- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dual Management of Electrons and Photons to Get High-Performance Light Emitting Devices Based on Si Nanowires and Si Quantum Dots with Al <sub/>2</sub> O <sub/>3</sub> -Ag Hybrid Nanostructures
摘要： Silicon quantum dot (Si QD)-based light emitting devices are fabricated on Si nanowire (Si NW) arrays. Through inserting Al2O3-Ag hybrid nanostructures (Al2O3-Ag HNs) between Si NWs and Si QDs, both photoluminescence (PL) and electroluminescence (EL) are remarkably enhanced compared to the control sample. The PL enhancement can be mainly attributed to passivation effect of Al2O3 to p-type Si NWs and enlarged absorption cross-section due to the local surface plasmon resonance effect of Ag nanoparticles. The EL intensity is enhanced by 14.9-fold at the same injection current under a lower applied voltage, which may result from the high injection efficiency of electrons and the promoted waveguide effect of nanowire structures with Al2O3-Ag HNs. It is demonstrated that light emitting device performances can be well improved by careful management of both electrons and photons via controlling the interface conditions of Si NWs/Si QDs.
关键词： hybrid nanostructures,silicon nanowires,light emitting devices,silicon quantum dots
更新于2025-11-21 11:01:37
-
White light emission from a mixture of silicon quantum dots and gold nanoclusters and its utilities in sensing of mercury( <scp>ii</scp> ) ions and thiol containing amino acid
摘要： White light emitting mixture (WLEM) was produced by controlled mixing of blue emitting silicon quantum dots (Si QDs) and orange red emitting gold nanoclusters (Au NCs). The chromaticity color co-ordinate of the WLEM studied using CIE (Commission Internationale del'Eclairage) diagram was found to be (0.33, 0.32), which was very close to that of perfect white light emitting source. The WLEM can also be achieved in the form of gel, solid and film with nearly the same CIE co-ordinates which enhances its utility as white light-emitting source in solid state devices. The reversible and thermo-responsive behaviour of the WLEM broadens its application in thermal sensing. Furthermore, the system was found to be showing fast, sensitive and selective detection of Hg2+ ions and thiol containing amino acid cysteine.
关键词： Hg2+ ions,white light emitting mixture,silicon quantum dots,cysteine,gold nanoclusters
更新于2025-11-20 15:33:11
-
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
-
Visible-Light Driven Photocatalytic Hydrogen Generation by Water-Soluble All-Inorganic Core-Shell Silicon Quantum Dots
摘要： The photocatalytic hydrogen (H2) generation by boron (B) and phosphorus (P) codoped silicon quantum dots (Si QDs) with diameters in the quantum confinement regime is investigated. The codoped Si QDs have an amorphous shell made from B, Si and P. The shell induces negative potential on the surface and makes codoped Si QDs dispersible in water. The hydrophilic shell offers enhanced stability and efficiency in the photocatalytic H2 generation and provides the opportunity to study the size dependence of the H2 generation rate. A drastic increase of the H2 generation rate with decreasing the QD size is observed. Analyses based on the Marcus theory reveal that the upper shift of the lowest unoccupied molecular orbital level of Si QDs by the quantum confinement effect is responsible for the enhanced photocatalytic activity.
关键词： silicon quantum dots,quantum confinement,Marcus theory,photocatalytic hydrogen generation
更新于2025-09-23 15:21:01
-
Silicon Quantum Dots Metal Enhanced Photoluminescence by Gold Nanoparticles in Colloidal Ensembles: Effect of Surface Coating
摘要： In the present study we report the photophysical properties of colloidal ensembles of silicon quantum dots (SiD) and gold nanoparticles (AuNP), particularly focused on investigating metal-enhanced photoluminescence effects. AuNP with different sizes, (27 ± 10) and (88 ± 12) nm, and ca. 3.4 nm size SiD with different surface groups, either covered with an oxidized surface film bearing Si-OH surface groups or grafted with propylamine leading to Si-(CH2)2-CH2-NH2 terminal functionalities, were tested to evaluate gold enhancement of SiD photoluminescence. Nanoparticles were characterized by HRTEM, FTIR, XPS, ICP-AES, and gel electrophoresis, while photophysical properties of nanoparticles alone and in colloidal ensembles at different concentrations were investigated by absorption and steady-state and time-resolved photoluminescence studies, including quantum yield determinations. Enhanced absorption and photoluminescence of SiD in the presence of AuNP was evidenced, leading in the most favorable cases to ca. 10-times increase in SiD brightness. This effect depends strongly on the SiD surface coating and its interaction with citrate-capped gold surfaces, where these interactions govern particles aggregation and relative distance distributions among SiD and AuNP in the ensembles. The nature of these interactions and how they affect metal-enhanced luminescence is thoroughly discussed. The present study provides significant information on the effect of SiD surface groups and surface charge on the metal-enhanced luminescence phenomenon in colloidal aqueous suspensions.
关键词： gold nanoparticles,colloidal ensembles,metal-enhanced photoluminescence,silicon quantum dots,surface coating
更新于2025-09-23 15:21:01
-
Tailoring Photoluminescence from Si-Based Nanocrystals Prepared by Pulsed Laser Ablation in He-N2 Gas Mixtures
摘要： Using methods of pulsed laser ablation from a silicon target in helium (He)-nitrogen (N2) gas mixtures maintained at reduced pressures (0.5–5 Torr), we fabricated substrate-supported silicon (Si) nanocrystal-based ?lms exhibiting a strong photoluminescence (PL) emission, which depended on the He/N2 ratio. We show that, in the case of ablation in pure He gas, Si nanocrystals exhibit PL bands centered in the “red - near infrared” (maximum at 760 nm) and “green” (centered at 550 nm) spectral regions, which can be attributed to quantum-con?ned excitonic states in small Si nanocrystals and to local electronic states in amorphous silicon suboxide (a-SiOx) coating, respectively, while the addition of N2 leads to the generation of an intense “green-yellow” PL band centered at 580 nm. The origin of the latter band is attributed to a radiative recombination in amorphous oxynitride (a-SiNxOy) coating of Si nanocrystals. PL transients of Si nanocrystals with SiOx and a-SiNxOy coatings demonstrate nonexponential decays in the micro- and submicrosecond time scales with rates depending on nitrogen content in the mixture. After milling by ultrasound and dispersing in water, Si nanocrystals can be used as e?cient non-toxic markers for bioimaging, while the observed spectral tailoring e?ect makes possible an adjustment of the PL emission of such markers to a concrete bioimaging task.
关键词： pulsed laser ablation in gases,pulsed laser deposition,silicon quantum dots,bioimaging,silicon nanoparticles,quantum con?nement,photoluminescence,silicon oxynitride
更新于2025-09-19 17:13:59
-
Fast Gate-Based Readout of Silicon Quantum Dots Using Josephson Parametric Amplification
摘要： Spins in silicon quantum devices are promising candidates for large-scale quantum computing. Gate-based sensing of spin qubits offers a compact and scalable readout with high fidelity, however, further improvements in sensitivity are required to meet the fidelity thresholds and measurement timescales needed for the implementation of fast feedback in error correction protocols. Here, we combine radio-frequency gate-based sensing at 622 MHz with a Josephson parametric amplifier, that operates in the 500–800 MHz band, to reduce the integration time required to read the state of a silicon double quantum dot formed in a nanowire transistor. Based on our achieved signal-to-noise ratio, we estimate that singlet-triplet single-shot readout with an average fidelity of 99.7% could be performed in 1 μs, well below the requirements for fault-tolerant readout and 30 times faster than without the Josephson parametric amplifier. Additionally, the Josephson parametric amplifier allows operation at a lower radio-frequency power while maintaining identical signal-to-noise ratio. We determine a noise temperature of 200 mK with a contribution from the Josephson parametric amplifier (25%), cryogenic amplifier (25%) and the resonator (50%), showing routes to further increase the readout speed.
关键词： quantum computing,spin qubits,gate-based sensing,silicon quantum dots,Josephson parametric amplification
更新于2025-09-19 17:13:59
-
Precise size separation of water-soluble red-to-near-infrared-luminescent silicon quantum dots by gel electrophoresis
摘要： A gel electrophoresis, which is a standard method for separation and analysis of macromolecules such as DNA, RNA and proteins, is applied for the first time to silicon (Si) quantum dots (QDs) for the size separation. In the Si QDs studied, boron (B) and phosphorus (P) are simultaneously doped. The codoping induces negative potential on the surface of a Si QD and makes it dispersible in water. Si QDs with different B and P concentrations and grown at different temperatures (950°C - 1200°C) are studied. It is shown that a native polyacrylamide gel electrophoresis can separate codoped Si QDs by size. The capability of gel electrophoresis to immobilize size-separated QDs in a solid matrix makes detailed analyses of size-purified Si QDs possible. For example, photoluminescence (PL) studies of dried gel of Si QDs grown at 1100°C demonstrate that a PL spectrum of a Si QDs solution with the PL maximum around 1.4 eV can be separated into more than 15 spectra with the PL maximum changing from 1.2 to 1.8 eV depending on the migration distance. It is found that the relation between the PL peak energy and the migration distance depends on the growth temperature of Si QDs as well as the B and P concentration. For all the samples with different impurity concentrations and grown at different temperatures, a clear trend is observed in the relation between the full width at half maximum (FWHM) and the peak energy of the PL spectra in a wide energy range. The FWHM increases with increasing the peak energy and it is nearly twice larger than those observed for undoped Si QDs. The large PL FWHM of codoped Si QDs suggests that excitons are further localized in codoped Si QDs due to the existence of charged impurities.
关键词： codoping,size separation,silicon quantum dots,photoluminescence,gel electrophoresis
更新于2025-09-19 17:13:59
-
A label-free fluorescent sensor based on silicon quantum dots–MnO <sub/>2</sub> nanosheets for the detection of α-glucosidase and its inhibitor
摘要： A label-free fluorescent sensor based on silicon quantum dots–MnO2 nanosheets for the detection of α-glucosidase and its inhibitor?. α-Glucosidase and its inhibitors play a key role in diagnosis and treatment of diabetes. In the present work, we established a facile, sensitive and selective fluorescence method based on silicon quantum dots (SiQDs) and MnO2 nanosheets for the determination of α-glucosidase and one of its inhibitors acarbose. The fluorescence of SiQDs was greatly quenched by MnO2 nanosheets due to the inner filter effect. α-Glucosidase could easily catalyze the hydrolysis of L-ascorbic acid-2-O-α-D-glucopyranosyl (AAG) to produce ascorbic acid (AA), which could reduce MnO2 nanosheets to Mn2+, resulting in dramatic recovery of the fluorescence of SiQDs. The proposed sensing platform could provide a good linear relationship between the fluorescence intensity of SiQDs and the concentration of α-glucosidase in the range of 0.02–2.5 U mL?1 with a detection limit of 0.007 U mL?1. In addition, the sensing platform could be used for α-glucosidase inhibition. Acarbose was one of the most common and typical inhibitors, and this sensing platform can be utilized to detect acarbose in the range of 1–1000 μM. The developed fluorescence method was successfully validated for the determination of α-glucosidase in human serum samples.
关键词： silicon quantum dots,acarbose,label-free fluorescent sensor,MnO2 nanosheets,α-glucosidase
更新于2025-09-12 10:27:22
-
The effects of drying technique and surface pre-treatment on the cytotoxicity and dissolution rate of luminescent porous silicon quantum dots in model fluids and living cells
摘要： Tailoring of the biodegradation of photoluminescent silicon quantum dots (Si QDs) is important for their future applications in diagnostics and therapy. Here, the effect of drying and surface pretreatment on the dissolution rate of Si QDs in model liquids and living cells was studied in-vitro by a combination of photoluminescence and Raman micro-spectroscopy. Porous silicon particles were obtained by mechanical milling of electrochemically etched mesoporous silicon films, and consist of interlinked silicon nanocrystals (QDs) and pores. The samples were subjected to super-critical drying with CO2 solvent (SCD) or air drying (AD) and then annealed at 600 C for 16 hours in 1% oxygen to achieve the nano-sized Si QDs. The obtained samples were characterized by a core-shell structure with a crystalline silicon core and a SiO2 layer on the surface. The sizes of the crystalline silicon core, calculated from the Raman scaterring spectra, were about 4.5 nm for initial AD-SiQDs, and about 2 nm for initial SCD-SiQDs. Both AD-Si QDs and SCD-Si QDs exhibited visible photoluminescene (PL) properties due to quantum confinement effects. The dissolution of nanocrystals was evaluated by their PL quenching , as well as by the presence of a low-frequency shift, broadening, and decrease in the intensity of the Raman signal. The stability of AD-Si QDs and the complete dissolution of SCD-Si QDs during 24 hours of incubation with cells have been demonstrated. This might explain the apparent lower cytoxicty observed for SCD-Si QDs.
关键词： air drying,silicon quantum dots,Raman micro-spectroscopy,biodegradation,photoluminescence,super-critical drying
更新于2025-09-12 10:27:22