Nanocrystallization and optical properties of CsPbBr3−xIx perovskites in chalcogenide glasses

The confinement of CsPbX₃ (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr_3?xI_x NCs with arbitrary I/Br ratio among an elaborately designed GeS₂–Sb₂S₃-based chalcogenide glass matrix. Spherical CsPbBr_3?xI_x NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr_3?xI_x NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX₃ NCs into glassy matrices, facilitating their future applications in photoelectronic fields.     

Carbon membrane bridged ZnSe and TiO2 nanotube arrays: Fabrication and promising application in photoelectrochemical water splitting

In this work, a cascade structure among ZnSe, carbon membrane and TiO₂ NTAs was constructed precisely. This carbon membrane bridged ZnSe and TiO₂ composite exhibits excellent H₂ evolution activity, the H₂ evolution rate of ZnSe/C/TiO₂ NTAs (866.76 μmol/cm²) is about 6.95 times higher than that of pure TiO₂ NTAs (124.64 μmol/cm²) after 200 min irradiation. The introduction of carbon membrane can greatly facilitate the electron transfer from ZnSe to TiO₂, ZnSe/C/TiO₂ ternary composite exhibits the highest transient photocurrent density (1.05 mA/cm²) and the lowest impedance (677.6 Ω) among all the samples. Besides, the contact between TiO₂ and electrolyte is improved after introducing carbon membrane, therefore C/TiO₂ NTAs shows more positive flat band potential of (1.86 V) compared with TiO₂ NTAs (0.50 V). It is also found that pure carbon powder can achieve H₂ production under visible light irradiation, its sensitization effect can further improve photocurrent density of the composite under 500 nm light radiation, the electrons produced in carbon film can inject into TiO₂, and holes from TiO₂ can quickly transfer to carbon film, leading to excellent H₂ evolution efficiency.     

Microstructure and synthesis mechanism of dysprosia-stabilized zirconia nanocrystals via chemical coprecipitation

In this study, zirconia (ZrO₂) and dysprosia-stabilized zirconia (DySZ) nanocrystals were synthesized using a chemical coprecipitation method. The crystal structure and micromorphology of the as-synthesized powders, as well as the structural evolution from precursors to oxides were investigated, and the synthesis mechanism was also examined. Results show that pure ZrO₂ powders mainly comprise the monoclinic ZrO₂ phase with trace tetragonal ZrO₂, while the DySZ powders exhibit a tetragonal ZrO₂ structure. In addition, the crystal growth rate of DySZ is far slower than that of the pure ZrO₂ under elevated calcination temperature. The addition of Dy could significantly improve the phase stability of DySZ powder and effectively inhibit the crystal growth of DySZ. In the DySZ precursor, the binding energy of chemical bonds is significantly difference than in the ZrO₂ precursor. A composite hydroxide can be formed with -Zr-OH-Dy- and -Zr-OH-Zr- units in the tetramer structure because of the in-situ substitution of Zr by Dy atoms. Both the ZrO₂ and DySZ precursors exhibit analogous dehydration and crystallization behaviours in calcination process. Dy-doping plays a significant role in stabilizing both the intermediate product and the DySZ crystal.     

碱性溶液中非晶/纳米晶Ni-Mo合金的形成机制研究

针对碱性溶液中Ni-Mo合金的形成机制,采用极谱法和循环伏安法进行研究。实验发现:Ni,Mo原子为多步氧化还原反应,Ni-Mo合金的形成过程为异常共沉积与诱导共沉积的复合沉积过程,进而形成致密光滑的结构镀层。非晶/纳米晶Ni-Mo合金具有一定的储氢能力,其化学活性较高,是较好的电极材料。     

阳极氧化法制备片状纳米ZnO及其光催化性能

采用阳极氧化法,以锌片为阳极,石墨板为阴极,水/无水乙醇(体积比1∶1)+1.2%氯化铵+不同体积30%双氧水的混合溶液作为电解液,制备了片状纳米ZnO,并利用冷场扫描电镜、X射线衍射和傅里叶红外光谱对试样的形貌、物相和结构进行表征。在紫外灯照射下对10mg/L的苯酚溶液进行光催化降解,考察了片状纳米ZnO的光催化活性。结果表明:当双氧水体积为0.4mL时,可以得到高结晶度、高纯度的片状纳米ZnO,且对苯酚的降解率高达96.37%。     

II3V2 (II: Zn,Cd; V: P,As) Semiconductors: From Bulk Solids to Colloidal Nanocrystals

II₃V₂ semiconductors have become increasingly popular for a variety of applications including solar light harvesting, near‐IR imaging, and low energy light detection. The bulk physical and electronic structure of these materials is highlighted, followed by an in‐depth survey on progress in synthesizing these semiconductors as colloidal nanocrystals. Interestingly, no universal synthetic approach has yet been developed to access all compounds within this family. A discussion on how the complex crystal structure of these materials translates to small domain sizes will highlight current challenges in the characterization of II₃V₂ nanocrystals. Finally, potential avenues for further research will be proposed as a way to advance this field towards greater utilization in light harvesting applications.     

A viewpoint on the gastrointestinal fate of cellulose nanocrystals

BackgroundCellulose nanocrystalline (CNC) particles possess unique functional properties such as vastly modifiable surface, considerable mechanical strength and acid resistance, as well as, high aspect ratio. CNCs have received great attention for application in diverse fields of technology including (composite) hydrogels fabrication for the gastric protection and enteral delivery of drugs and nutraceuticals.Scope and approachThe orogastrointestinal digestibility and absorbability of the orally administered CNCs is overviewed in the current article. At first, some surface charge-related characteristics of acid-isolated CNCs are communicated. Then, the biocompatibility and biodegradability of CNCs and CNC-reinforced hydrogels are reviewed, followed by presenting credible digestion and absorption scenarios. Finally, the post-absorption metabolism of CNCs is briefly debated.Key findings and conclusionsBacterial cellulose shows good biocompatibility and hemocompatibility. CNC oxidation provides biologically beneficial impacts; for instance, the TEMPO- and periodate-oxidized CNCs have been shown to regulate some blood metabolic variables and improve the degradability in simulated human blood plasma, respectively. Spherical and carboxyl-bearing cellulose nanoparticles can be isolated through ammonium persulfate digestion. The sphericity of particles results in faster cellular uptake. Negatively-charged CNCs are non-mucoadhesive and thus upon ingestion can penetrate into the buccal and intestinal mucosa. One may augment the absorption of CNCs by targeted receptor-mediated endocytosis. It was postulated that sodium bicarbonate secretion into the duodenum can alter CNCs surface chemistry and influence CNC interaction with gut microbiota.     

硅离子注入引入纳米晶对SIMOX材料进行总剂量辐射加固

本研究工作采用硅离子注入和高温退火工艺对SIMOX材料的BOX层进行总剂量辐射加固.辐射实验结果证明了该加固方法的有效性.PL谱和HRTEM图像显示了硅离子注入及退火工艺在材料的BOX层中引入了Si纳米晶,形成电子陷阱能级,有效俘获电子,从而提高了材料BOX层的抗总剂量辐射能力.