Excellent Photoluminescence Emission Research Articles

Synthesis and study of carbon quantum dots (CQDs) for enhancement of luminescence intensity of CQD@LaPO4:Eu3+ nanocomposite

The carbon nanodots are the newly emerging areas of research which have applications in many fields such as sensors, catalysts, bioimaging etc. Their excellent photoluminescence emission in visible region has prompted many researchers to explore new synthesis routes and precursors for better quantum yield. In this work carbon quantum dots are synthesized by using aloe vera biomass by facile carbonization process. The aqueous solution of carbon quantum dots (CQDs) shows blue light emission upon excitation by 365 nm ultra violet radiation. The field effect scanning electron microscopy images showed CQDs as spherical quantum dots of the size around 10 nm. The transmission electron microscopy (TEM) bright field images confirmed the size of the CQDs. The CQDs thus prepared can be used for bioimaging of plant cells and as an ink for security printing applications. A CQD@LaPO4:Eu3+ nanocomposite has been prepared and its photoluminescence property has been studied. The increased photoluminescence intensity of composite can be attributed to Förster Resonance Energy Transfer (FRET) from CQDs to Eu3+.

Growth Behavior, nucleation control and excellent optical properties of atomically thin WS2 thin films processed via Gas-phase chemical vapor deposition

Improving growth-rate of atomically thin transition metal dichalcogenides (TMDs) with precise thickness-control using a facile-approach is ever growing interest for nanoscale electronic devices. Here, using metalorganic precursors, we demonstrate the growth of WS2 layers on sapphire and SiO2/Si substrates at elevated temperatures via gas-phase chemical vapor deposition (CVD) approach. This choice of precursor for the CVD-process allowed us to rapidly produce the WS2 layers with a growth rate as high as 1-monolayer per 5 min at a growth temperature of 850 ℃. The layer thickness (number of layers), which linearly scales with growth time, can be manipulated with a monolayer precision. Our findings suggest that the initial-nucleation and growth behavior of the WS2 monolayers are very well controlled by reactor pressure and growth temperature. Grain size engineering and possible growth-mode switching from 2D lateral-growth to 3D vertical-growth is demonstrated by tuning the CVD reactor pressure between 10 and 30 Torr. A possible growth behavior is also discussed for the growth temperature range of 650 to 850 ℃. The as-grown WS2 monolayers exhibited excellent photoluminescence emission around 2.0 eV with a linewidth of 49 meV. Our gas-phase-precursor assisted CVD approach would enable a pathway for the rapid-production of atomically thin TMDs for electronic industry.

A CsPbBr3 quantum dots/ultra-thin BN fluorescence sensor for stability and highly sensitive detection of tetracycline

The abuse of tetracycline (TC) antibiotics would seriously affect human health and hence the detection had become essential. Here, we had constructed a hydrophobicity of fluorescence sensor based on the excellent photoluminescence emission of CsPbBr3 QDs and the hydrophobic ability of Boron Nitride (BN). This design effectively solved the instability of CsPbBr3 QDs and realized the sensitive detection of TC. Under optimum conditions, the linear range of TC was 0–0.44 mg L−1 with the 6.5 μg L−1. Furthermore, the sensor was successfully used for the recognition of TC in honey and milk samples. This work also provided an ideal for designing CsPbBr3 QDs-based on fluorescence sensor.

Influence of annealing temperature on photoluminescence of CePO4 thin films on silicon substrates prepared by electron beam evaporation

Nanostructured CePO4 thin films were prepared on silicon substrates by electron beam evaporation technique. In this work, the effects of annealing temperature on photoluminescence (PL) of CePO4 thin films were investigated. CePO4 thin films were annealed at different temperatures between 700 and 1100 °C for 30 min in nitrogen. The annealed CePO4 films show a strong ultraviolet emission at room temperature. Besides, a violet/blue emission was observed when the annealing temperature reached 1000 °C. The X-ray diffraction results show the monoclinic structure of CePO4 thin films. The scanning electron microscopy images were taken to confirm different crystallinities. The concentration of different elements was determined by energy-dispersive X-ray spectroscopy. The excellent PL emission in the annealed films indicates that the CePO4 thin films could be useful for silicon-based light sources.

Core-shell structured NaYF4:Yb,Tm@CdS composite for enhanced photocatalytic properties.

NaYF4:Yb,Tm upconversion nanocrystals with hexagonal structure possess excellent photoluminescence emission characteristics. Under near infrared (NIR) light irradiation, the Yb3+ ions act as sensitizers to absorb the NIR light and transform NIR light into ultraviolet (UV) and visible (Vis) light continuously. Hybrid NIR-activated photocatalysts can be fabricated by combining upconversion nanocrystals with various semiconductor nanocrystals. In this paper, NaYF4:Yb,Tm micro-rods were hydrothermally synthesized with oleic acid as capping ligand. The NaYF4:Yb,Tm@CdS composite was fabricated by in situ generation of CdS nanoclusters on the surface of NaYF4:Yb,Tm micro-rods. The morphologies and structures of NaY4:Yb,Tm and NaYF4:Yb,Tm@CdS were characterized by XRD, SEM, TEM, XPS, UV-Vis and PL spectroscopy. The results of photocatalytic experiments indicated that the NaYF4:Yb,Tm@CdS composite displayed photocatalytic activity under NIR irradiation. In comparison with pure CdS, the photocatalytic ability of NaYF4:Yb,Tm@CdS composite under Vis-NIR irradiation was obviously enhanced. 82% of RhB was degraded by NaYF4:Yb,Tm@CdS catalyst within 75 min under Vis-NIR irradiation, which was more effective than pure CdS (65% degradation of RhB).

Laser-induced fabrication of single crystal zinc hydroxyl dodecylsulfate nano-sheets with excellent fluorescence emission

The successful synthesis of single crystal zinc hydroxyl dodecylsulfate nano-sheets with excellent photoluminescence emission by laser ablation in liquid.

Formation of two-dimensional InAs quantum dot arrays by self-organized anisotropic strain engineering on InP (3 1 1)B substrates

The authors report the formation of two-dimensional InAs quantum dot (QD) arrays by self-organized anisotropic strain engineering of InAs/InGaAsP superlattice (SL) templates on InP (3 1 1)B substrates by chemical-beam epitaxy (CBE). The SL template and InAs QD growth conditions are studied in detail for optimized QD ordering. Excellent photoluminescence emission up to room temperature is achieved from buried QD arrays. The emission wavelength is tuned from above 1.9 μm to the 1.55 μm telecom wavelength region through the insertion of ultrathin GaAs interlayers beneath the QD arrays.

Formation of linear InAs/InGaAsP/InP (1 0 0) quantum dot arrays by self-organized anisotropic strain engineering in chemical beam epitaxy

The formation of laterally ordered linear InAs quantum dot (QD) arrays based on self-organized anisotropic strain engineering is demonstrated. An InAs/InGaAsP superlattice (SL) on InP (1 0 0) serves as a template for the QD arrays grown by chemical beam epitaxy. The InAs QD arrays exhibit excellent photoluminescence emission up to room temperature which is tuned into the 1.55-μm telecom wavelength region through the insertion of ultra-thin GaAs interlayers. Stacking of the QD arrays with identical emission wavelength upon adjusting the GaAs interlayer thickness produces a three-dimensionally self-ordered QD crystal.

Morphology Controllable ZnO Growth on Facet-Controlled Epitaxial Lateral Overgrown GaN/Sapphire Templates

High-quality epitaxial ZnO layers grown on facet-controlled epitaxial lateral overgrown (FACELO) GaN/sapphire templates were achieved by an evaporation−physical transport−condensation method. The ZnO/FACELO GaN heterostructures showed a substantial improvement in the crystalline quality with a lower defect density and excellent photoluminescence emission. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO were systematically studied. The determining factors for the formation of different morphologies were found to be gas-phase supersaturation and the surface energy of the growing planes. In addition, the lattice matching between the ZnO and GaN leads to the improvement of the electric and optical properties. With such kind of perfect ZnO/GaN heterostructure interfaces obtained on the semipolar (112̄2) surface, the new opportunities for the fabrication of hybrid ZnO/GaN optoelectronic devices on sapphire are proposed.

Structural evolution of nanocrystalline silicon studied by high resolution transmission electron microscopy

Abstract In this work, nanocrystalline silicon (nc‐Si) embedded in amorphous silicon nitride (a‐SixNy) films have been characterized by High Resolution Transmission Electron Microscopy (HRTEM). The films have been grown by remote plasma enhanced chemical vapour deposition (RPECVD) onto silicon substrates using a mixture of SiCl4, NH3 and H2. Subsequently, the sample has been introduced to an annealed process. The nanocrystalline inclusions have been measured from the analysis of HRTEM images. The size of nc‐Si inclusions is modified due to the annealing process. The diameter of nc‐Si inclusions in as‐grown films vary from 1.3 to 3.1 nm. In annealed films, a high density of new clusters with reduction of 1 nm of those diameters is observed, as well as the coalescence phenomenon among some nc‐Si inclusions is observed too. Consequently, the diameters of annealed films nc‐Si inclusions range from 0.7 to 4 nm. The thin films show an excellent photoluminescence emission. The density per unit area and size of the nc‐Si inclusions are correlated with the PL emissions. The influence of the structural changes of the nc‐Si on the PL emissions is discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)