SYNTHESIS AND OPTICAL PROPERTIES OF A NOVEL ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL POLYMER VIA SOL-GEL PROCESS

A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of an alkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4 ' -hydroxy azobenzene was covalently bonded to the triethoxysilane derivative, i.e, gamma -isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gel derived NLO polymer were studied and characterized by SEM, FTIR,H-1-NMR, UV-Vis, DSC and second harmonic generation (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO2 networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showed that the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r(33)) of 7.1 pm/V at 1.1 mum wavelength, and exhibit good SHG stability, the r(33) values can maintain about 92.7% of its initial value at room temperature for 90 days, and can maintain about 59.3% at 100 degreesC for 300 min.

Facile fabrication of nanoscale hierarchical porous zeolitic imidazolate frameworks for enhanced toluene adsorption capacity

The development of a simple and facile synthesis route is a highly desirable but challenging process in the fabrication of nanoscale hierarchical porous zeolitic imidazolate frameworks(ZIFs).Herein we describe a facile method for rapidly synthesizing hierarchically porous ZIF-90 nanocrystals(particle sizes of~300 nm)using hydroxyl double salts as intermediates at room temperature.The as-synthesized ZIF-90 contained hierarchical porous structures developed using a crystalline interior and a random stack of multiple nanoparticles.Both the morphology and particle size of ZIF-90 nanocrystals could be tuned by controlling the molar ratio of ICA/Zn^(2+).Note that the as-synthesized hierarchically porous ZIF-90 nanocrystals exhibited higher thermal stability compared with the conventional ZIF-90.Because of the introduction of hierarchical porous structures,the resultant hierarchically porous ZIF-90 nanocrystals showed enhanced toluene adsorption capacity than those of conventional metal organic frameworks and zeolites.

Modification of Ti_(3)C_(2) MXene nanosheets with tunable properties using a post-processing method

MXenes are a family of two-dimensional(2D)transition metal carbides and nitrides with many intriguing properties and applications,many of which require surface modification.Herein,as-synthesized Ti_(3)C_(2) was modified using different treatments(acid and base treatments)and then characterized by a complementary combination of X-ray powder diffraction(XRD),scanning electron microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),nitrogen adsorption-desorption isotherms,and pore size distribution analysis.The results indicated that the structure and surface properties of the obtained Ti_(3)C_(2) could be tuned using various treatments.The modification methods developed in this study may offer a new direction for tuning the structure and surface properties of MXenes for a wide range of applications.