RESUMO
Although photoelectrochemical (PEC) enzyme biosensors based on visible-light detection would have a high practical value, their development has been limited by the weak visible-light response of available photoactive substrates. Here, to enhance the visible-light response of a photoelectric substrate, a TiO2 nanorods (NRs)/TiO2 quantum dots (QDs)/polydopamine (PDA)/glucose oxidase nanocomposite was prepared via hydrothermal synthesis, followed by photopolymerization. TiO2 QDs with strong light absorption and excellent photocatalytic activity were introduced between the TiO2 NRs and the PDA. An efficient electron transport interface that formed as a result of the combination of the TiO2 NRs, TiO2 QDs, and the PDA could not only transfer electrons quickly and orderly, but also substantially improve the response of the TiO2 NRs under visible light. Through a series glucose detection, a sensor based on the nanocomposite was found to exhibit superior sensing performance under visible light with a sensitivity of 4.63 µA mM-1 cm-2, a linear response over the concentration 0.1-4 mM, and a detection limit of 8.16 µM. This work proposes a biosensor that can detect under visible light, thereby expanding the application range of PEC enzyme biosensors.
Assuntos
Técnicas Biossensoriais , Nanotubos , Pontos Quânticos , Técnicas Eletroquímicas , Glucose Oxidase , Indóis , Luz , Polímeros , TitânioRESUMO
In the field of photoelectrochemical (PEC) enzyme biosensors, constructing efficient photoelectrodes, in which the recombination of photogenerated carriers is an important factor affecting the performance, is of great significance. Herein, to enhance the separation efficiency of photogenerated carriers, titanium dioxide (TiO2) nanosheet (NS)/bismuth oxyiodide (BiOI) NS/glucose oxidase (GOx) composites were prepared via hydrothermal and solvothermal methods. Single-crystal anatase TiO2 NSs with a high percentage of (001) facets lead to better photocarrier separation due to heterojunctions between facets. After coupling with BiOI NSs, the photoelectrochemical performance of the electrode was greatly improved. The photogenerated electrons from TiO2 and BiOI gathered at TiO2 (101) and were exported through the fluorine-doped tin oxide (FTO) substrate to generate electrical signals. Photogenerated holes were transferred to TiO2 (001) and BiOI to participate in the enzymatic reaction, showing the outstanding separation of electrons and holes. The prepared TiO2 NS/BiOI NS/GOx glucose biosensor achieved satisfactory results, with sensitivity of 14.25 µA mM-1 cm-2, a linear measurement range of 0-1 mM, and a limit of detection (3S/N) of 0.01 mM in phosphate buffered saline (PBS) at a pH of 7.4. The mechanism for the efficient separation of photogenerated carriers based on the facet heterojunctions introduced in this paper also provides new insights into other optoelectronic biosensors.
RESUMO
Developing stable photoelectrochemistry (PEC) glucose biosensors with high sensitivity and a low detection limit is highly desirable in the biosensor field. Herein, a highly sensitive and stable enzymatic glucose PEC biosensor is rationally designed and fabricated using a TiO2NTs/Au/Pt/GOx electrode. First, we prepared one-dimensional TiO2 nanotube arrays which could realize the orthogonalization of the light-incident direction and the carrier diffusion direction via anodization. Subsequently, we used the method of photoassisted deposition for anchoring Pt nanoparticles on TiO2NTs after electrodepositing Au nanoparticles. Among them, Au nanoparticles promote light absorption via the surface plasmon resonance effect and the separation of photogenerated carriers through forming a Schottky junction. Moreover, the Pt nanoparticles on the electrode surface can react with hydrogen peroxide (H2O2) generated from glucose (Glu) oxidation by glucose oxidase (GOx), accelerating the electron-transfer process during glucose oxidation and greatly improving the sensitivity of the glucose biosensor. As a result, TiO2NTs/Au/Pt/GOx exhibited excellent PEC performance, achieving a high sensitivity of 81.93 µA mM-1 cm-2 and a low detection limit (1.39 µM), far exceeding the performance of TiO2NTs/M/GOx (M = Au, Pt). Therefore, the introduction of Pt nanoparticles as active substances to promote enzymatic reactions is important for designing high-performance enzyme biosensors.
RESUMO
Although jarosite and visible light are important factors for the formation of acid mine drainage (AMD), the effects of combined jarosite and visible light on chalcopyrite biodissolution have not been explored until now. In order to fill this knowledge gap, the combined effects of jarosite and visible light on chalcopyrite dissolution mediated by Acidithiobacillus ferrooxidans were investigated. The results indicated that jarosite and visible light could significantly accelerate chalcopyrite biodissolution, thus releasing more copper ions, iron ions and producing more acid. This in turn suggests enhanced generation of AMD under these conditions. Biodissolution results, mineral surface morphology, mineralogical phase and elemental composition analyses revealed that the promotion of chalcopyrite dissolution by additional jarosite and visible light was mainly attributed to the acceleration of ferric iron/ferrous iron cycling and the inhibition of the formation of a passivation layer (jarosite and Sn2-/S0) on the surface of chalcopyrite. This study provides a better understanding of the effects of jarosite and visible light on chalcopyrite biodissolution. In the future, the influences of jarosite and visible light on chalcopyrite dissolution should be considered in AMD evaluation to ensure reliability.