Stable Photoluminescence Emission Research Articles

Stretchable Metal Halide Perovskite Color Conversion Layers with Block Copolymer Dispersant

AbstractStretchable luminescent nanocomposites with metal halide perovskite (MHP) emitters are in high demand as deformable color‐conversion layers (CCLs) for vivid‐colored form‐factor free displays. However, the immiscibility of the MHP crystals with an elastomeric polymer matrix induces particle aggregation with resultant luminescence quenching, hindering the development of MHP‐based CCLs. Herein, a simple method is proposed to produce highly luminescent MHP nanoparticles (NPs) and stably disperse them in an elastomeric poly(dimethylsiloxane) (PDMS) polymer matrix with block copolymer (BCP) dispersant. The nanocomposites are developed through sequential steps of synthesis of MHP‐NP dispersion solution with BCP and blending with PDMS followed by thermal curing. It is revealed that Lewis basic poly(2‐vinylpyridine)‐block‐poly(dimethylsiloxane) (P2VP‐b‐PDMS) BCP added in the synthesis step promotes crystallization of the MHPs as nanocrystals with an average diameter of 5.9 ± 1.2 nm, whereas MHPs with hundreds of nm are produced without BCP. The resultant MHP‐NPs with P2VP‐b‐PDMS exhibit excellent photophysical properties, such as narrow band emission, high photoluminescence (PL) quantum yield, and long PL lifetime. The MHP‐NPs are stably dispersed in the PDMS matrix by P2VP‐b‐PDMS without particle aggregation, leading to highly deformable and stretchable nanocomposites with stable PL emission upon repetitive stretching, and excellent environmental stability.

Synthesis of N-Doped Micropore Carbon Quantum Dots with High Quantum Yield and Dual-Wavelength Photoluminescence Emission from Biomass for Cellular Imaging.

Pursuit of a simple, fast, and cost-effective method to prepare highly and dual-wavelength fluorescent carbon quantum dots (CQDs) is a persistent objective in recent years. Here, we fabricated N-doped micropore carbon quantum dots (NM-CQDs) with a high quantum yield and dual-wavelength photoluminescence (PL) emission from sustainable biomass using a pulsed laser ablation method. Interestingly, two coexisting indigo–blue photoluminescence (PL) emissions were clearly observed, elucidating that the excited electrons transited from the intrinsic π* orbital to the surface state (SS) formed from the saturation passivation. The quantum yield (QY) and fluorescence lifetime (FL) of the obtained NM-CQDs were as high as 32.4% and 6.56 ns. Further investigations indicated that the emission behaviors of NM-CQDs were still stable and independent in various conditions such as various excitation wavelengths, salt ionic concentrations, pH values, irradiation times, and temperatures. The obtained NM-CQDs are very suitable for cellular staining images due to strong and stable PL emission and show good internalization in different cells. Therefore, we propose a new and cost-effective preparation strategy for highly fluorescent NM-CQDs with great potential in biomedical imaging and engineering.

Construction of Acetaldehyde-Modified g-C3N4 Ultrathin Nanosheets via Ethylene Glycol-Assisted Liquid Exfoliation for Selective Fluorescence Sensing of Ag.

We successfully prepared acetaldehyde-modified graphitic carbon nitride (g-C3N4) ultrathin nanosheets (ACNNSs) by a simple ethylene glycol-assisted liquid exfoliation method. The introduction of acetaldehyde regulated the surface energy of g-C3N4 to better match with that of water, which improved the exfoliation efficiency. Moreover, acetaldehyde introduces defects into the g-C3N4 structure, which can act as excitation energy traps and cause considerable variation in the fluorescence emission. Benefiting from the stable photoluminescence emission, good water solubility, and biocompatibility, the obtained ACNNSs showed a selective fluorescent response to Ag+ in both aqueous solution and living cells. The strong absorption and intimate contact with Ag+ and its appropriate redox potential of ACNNSs contributed to this excellent fluorescent response. A simple and environmental friendly approach was proposed to simultaneously achieve modification and exfoliation of g-C3N4 in aqueous solution. These findings might lead to wider applications of carbon-based nanomaterials as active materials for fluorescence detection in the environment.

Erratum to: Enhancement of silicon nanowire opto-electric properties by combining acid vapor etching and lithium pore-filling

In this paper, we report a novel method combining acid vapor etching (AVE) and Lithium (Li) pore-filling aiming to enhance the opto-electrical properties of silicon nanowires (SiNWs). Images provided by both scanning and transmission electron microscopies (SEM and TEM) show that, the silver-Assisted Chemical Etching (Ag-ACE) method provides uniform and vertically aligned SiNWs with smooth sidewalls. AVE treatment leads to the formation of thin porous silicon (pSi) layer covering the initially solid SiNW sidewalls without affecting their initial length. The as-prepared porous SiNWs (pSiNWs) exhibit a quite strong photoluminescence (PL) band centered on 2 eV. An additional immersion of pSiNWs in LiBr aqueous solution leads to a significant change in the surface chemistry and a stable PL emission with fourfold increase in the intensity. The total reflectivity decreases with Li concentration and reaches 1% in the visible range. Simultaneously, the minority carrier lifetime (τeff) of pSiNWs is enhanced from 1.48 to 7.1 µs due to the formation of a stable passivation layer and the saturation of dangling bands. The dark I–V measurement shows a significant decrease of the series resistance from 340 to 85 Ω.

Photostability of the Oleic Acid-Encapsulated Water-Soluble Cd x Se y Zn1-x S1-y Gradient Core-Shell Quantum Dots.

Composite systems where quantum dots (QDs) are combined with other nanomaterials (e.g., gold nanorods) in aqueous solutions have attracted broad attention—both for their potential in applications and for studies of fundamental processes. However, high-quality QDs are typically prepared in organic solvents, and the transfer of QDs to an aqueous phase is needed to create the desired QD composites. Photostability of the transferred QDs—both the steady-state and photo-induced dynamic properties—is essential for studying the processes in the composites and for their applications. We present a detailed study of the photostability of aqueous CdxSeyZn1–xS1–y gradient core–shell QDs obtained by various approaches using linker exchange and surfactant encapsulation. Beside the steady-state photoluminescence (PL) emission stability, we also study changes in the PL decay. From the variety of the studied samples, the water-soluble QDs encapsulated by a double layer of oleic acid show superior properties, that is, stable PL emission and PL decay under continuous light or pulsed-laser light irradiation. We demonstrate that the double-layer encapsulation of QDs can be used to create QDs–metal nanoparticle composites.

One-pot evaporation–condensation strategy for green synthesis of carbon nitride quantum dots: An efficient fluorescent probe for ion detection and bioimaging

Herein, highly blue graphitic carbon nitride quantum dots (g-CNQDs) were synthesized by one-step microwave-assisted evaporation–condensation strategy using bulk g-C3N4 as the precursor within 5 min. In contrast with conventional chemical routes, the as-synthesized g-CNQDs exhibited a high crystalline quality, excellent fluorescence characteristics, and a narrow size distribution with an average diameter of 3.5 ± 0.5 nm. More importantly, by using a household microwave oven, this method has the advantages of wide accessibility, environmental friendliness, a high yield of ∼40%, and can be facilely synthesized in a large scale (scaled up to a gram scale). Notably, owing to the absence of any organic reagents, the blueas-prepared g-CNQDs show the excitation wavelength-independent photoluminescence (PL) behavior. Moreover, benefiting from the stable PL emission, good water solubility, and extraordinary biocompatibility with a high quantum yield of ∼17%, the fluorescent g-CNQDs can serve as a potential sensitive and selective probe for Fe3+ detection with a super low detection limit of 2 nM and an effective labeling agent for live-cell imaging. This work provides a unique opportunity to obtain g-CNQDs in large scale via a facile route, which may pave the way for the further design of g-CNQDs with other applications.

Synthesis of Mn doping Ag–In–Zn–S nanoparticles and their photoluminescence properties

Mn doped Ag–In–Zn–S nanoparticles (Mn:AgInZnS) were successfully synthesized by using a practical hot-injection method. The as-prepared Mn:AgInZnS nanoparticles were triangular shape with average radius of 6(±0.5) nm, and the composition of doped Mn was about 7.29 by wt.%. Moreover, the Mn:AgInZnS nanoparticles demonstrated strong and stable photoluminescence emission at about 620nm, and the UV–vis absorption spectrum further revealed band gap absorption around 600nm. Furthermore, the photoluminescence lifetime of Mn:AgInZnS nanoparticles was about 1.38μs which indicated the tremendous potential applications in cell labelings, fluorescent imaging, solar cells and LEDs.

Simple chemical aqueous synthesis of dahlia nanoflower consisting of finger-like ZnO nanorods and observation of stable ultraviolet photoluminescence emission

In this work, we have reported the synthesis of dahlia flower-like ZnO nanostructures consisting of human finger-like nanorods by the hydrothermal method at 120°C and without using any capping agent. Optical properties of the samples, including UV–vis absorption and photoluminescence (PL) emission characteristics are determined by dispersing the samples in water as well as in ethanol media. The quenching of PL emission intensity along-with the red shifting of the PL emission peak are observed when the samples are dispersed in water in comparison to those obtained after dispersing the samples in ethanol. It has been found that PL emission characteristic, particularly the spectral nature of PL emission, of the samples remains almost unaltered (except some improvement in UV PL emission) even after thermally annealing it for 2h at the temperature of 300°C. Also the synthesized powder samples, kept in a plastic container, showed a very stable PL emission even after 15 months of synthesis. Therefore, the synthesized samples might be useful for their applications in future optoelectronics devices.

Synthesis and Characterization of One-Dimensional Bifunctional Carbon Nanotubes/Fe3O4@SiO2 (FITC) Nanohybrids

A new type of one-dimensional bifunctional CNTs/Fe3O4 @ SiO2 (FITC) nanohybrids with both magnetic and fluorescent properties were fabricated by a polyol method combined with stöber method. The CNTs/Fe3O4 @ SiO2 (FITC) nanohybrids exhibit strong and stable photoluminescence emission at about 520 nm, display superparamagenetic behavior with high saturation magnetization and possess MRI function at room temperature. All these properties make the CNTs/Fe3O4 @ SiO2 (FITC) nanohybrids a potential candidate for biomedical agent such as MRI contrast agent, cells labelling, in-vivo image and drug deliver for cancer diagnosis and treatment.

High photoluminescence quantum yield of TiO2 nanocrystals prepared using an alcohothermal method

Highly dispersible TiO2 nanocrystals (approximately 6 nm) were prepared by an alcohothermal method. A strong and stable photoluminescence emission with a maximum at 450 nm was observed in the original TiO2 nanocrystals colloid. Compared with the emission from quinine sulphate in 0.05 mol/L sulphuric acid, the emission quantum yield of TiO2 nanocrystals was determined to be about 0.20, which was much higher than the values (0.002 and 0.001) reported in previous studies. The fluorescence micrograph of TiO2 nanocrystals encapsulated in lipsomes shows that TiO2 nanocrystals prepared in such a way have potential application as a fluorescence probe in biological imaging. Research on the luminescence mechanism indicates that the surface state and extent of crystallization of the TiO2 nanocrystals are crucial factors in the high photoluminescence quantum yield obtained in this study.