Second harmonic chalcone crystal: Synthesis, growth and characterization

The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.     

Hardness evaluation of cured urea–formaldehyde resins with different formaldehyde/urea mole ratios using nanoindentation method

To understand the influence of formaldehyde/urea (F/U) mole ratio on the properties of urea–formaldehyde (UF) resins, this study investigated hardness of cured UF resins with different F/U mole ratios using a nanoindentation method. The traditional Brinell hardness (H_B) method was also used for comparison. The H_B of cured UF resin films with different F/U mole ratios was determined after exposing the films to different post-curing temperatures. The nanoindentation method was employed for these films to measure Meyer hardness (H_M) and reduced modulus (E_r) which have been used to calculate the elastic modulus (E_s) of cured UF resins. As the F/U mole ratio decreased, the H_B decreased continuously, indicating a less rigid network structure in low F/U mole ratio UF resins. The higher the post-curing temperature, the greater the value of H_B. The H_M value also showed a similar trend as a function of F/U mole ratio. However, the E_r and E_s did not show a consistent trend as exhibited by H_M and H_B. Both H_M and E_r showed much greater variation in the coefficient of variation (COV) at lower F/U mole ratios 1.0 and 1.2, indicating a more heterogeneous composition of these resins. Linear relationships between H_M and E_r indicate that heterogeneity of the surface composition of samples contributes greatly to variations in the measured values. This variability is discussed in terms of crystal structures present in the cured UF resins of low F/U mole ratios.     

Fluorescence Studies of Solubilization and Dye Binding in Hypercoiled Poly(methacrylic Acid): A Connected Cluster Model

The compact conformation of poly(methacrylic acid) which is observed in the unneutralized polymer has been studied using the fluorescence probes 9-methyl anthracene and Rhodamine B. Steady-state and time-resolved fluorescence anisotropy measurements have been made. The results show that this conformation contains a number of binding sites which have molecular weights in the range 9,000–10,000 and which can rotate independently of the remainder of the chain.     

A displacement sensing nanoindentation study of tribo-mechanical properties of the Ni-Co system

An analysis of the tribo-mechanical properties of the Ni-Co system, at the submicrometric contact scale, is conducted using displacement sensing nanoindentation. In particular, the influence of contact depth and surface finishing methods on the hardness, H, and Young's modulus, E, of the materials is analysed. Mechanically and electrolitically polished samples were tested with a conospherical indenter using a range of loads between 0.05 and 10 mN. It is shown that the hardness of these materials depends on the surface finishing method and increases with decreasing contact depth, while the Young's modulus is relatively insensitive to contact depth. Furthermore, sample polycrystallinity leads to a large scattering of hardness values in Co-rich samples and of Young's modulus values in Ni-rich ones. The combined parametric ratio H/E, which can be related to the tribological behaviour of the material, was found to be higher in samples with Co content larger than 80 wt.%.     

基于二维相关光谱的壶瓶枣室温贮藏硬度动力学模型研究

为了实现鲜枣常温贮藏期的硬度实时监测并对贮藏时间进行预测,建立了室温下壶瓶枣贮藏期的近红外光谱硬度动力学模型。基于二维相关光谱技术,分析综合浓度影响下的壶瓶枣敏感波段,优选的敏感波段为904,980,1 072,1 200,1 630,1 941和2 215 nm。分析不同贮藏天数的壶瓶枣果肉平均硬度,并拟合出零级反应方程,模型的相关系数为0.991 3,标准误差为6.116×10-4。鲜枣的贮藏过程中,由于复杂的生理化学反应,主要物质的含量发生变化,并通过宏观的信息光谱特征和硬度得以体现。将敏感波段下的光谱信息和贮藏期的硬度指标进行信息耦合,建立壶瓶枣果肉硬度的偏最小二乘模型(partial least square, PLS),模型的预测精度R_P为0.942 7,RMSEP为0.021 0。进而以敏感波段的吸光度为自变量,壶瓶枣果肉硬度指标为应变量,进行多元回归定量分析,建立近红外光谱硬度动力学模型,模型的拟合优度即相关系数为0.983 9,标准误差为0.024 9,并在此基础上建立壶瓶枣贮藏时间与近红外光谱的线性回归关系。研究表明,基于二维相关光谱的硬度动力学模型可以实现对壶瓶枣果肉硬度指标的快速、无损检测并实现其贮藏时间的预测。     

Synthesis and structural characterization of copper nanoparticles doped activated carbon derived from coconut coir for drinking water purification

Modifying and functionalizing activated carbon using metal nanoparticles have received great scientific attention in recent decades as a method to improve its inherent properties. The synergistic effects between the dopant and the activated carbon could lead to advanced properties in the hybrid material compared to individual counterparts. In this study, copper-doped activated carbon from coconut coir (Cu-ACC) is synthesized by an in-situ reduction method. The successful doping of zerovalent copper nanoparticles (Cu np) into the activated carbon matrix was confirmed using several characterization techniques. Peaks related to zerovalent Cu np in the X-ray diffractogram confirmed the successful formation of zerovalent Cu np. The dopant-matrix interactions were confirmed through peak shifts in the Fourier Transform Infrared Spectroscopy and D and G band changes in the Raman spectrum of Cu-ACC. The Cu 2p band in XPS of the Cu-ACC showed a sharp doublet at 932.7 eV, confirming the presence of metallic Cu. As indicated in the TEM/SEM images, Cu np demonstrated a spherical morphology with an average diameter of 5 nm. It was further observed that the Cu-ACC nanohybrid material could remove fluoride (63%) and hardness (69%) in synthetic water. Cu-ACC further demonstrates an enhanced antimicrobial activity against three commonly found water pathogens; E. coli, S. typhi, and S. flexneri. The material is expected to be used in next-generation domestic water filters formulated as single-use sachet bags.