Search Results (411)

Shortwave infrared (SWIR) imaging technology, with its excellent penetration and anti-interference capabilities, is widely applied in military, medical, and industrial fields. However, traditional detectors (e.g., InGaAs) are expensive, have complex readout circuits, and exhibit insufficient low-light performance, limiting their large-scale promotion. This paper proposes and implements a single-pixel SWIR imaging system based on PbS quantum dot (QD) detectors. A single-pixel imaging system is constructed using PbS QD detectors with a formal device structure (ITO/ZnO/PbS/PbS-EDT/Au); through simulation studies, the effect of the PbS absorption layer thickness on device performance is investigated, and it is determined that a thickness of 450 nm yields optimal device performance. Based on the simulation results, a P-I-N structure PbS photovoltaic-type detector with high external quantum efficiency (EQE) and low dark current is fabricated, achieving a EQE of 62% at the 1300 nm wavelength, a dark current density of 8.54 × 10⁻⁴ mA·cm⁻² at −0.1 V bias voltage, and a −3 dB bandwidth of 324 kHz; a low-noise signal conditioning circuit is designed to optimize the −3 dB bandwidth to 337 kHz while maintaining low noise density, enabling the linear conversion of nA~μA level weak photocurrent from the detector to 0~3 V standardized voltage signals, meeting the requirements of single-pixel imaging (SPI) systems. Hadamard orthogonal encoding technology is employed to achieve spatial light modulation and signal encoding; after the PbS QD detector collects and integrates the projection signal, the image with 128 × 128 resolution is reconstructed through the inverse Hadamard orthogonal decoding algorithm. This work provides a novel solution for QD-based SWIR imaging, overcoming the cost and manufacturing limitations of traditional array systems and laying the foundation for the spectral expansion and practical application of SPI technology. Quantitative imaging characterization and low-light imaging tests are supplemented to verify the comprehensive performance of the system. Full article

Colloidal quantum dots (CQDs) provide size-tunable optoelectronic properties, enabling broadband photodetection from the visible to the short-wave infrared (SWIR). However, CQD photodetector performance depends on different processes such as optical absorption, charge transport, and photogain mechanisms in CQD solids. Here, we investigate the impact of PbS CQD size on the electrical conductivity and photodetection performance of CQD films and hybrid graphene/CQD photodetectors. Three CQD sizes are studied: d~3.06 nm, d~3.78 nm, and d~5.27 nm, with exciton peaks at λ_e~935 nm, λ_e~1080 nm, and λ_e~1550 nm, respectively. Electrical measurements show that the largest CQDs exhibit higher conductivity. In contrast, photodetection measurements reveal that the largest-sized CQDs (~5.27 nm) produce the lowest photoresponse, both as bare CQDs and as hybrid graphene/CQD photodetectors. Spectral and power-dependent measurements show decreasing responsivity with increasing optical power, consistent with trap-mediated photoconductive gain. These results indicate that the CQD size can have a significant effect on the optoelectronic performance of CQD devices, requiring materials, interfaces, and design optimization to maintain high photodetector performance. Full article

Lead (Pb) is a persistent environmental contaminant that poses a significant risk to aquatic primary producers by disrupting photosynthesis, cellular metabolism, and physiological homeostasis. This study investigated the physiological and biochemical responses of two freshwater green microalgae, Mucidosphaerium pulchellum and Micractinium pusillum, exposed to Pb(II) concentrations ranging from 0 to 30 mg L⁻¹. Species-specific responses were evaluated through growth kinetics, chlorophyll fluorescence, lipid accumulation, and fatty acid profiling to elucidate mechanisms underlying Pb stress tolerance. Pb(II) exposure resulted in concentration-dependent inhibition of growth and photosynthetic activity in both species, with marked reductions in quantum yield and increases in photosynthetic inhibition at the highest exposure concentration (30 mg L⁻¹), reaching approximately 95% in M. pulchellum and 93% in M. pusillum. Lipid metabolism exhibited distinct species-specific responses: M. pulchellum showed a progressive decline in total lipid content, whereas M. pusillum exhibited enhanced lipid accumulation under moderate Pb exposure followed by depletion under severe stress. Fatty acid analysis revealed significant membrane lipid remodeling, characterized primarily by reductions in polyunsaturated fatty acids, particularly α-linolenic acid (C18:3), with stronger alterations observed in M. pulchellum. These findings demonstrate that Pb toxicity involves interconnected effects on photosynthetic efficiency, carbon allocation, and membrane lipid composition, with species-specific differences in physiological resilience. The combined application of chlorophyll fluorescence and lipid-related biomarkers provides a sensitive approach for assessing heavy-metal stress responses and improving understanding of Pb tolerance mechanisms in freshwater microalgae. These findings provide a physiological basis for the development of sustainable biomonitoring approaches for freshwater ecosystems. Full article

Enrofloxacin residues in foods pose potential risks to food safety and public health, creating demand for rapid, sensitive, and matrix-compatible screening methods. All-inorganic CsPbBr₃ quantum dots (QDs) are promising fluorescent probes because of their strong photoluminescence, but their poor stability in polar media greatly restricts their practical use in food analysis. Herein, ZIF-8-confined and APTES-passivated CsPbBr₃ QDs were developed as an ethanol-compatible fluorescent sensor for enrofloxacin detection in foods. Unlike reported CsPbBr₃@ZIF-8 systems mainly used for metal-ion sensing in aqueous media, this work integrates ZIF-8-confined in-situ growth with APTES-assisted silane passivation to improve the stability and applicability of CsPbBr₃ QDs in ethanol-based food extracts. ZIF-8 provided a confined microenvironment, while the APTES-derived silane layer further enhanced fluorescence stability. The sensor exhibited a distinct turn-off fluorescence response toward enrofloxacin, with a linear range of 0.1–25.0 mg·L⁻¹ and a limit of detection of 0.058 mg·L⁻¹, mainly attributed to electron transfer with CsPbBr₃@ZIF-8. The method was successfully applied to honey, milk, fish, and shrimp samples, achieving recoveries of 85.2–106.8%. Results obtained for aquatic products showed no significant difference from HPLC analysis (p > 0.05), demonstrating the potential of this sensor for rapid enrofloxacin residue screening in complex food matrices. Full article

All inorganic CsPbBr₃ perovskite nanocrystals (NCs) exhibit outstanding luminescence for optoelectronics, yet poor environmental stability severely restricts their practical deployment. As a stable derivative phase, Cs₄PbBr₆ can effectively improve structural stability. Nevertheless, the rational fabrication of high-quality Cs₄PbBr₆/CsPbBr₃ hybrid NCs remains challenging owing to the lack of straightforward and scalable synthetic strategies. To overcome these hurdles, we synthesize well-defined Cs₄PbBr₆/CsPbBr₃ hybrid NCs via a temperature-controllable continuous-flow microfluidic route. This platform precisely modulates phase composition via systematic temperature tuning across a range of 110–170 °C, producing distinct compositions from Cs₄PbBr₆-dominant to high-purity CsPbBr₃. A direct correlation was elucidated between temperature-induced phase transformation and optical properties. The NCs synthesized at 130 °C exhibited a high photoluminescence quantum yield of 96.24% and bright 521 nm green emission. These NCs were successfully integrated into white light-emitting diodes incorporating a 478 nm blue excitation chip and K₂SiF₆:Mn⁴⁺ red phosphor, which demonstrated excellent color performance with a luminous efficiency of 86.3 lm W⁻¹ and Commission Internationale de l’Éclairage coordinates of (0.2991, 0.3784). This work highlights the potential of continuous-flow microfluidics for precise phase modulation and scalable production of high-quality perovskite NCs, offering a viable route for advanced optoelectronic applications. Full article

Perovskite solar cells (PSCs) have reached certified efficiencies exceeding 26%, yet the gap to the Shockley–Queisser limit and insufficient operational stability remain key obstacles to commercialization. Quantum dots (QDs) offer a versatile platform to address both challenges through their size-tunable bandgaps, high photoluminescence yields, and solution processability. This review systematically examines four QD integration strategies in PSCs: transport layer modification, active layer doping, UV conversion layers, and tandem sub-cells. The underlying mechanisms—including defect passivation, energy-level engineering, crystallization control, and ion migration suppression—are critically compared across these approaches. Despite significant advances, challenges persist, including the ligand–charge transport trade-off, the environmental toxicity of Pb/Cd-containing QDs, poor reproducibility, and the absence of standardized stability testing protocols. By providing a mechanism-oriented assessment across all device components, this review offers a clear framework for selecting appropriate QD strategies and identifies priority research directions. The perspective of QD strategies in this review provides a useful and significant reference for approaching the theoretical PCE limits of single-junction PSCs by reducing non-radiative recombination and improving light utilization, while QD-based tandem architectures offer a viable route toward surpassing the single-junction Shockley–Queisser limit. Full article

Short-wavelength infrared (SWIR) image sensors are of increasing interest for space applications, where ionizing radiation can significantly impact device performance. PbS colloidal quantum dot (CQD)-based thin-film photodiodes (TFPDs) are promising candidates due to their spectral tunability and compatibility with CMOS integration. However, their radiation response remains insufficiently understood. We investigated the effects of X-ray irradiation on PbS CQD-based SWIR TFPDs and image sensors up to a total ionizing dose of 220 krad. The results suggest that X-ray irradiation induces ligand-dependent modulation of the trap-state in PbS CQD films, leading to reduced recombination and enhanced carrier lifetime. Consequently, the TFPDs exhibit decreased dark current and improved external quantum efficiency (EQE), reaching 44.2% at 1420 nm. PbS CQD-based SWIR image sensors maintain stable operation after irradiation until 220 krad, achieving an EQE of 33.1%. These results provide an initial assessment of PbS CQD-based SWIR image sensors under X-ray total ionizing dose (TID) exposure, highlighting the importance of ligand-dependent CQD surface chemistry towards SWIR photodetectors in space applications. Full article

This study examines the influence of device architecture and substrate materials on the external quantum efficiency (EQE) of high-performance solar cells. A diverse array of photovoltaic technologies was evaluated, including formamidinium lead iodide CH₅N₂PbI₃ (FAPI) perovskite cells and various silicon-based designs, such as Passivated Emitter and Rear Cell (PERC), Back Integrated Contact (BIC), and Bifacial structures. Quantum characteristics were determined through wavelength-dependent photocurrent measurements utilizing a precision monochromator system. Our results reveal that device structure is a primary determinant of charge carrier collection efficiency; specifically, Bifacial and PERCs achieved superior short-circuit current densities (J_sc) of 40.98 mA/cm² and 39.42 mA/cm², respectively. Notably, the EQE(λ) profile of Bifacial cells under n-side illumination exhibits a near-ideal rectangular shape, indicating an optimized spectral response throughout the operating spectrum. Furthermore, the analysis investigates the role of surface recombination velocity and the efficacy of advanced passivation layers—specifically Al₂O₃ and SiN_x—in enhancing quantum performance by mitigating recombination state density. Our findings demonstrate that the strategic integration of advanced passivation layers (Al₂O₃ and SiN_x) with optimized architectures, such as PERC and Bifacial designs, is paramount for maximizing charge carrier collection and achieving record-high current densities reaching 40.98 mA/cm². A comprehensive analysis of solar cell performance involves spectral response (SR) and external quantum efficiency (EQE) as functions of wavelength. Additionally, SR-based current density analysis enables more accurate evaluation of cell parameters than standard I–V characterization. Full article

Lead isotope ratios are frequently used in archaeometric provenance analysis; however, the overlap of isotopic fields within the Andean metallogenic belt complicates reliable provenance determination. This study presents a reproducible fidelity-based kernel method for the unsupervised clustering of Andean lead-isotope data and investigates whether a quantum-mechanical similarity space can reveal geologically significant structures beyond the classical Euclidean partition. A dataset of 1522 measurements of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb was analyzed using a fidelity-based quantum kernel based on a three-qubit Pauli feature map and compared with classical K-means clustering, Gaussian mixture models, and Ward’s agglomerative clustering under various preprocessing strategies and cluster counts. The optimal quantum kernel setup achieved the highest silhouette score at k = 2. However, because analytical uncertainties were not consistently reported across all the compiled sources, an uncertainty-weighted similarity could not be applied. Geological insights indicate that this binary division separates less radiogenic, arc-related compositions from more radiogenic and thorogenic crustal signatures, a contrast that broadly follows the west-to-east crustal-contamination gradient across the Andes. Conversely, the traditional four-cluster approach provides more detailed subdivisions that align with the previously identified isotopic provinces. The reported separation reflects the geometry of the quantum feature space rather than any hardware-level speed-up, as this work represents only a simulation approach. Overall, these findings support a hierarchical and complementary approach to analyzing Pb isotope origins, in which quantum kernel clustering provides robust large-scale separation and classical clustering enhances regional understanding. Full article

In this work, we report an example of tuning the photophysical properties of a polypyridine ruthenium(II) complex via the coordination of a second cation. A new ruthenium(II) complex contains a thiacrown-ether fragment that allows selective binding of additional metal cations (Ba²⁺, Cd²⁺, Pb²⁺), leading to pronounced changes in the optical and electronic properties of the bimetallic system. Spectroscopic and electrochemical studies reveal that the monoruthenium precursor displays dual excitation pathways involving either intraligand charge transfer (ILCT) or triplet metal-to-ligand charge transfer (³MLCT) excited states. Upon coordination of a second metal ion, the ILCT channel is suppressed, and only the ³MLCT state remains emissive, resulting in a significant increase in phosphorescence quantum yields (up to 22.6% in degassed solutions) for the bimetallic derivative. Time-resolved emission studies confirm the conversion from biexponential to monoexponential luminescence decay upon complexation. Electrochemical analysis and density functional theory (DFT) calculations support the hypothesis that cation binding alters the electron density distribution within the chromophore, stabilizing the MLCT pathway. These results demonstrate that incorporation of a second cation provides an effective strategy to control excited-state dynamics in ruthenium complexes, offering opportunities for the rational design of photosensitizers and photofunctional materials. Full article

Rapid detection of heavy metals is vital for monitoring surface water contamination and preventing environmental and health risks. Traditional detection methods for metals such as lead and copper often require sophisticated, costly instrumentation, limiting their use in routine analyses. To address this challenge, we developed a cost-effective fluorescence-based approach using semiconductor quantum dots (QDs) as nanosensors for metal ion detection. The QDs were synthesized directly in aqueous medium through a reflux-assisted process employing cadmium precursors, selenium, thioglycolic acid (TGA), and branched polyethyleneimine (PEI, Mw ~25,000) as stabilizing agents. Structural analysis revealed nanoparticles with diameters below 5 nm, spherical morphology, and a zinc blende (face-centered cubic) crystalline structure. Optical characterization by UV–Vis, photoluminescence (PL), and FTIR spectroscopy confirmed effective surface functionalization and strong quantum confinement. PEI-capped QDs exhibited enhanced colloidal stability and showed pronounced fluorescence quenching in the presence of Pb²⁺ ions, indicating high sensitivity and selectivity toward lead. Both TGA- and PEI-capped QDs also demonstrated moderate responses to Co²⁺ but negligible interaction with Sn²⁺, confirming ion-specific detection. Overall, this study demonstrates that surface-engineered QDs constitute a simple, accessible platform for selective detection of toxic metals, with promising applications in environmental monitoring and water quality assessment. Full article

This work reports the colloidal synthesis of Nd-containing mixed-halide perovskite quantum dots described as CsPb(Nd)Br_3−γCl_γ, followed by post-synthetic surface modification with an acid-activated amino-functional siloxane. This notation is used deliberately because the available FE-SEM, DLS, EDX, and optical data confirm the formation of an Nd-containing mixed-halide colloidal perovskite system, but do not provide direct crystallographic proof of substitutional Nd³⁺ incorporation at the Pb²⁺ B-site. The obtained dispersions show stable blue emission with a maximum at about 458 nm, a photoluminescence quantum yield of about 56%, an essentially invariant emission maximum when the excitation wavelength is varied from 300 to 390 nm, and monoexponential decay kinetics with a characteristic lifetime of 6.67 ± 0.97 ns. Field-emission scanning electron microscopy combined with morphometric analysis of at least 150 particles indicates a nanoscale size distribution with an average equivalent diameter of 8.8 nm, a median of 7.3 nm, and 93.25% of particles smaller than 25 nm. Dynamic light scattering confirms a narrow hydrodynamic size distribution in the 7–9 nm range and a low polydispersity index. Elemental mapping by EDX confirms the co-presence of Cs, Pb, Br, Cl, and Nd in the analyzed particles. The observed blue shift is discussed in terms of the combined effect of chloride incorporation, nanoscale size, possible Nd-related perturbation of the local electronic/defect structure, and reduced non-radiative losses after surface passivation. No definitive crystallographic assignment of Nd to a specific lattice site is claimed; the composition is therefore treated as nominal, and the structural interpretation remains provisional pending XRD/XPS or related studies. Full article

Lead sulfide quantum dots (PbS QDs), as a functional-layer coating, enable non-volatile integration and neuromorphic computing in memristive structures to address the von Neumann bottleneck. Herein, the dual-interface mechanism of PbS QDs in the memristor film structure is reviewed. First, the local electric field enhancement effect generates tip electrode-like structures in the coating film through QD-mediated spatial charge gradients, thereby enabling precise control over the nucleation and growth of conductive filaments (CFs). As a result, the consistency of switching voltages and the thermal stability at elevated temperatures are significantly improved. Conversely, the anion reservoir effect exploits surface dangling bonds on QDs to efficiently capture anions from the dielectric layer, thereby synergistically regulating vacancy migration kinetics. This process enables zero-initialization behavior and ultra-low-power operation. In addition, the spatial distribution design and density modulation of QDs further reinforce both mechanisms. The structural optimization of QD/dielectric interface engineering can simultaneously improve cycling endurance and resistive switching uniformity. Furthermore, modification of QD surface chemistry through ligand decoration and passivation suppresses the stochasticity of ionic diffusion while improving the linearity of synaptic weight updates. This interfacial engineering strategy utilizing QDs as coating films advances the development of high-performance photonic–electronic systems for memory–computing convergence. Full article

Colloidal quantum dots (CQDs) are ideal for room-temperature gas sensors due to their high surface area, abundant dangling bonds, and excellent film-forming properties. However, the underlying conduction mechanism remains unclear, lacking in-depth analysis of gas–solid charge transfer and carrier transport, which hinders the rational design of high-performance gas sensors. To address this, we fabricated a PbS colloidal quantum dot thin-film transistor (TFT) gas sensor that enables in situ analysis of carrier concentration and mobility via gate voltage modulation. We systematically measured the variations in conductivity, carrier concentration, and mobility with NO₂ concentration and established a normalized weight variation model. The results show that the conductivity increase upon NO₂ exposure is primarily due to the rise in carrier concentration induced by gas adsorption. At low concentrations (below 0.5 ppm), the response is dominated by mobility variation. This work provides a physically meaningful theoretical framework for understanding the conduction mechanism. Full article

The field of infrared (IR) photodetection is undergoing rapid development through the emergence of solution-processable nanoparticle (NP)-based materials and fabrication strategies. This review critically examines recent advances in fabrication approaches for NP-based IR detectors, emphasizing the relationship between synthesis, surface engineering, deposition processes, and device architecture in determining detector performance. Representative material platforms are discussed, including colloidal quantum dots (CQDs) such as PbS and HgTe, which enable tunable operation from the near-infrared (NIR) and short-wave infrared (SWIR) to selected mid-wave (MWIR), long-wave (LWIR), and emerging very-long-wave infrared (VLWIR) regimes depending on material composition and operating conditions. Further platforms including plasmonic metal NPs, black phosphorus, and topological nanomaterials are evaluated for their unique mechanisms of optical enhancement and broadband response. Fabrication approaches including continuous-flow synthesis, ligand exchange, blade coating, inkjet printing, electrophoretic deposition, and other scalable solution-processing methods are analyzed with respect to their influence on film quality, charge transport, interface engineering, and integration compatibility. The review further compares major device architectures, including photoconductors, photodiodes, plasmonic absorbers, and phototransistors, using key performance metrics such as specific detectivity (D*), responsivity (R), response speed, and operating temperature, while emphasizing the importance of measurement conditions in cross-platform comparisons. Critical challenges including dark-current generation, 1/f noise, transport limitations associated with ligand chemistry, environmental instability of narrow-bandgap materials, manufacturability constraints, and toxicity considerations are also discussed. Emerging directions such as neuromorphic sensing, CMOS-compatible integration, and sustainable lead-free nanomaterials are highlighted. By linking nanoscale material design and fabrication processes to device-level performance, this review provides a framework for advancing NP-based IR technologies toward scalable and application-relevant sensing systems. Full article