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Wavefunction engineering for efficient photoinduced-electron-transfer in CuInS2 quantum dots sensitized solar cells
摘要： The high-efficiency of quantum dots (QDs) sensitized solar cells benefits from the highly efficient photoinduced-electron-transfer (PET) to external electrodes. Here, we investigated how the efficiency of the PET. Though the electron trapping can be suppressed after the ZnS surface surface defects and conduction-band (CB) offsets between core and shell materials affect the PET from CuInS2 QDs by means of time-resolved femtosecond transient-absorption and nanosecond photoluminescence spectroscopy. The transfer of 1S excited electrons from CuInS2 QDs to TiO2 films is demonstrated and we find that the surface electron-trapping can significantly reduce the efficiency of CuInS2 QDs sensitized solar cells. CB offset, which allows us to achieve a quasi-type II carrier confinement in CuInS2/CdS core/shell QDs because of their low electron-density at QD surface. The surface delocalization of electron wavefunction from CuInS2 core to CdS shell. Finally, we demonstrate that these new mechanistic understandings of the PET processes are of great crucial for improving the efficiency of CuInS2 QDs sensitized solar cells.
关键词： quantum dots sensitized solar cells,photoinduced electron-transfer,quantum dots,CuInS2,wavefunction engineering
更新于2025-09-23 15:19:57
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Photoinduced electron transfer within supramolecular hemoprotein co-assemblies and heterodimers containing Fe and Zn porphyrins
摘要： Electron transfer (ET) events occurring within metalloprotein complexes are among the most important classes of reactions in biological systems. This report describes a photoinduced electron transfer between Zn porphyrin and Fe porphyrin within a supramolecular cytochrome b562 (Cyt b562) co-assembly or heterodimer with a well-defined rigid structure formed by a metalloporphyrin–heme pocket interaction and a hydrogen-bond network at the protein interface. The photoinduced charge separation (CS: kCS = 320 – 600 s–1) and subsequent charge recombination (CR: kCR = 580 – 930 s–1) were observed in both the Cyt b562 co-assembly and the heterodimer. In contrast, interestingly, no ET events were observed in a system comprised of a flexible and structurally-undefined co-assembly and heterodimers which lack the key hydrogen-bond interaction at the protein interface. Moreover, analysis of the kinetic constants of CS and CR of the heterodimer using the Marcus equation suggests that a single-step ET reaction occurs in the system. These findings provide strong support that the rigid hemoprotein-assembling system containing an appropriate hydrogen-bond network at the protein interface is essential for monitoring the ET reaction.
关键词： Hydrogen bond network,Photoinduced electron transfer,Cytochrome b562,Marcus theory,Hemoprotein assembly
更新于2025-09-19 17:15:36
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Aptamer-Based Fluorometric Ochratoxin A Assay Based on Photoinduced Electron Transfer
摘要： This study describes a novel quencher-free fluorescent method for ochratoxin A (OTA) detection based on the photoinduced electron transfer (PIET) between guanine and fluorophore. In the absence of OTA, carboxyfluorescein (FAM)-labeled aptamer can partly hybridize with the complementary strand of OTA aptamer (OTA-cAPT), which contains four guanines at its 3'-end. As a result, the fluorescence of FAM is quenched due to PIET and stacked guanines. In the presence of OTA, FAM-labeled OTA aptamer can bind specifically to OTA, and thereby the high fluorescence intensity of the dye can be maintained. Under the optimal conditions, the method had a detection limit of 1.3 nM. In addition, the method we proposed is highly sensitive and specific for OTA. Furthermore, the method was proven to be reliable based on its successful application in the detection of OTA in red wine samples. Therefore, this promising, facile, and quencher-free method may be applied to detect other toxins by using other appropriate aptamers.
关键词： fluorescence,ochratoxin A,photoinduced electron transfer,quencher-free
更新于2025-09-19 17:15:36
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Light-Triggered, Spatially Localized Chemistry by Photoinduced Electron Transfer
摘要： It is of immense interest to exert spatial and temporal control of chemical reactions. It is now demonstrated that irradiation can trigger reactions specifically at the surface of a simple colloidal construct, obtained by adsorbing polyethyleneimine on fluorescent colloidal particles. Exciting the fluorescent dye in the colloid affords photoinduced electron transfer to spatially proximal amine groups on the adsorbed polymer to form free radical ions. It is demonstrated that these can be harnessed to polymerize acrylic acid monomer at the particle surface, or to break up colloidal assemblies by cleaving a cross-linked polymer mesh. Formation of free radical ions is not a function of the size of the colloid, neither is it restricted to a specific fluorophore. Fluorophores with redox potentials that allow photoinduced electron transfer with amine groups show formation of free radical ions.
关键词： temporal control,fluorescence,colloids,spatial control,photoinduced electron transfer
更新于2025-09-19 17:15:36
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Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Sterna??Volmer and Stochastic Kinetic Models
摘要： Photoinduced electron transfer from N-methylaniline (NMA) to a photoexcited CdTe quantum dot (QD*) is studied in toluene. The PET mechanism at low to moderate quencher (NMA) concentrations (< 0.08 M) remains mostly collisional with some contributions from QD-NMA complex formation. However, at high quencher concentrations (> 0.10 M), QDs form larger numbers of static complexes with NMA molecules leading to a steep positive deviation in the steady-state Stern–Volmer curves. An isothermal titration calorimetry (ITC) study confirms the formation of QD-NMA complexes (K ~ 150 M?1) at high quencher concentrations. Fitting our experimental data using a stochastic kinetic model indicates that the number of NMA molecules attached per QD at highest NMA concentration (~ 0.16 M) used in this study decreases from ~ 0.76 to ~ 0.47 with reducing the QD size from ~ 5.2 nm to ~ 3.2 nm. However, the PET rate increases with decreasing QD size, which is commensurate with the observation that the chemical driving force (ΔG) increases with decreasing the QD particle size. We have analyzed the PET kinetics mainly by using Stern-Volmer fittings. However, in some cases Tachiya’s stochastic kinetic model is used for stoichiometric analysis, which seems to be useful only at high quencher concentrations. The measured PET rate coefficients in all the cases are found to be at least an order of magnitude lower when compared to the diffusion-controlled rate of the reaction medium.
关键词： quantum dot,time-resolved fluorescence,photoinduced electron transfer,Stern–Volmer analysis,bimolecular quenching
更新于2025-09-19 17:13:59
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The Influence of Photoinduced Processes on a Quantum Dot Surface on the Electron Transfer Efficiency in TiO2 Nanoparticle/Quantum Dot Structures
摘要： The influence of photoinduced processes occurring on the surfaces of CdSe/ZnS quantum dots is considered in relation to the functional characteristics of hybrid TiO2 nanostructure/quantum dot systems. Preirradiation of quantum dots is shown to achieve a threefold increase in electron transfer efficiency within these structures. Photoinduced processes are found to impact both the efficiency of nonradiative phenomena in quantum dots and the electron transfer in the indicated systems.
关键词： photoinduced processes onto quantum dots,photoinduced electron transfer,photoactivation,semiconducting quantum dots,hybrid structures,titanium dioxide nanoparticles
更新于2025-09-16 10:30:52
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Oxygen Tolerant PET-RAFT Facilitated 3D Printing of Polymeric Materials under Visible LEDs
摘要： Photopolymerization-based 3D printing process is typically conducted using free radical polymerization, which leads to fabrication of immutable materials. An alternative 3D printing of polymeric materials using trithiocarbonate (TTC) reversible addition-fragmentation chain transfer (RAFT) agents has always been a challenge for material and polymer scientists. Herein we report 3D printing of RAFT-based formulations that can be conducted fully open to air using standard digital light processing (DLP) 3D printer and under mild conditions of visible light at blue (λ max = 483 nm, 4.16 mW/cm2) or green (λ max = 532 nm, 0.48 mW/cm2) wavelength. Our approach is based on activation of TTC RAFT agents using eosin Y (EY) as a photoinduced electron-transfer (PET) catalyst in the presence of a reducing agent (triethylamine (TEA)), which facilitated oxygen tolerant 3D printing process via a reductive PET initiation mechanism. Re-activation of the TTCs present within the polymer networks enables post-printing monomer insertion into the outer layers of an already printed dormant object under a second RAFT process, which provides a pathway to design a more complex 3D printing. To our best knowledge, this is the first example of oxygen tolerant EY/TEA catalyzed PET-RAFT facilitated 3D printing of polymeric materials. We believe that our strategy is a significant step forward in the field of 3D printing.
关键词： Oxygen Tolerant,Trithiocarbonate,3D Printing,Visible Light-Induced PET-RAFT Polymerization,Digital Light Processing,Photoinduced Electron-Transfer
更新于2025-09-16 10:30:52
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Novel “turn off-on” sensors for detection of DNA-acrylamide interaction usingZnS quantum dots as a phosphorescent probe
摘要： A novel “turn off-on” sensor for detection of interaction between DNA and acrylamide (ACR) was developed. In this method, L-cysteine capped Mn-doped ZnS quantum dots (QDs) were used as room temperature phosphorescent probes. In the “turn-off” mode, ACR was absorbed onto the surface of QDs via electrostatic interaction, which caused a quenching effect of room-temperature phosphorescence signal by photoinduced electron-transfer mechanism. ACR was removed from the QDs’ surface with the addition of DNA. Thus, the phosphorescence emission of QDs was recovered and the system was turned to the “turn-on” mode. The quenching mechanism of QDs by ACR was collisional (dynamic) and the quenching constant, binding constant, and binding site number were calculated as 3.2 × 10 4 M (cid:0)1 , 2.04 × 10 4 M (cid:0)1 , and 1.2, respectively. An absorption spectrometric method was also used to evaluate ACR-DNA interaction and the binding constant (K) was found as 2.4 × 10 5 M (cid:0)1 . The developed biosensor is simple, is free of interferences coming from autofluorescence and scattering light, and does not need any derivatization step or sample pretreatment.
关键词： quantum dots,DNA interaction,phosphorescence,photoinduced electron transfer,Acrylamide
更新于2025-09-16 10:30:52
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Guest Inclusion Modulates Concentration and Persistence of Photogenerated Radicals in Assembled Triphenylamine Macrocycles
摘要： Substituted triphenylamine (TPA) radical cations show great potential as oxidants and as spin containing units in polymer magnets. Their properties can be further tuned by supramolecular assembly. Here, we examine how the properties of photogenerated radical cations, intrinsic to TPA macrocycles, are altered upon their self-assembly into 1D columns. These macrocycles consist of two TPAs and two methylene ureas which drive the assembly into porous organic materials. Advantageously, upon activation the crystals can undergo guest exchange in a single-crystal-to-single-crystal transformation generating a series of isoskeletal host-guest complexes whose properties can be directly compared. Photoinduced electron transfer, initiated using 365 nm LED’s, affords radicals at room temperature as observed by EPR spectroscopy. The line shape of the EPR spectra and the quantity of radicals can be modulated by both polarity and heavy atom inclusion of the encapsulated guest. These photogenerated radicals are persistent, with half-lives between 1-7 days and display no degradation upon radical decay. Re-irradiation of the samples can restore the radical concentration back to a similar maximum concentration, a feature that is reproducible over several cycles. EPR simulations of a representative spectrum indicate two species, one containing two N hyperfine interactions and an additional broad signal with no resolvable hyperfine interaction. Intriguingly, TPA analogs without bromine substitution also exhibit similar quantities of photogenerated radicals, suggesting that supramolecular strategies can enable more flexibility in stable TPA radical structures. These studies will help guide the development of new photoactive materials.
关键词： photoinduced electron transfer,supramolecular assembly,radical cations,triphenylamine,EPR spectroscopy
更新于2025-09-12 10:27:22
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A Method for Estimating the Functionality of TiO2/Quantum Dot Multilayer Hybrid Structures Based on the Generation of Reactive Oxygen Species
摘要： A new technique for estimating the efficiency of electron transfer from a CdSe/ZnS quantum dot (QD) to TiO2 nanoparticles based on the generation of reactive oxygen species by hybrid structures is presented. It was demonstrated that in the formed multilayer hybrid structures of TiO2/QD, photoinduced electron transfer is realized with an efficiency of 26%.
关键词： hybrid structures,photoinduced electron transfer,semiconductor quantum dots,titanium dioxide nanoparticles,reactive oxygen species
更新于2025-09-12 10:27:22