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A pyrophosphatase biosensor with photocurrent analysis
摘要： A light-induced photochemical biosensor was developed for the analysis of inorganic pyrophosphatase (PPase). PPase hydrolyzes pyrophosphate (PPi) into two independent o-phosphate ions. Two PPi units can chelate a copper ion (Cu2+), forming a PPi–Cu2+–PPi complex and preventing the Cu2+ triggers other reactions. A transparent indium tin oxide (ITO) electrode was coated with a layer of CdS quantum dots (QDs), and then 3,4-diaminobenzoic acid (DBA) was deposited as the anchor. A solution of the PPi–Cu2+–PPi complex and o-phenylenediamine (OPD) was mixed with the analytical sample and then a drop of the mixture was placed on the modified ITO electrode. In the absence of PPase, no reaction occurred between OPD and DBA. A photocurrent was obtained upon excitation of the CdS QDs under light. In the presence of PPase, Cu2+ was released from the complex, triggering the reaction of OPD with DBA on the electrode surface, thereby shielding the CdS QDs from excitation by the light. The observed photocurrent decreased. The difference in the two measured photocurrents corresponded to the activity of PPase. This photochemical biosensor had excellent sensitivity for PPase in the range from 0.8 to 5000 mU, with a limit of detection of 0.41 mU.
关键词： Quantum dots,Biosensor,o-Phenylenediamine,Photocurrent,PPase
更新于2025-09-23 15:23:52
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Flexible photoluminescent humidity sensing material based on electrospun PVA nanofibers comprising surface-carboxylated QDs
摘要： Flexible humidity-sensitive materials have drawn increasing attention due to their vital function in monitoring ambient humidity for tactile sensors, allowing them to approach the functionality of human skin. In this work, an electrospun polyvinyl alcohol (PVA)-based nanofiber film comprising surface-carboxylated CdSe/CdxZn1-xS quantum dots (QDs) is fabricated as a high-performance flexible humidity sensing material, based on the relationship between its photoluminescence (PL) and the humidity. The as-prepared film shows excellent PL-humidity linearity, a wide sensing range from 10% to 90% relative humidity, a relatively fast response time, good recoverability, and flexibility. The humidity sensing mechanism can be attributed to the breaking and reforming of hydrogen bonds and proton transfer occurring at the PVA-QD interfaces. This flexible humidity-sensitive material is believed to be a good candidate for humidity-sensitive components in electronic skin.
关键词： Humidity sensing,Polymer,Photoluminescence,Quantum dots
更新于2025-09-23 15:23:52
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Model To Determine a Distinct Rate Constant for Carrier Multiplication from Experiments
摘要： Carrier multiplication (CM) is the process in which multiple electron?hole pairs are created upon absorption of a single photon in a semiconductor. CM by an initially hot charge carrier occurs in competition with cooling by phonon emission, with the respective rates determining the CM e?ciency. Up until now, CM rates have only been calculated theoretically. We show for the ?rst time how to extract a distinct CM rate constant from experimental data of the relaxation time of hot charge carriers and the yield of CM. We illustrate this method for PbSe quantum dots. Additionally, we provide a simpli?ed method using an estimated energy loss rate to estimate the CM rate constant just above the onset of CM, when detailed experimental data of the relaxation time is missing.
关键词： carrier multiplication,quantum yield,quantum dots,semiconductor,electron?hole pairs
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Accelerated Aging Procedures of Bending Piezoelectric Structures Using Electrical Stress Induced Approaches
摘要： Efficient AgInGaS quantum dot-based energy harvesting devices using electrical and mechanical approaches
关键词： energy harvesting,quantum dots,optoelectronics,AgInGaS,mechanical stress
更新于2025-09-23 15:22:29
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Separation of Spectroscopically Uniform Nanographenes
摘要： Excitation-dependent photoluminescence (PL) is a well-known property of graphene quantum dots (GQDs). For the development of carbon-based photofunctional materials, GQDs possessing uniform PL properties are in high demand. A protocol has been established to separate spectroscopically uniform lipophilic GQD-1 a from a mixture of GQD-1 mainly composed of GQD-1 a and GQD-1 b. The mixture of GQD-1 was synthesized through the reaction of p-methoxybenzylamine with GQD-2 prepared from graphite by common oxidative exfoliation. Size-exclusion chromatography gave rise to GQD-1 a and GQD-1 b, with diameters of 19.8 and 4.9 nm, respectively. Large GQD-1 a showed that the PL was fairly independent of the excitation wavelengths, whereas the PL of small GQD-1 b was dependent on excitation. The excitation-dependent nature is most likely to be associated with the structures of sp2 domains on the graphene surfaces. The large sp2-conjugated surface of GQD-1 a is likely to possess well-developed and large sp2 domains, the band gaps of which do not significantly vary. The small sp2-conjugated surface of GQD-1 b produces small sp2-conjugated domains that generate band gaps differing with domain sizes.
关键词： photochemistry,luminescence,quantum dots,graphene,chromatographic separation
更新于2025-09-23 15:22:29
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Impedance Spectroscopy: A Versatile Technique to Understand Solution-Processed Optoelectronic Devices
摘要： Solution-processed optoelectronic devices based on conjugated polymers, colloidal quantum dots (CQDs), halide perovskites, and so on are now emerging as a new-generation semiconductor technology which prevails its conventional counterparts in terms of low fabrication cost, ease of scalable manufacturing, and abundant material designability. However, the solution-processed thin films obtained through spin-coating, spray, inkjet printing, and doctor blading usually suffer from low film quality and a high defect density especially at the interfaces of different functional layers. Currently, the most significant subject is to address the non-ideal interfaces for achieving improved performance of the devices. Impedance spectroscopy (IS) is a universal technique that can help to examine the charge behavior at the interfaces in an electrochemical or solid-state multilayered device. Owing to its ability to elucidate the charge transfer, charge transport, and accumulation within the interfaces of electrochemical or multilayered devices with minimal effects to the devices themselves, the use of IS has increased vividly in the last decades. This review provides the basic principles of IS and its applications on solution-processed optoelectronic devices.
关键词： optoelectronic devices,metal halide perovskites,quantum dots,impedance spectroscopy,solution processing
更新于2025-09-23 15:22:29
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Interfacial Charge Transfer in 0D/2D Defect-Rich Heterostructures for Efficient Solar-Driven CO2 Reduction
摘要： Two-dimensional graphitic carbon nitride (g-C3N4) has been widely explored as a promising photocatalyst for solar CO2 conversion. However, rapid charge recombination and low visible-light utilization are severely detrimental to photocatalytic CO2 conversion. Zero-dimensional/two-dimensional (0D/2D) heterostructures are considered the promising materials with size tunability and enhanced charge separation efficiency for photocatalysis. Herein, a 0D/2D heterostructure of oxygen vacancy-rich TiO2 quantum dots confined in g-C3N4 nanosheets (TiO2-x/g-C3N4) was prepared by in-situ pyrolysis of NH2-MIL-125 (Ti) and melamine. Charge dynamics analysis by time-resolved photoluminescence (tr-PL) and femtosecond and nanosecond pump-probed transient absorption (TA) spectra revealed that charges transfer occured from 2D-g-C3N4 to 0D-TiO2 at an ultrafast subpicosecond time scale (<1 ps) through the intimate interface. The overall fast decay of the charge carriers was attributed to interfacial charge transfer, which was accompanied by recombination relaxation mediated by shallow trapped sites. Ultrafast interfacial charge transfer greatly promoted charge separation as well as electrons in shallow trapped sites were easily trapped by CO2. In addition, combing with the synergetic advantage of strong visible light absorption, high CO2 adsorption and large surface area, TiO2-x/g-C3N4 exhibited a superior CO evolution rate of 77.8 μmol g?1 h?1, roughly 5 times that of pristine g-C3N4 (15.1 μmol g?1 h?1). This work provides in-depth insights into optimizing the heterojunction for robust solar CO2 conversion.
关键词： TiO2 quantum dots,solar CO2 reduction,charge transfer,0D/2D heterostructures,oxygen vacancy
更新于2025-09-23 15:22:29
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Ultrasmall MoS2 Nanodots Doped Biodegradable SiO2 Nanoparticles for Clearable FL/CT/MSOT Imaging Guided PTT/PDT Combination Tumor therapy
摘要： Recently, we developed ultrasmall molybdenum disulfide (MoS2) quantum dots for computed tomography (CT) and multispectral optoacoustic tomography (MSOT) image-guided photothermal therapy (PTT). But, due to the rapid body elimination and the limited blood circulation time, the tumor uptake of the dots is low. In our study, this problem was solved via designing an amino modified biodegradable nanomaterial based on MoS2 quantum dots doped disulfide-based SiO2 nanoparticles (denoted MoS2@ss-SiO2) for multimodal application. By integrating the MoS2 quantum dots into clearable SiO2 nanoparticles, this nanoplatform with an appropriate particle size can not only degrade and excrete in a reasonable period induced by the redox-responsive with the glutathione (GSH), but also exhibits a high tumor uptake due to the longer blood circulation time. Moreover, hyaluronic acid (HA) and chlorin e6 (Ce6) were adsorbed on the outer shell for the tumor targeting effect and photodynamic therapy, respectively. So this biodegradable and clearable theranostic nanocomposite applicable in integrated fluorescence(FL)/CT/MSOT imaging guided combined photothermal therapy (PTT) and photodynamic therapy (PDT) is very optimistic in biomedical applications in the future.
关键词： biodegradable,multi-modal imaging,clearable,combination tumor therapy,ultrasmall MoS2 quantum dots
更新于2025-09-23 15:22:29
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Low-frequency spectroscopy for quantum multilevel systems
摘要： A periodically driven quantum system with avoided level crossing experiences both nonadiabatic transitions and wave-function phase changes. These result in coherent interference fringes in the system’s occupation probabilities. For qubits, with repelling energy levels, such interference, named after Landau-Zener-Stückelberg-Majorana, displays arc-shaped resonance lines. In the case of a multilevel system with an avoided level crossing of the two lower levels, we demonstrate that the shape of the resonances can change from convex arcs to concave heart-shaped and harp-shaped resonance lines. Indeed, the whole energy spectrum determines the shape of such resonance fringes and this also provides insight into the slow-frequency system spectroscopy. As a particular example, we consider this for valley-orbit silicon quantum dots, which are important for the emerging field of valleytronics.
关键词： valley-orbit silicon quantum dots,valleytronics,low-frequency spectroscopy,quantum multilevel systems,Landau-Zener-Stückelberg-Majorana interference
更新于2025-09-23 15:21:21
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Flexible TiO2-coated nanocellulose membranes incorporated with CdTe as electrodes in photoelectrochemical cells
摘要： Incorporation of quantum dots (QDs) into porous matrices has triggered the development of novel optical devices. In this work, TiO2 sensitized by CdTe incorporated into bacterial nanocellulose (BNC) membranes were tested as photoelectrodes in a photoelectrochemical cell directed to the water splitting for hydrogen generation. The flexible membranes were produced by immersing BNC membranes in an aqueous solution of CdTe capped with glutathione (CdTe–GSH) and further deposited over a thin layer of TiO2. Incorporation of CdTe–GSH into BNC membranes was confirmed by infrared spectroscopy. Fluorescence spectroscopy revealed that the luminescence intensity increased with the immersion time in the CdTe–GSH solution. Field-emission gun scanning electron microscopy (FEG-SEM) images revealed that the CdTe/QDs (5 nm) were homogeneously dispersed on the cellulose nanofibers. BNC/CdTe–GSH membranes was tested as photoelectrodes. Photoelectrochemical cells exhibited a significant photocurrent in wavelengths ranging from 400 to 800 nm, which indicates their potential for applications as flexible electrodes, sensors and photovoltaic systems.
关键词： Photoelectrochemical cell,Quantum dots,Bacterial nanocellulose,Water splitting,Hydrogen generation
更新于2025-09-23 15:21:21