Behavior Of Carriers Research Articles

Ordered mesoporous silica and carbon as controlled release systems for cephalexin: Influence of surface modification and porosity

This study compares two in vitro loading and release systems for the antibiotic cephalexin (CFX), based on ordered mesoporous silica (SBA-15) and carbon (CMK-5) materials, both pure and modified with 3-aminopropyltriethoxysilane. Drug loading was performed using the adsorption method under constant conditions (pH: 6, T: 30°C, and t: 8 h), and the release mechanisms were investigated at gastric and intestinal pH to understand the phenomena involved in the oral delivery of CFX studied. The results revealed a higher adsorption capacity of CMK-5 due to its microporosity and π-π stacking interactions compared to SBA-15. Furthermore, the presence of functional groups prevented the formation of crystalline phases by adsorption on the external surface. A reduction in the release rate of CFX was observed with both carriers, governed by a Fickian diffusion mechanism. Notably, CMK-5 exhibited a higher release rate at gastric pH compared to SBA-15, while the opposite was true at intestinal pH. These findings provide deeper insights into the behavior of carriers with different chemical compositions in antibiotic release, suggesting their potential as an alternative to address issues associated with the dosing frequency of these drugs.

Preparation of carbon dot/polyaniline composites as voltage based dielectric material for capacitor applications

Polyaniline-carbon dot (CD/PANI) composites were prepared via in-situ oxidative polymerization of aniline in the presence of carbon dots, with specific concentrations carefully controlled during synthesis. The composite was characterized using spectroscopic (FT-IR), morphological (TEM, SEM) and electrical methods. Impedance analysis was employed to investigate the transport behavior of charge carriers in the frequency range of 500 Hz to 10 MHz at 25 °C. This study provides a comprehensive analysis of the dielectric properties of the CD/PANI composite, including dielectric constant, dielectric loss, loss factor, AC conductivity, admittance, impedance, and Cole–Cole plots. The dielectric constant of the CD/PANI composite was 6.97 for 1 kHz at 0.5 V and 12.87 for 1 kHz at 5 V. The values indicate that the increase in the dielectric constant of nanocomposite with increasing voltage. This suggests that CD/PANI composite is a dielectric material whose dielectric constants are controlled by applied voltage. Notably, the dielectric constant increased with rising applied voltage and decreased with increasing frequency. Current-voltage (I-V) measurements revealed that the composite's dielectric parameters could be tuned by varying the applied DC voltage, suggesting its potential as a voltage-dependent dielectric (VDD) material for capacitor applications. Furthermore, the enhanced electrical conductivity indicates that the CD/PANI composite is a promising candidate for next-generation dielectric devices.

Carbon Nanotube-Phenyl Modified g-C3N4: A Visible Light Driven Efficient Charge Transfer System for Photocatalytic Degradation of Rhodamine B.

In this study, we report the synthesis and characterization of a novel photocatalyst composite composed of functionalized carbon nanotubes (f-CNT) and phenyl-modified graphitic carbon nitride (PhCN). The incorporation of the phenyl group extends the absorption range into the visible spectrum compared to pure g-C3N4. Additionally, the formation of the heterostructure in the f-CNT/PhCN composite exhibits improved charge transfer efficiency, facilitating the separation and transfer of photogenerated electron-hole pairs and reducing recombination rates. The photocatalytic performance of this composite was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. The f-CNT/PhCN composite exhibits remarkable efficiency in degrading RhB, achieving 60% degradation after 4 h, and 100% after 24 h under low-power white LED excitation. This represents a substantial improvement over the non-functionalized CNT/PhCN composite, which shows much lower performance. In contrast, pure PhCN demonstrates very little activity. Structural and optical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and UV-Vis spectroscopy. Time-resolved photoluminescence measurements were used to study the behavior of photoexcited carriers, confirming that the composite improves charge transfer efficiency for photogenerated carriers by approximately 30%. The results indicate that the functionalization of CNTs significantly enhances the photocatalytic properties of the composite, making f-CNT/PhCN a promising candidate for environmental remediation applications, particularly in the degradation of organic pollutants in wastewater.

Electric-Field-Driven Redistribution of Carriers on Catalyst Particles to Improve Photocatalytic Performance.

The photocatalytic performance is primarily determined by carrier separation efficiency. Applying electric fields to enhance carrier separation efficiency and thereby boost catalytic performance has emerged as a promising approach. However, the carrier behavior on catalyst particles under electric fields was still hardly acknowledged. Herein, using single-molecule fluorescence microscopy with high spatiotemporal resolution, the redistribution behavior of carriers on catalyst particles under an electric field was visualized for the first time, which was closely related to the direction and intensity of the electric field. Single-molecule kinetics of the photocatalytic redox reactions induced by carriers have been further obtained, and the results showed that the external electric field had an obvious regulating role in the conversion process and desorption process in this work, which was attributed to the dynamic redistribution of carriers. The improvement of photocatalytic hydrogen evolution reaction (HER) activity further supports the impact of the external electric field on photocatalysis. This work offers new insight into the microscopic regulation mechanism of photocatalytic activity by electric fields and provides new methods for studying the structure-activity relationship in photocatalytic processes.

Charge Dynamics and Defect States under “Spot‐Light”: Spectroscopic Insights into Halide Perovskite Solar Cells

Halide perovskite solar cells (PSCs) have shown remarkable power conversion efficiencies. However, the inherent defect issues of perovskite materials still limit their performance and long‐term stability, resulting in lifespans far from commercial standards. With their noninvasive approach to probing the electronic and vibrational properties of materials, spectroscopic techniques have become crucial tools for uncovering and understanding defect states and complex charge carrier dynamics in halide perovskites. This review explores the application of various advanced spectroscopic techniques in PSCs to elucidate the complex behaviors of charge carriers within PSCs. These techniques reveal detailed temporal and spatial distributions of charge carriers, enabling precise analysis of defect impacts and interfacial charge transfer processes. By integrating spectroscopic data, it is possible to more accurately identify and mitigate defect‐induced nonradiative recombination and charge transfer, thereby enhancing the stability and efficiency of PSCs. This comprehensive spectroscopic understanding is crucial for developing innovative technologies to accelerate the commercial viability of PSCs.

Exploring Ultrafast Carrier Dynamics in Photoelectrochemical Water Splitting Using Transient Absorption Spectroscopy

AbstractHydrogen fuel produced from water splitting using sunlight remains one of the cleanest and most sustainable energy sources. However, photoelectrochemical hydrogen production faces several challenges, including poor sunlight absorption, deficient charge carrier lifetime and transfer rates, and very sluggish kinetics of the water oxidation half‐reaction. To address these challenges, researchers have concentrated on enhancing the efficiency of photoelectrochemical water splitting. A critical factor in this enhancement is a deeper understanding of the fundamental processes involved in photoabsorption and the subsequent oxidation evolution reaction. The advent of ultrafast lasers has enabled the detailed tracking of charge carriers within materials after sunlight absorption, including their separation and migration to the surface for water oxidation. Ultrafast transient absorption spectroscopy is a powerful technique that allows real‐time observation of the behavior of excited states and charge carriers on femtosecond to nanosecond timescales. Recent studies utilizing ultrafast transient absorption spectroscopy are explored to investigate the dynamics of charge carriers in photoelectrochemical water splitting, providing insights into the mechanisms that lead to the design of enhanced photoanodes with improved efficiency.

Defect Engineering Advances Thermoelectric Materials.

Defect engineering is an effective method for tuning the performance of thermoelectric materials and shows significant promise in advancing thermoelectric performance. Given the rapid progress in this research field, this Review summarizes recent advances in the application of defect engineering in thermoelectric materials, offering insights into how defect engineering can enhance thermoelectric performance. By manipulating the micro/nanostructure and chemical composition to introduce defects at various scales, the physical impacts of diverse types of defects on band structure, carrier and phonon transport behaviors, and the improvement of mechanical stability are comprehensively discussed. These findings provide more reliable and efficient solutions for practical applications of thermoelectric materials. Additionally, the development of relevant defect characterization techniques and theoretical models are explored to help identify the optimal types and densities of defects for a given thermoelectric material. Finally, the challenges faced in the conversion efficiency and stability of thermoelectric materials are highlighted and a look ahead to the prospects of defect engineering strategies in this field is presented.

Exciton Dissociation and Long‐Lived Delayed Components in High‐Efficiency Quasi‐Two‐Dimensional Green Perovskite Light‐Emitting Diodes

AbstractQuasi‐two‐dimensional (quasi‐2D) perovskites, consisting of multi‐quantum wells (MQWs) separated by organic intercalating cations, exhibit high luminescence efficiency while the photophysical processes involved remain partially obscure due to the uncertainty of the MQWs structure. Herein, a synergetic dual‐additive strategy is adopted to prepare quasi‐2D perovskite films, where 18‐crown‐6 and tris(4‐fluorophenyl)phosphine oxide are utilized to suppress the formation of low‐dimensional perovskites, diminish defect density, and enhance photoluminescence quantum yield to 93.7%. Notably, a long‐lived delayed component, spanning hundreds of microseconds, is identified for the first time in perovskite emitters, which correlates with exciton dissociation and recombination, and the differences in temperature‐dependent radiative lifetime of the delayed components match with the luminescence properties. Finally, benefiting from lower trap density and more efficient energy‐funneling, green PeLEDs treated with dual additives have achieved a high external quantum efficiency of 28.9% and a commendable operating half‐lifetime of 17.8 h at an initial brightness of 500 cd m−2. The observation of the long‐lived delayed components, coupled with insights into exciton dissociation, provides a profound and comprehensive understanding of the fundamental carrier behavior in perovskite emitters and establishes a direct correlation between the properties of perovskite emitters and their photophysical processes.

Re3P4@C/TiO2 Ohmic junction Boosts charge carrier separation for photocatalytic hydrogen evolution

Construction of heterostructures featuring a well-designed transport pathway is pivotal in regulating the behavior of charge carriers, thereby achieving boosted separation efficiency. One of the primary factors leading to poor charge transfer and separation efficiency in heterostructures lies in the presence of interface barriers that hinder their transfer. Establishing an Ohmic contact with a low energy barrier can significantly reduce charge transfer resistance during photocatalysis. In this contribution, we have successfully developed an Re3P4@C/TiO2 Ohmic junction for highly improved photocatalytic H2 evolution rate, which exhibited a 68-fold increase compared to pristine TiO2. Experimental results combined with density functional theory calculations confirm the successful construction of Ohmic junction, which effectively facilitates the separation and transfer of photogenerated charge carriers while prolongs their lifetimes. This heterojunction also enhances the adsorption capacity for reactants and thus promotes the surface photocatalytic reactions. This work provides valuable insights into novel Ohmic junction construction to improve the photocatalytic activity.

Enhancing Carrier Behavior via Controlled Molecular Film Formation Engineering Leads to Significant Improvement in Electroluminescence

AbstractThe quality of organic thin films critically influences carrier dynamics in organic semiconductors. In neat/doped films, even tiny voids can be penetrated by water or oxygen molecules to create charge‐trap states called water/oxygen‐induced traps that significantly hinder carrier mobility. While the water/oxygen‐induced traps in non‐doped films and crystalline states have been investigated comprehensively, there is a lack of thorough examination regarding their properties in the doped state. Therefore, there is a high demand for a molecular design strategy that effectively modulates the molecular stacking behavior in doped films and practical devices and enhances the quality of these films. Herein, we proposed a versatile molecular design principle that enables the formation of “nano‐cluster” structures on both the surface and interior of doped films in target molecule 10‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl)‐1′‐(4‐fluorophenyl)‐10H‐spiro[acridine‐9,9′‐xanthene] (DspiroO‐F‐TRZ), which is modified with a fluorophenyl group. These “nano‐cluster” structures exhibit more uniform shapes within doped films and effectively reduce defective state densities while enhancing carrier injection and transport properties, ultimately improving device performance. Notably, TADF‐OLED based on DspiroO‐F‐TRZ demonstrates nearly twice as much efficiency as its control counterpart due to contributions from ′nano‐cluster′ structure enhancements toward improved electroluminescence performance.

Enhancing Carrier Behavior via Controlled Molecular Film Formation Engineering Leads to Significant Improvement in Electroluminescence.

The quality of organic thin films critically influences carrier dynamics in organic semiconductors. In neat/doped films, even tiny voids can be penetrated by water or oxygen molecules to create charge-trap states called water/oxygen-induced traps that significantly hinder carrier mobility. While the water/oxygen-induced traps in non-doped films and crystalline states have been investigated comprehensively, there is a lack of thorough examination regarding their properties in the doped state. Therefore, there is a high demand for a molecular design strategy that effectively modulates the molecular stacking behavior in doped films and practical devices and enhances the quality of these films. Herein, we proposed a versatile molecular design principle that enables the formation of "nano-cluster" structures on both the surface and interior of doped films in target molecule 10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1'-(4-fluorophenyl)-10H-spiro[acridine-9,9'-xanthene] (DspiroO-F-TRZ), which is modified with a fluorophenyl group. These "nano-cluster" structures exhibit more uniform shapes within doped films and effectively reduce defective state densities while enhancing carrier injection and transport properties, ultimately improving device performance. Notably, TADF-OLED based on DspiroO-F-TRZ demonstrates nearly twice as much efficiency as its control counterpart due to contributions from 'nano-cluster' structure enhancements toward improved electroluminescence performance.

All‐Electronic Memristor Based on Charge Carrier Confinement in Bulk Semiconductor of Metal–Semiconductor–Metal Structure

AbstractMemristors have gained significant attention in recent years due to their potential applications in computing and memory technology by offering higher performance, lower power consumption, and increased storage capacity. In this paper, a new type of volatile memristor is presented by analyzing the dynamic behavior of charge carriers within a metal–semiconductor–metal (MSM) structure. It is shown that an all‐electronic memristor is achieved through the confinement of majority charge carriers within the bulk semiconductor by the favor of high barrier Schottky contacts. The findings reveal a remarkable current offset between forward and backward scans, along with exceptional current pulse consistency with a tunable current level using pulse frequency. These characteristics greatly simplify the process of designing electrical circuits incorporating this memristor variant. Furthermore, this research paves the way for the development of crystalline semiconductor‐based memristors. While various semiconductors with controllable doping densities can be considered as potential candidates for this type of memristor, the calculations using silicon demonstrate the integration of this semiconductor with the current technology holds significant promise for two terminal memristors.

Self-powered Schottky barrier photodetectors based on P3HT:PC61BM bulk heterojunction films

By employing the classic system poly(3-hexylthiophene-2,5-diyl): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM), organic bulk heterojunction films were applied on an indium tin oxide substrate using a one-step spin-coating method, without requiring any complex manufacturing processes, to obtain self-powered photodetectors (PDs) with a simple preparation process. The fullerene material was introduced to create a bulk heterojunction film with proper phase separation and greatly enrich the donor/acceptor dissociation interface, thus improving the high exciton binding energy and short exciton diffusion distance. The built-in electric field formed by the Schottky junction at the interface between the active layer and electrode can enhance the separation of excitons and the transport of charge carriers, realizing optical detection without external energy sources. Moreover, femtosecond transient absorption was employed to investigate the exciton dynamics in organic films and analyze the working mechanism of self-powered detection performance. The long-lived behavior of carriers and the formation of charge transfer states were further verified, which contributed to the enhanced performance of the device. As a result, the self-powered PD-based Schottky bulk heterojunction presents a high light on/off ratio of over 104 (0 V) and fast response speed with rise and decay times of 33 and 36 µs, respectively, under a 532 nm light illumination. These results provide theoretical and experimental verification of this technique for the development of self-powered PDs in the field of organic materials.

Unveiling full-dimensional distribution of trap states toward highly efficient perovskite photovoltaics

To gain a deep understanding and address key issues in perovskite photovoltaics, such as power conversion efficiency (PCE) and long-term stability, defect passivation and analysis of the device performance are required. Here, we proposed a non-contact characterization technique named scanning photocurrent measurement system (SPMS) for device surface detection, having conducted signal analysis and method adjustments based on perovskite photovoltaic devices. This technique enables the monitoring of minority carriers in the device, allowing for the investigation of carrier behavior based on photocurrent signals. By integrating SPMS with thermal conductance spectroscopy (TAS) and drive-level capacitance profiling (DLCP), we further simulated a spatial three-dimensional (3D) distribution of trap states in the device and analyzed the distribution of trap states matched with energy space. Through extensive case studies, we have validated the universality and accuracy of this method. The integration of trap state characterization techniques provides strong support for targeted defect passivation and performance evaluation of perovskite photovoltaic devices, yielding a highly efficient perovskite solar cell with PCE as high as 25.74%.

Reply to the “Comment on ‘Modification of Gas Sensitivity in ZnSnO3 Film from Carrier Behaviors: Derivation, Concentration, and Depletion’: Rather SnO2 than ZnSnO3”

Reply to the “Comment on ‘Modification of Gas Sensitivity in ZnSnO₃ Film from Carrier Behaviors: Derivation, Concentration, and Depletion’: Rather SnO₂ than ZnSnO₃”

Comment on “Modification of Gas Sensitivity in ZnSnO3 Film from Carrier Behaviors: Derivation, Concentration, and Depletion”: Rather SnO2 than ZnSnO3

Comment on “Modification of Gas Sensitivity in ZnSnO₃ Film from Carrier Behaviors: Derivation, Concentration, and Depletion”: Rather SnO₂ than ZnSnO₃

Precise control of photogenerated carrier behavior of zinc oxide through band reconstruction to enhance photocatalytic treatment of dye wastewater

In the field of photocatalytic treatment of dye wastewater, zinc oxide (ZnO) is a typical semiconductor photocatalyst, but it has some disadvantages such as wide band gap, low carrier yield and easy recombination. In this study, Cr-ZnO/N-CQDs catalyst was synthesised using the strategy of p-type doping and construction of Z-scheme heterojunction. The results showed that the removal rate of Cr-ZnO/N-CQDs for MB dye was 97.42 %, which was 70.56 % higher than that of ZnO, and was still 92.16 % after 5 cycles, and the TOC removal rate of methylene blue wastewater was 88.60 %. The reason for the enhanced photocatalytic activity of Cr-ZnO/N-CQDs is that the π* electron (e−) in the N-CQDs interact with the 3d orbitals of Cr-ZnO, so that e− is more easily transferred from the valence band of Cr-ZnO to the conduction band of N-CQDs. The band gap of p-type Cr-ZnO is narrowed, which makes its photogenerated carrier yield increase, hole concentration raise, and the adsorption capacity of H2O molecules reduce by 1.04 eV. The density functional theory calculation shows that the maximum Gibbs free energy of Cr-ZnO for the production of hydroxyl radical is 0.05 eV lower than that of ZnO. This study lays theoretical and practical foundation for the photocatalytic treatment of dye wastewater with ZnO.

Photocurrent EDMR Measurement and Carrier Behavior of TIPS-Pentacene Under FET Device Operation

Photocurrent EDMR Measurement and Carrier Behavior of TIPS-Pentacene Under FET Device Operation

Advances in the heterostructures for enhanced hydrogen production efficiency: a comprehensive review.

The growing global energy demand and heightened environmental consciousness have contributed to the increasing interest in green energy sources, including hydrogen production. However, the efficacy of this technology is contingent upon the efficient separation of charges, high absorption of sunlight, rapid charge transfer rate, abundant active sites and resistance to photodegradation. The utilization of photocatalytic heterostructures coupling two materials has proved to be effective in tackling the aforementioned challenges and delivering exceptional performance in the production of hydrogen. The present article provides a comprehensive overview of operational principles of photocatalysis and the combination of photocatalytic and piezo-catalytic applications with heterostructures, including the transfer behavior and mechanisms of photoexcited non-equilibrium carriers between the materials. Furthermore, the effects of recent advances and state-of-the-art designs of heterostructures on hydrogen production are discussed, offering practical approaches to form heterostructures for efficient hydrogen production.

Bi2SiO5 nanosheets as piezo-photocatalyst for efficient degradation of 2,4-Dichlorophenol

Piezo-photocatalysis is an effective solution for degrading organic pollutants. In this study, Bi2SiO5 nanosheets are successfully synthesized via a one-step hydrothermal method. The piezo-photocatalytic degrading mechanisms of 2,4-Dichlorophenol (2,4-DCP) on Bi2SiO5 nanosheets are thoroughly investigated through the integration of experimental study and density functional theory (DFT) calculations. Experimental results revealed outstanding piezoelectric properties for Bi2SiO5 nanosheets with a piezoelectric coefficient of 250 pC/N, outperforming previously reported piezo-photocatalysts. The degradation rate constant of 2,4-DCP on Bi2SiO5 nanosheets reached 0.0891 min−1 by piezo-photocatalysis, which is 17 and 1.8 times higher than that by solitary photo- and piezo-catalysis, respectively. Furthermore, DFT calculations for Bi2SiO5 explain the crucial role of piezoelectric effects in bending its band structure, regulating photogenerated carrier behaviors, and promoting reactive oxygen species (ROS) generation. Finally, the degradation pathways of 2,4-DCP on Bi2SiO5 nanosheets were revealed with details. The results of this study offer valuable insights for water treatment with piezo-photocatalysis.