Sol–gel synthesis and characterization of adsorbent and photoluminescent nanocomposites of starch and silica

Using sol–gel method, mesoporous and photoluminescent silica nanocomposites of soluble starch have been synthesized and characterized. Different ratios of H2O, TEOS and EtOH were used at fixed template (soluble starch) and catalyst (NH4OH) concentrations to obtain materials of different performances in terms of heavy metal binding from a solution which has been monitored using Cd(II) as representative divalent heavy metal ion. Optimum material was obtained when H2O, TEOS and EtOH were used in 14:1:2 ratio. This sample was not only an efficient metal ion adsorbent but also had an intense luminescence in ultra-violet region and potentially may be used in silicon-based UV-emitting devices. Metal binding by the material was further enhanced after calcination (at 800 °C in air) while its luminescence had a multipeak profile in UV–visible region. In a batch adsorption study, calcined hybrid composite (0.25 g/L) could remove 98.5% Cd(II) from 100 mg/L Cd(II) solution in 2 h. The chemical, structural and textural characteristics of the synthesized materials have been investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-rays Diffraction (XRD), Thermal Analysis (TGA/DTA), Photoluminescence (PL), Brunauer–Emmett–Teller Analysis (BET) and Scanning Electron Microscopy (SEM).