Charge Transfer Process Research Articles

Cu single atoms regulating nitrogen active-sites of g-C3N4 for sodium ion storage

Nitrogen-rich material of graphitic carbon nitride (g-C3N4) with cost-effectiveness and easy accessibility has been considered as one of the most promising anode materials for sodium ion batteries (SIBs). However, the excessive presence of non-stable nitrogen sites in low crystallinity carbon nitrides would result in significant irreversibility, inadequate ion conductivity and structural instability, thereby limiting its practical application. Herein, a novel low-temperature strategy is proposed to stabilize the g-C3N4 by modulating the nitrogen configuration with single-atoms copper. The formed copper single atoms serving as anchors effectively regulate the coordination environment of nitrogen atoms in carbon nitride, thereby constructing stable nitrogen active sites for Na+ storage and conductive networks for rapid Na+ transport. Therefore, the Cu1.0/NC exhibits superior capacity (350.4 mAh g−1 at 50 mA g−1), exceptional rate performance (252.3 mAh g−1 at 1000 mA g−1), and long-cycle stability (capacity retention rate of 80.3 % after 1000 cycles at 5A g−1). Furthermore, in-situ Raman, ex-situ XANES and XPS technologies jointly reveal that the Cu atoms significantly influence the charge transfer process of Na+ and change the storage mode of sodium through redox effects during the sodiation/desodiation process. This work proves that single-atom engineering is a novel and feasible strategy to optimize the high-performance electrode materials for rechargeable batteries.

Photophysical mechanism study of photophysical properties of new red BODIPY chromophores with or without methyl substitution

The relationship between the photophysical properties and structure of BODIPY derivatives always has attracted much attention. Two new BODIPY derivative chromophores with phenyl group substitutions at meso-/6- positions, with or without methyl substitutions at 1/3/5/7 positions were investigated by ways of combination of multiple experimental techniques and theoretical methods. The chromophore without methyl substitutions has a larger Stokes shift and better viscosity sensitivity compared to the other one. The intrinsic reason is that considerable charge transfer between the BODIPY core and the 6- position group is achieved in chromophore. However, this charge transfer process is severely weakened, if 1-/3-/5-/7- methyl substitutions existing, via restricting rotation between the core and side groups. At the same time, the non-radiative process is amplified significantly in chromophore without methyl substitution and the fluorescence efficiency decrease from 51.7% (with methyl substitutions) to 1.84% (without methyl substitutions) in DMSO. Quantum calculations indicate the presence or absence of methyl substitution can change both the shape and height of the torsional potential energy curve of the side groups, thereby affecting the fluorescence quantum yield and viscosity response performance of chromophores. Our work can provide foundation and ideas for designing and optimizing BODIPY derivatives with objective photophysical properties.

A-Site Engineering of the High-Entropy Perovskite Pr0.4La0.4Ba0.4Sr0.4Ca0.4Fe2O5+δ Cathode for Intermediate-Temperature SOFCs.

Mixed-oxygen ionic and electronic conduction is crucial for the cathode materials of solid oxide fuel cells, ensuring high efficiency and low-temperature operation. However, the electronic and oxygen ionic conductivity of traditional Fe-based layered perovskite cathode materials is low, resulting in insufficient oxygen reduction reactivity. Herein, a type of high-entropy perovskite oxide consisting of five equimolar metals, Pr0.4La0.4Ba0.4Sr0.4Ca0.4Fe2O5+δ (PLBSCF), a high-performance cobalt-free cathode derived from the PrBaFe2O5+δ (PBF), is proposed. Such A-site engineering could not only increase the oxygen vacancy concentration of PLBSCF but also give higher conductivity than PBF, thus significantly reducing the polarization impedance of the symmetric cell to only 0.052 Ω·cm2 at 750 °C. The good output performance of a single cell is also realized. The peak power density of the single cell with PLBSCF-Ce0.9Gd0.1O2-δ (GDC) as the cathode at 750 °C was 0.853 W·cm-2. Additionally, the single cell with the PLBSCF cathode exhibits a good durable performance of 100 h at 750 °C. Combining the distribution of relaxation time analysis, it can be seen that the enhancement of the oxygen reduction reaction is due to the reduction of intermediate-frequency and low-frequency resistance, indicating an improvement in the charge transfer process and adsorption/dissociation process of molecular oxygen.

Facile synthesis, enhanced annealing-structural investigation and supercapacitive potentials of NiFe2O4 spinel nanopowder

Herein, we examined and optimized the influence of annealing temperature on microstructural and electrochemical charge storage properties of spinel NiFe2O4 nanopowder synthesized from a simple one-pot sol-gel route. Microstructural techniques encompassing Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffractometry, and Fourier transform infra-red spectroscopy indicate the resulting powder are composed of spinel NiFe2O4 nanoparticle with metal oxygen vibration, crystal properties and lattice strain, all dependent on annealing temperature. Electrochemical charge storage performance of the electrode fabricated from the synthesized material were investigated with the aid of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The obtained results showed that the charge storage performance and rate capability of NiFe2O4 electrode is dependent on the annealing temperature. The study also showed that the electrode from the material annealed at 400 °C demonstrated optimum electrochemical charge storage performance having exhibited optimum specific capacitance and capacity values of 1128 Fg−1 and 58 mAh g−1 at 5 mVs−1 scan rate and 0.5 Ag−1 current density, respectively. The electrode EIS fitted equivalent circuit values were also found dependent on annealing temperature indicating the charge transfer process and rate capability of spinel NiFe2O4 nano-powder can be tailored by simply varying the annealing temperature. The study demonstrates cheap route by which spinel NiFe2O4 powder can be prepared. It also unveils the effect annealing temperature on the microstructural build-up and electrochemical charge storage performance of the material.

Red‐Shifting ESIPT Fluorescence by Site‐Specific Functionalization in 2‐(2’‐hydroxyphenyl)benzazole Derivatives

AbstractWe describe the synthesis, full photophysical study, and ab initio calculations of 2‐(2’‐hydroxyphenyl)benzazole (HBX) fluorophores substituted, at the meta position of the phenol group, by pyridine derivatives. HBX are commonly used as model dyes to study the stimuli‐induced modulation of the Excited State Intramolecular Proton Transfer (ESIPT) process. The meta‐substituted fluorophores reported herein, display a photophysical profile different from the previously reported ortho‐ and para‐substituted HBO pyridine isomers. Indeed, while all dyes undergo spontaneous deprotonation in neutral conditions, leading to highly emissive anionic species; upon protonation, ortho‐ and para‐pyridine substitution leads to resonance‐stabilized keto isomers, formed after ESIPT. Protonated meta derivatives, unable to stabilize their excited structure by such electronic delocalization process, display sizable intramolecular charge transfer (ICT) processes, translating into significantly redshifted emission. In addition, all dyes present a strong emission intensity, not only in neutral and acidic solutions, but also in the solid‐state. The nature of the emissive transitions was confirmed in each case by theoretical calculations combining Time‐Dependent Density Functional Theory (TD‐DFT) and second‐order Coupled Cluster (CC2) methods.

Harnessing Electro-Descriptors for Mechanistic and Machine Learning Analysis of Photocatalytic Organic Reactions.

Photocatalysis has emerged as an effective tool for addressing the contemporary challenges in organic synthesis. However, the trial-and-error-based screening of feasible substrates and optimal reaction conditions remains time-consuming and potentially expensive in industrial practice. Here, we demonstrate an electrochemical-based data-acquisition approach that derives a simple set of redox-relevant electro-descriptors for effective mechanistic analysis and performance evaluation through machine learning (ML) in photocatalytic synthesis. These electro-descriptors correlate to the quantification of shifted charge transfer processes in response to the photoirradiation and enabled construction of reactivity diagram where high-yield reactive "hot zones" can reflect subtle changes of the reaction system. For the model reaction of photocatalytic deoxygenation reaction, the influence of varying carboxylic acids (substrate A, oxidation-intended) and alkenes (substrate B, reduction-intended) and varying reaction conditions on the reaction yield can be visualized, while mathematical analysis of the electro-descriptor patterns further revealed distinct mechanistic/kinetic impacts from different substrates and conditions. Additionally, in the application of ML algorithms, the experimentally derived electro-descriptors reflect an overall redox kinetic outcome contributed from vast reaction parameters, serving as a capable means to reduce the dimensionality in the case of complex multiparameter chemical space. As a result, utilization of electro-descriptors enabled efficient and robust quantitative evaluation of chemical reactivity, demonstrating promising potential of introducing operando-relevant experimental insights in the data-driven chemistry.

Unlocking the Potential of Deep Eutectic Solvents and Ligand-to-Metal Charge Transfer Processes: A Reusable Iron-and-UV-Based System for Sustainable C-C Bond Formation.

Catalytic C-H functionalization has provided new opportunities to access novel organic molecules more sustainably and efficiently. However, these procedures typically rely on precious metals or complex organic catalysts as well as on hazardous solvents or reaction conditions. Herein, a pioneering methodology for direct C-C bond formation enabled by Ligand-to-Metal Charge Transfer (LMCT) and mediated by UV irradiation has been developed using Deep Eutectic Solvents (DESs) as sustainable reaction media. This direct C-H bond functionalization via a radical addition to electrophiles was successfully confirmed over a broad scope of substrates. More importantly, this is the first example of photocatalytic C-C bond formation in DESs. An inexpensive and abundant iron catalyst (FeCl3) was used under air and mild conditions. Different functional groups were well tolerated obtaining promising results that were comparable to those reported in the literature. Additionally, the reaction medium along with the catalyst could be reused for up to 5 consecutive cycles without a significant loss in the reaction outcome. Several green metrics were calculated and compared to those of conventional procedures, revealing the advantages of using DESs.

On the timescale of electrochemical processes

There is an ongoing discussion in the literature if simulations of electrochemical reactions should be performed at constant electrode potential. In this context we examine the timescales at which electrochemical processes take place. We take molecular dynamics simulation of hydrogen desorption from graphene and gold as examples. Charge transfer processes are governed by the accompanying solvent reorganization, and their speed is determined by the solvent dynamics, whose timescale is of the order of picoseconds — the exact value depends on the details of the system. In contrast, double layer relaxation, which controls the electrode potential, requires times of the order of nanoseconds. We suggest that this difference is due to the fact, that solvent reorganization is a local phenomenon, while double layer relaxation involves the whole solvent between working and reference electrodes, which is of macroscopic dimensions. We conclude, that simulations of electrochemical reactions should not be performed at constant potential. In contrast, calculations for thermodynamic properties can be performed at constant potential or at constant charge, since the question of timescales does not arise in this case.

2D/2D Heterojunctions of Layered TiO2 and (NH4)2V3O8 for Sunlight-Driven Methylene Blue Degradation

Photocatalysis based on titanium dioxide (TiO2) has become a promising method to remediate industrial and municipal effluents in an environmentally friendly manner. However, the efficiency of TiO2 is hampered by problems such as rapid electron–hole recombination and limited solar spectrum absorption. Furthermore, the sensitization of TiO2 through heterojunctions with other materials has gained attention. Vanadium, specifically in the form of ammonium vanadate ((NH4)2V3O8), has shown promise as a photocatalyst due to its ability to effectively absorb visible light. However, its use in photocatalysis remains limited. Herein, we present a novel synthesis method to produce lamellar (NH4)2V3O8 as a sensitizer in a supramolecular hybrid photocatalyst of TiO2–stearic acid (SA), contributing to a deeper understanding of its structural and magnetic characteristics, expanding the range of visible light absorption, and improving the efficiency of photogenerated electron–hole separation. Materials, such as TiO2–SA and (NH4)2V3O8, were synthesized and characterized. EPR studies of (NH4)2V3O8 demonstrated their orientation-dependent magnetic properties and, from measurements of the angular variation of g-values, suggest that the VO2+ complexes are in axially distorted octahedral sites. The photocatalytic results indicate that the 2D/2D heterojunction layered TiO2/vanadate at a ratio (1:0.050) removed 100% of the methylene blue, used as a model contaminant in this study. The study of the degradation mechanism of methylene blue emphasizes the role of reactive species such as hydroxyl radicals (•OH) and superoxide ions (O2•−). These species are crucial for breaking down contaminant molecules, leading to their degradation. The band alignment between ammonium vanadate ((NH4)2V3O8) and TiO2–SA, shows effective separation and charge transfer processes at their interface. Furthermore, the study confirms the chemical stability and recyclability of the TiO2–SA/(NH4)2V3O8 photocatalyst, demonstrated that it could be used for multiple photocatalytic cycles without a significant loss of activity. This stability, combined with its ability to degrade organic pollutants under solar irradiation, means that the TiO2–SA/(NH4)2V3O8 photocatalyst is a promising candidate for practical environmental remediation applications.

Understanding the Adsorption Mechanism of BTPA, DEPA, and DPPA in the Separation of Malachite from Calcite and Quartz: DFT and Experimental Studies

The relationship between the structure of bis (2,4,4-trimethylpentyl) phosphinic acid (BTPA), diethyl phosphinic acid (DEPA), and diphenyl phosphinic acid (DPPA) on the flotation performance of malachite was investigated. Through a series of flotation experiments, density functional theory (DFT) calculations, and surface analysis methods, we aimed to deeply understand the microscopic mechanism of the interactions between these collectors and the malachite surface. The experimental results showed that BTPA exhibited excellent selectivity and flotation performance for malachite in the pH range of 5.0–11.0, significantly better than DEPA and DPPA. Surface analysis evidence from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) further confirmed the chemical adsorption characteristics of BTPA on the malachite surface. DFT calculations revealed that the adsorption capacity of BTPA on the malachite surface exceeds that of DEPA and DPPA. Electron transfer analysis, especially through frontier molecular orbital theory, differential charge density, PDOS, and COHP analysis, indicated that the charge transfer process from the s orbitals of oxygen atoms in the collectors to the d orbitals of copper atoms on the mineral surface is the decisive factor for the adsorption strength.

Influence of Ho, Gd, La Doping on Grain-Grain Boundary Characteristics and Minimization of Leakage Current in Nickel Ferrites

This study explores the impact of doping with Ho, Gd, and La on sol-gel-derived nickel ferrites through a comprehensive analysis using various analytical techniques. The combination of X-ray diffraction (XRD) analysis, X-ray fluorescence (XRF) spectra analysis, impedance spectroscopy, and I-V analysis enables a detailed exploration of the structural, compositional, and electrical characteristics of the samples. Williamson-Hall plots in XRD analysis reveal crucial insights into grain and grain boundary impacts, revealing a shift in trends for doped samples indicative of tensile strain and underscores the influence of dopant ions on lattice distortion. XRF study confirms the elemental composition of the samples, validating the experimental approach. Impedance spectroscopy sheds light on conduction mechanisms and charge transfer processes, while the modulus study identifies distinct relaxation peaks corresponding to grain and grain boundary relaxation mechanisms. IV analysis demonstrates a significant reduction in leakage current with rare Earth element doping, suggesting promising applications.

Physical vapour deposition fabrication of MoO3-based photoanode for water splitting to generate hydrogen.

MoO3 thin film was fabricated on an indium tin oxide substrate using the physical vapor deposition technique. X-ray diffraction and scanning electron microscopy study to investigate surface morphology, grain size, and surface structure, which are critical for absorbing solar spectra in water splitting for hydrogen energy generation. Ultraviolet-visible spectroscopy was used to confirm the absorption of solar spectra and the percentage of transmittance. Fourier-transform infrared analysis provided the functional groups present in the deposited thin film. The Tauc plot was used to determine the thin-film band gap, which allowed for the analysis of charge carrier transitions from the conduction band to the valence band. Electrochemical impedance spectroscopy investigations confirmed the charge transfer processes to the counter electrode and electrolyte interfaces. The observed low curve for MoO3 indicated low resistance and allowed efficient charge transfer. Linear sweep voltammetry analysis was used to measure photocurrent and solar light to hydrogen emission when the thin film was exposed to solar spectra. The thin film's observed hydrogen emission rate was 3731.74 mol g-1 h-1, and the STH% of MoO3 was found to be 0.345% at 0.8 V. These findings highlight the promising potential of MoO3 as a material for hydrogen energy generation using solar light.

Dynamic in situ reconstruction of NiSe2 promoted by interfacial Ce2(CO3)2O for enhanced water oxidation

Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity. Herein, we present a synthesis of NiSe2-Ce2(CO3)2O heterostructure and demonstrate the efficacy of interfacial Ce2(CO3)2O in promoting the formation of catalytically active centers to improve oxygen evolution activity. In-situ Raman spectroscopy shows that incorporation of Ce2(CO3)2O into NiSe2 causes a cathodic shift of the Ni2+→Ni3+ transition potential. Operando electrochemical impedance spectroscopy reveals that strong electronic coupling at heterogeneous interface accelerates charge transfer process. Furthermore, density functional theory calculations suggest that actual catalytic active species of NiOOH transformed from NiSe2, which is coupled with Ce2(CO3)2O, can optimize electronic structure and decrease the free energy barriers toward fast oxygen evolution reaction (OER) kinetics. Consequently, the resultant NiSe2-Ce2(CO3)2O electrode exhibits remarkable electrocatalytic performance with low overpotentials (268/304 mV @ 50/100 mA cm−2) and excellent stability (50 mA cm−2 for 120 h) in the alkaline electrolyte. This work emphasizes the significance of modulating the dynamic changes in developing efficient electrocatalyst.

Corrosion inhibition by amino acid functionalized chitosan derivative at Q235 steel/ H2SO4 solution interface: Experimental and surface investigations

The present work describes the chitosan derivative development using amino acid (Vanilline) (CASB). The developed compound was used as Q235 steel corrosion inhibitor in 1 M H2SO4 using weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). The EIS results disclosed that CASB inhibits corrosion via charge transfer process. The PDP data indicated that CASB suppresses both the cathodic and anodic corrosion process. The maximum inhibition efficiency of CASB (100 mg/L) and KI+75 mg/L (CASB) are 95.8 % and 97.9 % respectively. The adsorption of CASB over the Q235 steel surface was confirmed using X-ray photoelectron spectroscopy (XPS). Morphological changes on the steel surface were monitored by scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The Langmuir adsorption isotherm provided best fitting of experimental data. Density functional theory (DFT) and Molecular dynamic simulation (MD) suggests that neutral forms of CASB have more adsorption ability than neutral forms.

The Role of Intraligand Charge Transfer Processes in Iridium(III) Complexes with Morpholine-Decorated 4'-Phenyl-2,2':6',2″-terpyridine.

To investigate the impact of the electron-donating morpholinyl (morph) group on the ground- and excited-state properties of two different types of Ir(III) complexes, [IrCl3(R-C6H4-terpy-κ3N)] and [Ir(R-C6H4-terpy-κ3N)2](PF6)3, the compounds [IrCl3(morph-C6H4-terpy-κ3N)] (1A), 4[Ir(morph-C6H4-terpy-κ3N)2](PF6)3 (2A), [IrCl3(Ph-terpy-κ3N)] (1B) and [Ir(Ph-terpy-κ3N)2](PF6)3 (2B) were obtained. Their photophysical properties were comprehensively investigated with the aid of static and time-resolved spectroscopic methods accompanied by theoretical DFT/TD-DFT calculations. In the case of bis-terpyridyl iridium(III) complexes, the attachment of the morpholinyl group induced dramatic changes in the absorption and emission characteristics, manifested by the appearance of a new, very strong visible absorption tailing up to 600 nm, and a significant bathochromic shift in the emission of 2A relative to the model chromophore. The emission features of 2A and 2B were found to originate from the triplet excited states of different natures: intraligand charge transfer (3ILCT) for 2A and intraligand with a small admixture of metal-to-ligand charge transfer (3IL-3MLCT) for 2B. The optical properties of the mono-terpyridyl iridium(III) complexes were less significantly impacted by the morpholinyl substituent. Based on UV-Vis absorption spectra, emission wavelengths and lifetimes in different environments, transient absorption studies, and theoretical calculations, it was demonstrated that the visible absorption and emission features of 1A are governed by singlet and triplet excited states of a mixed MLLCT-ILCT nature, with a dominant contribution of the first component, that is, metal-ligand-to-ligand charge transfer (MLLCT). The involvement of ILCT transitions was reflected by an enhancement of the molar extinction coefficients of the absorption bands of 1A in the range of 350-550 nm, and a small red shift in its emission relative to the model chromophore.

Coordination engineering of defective F and N co-doped carbon dots anchored silver nanoparticles for boosting oxygen reduction reaction

The carbon-based catalysts exhibit excellent electrocatalytic and stable performance toward oxygen reduction reaction (ORR), which are expected to replace expensive and scarce Pt-based catalysts. However, how to regulate the interaction between silver and carrier carbon dots (CD) to improve electrocatalytic performance toward oxygen reduction reaction (ORR) and stability, has not been systematically studied. In this study, we in-situ synthesized fluorine and nitrogen co-doped CD anchoring Ag nanoparticles by UV irradiation reduction method. The peak potential, onset-potential and half-wave potential of F, N-CD@Ag-0.1 are 0.85 V, 1.056 V, and 0.9 V, respectively, indicating outstanding ORR performance. The current density of F, N-CD@Ag-0.1 remains 97.5 % after 50, 000 s, showing more excellent stability than Pt/C. The impressive ORR catalytic activity and stability of F, N-CD@Ag-0.1 could be attributed to the strong anchoring effect of nitrogen-doped CD on Ag. This effect leads to a significant interaction and charge transfer between Ag and CD, thereby enhancing the charge transfer process during the catalytic reaction. This project aims to design a carbon dot/silver composite catalyst with high ORR catalytic performance and favorable stability. The implementation of this project provides good theoretical guidance for the design of carbon nanomaterial-based catalytic systems.

Optically Active Defect Engineering via Plasma Treatment in a MIS‐Type 2D Heterostructure

AbstractAt the interface of 2D heterostructures, the presence of defects and their manipulation play a crucial role in the interfacial charge transfer behavior, further influencing the device functionality and performance. In this study, the impact of deliberately introduced photo‐active defects in the h‐BN layer on the interfacial charge transfer and photoresponse performance of a metal‐insulator‐semiconductor type heterostructure device is explored. The formation and concentration of defects are qualitatively controlled using an inductive coupled plasma treatment method, as evidenced by enhanced h‐BN defect emission and more efficient optically induced doping of graphene at the graphene/h‐BN interface. Besides, the use of the h‐BN layer between graphene and WS2 not only suppresses charge carriers in the dark state, but also promotes the separation of photo‐generated electron‐hole pairs and interfacial charge transfer due to the existence of defect levels, leading to orders of magnitude improvement in the light on/off ratio and self‐driving performance of the heterostructure photodetector. This strategy of controlling defect states in the insulating layer provides a new approach to optimize the charge transfer processes at the 2D interfaces, so as to expand its potential applications in the fields of electronic and optoelectronic devices.

Rational design of g-C3N4-based photocatalysts with intramolecular donor-acceptor structures for deep oxidation of emerging organic micropollutants

An in-situ route for the fabrication of intramolecular electron donor-acceptor (D-A) structured g-C3N4 photocatalysts is developed by the preorganization of urea with the precursor of electron donor units, such as 4-iodobenzaldehyde, 5-bromo-2-thiophenaldehyde and 5-bromo-2-furaldehyde, followed by thermal polymerization. In the resulting benzene unit-, thiophene unit- and furan unit-based D-A structured g-C3N4 photocatalysts, namely, BHCNx, SCNx, and OCNx, the incorporated electron donor units (i.e., benzene units, thiophene units and furan units) link with the electron acceptors (i.e., heptazine units) through CN and CN covalent bonds. In comparison of bulk g-C3N4, all D-A structured g-C3N4 display notably enhanced visible-light photocatalytic oxidation activity in the degradation of emerging organic micropollutants, p-nitrophenol (PNP) and methylparaben (MPB), in which the apparent first-order kinetic constant of the optimized BHCN2, SCN2, and OCN2 is 1.6, 3.0 and 6.8 times higher than bulk g-C3N4 for PNP degradation and 1.9, 3.4 and 2.6 times higher than bulk g-C3N4 for MPB degradation. Importantly, the micropollutants can be not only degraded but also mineralized completely. The catalysts are also robust in the removal of mixed emerging organic micropollutants in pharmaceutical wastewater, exhibiting potential of dealing with organic micropollutants in wastewater. Mechanism studies reveal that the unique intramolecular charge transfer process in the catalysts enhances visible-light harvesting capacity, boosts directional transfer of the photogenerated charges and increases adsorption towards oxygen molecules. These collective improvements can maximum utilization the photogenerated electrons and holes to yield plentiful reactive oxygen species for deep oxidization of the pollutants.

N-rich carbon nanosphere as fluorescent nanoprobe for intracellular iron

Nitrogen rich carbon nanoparticles are known to provide higher fluorescence stokes shift, and thereby are potential candidates for fluorescent sensors. Herein, a facile one-step hydrothermal synthesis is reported for N-rich carbon nanospheres (G-CNS) from caffeine and o-phenylenediamine as precursors. The as-synthesized G-CNS showed high fluorescence with λem at 509 nm, with a highly selective fluorescence turn-off response towards Fe2+/Fe3+, rendering these carbon nanospheres as potential candidates to detect intracellular labile iron pool in live cells. The intracellular labile iron pool in iron-overloaded cells was sensed using the synthesized G-CNS. Mechanistically, the fluorescence quenching via dynamic pathway involves the formation of an excited state charge transfer process, which undergoes non-radiative decay.

Unexpected large charge transfer rate mediated by adenine in twisted DNA structure.

DNA exhibits remarkable charge transfer ability, which is crucial for its biological functions and potential electronic applications. The charge transfer process in DNA is widely recognized as primarily mediated by guanine, while the contribution of other nucleobases is negligible. Using the tight-binding models in conjunction with first-principles calculations, we investigated the charge transfer behavior of homogeneous GC and AT pairs. We found that the charge transfer rate of adenine significantly changes. With overstretching, the charge transfer rate of adenine can even surpass that of guanine, by as much as five orders of magnitude at a twist angle of around 26°. Further analysis reveals that it is attributed to the turnover of the relative coupling strength between homogeneous GC and AT base pairs, which is caused by the symmetry exchange between the two highest occupied molecular orbitals of base pairs occurring at different twist angles. Given the high degree of flexibility of DNA in vivo and in vitro conditions, these findings prompt us to reconsider the mechanism of biological functions concerning the charge transfer in DNA molecules and further open the potential of DNA as a biomaterial for electronic applications.