (MO) under visible light. The results revealed that the as-prepared Ag/AgBr/ZnFe₂O₄ nanocomposite exhibited excellent photocatalytic activity. The degrading efficiency of MO could still reach 90% after four cycles, and the Ag/AgBr/ZnFe₂O₄ nanocomposite could be recycled easily by a magnet. Additionally, the enhanced photocatalytic mechanism was discussed according to the trapping experiments, which indicated that the photo-generated holes (h⁺) and •O₂⁻ played important roles in photodegradation process. At last, a possible photocatalytic oxidation pathways of toluene was proposed based on the results of GC–MS. The Ag/AgBr/ZnFe₂O₄ composites showed potential application for efficient removal of organic pollutant.     

Templated synthesis and assembly with sustainable cellulose nanomaterial for functional nanostructure

Cellulose - Templated synthesis and assembly for nanostructured materials with tailored properties have received considerable attention. The powerful templates with predefined structures can guide...     

Compact layer influence on hysteresis effect in organic–inorganic hybrid perovskite solar cells

Organic–inorganic hybrid perovskite solar cells have attracted great attention due to their high power conversion efficiency and low cost. However, an anomalous hysteresis effect exists in the perovskite solar cells, especially with TiO₂ as the n-type electron extraction layer. In this communication, we prepare two kinds of TiO₂ compact layers using Atomic Layer Deposition (ALD) and Spin-Coating (SC) methods and compare their influences on the hysteresis effect. By efficiency comparison and AC impedance spectroscopy study, we find that the thickness and morphology of compact layer have a significant influence on the hysteresis effect. Compared to the SC approach, the ALD prepared compact layer is ultra-thin with uniform morphology and shows small interfacial capacitance and large recombination resistance, meaning reduced interfacial charge accumulation and accelerated electron transport, which would relieve the hysteresis effect.     

Ultra-thin CoAl layered double hydroxide nanosheets for the construction of highly sensitive and selective QCM humidity sensor

To achieve real-time monitoring of humidity in various applications, we prepared facile and ultra-thin CoAl layered double hydroxide (CoAl LDH) nanosheets to engineer quartz crystal microbalances (QCM). The characteristics of CoAl LDH were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), Brunauer–Emmett–Telle (BET), atomic force microscopy (AFM) and zeta potential. Due to their large specific surface area and abundant hydroxyl groups, CoAl LDH nanosheets exhibit good humidity sensing performance. In a range of 11.3% and 97.6% relative humidity (RH), the sensor behaved an ultrahigh sensitivity (127.8 Hz/%RH), fast response (9.1 s) and recovery time (3.1 s), low hysteresis (3.1%RH), good linearity (R² = 0.9993), stability and selectivity. Besides, the sensor can recover the initial response frequency after being wetted by deionized water, revealing superior self-recovery ability under high humidity. Based on in-situ Fourier transform infrared spectroscopy (FT-IR), the adsorption mechanism of CoAl LDH toward water molecules was explored. The QCM sensor can distinguish different respiratory states of people and wetting degree of fingers, as well as monitor the humidity in vegetable packaging, suggesting excellent properties and a promising application in humidity sensing.     

Enhancing electrochemical conversion of lithium polysulfide by 1T-rich MoSe2 nanosheets for high performance lithium–sulfur batteries

The sluggish conversion kinetics and shuttle effect of lithium polysulfides (LiPSs) severely hamper the commercialization of lithium–sulfur batteries. Numerous electrocatalysts have been used to address these issues, amongst which, transition metal dichalcogenides have shown excellent catalytic performance in the study of lithium–sulfur batteries. Note that dichalcogenides in different phases have different catalytic properties, and such catalytic materials in different phases have a prominent impact on the performance of lithium–sulfur batteries. Herein, 1T-phase rich MoSe₂ (T-MoSe₂) nanosheets are synthesized and used to catalyze the conversion of LiPSs. Compared with the 2H-phase rich MoSe₂ (H-MoSe₂) nanosheets, the T-MoSe₂ nanosheets significantly accelerate the liquid phase transformation of LiPSs and the nucleation process of Li₂S. In-situ Raman and X-ray photoelectron spectroscopy (XPS) find that T-MoSe₂ effectively captures LiPSs through the formation of Mo-S and Li-Se bonds, and simultaneously achieves fast catalytic conversion of LiPSs. The lithium–sulfur batteries with T-MoSe₂ functionalized separators display a fantastic rate performance of 770.1 mAh/g at 3 C and wonderful cycling stability, with a capacity decay rate as low as 0.065% during 400 cycles at 1 C. This work offers a novel perspective for the rational design of selenide electrocatalysts in lithium–sulfur chemistry.