Search Results (45)

For the first time, a mixture of PbTe and Pb- and Te-oxides coated with carbon, under electron beam irradiation (EBI), was transformed into quantum dots, nanocrystals, nanoparticles and grains of PbTe with a sintered appearance. A small portion of non-stoichiometric phases was also obtained. By selecting conditions that favor the instantaneous transformation, the Gibbs free energy barrier is lowered for obtaining different PbTe structures. The driving force associated with the high-energy milling requires 4 h of processing time to reach a complete transformation, while a high-energy source kinetically affects precursor surfaces to cause an abrupt global chemical transformation instantly. Importantly, the size of the PbTe structures increases as they approach the irradiation point, implying a growth process that is affected by the local temperature reached during the EBI. Imaging after the EBI process revealed morphological variations in PbTe, which can be attractive for use in thermoelectric materials. The results of this study provide the first insights into electron-beam-induced reactions using a multiphase mixture of precursors. Therefore, it is believed that this proposal can also be applied to obtain other binary semiconductor structures, even ternary ones. Full article

Ternary metal chalcogenide quantum dots (QDs), such as CuInS₂, have attracted significant attention due to their lower toxicity compared to binary counterparts containing cadmium or lead, making them promising candidates for biomedical imaging and solar energy applications. The surfactant choice is critical for controlling nanocrystal nucleation, growth kinetics, and functionalization. This directly affects the toxicity and applications of QDs. In this work, we report a synthesis protocol for PVP-capped CuInS₂ QDs in an aqueous solution. Using density functional theory (DFT) calculations, we predicted the coordination patterns of PVP on the CuInS₂ QDs surface, providing insights into the stabilization mechanism. The synthesized QDs were characterized using TEM, XRD, XPS, and FTIR to assess their morphology, chemical composition, and surface chemistry. The QDs exhibited dual photoluminescence (PL) maxima at 550 nm and 680 nm, attributed to defect-related emissions, making them suitable for cell imaging applications. Cytotoxicity studies and cell imaging experiments demonstrate the excellent biocompatibility and effective staining capabilities of the PVP-capped CuInS₂ QDs, highlighting their potential as fluorescent probes for long-term, multicolor cell imaging including two-photon microscopy. Full article

g-C₃N₄, a biocompatible material, has prominent applications in biology and is ideal for nano-enzyme studies. Though reported as a peroxidase mimic, its activity remains low. This group combined N,S-doped carbon quantum dots (NS-CQDs) with g-C₃N₄ (7NSC-g), verifying its peroxidase-like activity. Based on this, a ternary composite of Co₃O₄ in different forms and 7NSC-g was developed to enhance peroxidase activity, to design a g-C₃N₄-based composite enzyme. Characterizations determined the composition and morphology. Colorimetry evaluated peroxidase activity, where the simulated enzyme catalyzes blue product formation from the TMB substrate in the presence of H₂O₂. UV-Vis spectrophotometry measured absorbance changes to determine target concentrations. The results show Co₃O₄ doping improves catalytic activity, with larger specific surface area providing more activation sites. The highest activity of g-C₃N₄/NS-CQDs/Co₃O₄ was at 5% floral Co₃O₄, being efficient due to Co₃O₄’s electron-transfer acceleration and hydroxyl-radical mechanism. Under optimal conditions, the composite detected H₂O₂ (10.0–230.0 μM, detection limit of 0.031 μM) and glucose (10.0–650.0 μM, detection limit of 1.024 μM). Full article

The traditional von Neumann architecture encounters significant limitations in computational efficiency and energy consumption, driving the development of neuromorphic devices. The optoelectronic synaptic device serves as a fundamental hardware foundation for the realization of neuromorphic computing and plays a pivotal role in the development of neuromorphic chips. This study develops a ternary heterojunction synaptic transistor based on perovskite quantum dots to tackle the critical challenge of synaptic weight modulation in organic synaptic devices. Compared to binary heterojunction synaptic transistor, the ternary heterojunction synaptic transistor achieves an enhanced hysteresis window due to the synergistic charge-trapping effects of acceptor material and perovskite quantum dots. The memory window decreases with increasing source-drain voltage (V_DS) but expands with prolonged program/erase time, demonstrating effective carrier trapping modulation. Furthermore, the device successfully emulates typical photonic synaptic behaviors, including excitatory postsynaptic currents (EPSCs), paired-pulse facilitation (PPF), and the transition from short-term plasticity (STP) to long-term plasticity (LTP). This work provides a simplified strategy for high-performance optoelectronic synaptic transistors, showcasing significant potential for neuromorphic computing and adaptive intelligent systems. Full article

Ternary g-C₃N₄/CQD/Ag photocatalysts were synthesized via deposition of carbon quantum dots (CQDs) and silver nanoparticles (Ag) onto graphitic carbon nitride (g-C₃N₄) for efficient acetaminophen degradation. The nanocomposites exhibited enhanced photoresponse and broad-spectrum photocatalytic activity under both UV (254 nm, 250 W) and Xenon (>420 nm, 500 W) irradiation. Characterization by XRD, FTIR, SEM, PL, and EDX elucidated the material’s composition, structure, morphology, and optical properties. Optimized photocatalytic degradation of acetaminophen (50 mg/L) was achieved at pH 7 with 0.6 g/L catalyst loading and 60 min irradiation, yielding degradation efficiencies of 87.5% (UV) and 85.3% (Xenon). Radical quenching experiments and GC-MS analysis identified hydroxyl radicals as the primary reactive species and revealed a gradual decrease in intermediate toxicity during mineralization. This study demonstrates the superior photocatalytic performance of the ternary g-C₃N₄/CQD/Ag nanocomposites compared to binary systems for effective acetaminophen removal. Full article

In this study, a RGB based ternary-emission molecularly imprinted ratiometric fluorescence (MI-RFL) sensor was facilely constructed by using a post-imprinting mixing strategy for the sensitive detection of enrofloxacin (ENR). Upon excitation at 365 nm, the MI-RFL sensor exhibited significant emission peaks at 450, 550, and 620 nm. As the ENR concentration increased, the blue fluorescence generated by ENR in the sensing system gradually intensified, while the red and green fluorescence emitted by the quantum dots in the molecularly imprinted polymers (MIPs) was significantly quenched. Sensing conditions were systematically investigated, including the excitation wavelength, mixing ratio of red/green MIPs, the pH of the buffer solution, and the reaction time. Under the optimal conditions, the developed sensor showed a good linear relationship within the range of 0.25–4 ppm along with obvious color change, with a low detection limit of 0.134 ppm. High selectivity was also attained with an imprinting factor up to 11.65. When applied to real samples of seawater and seafood, the sensor showed good recovery rates of 94.3–126.4% and accuracy with a relative standard deviation of less than 3.97%. Furthermore, the sensor-based kit was easily fabricated and, thus, naked-eye detection of ENR was realized onsite. This study can provide a universal approach for the rapid and visual detection of ENR in complicated matrices. Full article

Carcinoembryonic antigen (CEA) is an important tumor biomarker for the early clinical diagnosis of various cancers, and, therefore, the accurate and sensitive quantitative determination of CEA is of vital significance. In this study, we demonstrated the in situ growth of Au nanoparticles (AuNPs) on nitrogen-doped graphene quantum dots (N-GQDs) decorated reduced graphene oxide (rGO) nanocomposites by using simple drop-coating and electrochemical deposition methods. N-GQDs@rGO can be formed through the π–π stacking interaction and possesses a high specific surface area and many functional groups, providing lots of anchor sites (amino moieties in NGQDs) for the in situ electrochemical growth of AuNPs without the addition of reductants and protective agents. Such AuNPs/N-GQDs@rGO ternary nanocomposites combine the characteristics of three nanomaterials, showing a large surface area, excellent solubility, good conductivity, catalytic activity, a simple fabrication process, and notable stability, which are further used to construct a label-free electrochemical immunosensor for the determination of CEA. Under the optimized experimental conditions, the AuNPs/N-GQDs@rGO-based electrochemical immunosensor achieves a broad linear response, ranging from 1 pg/mL to 0.5 μg/mL and a low detection limit of 0.13 pg/mL. Moreover, the AuNPs/N-GQDs@rGO-based electrochemical immunosensor shows exceptional selectivity, anti-interference, and anti-fouling capabilities for the direct analysis of CEA amounts in fetal bovine serum samples, showing vast potential in the clinical screening of cancer. Full article

We propose a temperature-dependent optimization procedure for the second-nearest neighbor (2NN) sp³s* tight-binding (TB) theory parameters to calculate the effects of strain, structure dimensions, and alloy composition on the band structure of heterostructure spherical core/shell quantum dots (QDs). We integrate the thermoelastic theory of solids with the 2NN sp³s* TB theory to calculate the strain, core and shell dimensions, and composition effects on the band structure of binary/ternary CdSe/Cd(Zn)S and ZnSe/Zn(Cd)S QDs at any temperature. We show that the 2NN sp³s* TB theory with optimized parameters greatly improves the prediction of the energy dispersion curve at and in the vicinity of L and X symmetry points. We further used the optimized 2NN sp³s* TB parameters to calculate the strain, core and shell dimensions, and composition effects on the nanocrystal bandgaps of binary/ternary CdSe/Cd(Zn)S and ZnSe/Zn(Cd)S core/shell QDs. We conclude that the 2NN sp³s* TB theory provides remarkable agreement with the measured nanocrystal bandgaps of CdSe/Cd(Zn)S and ZnSe/Zn(Cd)S QDs and accurately reproduces the energy dispersion curves of the electronic band structure at any temperature. We believe that the proposed optimization procedure makes the 2NN sp³s* TB theory reliable and accurate in the modeling of core/shell QDs for nanoscale devices. Full article

Ternary In_1−xGa_xP quantum dots (QDs) have emerged as promising materials for efficient blue emission, owing to their tunable bandgap, high stability, and superior optoelectronic properties. However, most reported methods for Ga incorporation into the InP structure have predominantly relied on cation exchange in pre-grown InP QDs at elevated temperatures above 280 °C. This is largely due to the fact that, when heating In and P precursors in the presence of Ga, an InP/GaP core–shell structure readily forms. Herein, we introduce a novel synthesis approach using the indium precursor [In(btsa)₂Cl]₂ and GaI₃ to fabricate In_1−xGa_xP QDs in a single step at relatively low temperatures (200 °C). By adjusting the GaI₃ content, we achieved controlled emission tuning from red to blue. Structural and compositional analysis through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed successful Ga³⁺ incorporation into the QD core, with a corresponding blue shift in the emission as GaI₃ content increased. The synthesized QDs demonstrated a photoluminescence quantum yield (PLQY) of ~50% and a full width at half maximum (FWHM) of 45~62 nm, highlighting the potential of this synthesis method for advanced optoelectronic applications. Full article

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD’s emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30–60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 10¹⁴ cm⁻² dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells. Full article

A fluorescent probe based on ternary AgFeS₂ quantum dots has been prepared for the design of ternary chalcogenides. The nanoparticles are synthesized with oleylamine as a stabilizer at a low temperature (particle size in the range of 2 to 3 nm) and they exhibit an intense blue emission in aqueous media. As for their internal structure, each nanoparticle’s relative stoichiometric ratio (AgFe_1.01S_1.91) is very close to the theoretical value of 1:1:2. Their magnetic properties have been studied with a vibrating sample magnetometer and they have ferromagnetism between 4 K and 298 K (applied magnetic field ranging between −10,000 and 10,000 Oe). In the presence of iodide ions, the emission at 458 nm derived from AgFeS₂ QDs has been observed to give rise to fluorescence quenching. The detection system is based on a static quenching process and morphological change between iodide ions and AgFeS₂, which has a good linear range from 0 to 37.5 μmol/L, with a limit of detection of 0.99 μM. The nanoprobe responds within 30 s for the efficient detection of iodide. Such functional quantum dots will provide a powerful indicator in environmental and bio-sensing applications. Full article

In this study, graphene quantum dots (GQDs) have been incorporated into the g-C₃N₄/ZIF-67 heterojunction system as a photosensitizer to enhance photocatalytic conversion of CO₂-to-CO. The GQDs are deposited onto the surface of g-C₃N₄/ZIF-67 using a simple water bath procedure. As expected, GQDs/g-C₃N₄/ZIF-67 presents outstanding performance in CO₂ photoreduction. Among the GQDs/g-C₃N₄/ZIF-67 ternary photocatalysts, 7 GQDs-CN/ZIF-67 exhibits the best photocatalytic CO₂ reduction ability with a CO yield of 51.71 μmol g⁻¹, which is 5.05 and 1.87 times more than pristine g-C₃N₄ (10.24 μmol g⁻¹) and g-C₃N₄/ZIF-67 (27.65 μmol g⁻¹), respectively. This result shows that upon combination of GQDs with ZIF-67/g-C₃N₄, GQDs can be used as photosensitizers to improve the optical absorption capacity of the photocatalyst. Furthermore, GQDs serve as electron channels, facilitating the transport of photo-induced electrons from ZIF-67 to g-C₃N₄, which promotes photogenerated carrier separation efficiency. This study innovatively adds GQDs to the heterojunction and applies the prepared ternary composite to the CO₂ photoreduction, which inspires a novel direction for the design of non-noble metal photocatalysts. Full article

In this work, Au nanoparticle-decorated ZnO@graphene core–shell quantum dots (Au-ZnO@graphene QDs) were successfully prepared and firstly used to modify an ITO electrode for the construction of a novel photoelectrochemical biosensor (Au-ZnO@graphene QDs/ITO). Characterization of the prepared nanomaterials was conducted using transmission electron microscopy, steady-state fluorescence spectroscopy and the X-ray diffraction method. The results indicated that the synthesized ternary nanomaterials displayed excellent photoelectrochemical performance, which was much better than that of ZnO@graphene QDs and pristine ZnO quantum dots. The graphene and ZnO quantum dots formed an effective interfacial electric field, enhancing photogenerated electron–hole pairs separation and leading to a remarkable improvement in the photoelectrochemical performance of ZnO@graphene QDs. The strong surface plasmon resonance effect achieved by directly attaching Au nanoparticles to ZnO@graphene QDs led to a notable increase in the photocurrent response through electrochemical field effect amplification. Based on the specifical recognition between cysteine and Au-ZnO@graphene QDs/ITO through the specificity of Au-S bonds, a light-driven photoelectrochemical sensor was fabricated for cysteine detection. The novel photoelectrochemical biosensor exhibited outstanding analytical capabilities in detecting cysteine with an extremely low detection limit of 8.9 nM and excellent selectivity. Hence, the Au-ZnO@graphene QDs is a promising candidate as a novel advanced photosensitive material in the field of photoelectrochemical biosensing. Full article

Organic dyes in natural waters jeopardize human health. Whether semiconductor materials can effectively degrade dyes has become a challenge for scientific research. Based on this, this study rationally prepared different nanocomposites to remove organic dyes effectively. Pure SnO₂ quantum dots, ZnO nanosheets, and SnO₂/ZnO (ZS) binary nanocomposites are prepared using the hydrothermal method. Subsequently, SnO₂/ZnO@GO (ZSG) ternary composites containing different amounts of GO, i.e., ZSG-5, ZSG-15, and ZSG-25, are synthesized by an ultrasonic water bath method, in which ZS was coupled with GO to form Z-type heterojunctions. The ZSG-15 ternary composites exhibited excellent photocatalytic activity for the degradation of rhodamine B by simulating sunlight. The test results show that the degradation rate of ZSG-15 is about 7.6 times higher than ZnO. The increase in photocatalytic activity is attributed to the synergistic effect of SnO₂ and GO to improve the separation efficiency of photogenerated carriers in ZnO. Notably, the large specific surface area of GO increases the reactive sites. Compared with binary nanocomposites, ZSG-15 broadens the response range to light while further accelerating the electron transport rate and improving the photoelectric stability. Full article

Silver-based chalcogenide semiconductors exhibit low toxicity and near-infrared optical properties and are therefore extensively employed in the field of solar cells, photodetectors, and biological probes. Here, we report a facile mixture precursor hot-injection colloidal route to prepare Ag₂Te_xS_1−x ternary quantum dots (QDs) with tunable photoluminescence (PL) emissions from 950 nm to 1600 nm via alloying band gap engineering. As a proof-of-concept application, the Ag₂Te_xS_1−x QDs-based near-infrared photodetector (PD) was fabricated via solution-processes to explore their photoelectric properties. The ICP-OES results reveal the relationship between the compositions of the precursor and the samples, which is consistent with Vegard’s equation. Alloying broadened the absorption spectrum and narrowed the band gap of the Ag₂S QDs. The UPS results demonstrate the energy band alignment of the Ag₂Te_0.53S_0.47 QDs. The solution-processed Ag₂Te_xS_1−x QD-based PD exhibited a photoresponse to 1350 nm illumination. With an applied voltage of 0.5 V, the specific detectivity is 0.91 × 10¹⁰ Jones and the responsivity is 0.48 mA/W. The PD maintained a stable response under multiple optical switching cycles, with a rise time of 2.11 s and a fall time of 1.04 s, which indicate excellent optoelectronic performance. Full article