In the field of environmental remediation and sustainability, the built-in electric field of ferroelectrics has been regarded as a promising strategy to enhance photocatalytic (PC) dye degradation and photoelectrochemical (PEC) water splitting. Here, we report on Ce-doped BaTiO 3 (BT) nanoassemblies prepared by a hydrothermal route. X-ray diffraction reveals the phase transformation from tetragonal to cubic on the sintering temperature and Ce doping. From X-ray photoelectron spectroscopy (XPS), the oxygen vacancies are found to be maximum for 4 mol % of Ce concentration. The ferroelectric and piezoelectric measurements disclose a higher remnant polarization (1.76 μC cm −2 ) and d 33 coefficient (15 pCN −1 ) at 4 mol % due to the built-in electric field. Thus, we observed a significantly improved PC dye degradation with the rate constant (k) of 0.0139 m −1 (methylene blue), 0.0147 m −1 (methyl violet) at 4 mol %, and 0.0117 m −1 (congo red) at 6 mol %. PEC water splitting showed that the photoanode fabricated at 4 mol % of Ce exhibits enriched photocurrent density (1.45 mA cm −2 ), impressive early onset of water oxidation (−0.504 V), and hydrogen gas evolution (22.50 μmol h −1 cm −2 ). Poling studies display a significant enhancement in both PC and PEC properties indicating the built-in electric field assisted activities of Ce-doped BT nanoassemblies. The underlying mechanisms behind the degradation efficiency and improved photocurrent density are established via the built-in electric field facilitating charge carrier detachment and transport as evidenced by the photoluminescence decay and XPS valence band spectra.

Graphene oxide (GO) was synthesized from graphite through a chemical oxidation process and heat treated at 110 and 220 C in a vacuum atmosphere. The partial reduction and sp 3 to sp 2 phase transition of GO was characterized by powder X-ray diffraction, Fourier-transform infrared, micro Raman, ultraviolet-visiblenear infrared spectroscopy techniques. Dielectric properties of pristine GO and heat-treated GO were studied in the frequency range 10 2 to 10 6 Hz at 27 C. Hydroxyl, carboxyl functional groups removed GO after 220 C heat treatment, expressed higher electrical conductivity, dielectric constant and dielectric loss in the order of 10 À2 S m À1 , 10 3 and 10 5 respectively than the pristine GO (10 À6 S m À1 , 10 1 and 10 1 ).Pristine and heat-treated GO were coated on the partially cladding removed poly-methyl methacrylate optical fiber and used as fiber optic gas sensors. GO and heat treated GO coated fibers were responsive to detect ammonia, ethanol and methanol vapors from 0 to 500 ppm at 27 C. Sensitivities of GO coated fiber optic sensor were calculated as À0.32, À0.26 and À0.20 counts per ppm for ammonia, ethanol and methanol vapors respectively. The effect of functional groups on dielectric and gas sensing properties of GO was investigated and reported.

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