Electrophotocatalysis: Cyclic Voltammetry as an Analytical Tool

Application of Biosensors in Detecting Breast Cancer Metastasis

Breast cancer has garnered global attention due to its high incidence worldwide, and even more noteworthy is that approximately 90% deaths due to breast cancer are attributed to cancer metastasis. Therefore, the early diagnosis of breast cancer metastasis holds significant importance for reducing mortality outcomes. Biosensors play a crucial role in the early detection of metastatic breast cancer due to their advantages, such as ease of use, portability, and real-time analysis capabilities. This review primarily described various types of sensors for detecting breast cancer metastasis based on biomarkers and cell characteristics, including electrochemical, optical, and microfluidic chips. We offered detailed descriptions of the performance of these various biosensors and made comparisons between them. Furthermore, we described the pathology of breast cancer and summarized commonly used biomarkers for metastatic breast cancer. Finally, we discussed the advantages of current-stage biosensors and the challenges that need to be addressed, as well as prospects for their future development.

Photosensitized Radical-Anion-Driven Metal-Free Selective Reduction of Aldehydes Using Graphene Oxide as an Electron Relay Mediator under Visible Light

Despite the modern boost, developing a new photocatalytic system for the reduction of aldehydes is still challenging due to their high negative reduction potential. Herein, we have used a metal-free photoinduced electron-transfer system based on a cheap and readily available organic dye eosin Y (EY), graphene oxide (GO), and ammonium oxalate (AO) for photocatalytic reduction of structurally diverse aldehydes under sustainable conditions. The protocol shows remarkable selectivity for the photocatalytic reduction of aldehydes over ketones. The decisive interaction of GO and AO with the various states of EY (ground, singlet, triplet, and radical anions), which are responsible for the commencement of the reaction, was examined by various theoretical, optical, electrochemical, and photo-electrochemical studies. The synergetic system of GO, EY, and AO is appropriate for enhancing the separation efficiency of visible-light-induced charge carriers. GO nanosheets act as an electron reservoir to accept and transport photogenerated electrons from the photocatalytic system to the reactant. The reduction of the GO during the process ruled out the back transfer of photoexcited charges. Control experiments explained that the reaction involves two stages: electron transfer and protonation. This process eliminates the necessity of precious-metal-based photocatalysts or detrimental sacrificial agents and overcomes the redox potential limitations for the photoreduction of aldehydes.

Photoinduced Charge Transfer from Quantum Dots Measured by Cyclic Voltammetry

Measuring and modulating charge-transfer processes at quantum dot interfaces are crucial steps in developing quantum dots as photocatalysts. In this work, cyclic voltammetry under illumination is demonstrated to measure the rate of photoinduced charge transfer from CdS quantum dots by directly probing the changing oxidation states of a library of molecular charge acceptors, including both hole and electron acceptors. The voltammetry data demonstrate the presence of long-lived charge donor states generated by native photodoping of the quantum dots as well as a positive correlation between driving force and rate of charge transfer. Changes to the voltammograms under illumination follow mechanistic predictions from the E_rC_i' zone diagram, and electrochemical modeling allows for measurement of the rate of productive electron transfer. Observed rates for photoinduced charge transfer are on the order of 0.1 s^-1, which are distinct from the picosecond dynamics measured by conventional transient optical spectroscopy methods and are more closely connected to the quantum yield of light-mediated chemical transformations.

Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity*

Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2 )-N and C(sp2 )-O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.

How Radical Are "Radical" Photocatalysts? A Closed-Shell Meisenheimer Complex Is Identified as a Super-Reducing Photoreagent

Super-reducing excited states have the potential to activate strong bonds, leading to unprecedented photoreactivity. Excited states of radical anions, accessed via reduction of a precatalyst followed by light absorption, have been proposed to drive photoredox transformations under super-reducing conditions. Here, we investigate the radical anion of naphthalene monoimide as a photoreductant and find that the radical doublet excited state has a lifetime of 24 ps, which is too short to facilitate photoredox activity. To account for the apparent photoreactivity of the radical anion, we identify an emissive two-electron reduced Meisenheimer complex of naphthalene monoimide, [NMI(H)]^-. The singlet excited state of [NMI(H)]^- is a potent reductant (-3.08 V vs Fc/Fc⁺), is long-lived (20 ns), and its emission can be dynamically quenched by chloroarenes to drive a radical photochemistry, establishing that it is this emissive excited state that is competent for reported C-C and C-P coupling reactivity. These results provide a mechanistic basis for photoreactivity at highly reducing potentials via singlet excited state manifolds and lays out a clear path for the development of exceptionally reducing photoreagents derived from electron-rich closed-shell anions.

Mechanochemical synthesis of MAPbBr3/carbon sphere composites for boosting carrier-involved superoxide species

Lead halide perovskites MAPbX₃ (MA = CH₃NH₃ or Cs; X = I, Br, Cl) are well considered to be potential candidates for photocatalytic reaction due to its excellent photoelectrical properties, but they still suffer from the low charge separation efficiency and slow catalytic reaction dynamics. To tackle the drawbacks, herein, MAPbBr₃/carbon sphere (CS) composite photocatalysts using glucose as the carbon source were elaborately designed and fabricated via a dry mechanochemical grinding process. The interfacial interaction Pb-O-C chemical bonds were constructed between MAPbBr₃ and the carbon sphere surface containing organic functional groups. By optimizing the content of CSs, the enhanced photocatalytic degradation kinetic rate of Malachite Green (MG) pollutants (92% within 20 min) for MAPbBr₃/CS_x (x = 17 wt.%) is about 3.6-fold of that for pristine MAPbBr₃, which is attributed to the corporative adsorption and enhanced carrier transportation and separation of MAPbBr₃/CS_x. Furthermore, the possible degradation mechanism was proposed on basis of the electrochemical, mass spectrometry and optical characterization results. Owing to the robust interfacial interaction, effective electron extraction rate (k_et = 4.6 × 10⁷ sec^-1) from MAPbBr₃ to CS can be established, which driven oxygen activation where superoxide radicals (•O₂^-) played an important role in MG degradation. It is expected that mechanochemistry strategy may provide a new route to design efficient lead halide perovskite-carbon or metal oxide or sulfide composite photocatalysts.

A Review of the Use of Carbon Nanotubes and Graphene-Based Sensors for the Detection of Aflatoxin M1 Compounds in Milk

This paper presents a comprehensive review of the detection of aflatoxin compounds using carbon allotrope-based sensors. Although aflatoxin M1 and its derivative aflatoxin B1 compounds have been primarily found in milk and other food products, their presence above a threshold concentration causes disastrous health-related anomalies in human beings, such as growth impairment, underweight and even carcinogenic and immunosuppressive effects. Among the many sensors developed to detect the presence of these compounds, the employment of certain carbon allotropes, such as carbon nanotubes (CNTs) and graphene, has been highly preferred due to their enhanced electromechanical properties. These conductive nanomaterials have shown excellent quantitative performance in terms of sensitivity and selectivity for the chosen aflatoxin compounds. This paper elucidates some of the significant examples of the CNTs and graphene-based sensors measuring Aflatoxin M1 (ATM1) and Aflatoxin B1 (AFB1) compounds at low concentrations. The fabrication technique and performance of each of the sensors are shown here, as well as some of the challenges existing with the current sensors.

Unveiling Potent Photooxidation Behavior of Catalytic Photoreductants

We describe a photocatalytic system that reveals latent photooxidant behavior from one of the most reducing conventional photoredox catalysts, N-phenylphenothiazine (PTH). This aerobic photochemical reaction engages difficult to oxidize feedstocks, such as benzene, in C(sp²)-N coupling reactions through direct oxidation. Mechanistic studies are consistent with activation of PTH via photooxidation and with Lewis acid cocatalysts scavenging inhibitors inextricably formed in this process.