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1T-Phase Tungsten Chalcogenides (WS <sub/>2</sub> , WSe <sub/>2</sub> , WTe <sub/>2</sub> ) Decorated with TiO <sub/>2</sub> Nanoplatelets with Enhanced Electron Transfer Activity for Biosensing Applications
摘要： Layered transition metal dichalcogenides (TMDs) have received a great deal of attention due to fact that they have varied band gap, depending on their metal/chalcogen composition and on the crystal structure. Furthermore, these materials demonstrate great potential application in a myriad of electrochemical technologies. Heterogeneous electron transfer (HET) abilities of TMD materials toward redox-active molecules occupy a key role in their suitability for electrochemical devices. Herein, we introduce a promising biosensing strategy based on improved heterogeneous electron transfer rate of WS2, WSe2, and WTe2 nanosheets exfoliated using tert-butyllithium (t-BuLi) and n-butyllithium (n-BuLi) intercalators decorated with vertically aligned TiO2 nanoplatelets. By comparison of all the nanohybrids, decoration of TiO2 on t-BuLi WS2 (TiO2@t-BuLi WS2) results in the fastest HET rate of 5.39 × 10?3 cm s?1 toward ferri/ferrocyanide redox couple. In addition, the implications of decorating tungsten dichalcogenides (WX2) with TiO2 nanoplatelets in enzymatic biosensor applications for H2O2 detection are explored. TiO2@t-BuLi WS2 outperforms all other nanohybrid counterparts and is demonstrated to be an outstanding sensing platform in enzyme-based biosensor with wide linear range, low detection limit, and high selectivity. Such conceptually new electrocatalytic detection systems shall find the way to the next generation biosensors.
关键词： heterogeneous electron transfer,H2O2 detection,nanosheets,TiO2 nanoplatelets,transition metal dichalcogenides
更新于2025-09-04 15:30:14
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Tuning the Potential of Electron Extraction from Microbes with Ferrocene‐Containing Conjugated Oligoelectrolytes
摘要： Synthetic systems that facilitate electron transport across cellular membranes are of interest in bio-electrochemical technologies such as bio-electrosynthesis, waste water remediation, and microbial fuel cells. The design of second generation redox-active conjugated oligoelectrolytes (COEs) bearing terminal cationic groups and a π-delocalized core capped by two ferrocene units is reported. The two COEs, DVFBO and F4-DVFBO, have similar membrane affinity, but fluorination of the core results in a higher oxidation potential (422 ± 5 mV compared to 365 ± 4 mV vs Ag/AgCl for the neutral precursors in chloroform). Concentration-dependent aggregation is suggested by zeta potential measurements and confirmed by cryogenic transmission electron microscopy. When the working electrode potential (ECA) is poised below the oxidation potential of the COEs (ECA = 200 mV) in three-electrode electrochemical cells containing Shewanella oneidensis MR-1, addition of DVFBO and F4-DVFBO produces negligible biocurrent enhancement over controls. At ECA = 365 mV, DVFBO increases steady-state biocurrent by 67 ± 12% relative to controls, while the increase with F4-DVFBO is 30 ± 5%. Cyclic voltammetry supports that DVFBO increases catalytic biocurrent and that F4-DVFBO has less impact, consistent with their oxidation potentials. Overall, electron transfer from microbial species is modulated via tailoring of the COE redox properties.
关键词： conjugated oligoelectrolytes,bio-electrochemical systems,transmembrane electron transfer,exoelectrogenic microbes,redox-active molecules
更新于2025-09-04 15:30:14
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Magnesium and nitrogen co-doped carbon dots as fluorescent probes for quenchometric determination of paraoxon using pralidoxime as a linker
摘要： Carbon dots codoped with magnesium and nitrogen (Mg,N-CDs) were synthesized via a one-step microwave-assisted method. They display blue fluorescence (with excitation/emission peaks at 380/460 nm and a 33% quantum yield) and possess high dispersity in aqueous solution. The fluorescence of the Mg,N-CDs is highly sensitive to paraoxon in the presence of pralidoxime (PAM) acting as the linking agent. Electron transfer from Mg,N-CDs to paraoxon in the presence of PAM leads to the fluorescence quenching of Mg,N-CDs. The concentration of paraoxon is determined by measuring the quenching efficiency of the Mg,N-CD-PAM assay system. Fluorescence drops with increasing concentrations of paraoxon in the 0.005–3.0 μM range, and the limit of detection is 0.87 nM. The method is highly selective for paraoxon even in the presence of possible interferences. Real sample study of tap and river water showed the assay to have good repeatability and accuracy.
关键词： Quantum yield,Oxime,Electron transfer,Fluorescence quenching,Organophosphorus pesticides
更新于2025-09-04 15:30:14
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Adsorption properties of O2 on the unequal amounts of binary co-doped graphene by B/N and P/N: A density functional theory study
摘要： Graphene acts as an advanced substrate material, and it has been used as an electrode in fuel cells because it can efficiently adsorb oxygen molecules. In this study, density functional theory (DFT) calculation has been performed to exactly simulate the adsorption and dissociation of oxygen molecules on the XY3-co-doped graphene. The results show that the positively charged P and B atoms act as active sites for oxygen adsorption on the surface of graphene. In addition, PN3-G and NP3-G exhibit higher catalytic activity than the other samples because of the facile transfer of electrons from the highest occupied molecular orbital (HOMO) of O2 to the orbital above the Fermi level in the samples. More interestingly, excessive adsorption leads to the direct dissociation of oxygen molecules and making further dissociation difficult. In conclusion, the adsorption of oxygen molecules at the hollow sites on the PN3-G and NP3-G occurs via the formation of a triangular ring or trans-formation into O2? is proposed as the optimal strategy because these routes are thermodynamically favorable and the associated energy barrier is low. Furthermore, after dissociation, it was found that the oxygen atoms preferably approach the P atom. This work may be useful as a reference for future experimental studies to develop effective metal-free catalysts for fuel-cell cathodes.
关键词： Density functional theory (DFT),XY3 co-doping,Graphene,Electron transfer,Adsorption
更新于2025-09-04 15:30:14
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Understanding Biophotocurrent Generation in Photosynthetic Purple Bacteria
摘要： Establishing an efficient extracellular electron transfer (EET) process between photo-electroactive microorganisms and an electrode surface is critical for the development of photo-bioelectrocatalysis. Soluble and immobilized redox mediators have been applied with purple bacteria Rhodobacter capsulatus for this purpose. However, detailed information on its EET with an electrode surface is not available and, therefore, choice of mediators has been by trial and error. Herein, we experimentally evaluated the capability of different soluble, quinone-based redox mediators to support EET and compared the experimental data with a computational model based on density functional theory calculations. We show that computed electrochemical redox properties of redox mediators in a lipophilic environment correlate to EET processes of Rhodobacter capsulatus, suggesting that intermembrane mediator characteristics are more diagnostic than redox properties of the mediators in an aqueous solution, and that the limiting electron transfer step takes place in the lipophilic membrane of the bacterial cells. This knowledge provides critical insight into designing future mediated bioelectrocatalysis systems.
关键词： quinones,photo-bioelectrocatalysis,lipophilic membrane,Rhodobacter capsulatus,rate determining step,extracellular electron transfer
更新于2025-09-04 15:30:14