A facile construction of heterostructured ZnO/Co_3O_4 mesoporous spheres and superior acetone sensing performance

The rapid development of internet and internet of things brings new opportunities for the expansion of intelligent sensors,and acetone as a major disease detection indicator(i.e.,diabetes) making it become extremely important clinical indicator.Herein,uniform mesoporous ZnO spheres were successfully synthesized via novel formaldehyde-assisted metal-ligand crosslinking strategy.In order to adjust the pore structure of mesoporous ZnO,various mesoporous ZnO spheres were synthesized by changing weight percentage of Zn(NO_3)_2·6 H_2 O to tannic acid(TA).Moreover,highly active heterojunction mesoporous ZnO/Co_3 O_4 has been fabricated based on as-prepared ultra-small Co_3 O_4 nanocrystals(ca.3 nm) and mesoporous ZnO spheres by flexible impregnation technique.Profit from nano-size effect and synergistic effect of p-n heterojunction,mesoporous ZnO/Co_3 O_4 exhibited excellent acetone sensing performance with high selectivity,superior sensitivity and responsiveness.Typically,5 wt% Co_3 O_4 embedded mesoporous ZnO sphere showed prominent acetone response(ca.46 for 50 ppm),which was about 11.5 times higher than that in pure ZnO sensing device,and it was also endowed high cyclic stability.The nanocrystals embedded hybrid material is expected to be used as promising efficient material in the field of catalysis and gas sensing.     

镧系金属有机骨架比例荧光检测萘普生

该文构筑了双荧光发射的比例型荧光传感器,并将其用于萘普生检测。以Eu3+为金属节点,1,3,5-苯三甲酸为配体,通过超声法合成了比例型荧光传感材料Eu-MOF。探究了Eu-MOF的形貌特征、光学性质及对萘普生的检测机理。单一激发光照射下,Eu-MOF呈现源于配体和Eu3+的双荧光发射峰。萘普生的荧光发射峰与Eu-MOF在375 nm处的荧光发射峰重合,且两者之间具有内滤光效应。因此,随着萘普生的逐渐加入,Eu-MOF在375 nm处的荧光发射峰强度逐渐增强,而623 nm处则逐渐减弱,从而可实现对萘普生的比例荧光检测。Eu-MOF检测萘普生的线性范围为0.07~2.3μmol/L,检出限为0.039μmol/L。Eu-MOF在萘普生的检测中表现出良好的选择性和抗干扰能力,是实际样品中萘普生检测的优势材料。     

Carbazole- and Fluorene-Fused Aza-BODIPYs: NIR Fluorophores with High Brightness and Photostability

Three new aza-BODIPY dyes incorporating fused fluorene or carbazole moieties have been prepared. The dyes show significant enhancement of photophysical properties compared to the parent 1,3,5,7-tetraphenyl aza-BODIPY (TPAB): a bathochromic shift of the absorption maximum (up to 2700 cm⁻¹) and emission maximum (up to 2270 cm⁻¹); an almost threefold increase in molar absorption coefficients (to ca. 230 000 M⁻¹ cm⁻¹) and a significant increase in the fluorescence quantum yield to 49–66 %. Owing to the combination of these properties, the new aza-BODIPY dyes belong to the brightest NIR dyes reported. The dyes also show excellent photostability. Due to their outstanding properties, the new dyes represent a promising platform for further exploration in biomedical research. A pH indicator containing only one fused carbazole unit was also prepared and shows absorption and emission spectra that are bathochromically shifted by about 110 and 100 nm, respectively, compared to the indicator dye based on the TPAB chromophore.     

用于压力传感的还原氧化石墨烯/丝蛋白基多孔复合材料

利用丝蛋白能够在还原氧化石墨烯片层上发生选择性聚集的特性,制备了还原氧化石墨烯片层上富集有丝蛋白微纤且分散性良好的还原氧化石墨烯片和丝蛋白混合溶液,并通过冷冻以及低温乙醇处理的方法得到一系列不同比例的还原氧化石墨烯/丝蛋白基多孔复合材料.随后,采用溶液浸泡的方法在多孔材料表面再次沉积还原氧化石墨烯,以进一步提高还原氧化石墨烯/丝蛋白基多孔复合材料的压敏导电性.系统观察和测试结果表明,还原氧化石墨烯的引入,不仅使得多孔材料内部出现了相应的微纳结构,同时也提高了多孔材料的力学性能.还原氧化石墨烯/丝蛋白基多孔复合材料在完全湿态下兼具较好的强度和弹性,可以在0%~80%的压缩应变之间实现良好的压缩回复效果和压力传感性能.其中,最佳比例下的还原氧化石墨烯/丝蛋白基多孔复合材料在低压力下的灵敏度可达0.15 kPa?1,在0~17.3 kPa范围内能够高效工作并且具有优异的电学稳定性和耐疲劳性.因此,还原氧化石墨烯/丝蛋白基多孔复合材料因其高灵敏度、宽工作范围、结构可调以及可塑性好等诸多优点,有望在柔性压力传感方面获得较好的应用.     

基于微波光子学的准分布式光纤传感解调技术

准分布式光纤传感系统在土木工程、能源勘测、航空航天、国防、化工等领域一直发挥着不可替代的重要作用。以微波光子学为基础的准分布式光纤传感解调技术被广泛应用于光纤复用系统的快速、高精度的信号解调与传感器定位。与传统的光学波长解调方案相比,该技术大幅提高了系统的解调速率,弥补了传统解调方法在传感器定位方面的缺陷。本文主要介绍了近年来国内外在基于微波光子学的准分布式光纤传感解调领域的研究进展,从光纤光栅准分布式传感系统和光纤法布里-珀罗准分布式传感系统两方面入手,对比分析了现有的数种微波解调光纤准分布式系统的优缺点,并对基于微波光子学的准分布式光纤传感解调技术的未来发展方向进行了总结与展望。     

基于L型延迟阵列调制宽带转换器的信号载频和二维到达角联合估计

针对现有的基于欠采样的频率和二维到达角的联合估计存在结构复杂问题,本文提出了一种基于调制宽带转换器技术的L型延迟阵列接收结构.利用延迟通道与未延迟通道采样值之间的相位差可直接估计载频,进而计算二维到达角,无需额外的参数配对操作,避免了配对步骤引入的误差和复杂度的提升.并结合所提L型延迟阵列结构的特点构造相关矩阵和三线性模型,提出了两种参数估计算法,一种基于旋转不变子空间算法,计算量小,适用于需要实时处理的场景;另一种基于正则分解技术,鲁棒性较好,适用于信噪比较低的应用场景.仿真实验表明该方法能较好地从欠奈奎斯特样本中估计目标的载频和二维到达角参数.     

锐钛矿型氧化物XO2（X=Ti,Sn,Zr,Ir）表面氧化性对NH3气体光学气敏传感特性的影响

摘要 金属氧化物气敏传感材料一直是当今的热门研究课题,锐钛矿相金属氧化物XO2（X=Ti,Sn,Zr,Ir）是具有传感特性的常见材料。光学气敏效应是指气体分子吸附在气敏传感材料上,与表面氧空位发生氧化还原反应,由于光学性质发生改变而检测出气体的成分和浓度,因此,氧化还原反应的强弱是反应传感性能的核心原因。本文采用密度泛函理论(DFT)体系下广义梯度近似(GGA)第一性原理平面波超软赝势方法,分析和计算了含氧空位的锐钛矿相XO2（X=Ti,Sn,Zr,Ir）表面特性。通过以NH3为目标分子,研究分子表面吸附引起的氧化还原反应的机理,分析不相同的氧化物表面的几何结构、吸附能、态密度、差分电荷密度、电荷布居、电荷转移、光学性质等。研究发现：目标分子稳定吸附在氧化物表面后改变材料光学性质。SnO2表面对分子的吸附能最大,IrO2表面与分子的吸附距离最小。NH3分子与表面间存在电荷转移,其转移电子数目大小为:IrO2＞TiO2＞ZrO2＞SnO2,氧化物表面氧化性的大小为:IrO2氧空位＞TiO2氧空位＞ZrO2氧空位＞SnO2氧空位;比较吸收谱和反射谱发生变化最为明显的是TiO2表面。结论,在可见光范围内,波长在400~530nm时,SnO2表面光学气敏传感效应更好。而在530~760nm范围TiO2表面光学气敏传感效应更好。     

Novel high-quality Fano resonance based on metal-insulator-metal waveguide with L-shaped resonators

Developing a convenient method that can be routinely applied for ascertaining proportions of different vegetable oils employed in commercial blended edible oils remains a significant challenge. We address this issue by proposing a novel method for detecting volume fraction of different oils based on the fact that these oils are optically transparent and have slightly different indices of refraction at a given temperature and wavelength. Accordingly, we develop a highly sensitive sensor for measuring the index of refraction of oil blends based on Fano resonance spectra obtained using a metal-insulatormetal(MIM) waveguide structure comprising a gapped straight waveguide coupled with two L-shaped resonators. The index of refraction sensitivity and figure of merit of the structure are calculated based on modeling using the finite element method, and the waveguide structure is accordingly optimized by adjusting the different geometric parameters to achieve a high-quality Fano resonance spectrum. The optimized structure achieves an ultra-high refractive index sensitivity of 770 nm/RIU in terms of a refractive index unit(RIU) of 1. Moreover, a highly stable linear relationship is obtained between the refractive index of mixed edible oils and the resonance wavelength. Experimental results demonstrate that the proposed structure can detect slight changes in the volume fractions of the components in blended oils.     

Three-pillared layer metal–organic frameworks assembled by imidazole-4,5-dicarboxylate and rigid bisimidazole ligands: synthesis,crystal structure,and sensing nitroaromatics

Three-pillared layer metal–organic frameworks based on 1H-imidazole-4,5-dicarboxylate and linear bis(imidazole) ligands generally formulated as {[Co₃(idc)₂(bib)₃]·8H₂O}_n (1), {[Cd(Hidc)(bib)_0.5]}_n (2) and {[Cd(Hidc)(bibp)]}_n (3), where H₃idc = 1H-imidazole-4,5-dicarboxylate, bib = 1,4-bis(1-imidazolyl)benzene and bibp = 4,4′-bis(1-imidazolyl)biphenyl, have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound 1 features a 3-D-pillared layer structure with 1-D channels, generated by honeycomb-like 2-D layer linked by bib ligands. Compound 2 consists of 2-D lumpy layers of [Cd₄(Hidc)₄], which are further connected by bridging ligands of bib to generate a pillared layer 3-D framework with 1-D channels. In 3, the 2-D corrugated honeycomb networks, structurally analogous to CFx, are pillared by bibp ligands to form a 3-D architecture with 1-D channels. Through selecting different metal ions and the length of pillared ligands, the pore sizes are adjusted in the three complexes. The potential of 2 and 3 for nitro explosive sensing is investigated through luminescence quenching experiments, which show that 3 can be applied as a fluorescent sensor for nitro compounds.