Sensor surface via inspiration from Nature: The specific case of electron trapping in TiO2/WO3(∙0.33H2O) and reaction center/WO3(∙0.33H2O) systems

Bíborka Boga,István Székely,Monica Focșan,Monica Baia,Tibor Szabó,László Nagy,Zsolt Pap

doi:10.1016/j.apsusc.2021.151139

Bíborka Boga, István Székely + Show 5 more

Open Access

https://doi.org/10.1016/j.apsusc.2021.151139

Copy DOI

Abstract

In this work, reaction center protein (RC) isolated from Rhodobacter sphaeroides purple bacteria was coupled with WO3(∙0.33H2O) via physical adsorption, where vectorial electron transfer (from RCs towards the inorganic carrier) was demonstrated using flash kinetics and photoluminescence measurements. The efficiency of the interaction between RCs and WO3(∙0.33H2O) was correlated to the components’ surface charge at the working pH and the structural/morphological and surface properties of the inorganic carrier (e.g., anchoring capacity assured by HO, WO bonds). The role of WO3(∙0.33H2O) as final electron trap and charge separator was proven not only in RCs/WO3(∙0.33H2O) biohybrid systems but also in TiO2/WO3(∙0.33H2O) composites. The charge transfer in the inorganic composites was evaluated by monitoring the reverse process of the color reaction (W5+ → W6+) via diffuse reflectance spectroscopy (DRS) after a previous UV-A (320–400 nm) exposure. The efficiency of the charge transfer process in inorganic systems was correlated to the initial W5+ content of WO3(∙0.33H2O), followed by the photocatalytic efficiency evaluation of these inorganic composites under UV-A irradiation.

Highlights

The integration of biological components exploiting unique peculiarities and properly engineered structures has led to creating specific structures such as bio-hybrid actuators and biohybrid sensors, contributing significantly to a sustainable development [1,2]
The question would be: how can we monitor spectroscopically the charge transfer in the latter mentioned inorganic systems in the most convenient way? In this work, we propose the recording of the reflectance spectra (DRS) in the UV-Vis-NIR range at certain well-defined moments, because while the absorption maximum of W6+ centers is situated at 340 nm, this value is 970 nm in the case of W5+ centers [59]
This work can be considered as a comparative study of specific photoinducible WO3-based composites (biohybrid photosynthetic reaction center (RC)/WO3(∙0.33H2O) and inorganic TiO2/WO3(∙0.33H2O) systems), where the functionality of the final electron trap were analyzed and discussed from different point of views

Summary

Introduction

The integration of biological components exploiting unique peculiarities and properly engineered structures has led to creating specific structures such as bio-hybrid actuators and biohybrid sensors, contributing significantly to a sustainable development [1,2]. The absorption spectra of RC (in an equilibrium state and after excitation at λ excitation = 808 nm) in the range of 480-900 nm was recorded via a home-made Vis-NIR experimental setup equipped with a white light of DHL2000 light source as measuring light and CCD detector of a spectrophotometer (both from Avantes) and with a laser diode (2 W, 808 nm, Roithner). The details regarding this experimental setup were already described [31]. Merck-Hitachi D-7000 chromatograph and L-4250 UV-Vis detector are some important constitutive elements of HPLC

Results and Discussion

REPEATED WASHING STEPS

Charge transfer

Conclusions