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A new electrochromic conjugated polymer, poly 2-(9,9-dicotyl-9 H-fluorene-2-yl)-3,6-bis(5-hexylthiophen-2-yl)thieno[3,2- b]thiophene), containing fluorene (F8-DT6) substituted thieno[3, 2-b]thiophene has been designed by Stille and Suzuki coupling reactions and then polymerized at different potentials through electrochemical polymerization. The as-synthesized polymer is characterized by nuclear magnetic resonance (NMR) spectroscopy, cyclic-voltammetry (CV), ultraviolet-visible spectroscopy (UV-vis), and atomic force microscopy (AFM). The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels are −2.67 eV and −5.21 eV respectively, as determined by cyclic voltammetry. As the film, P(F8-DT6-TT) exhibits UV-vis at 502 nm, the bandgap values from electrochemical and optical measurements are in excellent agreement. The CIE colour coordinates L*, a*, and b* of neutral and oxidized states are (76.81, −3.04, 67.46) and (68.90, −10.92, 32.04) respectively giving vivid orange colour in the bleached/oxidation state and a very light-yellow colour in the reduced state. P(F8-DT6-TT) exhibits better stability between −0.1 and 2 V and the stability pattern moves towards a stable position by increasing the number of cycles. AFM images reveal a higher root-mean-square value (51.83 nm) that is useful for providing a convenient optical response and film stability. Effective colour tuning by substituting fluorene (F8-DT6) in thieno[3,2-b] thiophene units is a notable property of P(F8-DT6-TT), which renders it an appropriate electrochromic material.

We explore the photoluminescence properties of zinc silicate (Zn2SiO4) nanostructures synthesized by vapor-liquid-solid (VLS) mode of growth using three different catalysts (Sn, Ag, and Mn). Different catalysts significantly influence the growth rate which in turn has an impact on the structure and hence the photoluminescence of the prepared zinc silicate nanostructures. Zn2SiO4 has a wide bandgap of about 5.5 eV and in its pure form, it does not emit in visible region due to its inner shell electronic transitions between the 3d5 energy levels. However, the incorporation of different catalysts (Sn, Ag and Mn) at different growth temperatures into the Zn2SiO4 crystal growth kinetics provides wide visible spectral range of photoluminescence (PL) emissions. PL analysis shows broad multi-band spectrum in the visible region and distinct colors (red, yellow, green, blue, cyan and violet) are obtained depending on the crystalline structure of the prepared nanostructures. The allowed transitions due to the effect of different catalysts on zinc silicate lattice offer a huge cross-section of absorption that generates strong photoluminescence. The correlation between the structural and optical properties of the synthesized nanostructures is discussed in detail. The synthesized photoluminescent nanostructures have potential applications in solid-state lighting and display devices.