Microstructural tuning and band gap engineering of calcium hydroxides: a novel approach by pH variation

Abstract

Here we report a simple, inexpensive, energy benign, yet novel pH‐driven chemical precipitation technique to achieve microstructural and band gap engineering of calcium hydroxide nanoparticles (CHNPs). The chemical precipitation route involved the use of 0.4–1.6 M Ca(NO3)2.4H2O solutions as the precursor and 1 M NaOH solution as the precipitator. The simple variation in precursor molarity induces a pH change from about 12.4 to 11.3 in the reactant solution. The CHNPs characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and ultraviolet–visible (UV–Vis) spectroscopy techniques confirm a jump of nanocrystallite size from ~50–70 nm with a concomitant reduction of direct optical band gap energy from ~5.38–5.26 eV. The possible mechanisms that could be operative behind obtaining microstructurally tuned (MT)‐CHNPS and band gap engineering (BGE) are discussed from both theoretical and physical process perspectives. Furthermore, the implications of these novel results for possible futuristic applications are briefly hinted upon.

Smart and intelligent optical materials for sensing applications

“…They reported that the synthesized CDs had a linear range 0.00080-0.0050 mg/ml and an LOD of 0.00030 mg/ml. Akash et al [47]…”

“…They reported that the synthesized CDs had a linear range 0.00080–0.0050 mg/ml and an LOD of 0.00030 mg/ml. Akash et al [47] synthesized Ca(OH) 2 via a chemical precipitation method and size modification of nanocrystallites from 5.38 to 5.26 eV just by monitoring the pH. Moreover, the rise in the nanocrystallite size decreased the bandgap energy from 5.38 to 5.26 eV for the calcium hydroxide NPs (CHNPs).…”