Luminescence enhancement in bromine and samarium co-doped TiO2 semiconductor nanocrystalline powders

In this paper, TiO₂:Sm³⁺ (0.75 mol%) nanoparticles doped with different amounts of Br⁻ were prepared by an improved sol-gel method and were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), VG ESCALAB MKIIX-ray photoelectron spectrometer (XPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). Their photoluminescence (PL) properties were investigated at room temperature. The emissions of ⁴G_5/2-⁶H_J (J=5/2, 7/2, 9/2) transitions of Sm³⁺ ions were observed under the excitation wavelength at 350 nm and the emission intensity depended strongly on the doping amount of Br⁻. TiO₂:Sm³⁺ (0.75 mol%) nanoparticles doped with 1 mol% of Br⁻ calcined at 700 °C exhibit highest intensity of luminescence, which is nearly three times than the undoped one. The mechanism of photoluminescence in the co-doped system was discussed.     

Modulating Ligand-Exchange Dynamics on Metal-Organic Polyhedra for Reversible Sorting and Hybridization of Miktoarm Star Polymers

The precise synthesis of miktoarm star polymers (MSPs) remains one of the great challenges in synthetic chemistry due to the difficulty in locating appropriate structural templates and polymer grafting/growing strategies with high selectivity and efficiency. Herein, ≈2 nm metal-organic polyhedra (MOPs), constructed from the coordination of isophthalic acid (IPA) and Cu²⁺, are applied as templates for the precise synthesis of 24-arm MSPs for their unique logarithmic ligand-exchange dynamics. Six different polymers are prepared with IPA as an end group and they further coordinated with Cu²⁺ to afford the corresponding 24-arm star homo-polymers. MSPs can be obtained by mixing targeted homo-arm star polymers in solutions upon thermal annealing. The compositions of MSPs can be facilely and precisely tuned by the recipe of the star polymer mixtures used. Interestingly, the obtained MSPs can be sorted into homo-arm star polymers through a typical solvent extraction procedure. The hybridization and sorting process can be reversibly conducted through the cycle of thermal annealing and solvent treatment. The complex coordination framework not only opens new avenues for the facile and precise synthesis of MSPs and MOPs with hybrid functionalities, but also provides the capability to design sustainable polymer systems.     

Dual-Crossbar Configurated Bi2O2Se Device for Multiple Optoelectronic Applications

Two-dimensional (2D) materials are widely used in numerous optoelectronic devices due to their ultra-thin dimensions and versatile surfaces. However, less attention is paid to distinguishing the light-matter interactions along the vertical and horizontal paths within the same 2D lattice, as well as comparatively investigating the optoelectronic behaviors between the sensitive top and bottom surfaces. Here, a dual-crossbar configured architecture is designed and constructed based on Bi₂O₂Se semiconductor, featuring highly compact three-in-one assembly, namely bottom surface horizontal (BSH), middle sandwich vertical (MSV) and top surface horizontal (TSH) devices. The MSV with nanoscale channel possesses efficient separation and transportation of the photogenerated electrons and holes, responding faster to the light stimulation and compared favorably to the BSH and TSH devices. The optoelectric behaviors of the BSH device can be regulated by the characteristics of the substrate due to closer contact. Nevertheless, the performance of the TSH device is more sensitive to the environment, such as dopant absorption and heat dispersion, thus enabling the non-volatile photoresponse and can be employed as an artificial optoelectronic synapse. This work highlights the importance of designing the device architecture based on the intrinsic structural advantages of 2D materials, paving the way toward integrated optoelectronics.     

超导量子器件片上皮法电容的制备及测量

片上集成电容是超导量子芯片上的核心器件，其数值一般在百飞法(fF)至皮法(pF)范围.采用常规微纳加工技术在蓝宝石基片上制备了铌-氧化硅-铝(Nb/SiO₂/Al)平行板电容.利用刻蚀工艺制备了平行板电容器的下极板Nb,利用剥离工艺制备平行板电容器的上极板Al和介电层SiO₂.室温下利用锁相放大原理和桥式电路原理测定电容大小，两种方法测定电容值基本一致，表明锁相放大原理测试pF级电容的可靠性.利用该电容与铝基约瑟夫森结组成谐振器，制备了中心频率位于4.35 GHz的约瑟夫森参量放大器.在稀释制冷机中10 mK温度下测定直流偏置谐振器的磁通-频率相位图，拟合数据获得的电容值与室温测定电容值接近，表明在mK、GHz条件下工作的片上集成电容可在室温、kHz条件下测定其数值大小.     

L-tyrosine-assisted synthesis of nanosilver/titanium nitride with hollow microsphere structure for electrochemical detection of hydrogen peroxide

Journal of Solid State Electrochemistry - The nano-Ag–TiO2 hollow microsphere precursors were prepared by the one-pot solvothermal method using L-tyrosine as the template agent and reducing...