Journal of Electroanalytical Chemistry
– Non-enzymatic photoelectrochemical glucose sensors based on BiVO4 coatings were developed.
– BiVO4 coatings were deposited on fluoride-doped tin oxide (FTO) substrate by sol-gel method.
– The effect of polyethylene glycol, urea, citric acid and PVA on photoelectrochemical activity was investigated.
– Results revealed that morphology of BiVO4 coatings plays critical role for sensitivity of sensor.
– Sensitivity of some BiVO4 coatings towards glucose was 0.0056 mA cm-2 mM-1 –and limit of detection – 6.87 μM.
BiVO4 is known as a promising material for the design of analytical systems dedicated for non-enzymatic photoelectrochemical (PEC) glucose determination. In this work BiVO4 coatings were deposited on fluoride-doped tin oxide substrate by simple sol-gel method. The influence of different stabilizers, such as polyethylene glycol, urea, citric acid and polyvinyl alcohol (PVA) on the morphology and photoelectrochemical activity of the BiVO4 coatings was investigated. X-ray diffraction, scanning electron microscopy, UV-vis optical absorbance and photoluminescence techniques were used to evaluate structural and optical properties of BiVO4 films. PEC performance was characterized by means of voltammetry, electrochemical impedance spectroscopy and chronoamperometry. It is shown that the combination of urea and polyvinyl alcohol leads to the formation of BiVO4 coatings with lower charge transfer resistance as well as higher affinity towards adsorption of glucose, resulting in higher sensitivity of these photoelectrodes in glucose sensing. Sensitivity of BiVO4 coatings synthesized with urea (Bi_Urea) or with urea and PVA (Bi_Urea_PVA) towards glucose was 0.0033 mA cm-2 mM-1 and 0.0056 mA cm-2 mM-1, respectively. The limit of detection was estimated to be 7.94μM for Bi_Urea and 6.87μM for Bi_Urea_PVA.
BiVO4 thin films on fluoride-doped tin oxide (FTO) substrates (5 – 7 Ω/sq) were prepared by aqueous sol-gel method. BiVO4 sol-gel, denoted as Bi_Urea, was prepared by mixing of 5 mmol of Bi(NO3)3×5H2O, 5 mmol of NH4VO3 and 2.5 mmol of urea in 23.3 wt % HNO3. The solution was stirred for about 24 h at room temperature until a homogeneous transparent blue sol-gel was formed.
The same procedure was applied for the preparation of other BiVO4 sol-gels denoted as Bi_PEG and Bi_CA, where 10 mmol of PEG or 10 mmol of citric acid were used as chelating agents instead of urea, respectively.
Sol-gel containing urea and polyvinyl alcohol (Bi_Urea_PVA) was prepared by the same steps, just 2.6 wt % of PVA and 0.5 ml of acetic acid were added at the end of the synthesis. Prepared sol-gels were used for the deposition of BiVO4 thin layers on FTO substrate by dip-coating technique (Nadetech, ND-DC 11/1). Before the coating procedure FTO substrates were cut into 1 × 2.5 cm2 slides and washed in acetone, ethanol, and deionized water for 15 min under ultrasonification. The dip-coating procedure was performed at the speed of 100 mm min-1 for immersing and pulling out. After immersion, FTO substrate was kept in prepared sol-gel for 60 s. In order to obtain 2 layers of BiVO4 films, dip-coating procedure was repeated two times. After the deposition of each layer the samples were annealed at 450 °C for 2 h in air (1 °C min-1).
Keywords: Bismuth Vanadate (BiVO4); sol-gel deposition; photoelectrochemical glucose sensor; photoelectrochemistry; photoluminescence; UV-vis optical absorbance.