Search Results (72)

The increasing global demand for renewable energy has intensified the search for high-efficiency and cost-effective solar cell technologies. Quantum dot-sensitized solar cells (QDSSCs) have emerged as promising candidates due to their tunable optoelectronic properties and enhanced light absorption. In this study, SnS quantum dots were synthesized from dithiocarbamate complexes using different ligands, namely m-toluidine (SnS1), aniline (SnS2), and p-toluidine (SnS3), to investigate the influence of precursor chemistry on material properties and device performance. Structural analysis confirmed the formation of an orthorhombic phase for all samples, while morphological studies revealed well-dispersed nanocrystals for SnS1 (5.93 nm), increased aggregation for SnS2 (8.57 nm), and partially fused domains with an intermediate size for SnS3 (6.67 nm). Optical measurements showed bandgap energies of 2.8, 2.2, and 2.7 eV for SnS1, SnS2, and SnS3, respectively, with SnS3 exhibiting reduced charge-recombination behaviour. Photovoltaic devices fabricated using these materials yielded power conversion efficiencies of 3.40, 2.03, and 7.63% for SnS1, SnS2, and SnS3, respectively, with no significant improvement observed for bifacial configurations. The superior performance of SnS3 is attributed to an optimal balance between light absorption, morphology, and charge transport properties, highlighting the critical role of precursor ligand selection in tuning quantum dot characteristics for improved QDSSC performance. Full article

Ultrasmall near-infrared (NIR)-responsive quantum dots (QDs) are highly promising for deep-tissue phototherapy but often face challenges with biocompatibility and clearance. In this study, Cu₂ZnSnS₄ quantum dots (CZTS QDs) were synthesized via a non-injection method and surface-functionalized with glutathione (GSH) to create water-dispersible and biocompatible CZTS@GSH QDs. Comprehensive characterization using XRD, TEM, DLS, XPS, and UV-Vis spectroscopy confirmed a sphalerite-type ZnS crystal structure, an average hydrodynamic diameter of ~6.2 nm, and a band gap of 1.47 eV (843.5 nm). The CZTS@GSH QDs demonstrated effective photothermal conversion under 808 nm laser irradiation, achieving a temperature increase sufficient for photothermal therapy (PTT). Furthermore, using a DPBF assay, the QDs were shown to generate singlet oxygen, confirming their photodynamic therapy (PDT) capability. Owing to their ultrasmall size, strong NIR absorption, and demonstrated dual PTT/PDT functions, the CZTS@GSH QDs are established as a nanoplatform with potential for combined cancer treatment. Full article

The increasing presence of pharmaceutical residues such as ibuprofen in aquatic environments represents a growing concern due to their persistence and limited biodegradability. In this study, selenium-doped tin oxide (SnO₂:Se) nanoparticles covered with glycerol were synthesized via a microwave-assisted method to evaluate their photocatalytic performance in the degradation of ibuprofen under ultraviolet (UV) and visible light. Optimal synthesis parameters were determined at pH 7.5–8.0 and 130 °C, yielding stable, dark-brown colloidal suspensions. HRTEM analysis revealed a coexistence of one-dimensional (1D) nanowires and zero-dimensional (0D) quantum dots, confirming nanoscale morphology with crystallite sizes between 8 and 100 nm. EDS analysis confirmed the presence of Sn, O, and trace Se (0.1 wt%), indicating Se incorporation as a dopant. UV–Vis spectroscopy showed strong absorption near 324 nm and slight band-gap narrowing in the Se-doped samples, suggesting enhanced visible-light responsiveness. Photocatalytic experiments demonstrated an ibuprofen degradation efficiency of ~60% under visible light and 80% under UV irradiation with aeration, compared to only 5% removal using commercial SnO₂. The enhanced performance was attributed to Se-induced band-gap modulation, effective charge-carrier separation, and singlet oxygen generation. Full article

Given the potential hazards of enrofloxacin (ENR) residues to human health, establishing an accurate, rapid, and stable detection method is of importance. To enable the direct detection of ENR, an electrochemical sensor was constructed in this study. N- and S-doped carbon quantum dots (CQDs) with peroxidase-like activity were prepared using DL-malic acid, L-alanine, and L-cysteine as precursors and compounded with a tetrakis (4-carboxyphenyl) porphyrin (TCPP) and Fe(NO₃)₃·9H₂O to make novel N/S CQDs@Fe-TCPP composite carbon-based nanozymes to construct an electrochemical sensor, and the electrochemical behavior was investigated. Under optimal experimental conditions, the sensor exhibited a linear current response to ENR concentrations in the range of 1–1300 nM (I (μA) = 0.0106c (nM) + 2.9861, R² = 0.9962), with a calculated detection limit of 0.872 nM (S/N = 3). The recovery rate of this sensor in actual milk samples ranged from 99.02% to 100.9%. The reproducibility experiments demonstrated the high precision of the method, with a relative standard deviation (RSD) of 1.27%. Stability testing revealed a peak current retention rate of 93.51% on day 21, indicating excellent system stability. These findings indicate that the sensor shows great capability for ENR detection in food products. Full article

Highly accurate quantitative detection of heavy metals is crucial for preventing environmental pollution and safeguarding public health. To address the demand for sensitive and specific detection of Cu²⁺ ions, we have developed carbon dots using a simple hydrothermal process. The synthesized carbon dots are highly stable in aqueous media, environmentally friendly, and exhibit strong blue photoluminescence at 440 nm when excited at 352 nm, with a quantum yield of 5.73%. Additionally, the size distribution of the carbon dots ranges from 2.0 to 20 nm, and they feature excitation-dependent emission. They retain consistent optical properties across a wide pH range and under high ionic strength. The photoluminescent probes are selectively quenched by Cu²⁺ ions, with no interference observed from other metal cations such as Ag⁺, Ca²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Hg²⁺, K⁺, Mg²⁺, Sn²⁺, Pb²⁺, Sr²⁺, and Zn²⁺. The emission of carbon dots exhibits a strong linear correlation with Cu²⁺ concentration in the range of 0–14 μM via a static quenching mechanism, with a detection limit (LOD) of 4.77 μM in water. The proposed carbon dot sensor is low cost and has been successfully tested for detecting Cu²⁺ ions in general water samples collected from rivers in Taiwan. Full article

We report a novel approach to fabricating high-performance and robust quantum dot light-emitting diodes (QLEDs) utilizing sputtered SnO₂ thin films as the electron transport layer (ETL). While conventional solution-processed ZnMgO NP ETLs face limitations in mass production, the sputtering process offers advantages for uniform and reproducible thin film deposition. Herein, the structural, optical, and electrical properties of SnO₂ thin films were optimized by controlling the Ar/O₂ ratio and substrate heating temperature during sputtering. SnO₂ thin films with O₂ gas improve charge balancing in QLEDs by lowering the conduction band minimum. Furthermore, it was observed that oxygen vacancies in SnO₂ function as exciton quenching sites, which directly impacts the long-term stability of the device. QLEDs fabricated under optimal conditions (Ar/O₂ = 35:5, 200 °C heating) achieved a peak luminance of 99,212 cd/m² and a current efficiency of 21.17 cd/A with excellent device stability. The findings suggest that sputtered SnO₂ ETLs are a highly promising technology for the commercial production of QLEDs. Full article

Sensors based on nanocomposites of quantum dots (QDs) and wide-gap metal oxides are of exceptional interest for photoactivated detection of toxic and pollutant gases without thermal heating. However, the class of detecting gases has been limited almost exclusively to oxidizing gases like NO₂. Here, we designed a photoactivated sensor for the selective detection of primary alcohols at room temperature using CdSe quantum dots coupled to a wide-gap SnO₂ semiconductor matrix. Our concept of the sensor operations is based on the photochemical reaction of primary alcohols via photoactivated QD-SnO₂ charge transfer and does not involve chemisorbed oxygen, which is traditional for the operation of metal oxide sensors. We demonstrated an efficient sensor response to C₁–C₄ primary alcohols of ppm concentration under photoexcitation with a yellow LED in the absence of a signal from other volatile organic compounds (VOCs). We believe that proposed sensor concept opens up new ways to design photoactivated sensors without heating for the detection of VOCs. Full article

Oseltamivir is a drug that has been widely used to prevent and treat influenza A and B. In this work, an ultrasensitive, simple, and novel electrochemiluminescence (ECL) sensor combined with molecularly imprinted polymers (MIP-ECL) based on a graphene-like two-dimensional material, Mxene quantum dots (MQDs) was constructed to selectively detect oseltamivir. A molecularly imprinted polymer membrane containing an oseltamivir template was constructed by electropolymerization and elution of modified MQDs on a glassy carbon electrode. Under optimized experimental conditions, the MIP-ECL sensor could detect oseltamivir in the range of 10⁻¹⁰ to 10⁻⁶ M (R² = 0.9816), with a low limit of detection of 6.5 × 10⁻¹¹ M (S/N = 3), and the recovery rates of oseltamivir in biological samples were 92.21–104.2%, with relative standard deviations of 3.70%~5.70%. The developed MIP-ECL sensor provides a new idea for detecting oseltamivir, which was successfully applied to the determination of oseltamivir in serum samples, indicating great potential for application in clinical diagnostics. Full article

A sonochemical synthesis of SnS₂ quantum dots using acetone as a solvent is investigated. Two different tin sources (SnCl₂∙2H₂O or SnCl₄∙5H₂O) as well as two different sulfur sources (thioacetamide or Na₂S₂O₃) were applied. The sonication time was also varied between 60 and 120 min. Resulting products of syntheses were characterized with the following techniques: powder X-ray diffraction, electron microscopy (SEM and HR-TEM), Raman and FT-IR spectroscopies, the Tauc method, and X-ray photoelectron spectroscopy. Obtained SnS₂ nanostructures were in the form of quantum dots in the case of synthesis lasting 60 min (size of crystallites in the range of 3.5–7 nm) and in the form of elongated nanorods of length ca. 25–30 nm and width of 5–6 nm in the case of synthesis lasting 120 min. XPS analyses revealed that the surface of the obtained products contained a significant amount of tin at the second oxidation state (i.e., SnS). The quantum dots produced in the synthesis lasting 60 min showed a value of energy bandgap of 2.7 eV indicating potential applications in photocatalysis. Full article

Energy generation and storage are critical challenges for developing economies due to rising populations and limited access to clean energy resources. Fossil fuels, commonly used for energy production, are costly and contribute to environmental pollution through greenhouse gas emissions. Quantum dot-sensitized solar cells (QDSSCs) offer a promising alternative due to their stability, low cost, and high-power conversion efficiency (PCE) compared to other third-generation solar cells. Kesterite materials, known for their excellent optoelectronic properties and chemical stability, have gained attention for their potential as hole transport layer (HTL) materials in solar cells. In this study, the SCAPS-1D numerical simulator was used to analyze a solar cell with the configuration FTO/TiO₂/MoS₂/HTL/Ag. The electron transport layer (ETL) used was titanium dioxide (TiO₂), while Cu₂FeSnS₄ (CFTS), Cu₂ZnSnS₄ (CZTSe), Cu₂NiSnS₄ (CNTS), and Cu₂ZnSnSe₄ (CZTSSe) kesterite materials were evaluated as HTLs. MoS₂ quantum dot served as the absorber, with FTO as the anode and silver as the back metal contact. The CFTS material outperformed the others, yielding a PCE of 25.86%, a fill factor (FF) of 38.79%, a short-circuit current density (J_SC) of 34.52 mA cm⁻², and an open-circuit voltage (V_OC) of 1.93 V. This study contributes to the advancement of high-performance QDSSCs. Full article

Developing new nanomaterials and performing functionalization to increase their photocatalytic capacity are essential in developing low-cost, eco-friendly, and multipurpose-capacity catalysts. In this research, SnO₂/Se-doped quantum dots (QDs) covered with glycerol (SnO₂/Se-GLY) were synthesized using microwave irradiation. Then, their cover was replaced with glutaraldehyde through a ligand exchange procedure (SnO₂/Se-GLUT). The XRD analyses confirmed a tetragonal rutile structure of SnO₂. The HR-TEM analysis confirmed the generation of QDs with a size around 8 nm, and the optical analysis evidenced low bandgap energies of 3.25 and 3.26 eV for the SnO₂/Se-GLY and SnO₂/Se-GLUT QDs, respectively. Zeta-sizer analysis showed that the hydrodynamic sizes for both nanoparticles were around 230 nm (50 mg/L), and the zeta potential confirmed that SnO₂/Se-GLUT QDs were more stable than SnO₂/Se-GLY QDs. The cover-modified QDs (SnO₂/Se-GLUT) showed a higher and faster adsorption capacity, followed by a slower photocatalytic process than the original QDs (SnO₂/Se-GLY). The QTOF-LC-MS analysis confirmed MB degradation through the identification of intermediates such as azure A, azure B, azure C, and phenothiazine. Adsorption isotherm analysis indicated Langmuir model compliance, supporting the high monolayer adsorption capacity and efficiency of these QDs as adsorbent/photocatalytic agents for organic pollutant removal. This dual capability for adsorption and photodegradation, along with the demonstrated reusability, highlights the potential of SnO₂/Se QDs in wastewater treatment and environmental remediation. Full article

Ammonia (NH₃) gas is prevalent in industrial production as a health hazardous gas. Consequently, it is essential to develop a straightforward, reliable, and stable NH₃ sensor capable of operating at room temperature. This paper presents an innovative approach to modifying SnO₂ colloidal quantum dots (CQDs) on the surface of Ti₃C₂T_x MXene to form a heterojunction, which introduces a significant number of adsorption sites and enhances the response of the sensor. Zero-dimensional (0D) SnO₂ quantum dots and two-dimensional (2D) Ti₃C₂T_x MXene were prepared by solvothermal and in situ etching methods, respectively. The impact of the mass ratio between two materials on the performance was assessed. The sensor based on 12 wt% Ti₃C₂T_x MXene/SnO₂ composites demonstrates excellent performance in terms of sensitivity and response/recovery speed. Upon exposure to 50 ppm NH₃, the frequency shift in the sensor is −1140 Hz, which is 5.6 times larger than that of pure Ti₃C₂T_x MXene and 2.8 times higher than that of SnO₂ CQDs. The response/recovery time of the sensor for 10 ppm NH₃ was 36/54 s, respectively. The sensor exhibited a theoretical detection limit of 73 ppb and good repeatability. Furthermore, a stable sensing performance can be maintained after 30 days. The enhanced sensor performance can be attributed to the abundant active sites provided by the accumulation/depletion layer in the Ti₃C₂T_x/SnO₂ heterojunction, which facilitates the adsorption of oxygen molecules. This work promotes the gas sensing application of MXenes and provides a way to improve gas sensing performance. Full article

The development of advanced functional composite materials for degrading industrial pollutants and achieving photocatalytic hydrogen (H₂) production using abundant solar energy is pivotal in new and renewable energy research. This study presents the synthesis of a nanostructure comprising SnO₂ quantum dots (QDs) randomly dispersed on the surface of graphitic carbon nitride (C₃N₄) nanosheets (Sn-C₃N₄), achieved through the thermal decomposition of melamine and a tin precursor. The synthesized materials were extensively characterized using various analytical techniques, with HRTEM analysis confirming the strong interaction between SnO₂ QDs and C₃N₄. The influence of SnO₂ QDs on the nanocomposite’s photocatalytic performance was evaluated, particularly regarding H₂ production and the degradation of crystal violet (CV) dye under simulated solar-light irradiation. The SnO₂-loaded C₃N₄ nanostructure exhibited a marked enhancement in photocatalytic activity, attributed to the synergistic effects of the quantum-sized SnO₂ nanoparticles. The optimized photocatalyst, 3-Sn-C₃N₄, demonstrated superior photocatalytic efficiency, achieving 95% degradation of CV dye within 45 min under simulated sunlight, significantly outperforming bare C₃N₄. Furthermore, the 3-Sn-C₃N₄ nanostructure attained the highest H₂ yield of 1305.4 μmol/h/g, a 4.6-fold increase compared with bare C₃N₄ (281 μmol/h/g). Enhanced photocatalytic performance was corroborated by photocurrent and EIS studies, which highlighted reduced charge carrier recombination as a critical factor in the improved activity. The underlying photocatalytic mechanisms were also examined. Full article

This study presents a straightforward and cost-effective method to enhance the photoelectrochemical (PEC) water-splitting performance of α-Fe₂O₃ (F), SnO₂ (S), and α-Fe₂O₃ decorated with SnO₂ quantum dots (FS) photoanodes in a NaOH electrolyte. The FS electrode demonstrated a notable improvement in PEC efficiency within the electrolyte. In particular, the generated charges of the FS anode in the NaOH electrolyte reached approximately 12.01 mA cm⁻² under illumination, indicating that the developed heterostructures effectively enhanced kinetics, leading to improved separation of induced carrier pairs. This active carrier-pair separation mechanism contributed considerably to the increased PEC activity in the 0.1 M NaOH electrolyte. The reduction in the bandgap of FS increased its absorption capability in visible light, which further enhanced the current density. Furthermore, the reduction in electrolyte resistance (9.71 Ω), internal resistance (20.19 Ω), charge transfer resistance (3.21 kΩ), Tafel slope (45.5 mV dec-1), limiting current density (−2.09 mA cm⁻²), and exchange current density (−3.68 mA cm⁻²) under illumination at the interface enhanced the charge density of FS. Further, a strong interaction among photoanode nanostructures significantly enhances PEC activity by improving efficient charge separation and transport, reducing recombination rates, and enabling quicker movement of charge carriers to the electrode/electrolyte interface. Thus, this study provides an effective approach to increasing the PEC activity of heterostructures. Full article

The recombination of charges and thermal excitation of carriers at the interface between methylammonium lead iodide perovskite (PVK) and the carbon electrode are crucial factors that affect the optoelectronic performance of carbon-based hole transport layer (HTL)-free perovskite photodetectors. In this work, a method was employed to introduce SnS quantum dots (QDs) on the back surface of perovskite, which passivated the defect states on the back surface of perovskite and addressed the energy-level mismatch issue between perovskite and carbon electrode. Performance testing of the QDs and the photodetector revealed that SnS QDs possess energy-level structures that are well matched with perovskite and have high absorption coefficients. The incorporation of these QDs into the interface layer effectively suppresses the dark current of the photodetector and greatly enhances the utilization of incident light. The experimental results demonstrate that the introduction of SnS QDs reduces the dark current by an order of magnitude compared to the pristine device at 0 V bias and increases the responsivity by 10%. The optimized photodetector exhibits a wide spectral response range (350 nm to 750 nm), high responsivity (0.32 A/W at 500 nm), and high specific detectivity (>1 × 10¹² Jones). Full article