Multimode Luminescence with Temperature and Energy Level Synergistic Dependence in Rare Earth Halide DPs for Advanced Multifunctional Applications.

Rare-earth halide double perovskites (DPs) have attracted extensive attention due to their excellent optoelectronic performance. However, the correlation between luminescence performance, crystal structure, and temperature, as well as the inherent energy transfer mechanism, is not well understood. Herein, Lanthanide ions (Ln3+: Nd3+ or Dy3+) as the co-dopants are incorporated into Sb3+ doped Cs2NaYbCl6 DPs to construct energy transfer (ET) models to reveal the effects of temperature and energy levels of rare earth on luminescence and ET. The different excited state structures of Sb3+-Ln3+ doped Cs2NaYbCl6 DPs at different temperatures and relative positions of energy levels of rare earth synergistically determine the physical processes of luminescence. These multi-mode luminescent materials exhibit good performance in anti-counterfeiting, NIR imaging, and temperature sensing. This work provides new physical insights into the effects of temperature and energy levels of rare earth on the energy transfer mechanism and related photophysical process.

A Room-Temperature Strategy to Synthesize Ce/Tb-Codoped NaYF4 Nanoparticles with a Photoluminescence Quantum Yield Exceeding 50.

NaYF4:Ce3+,Tb3+ down-conversion nanoparticles with a photoluminescence quantum yield (PLQY) of 54.8% are synthesized by using a ligand-assisted coprecipitation method in this study. The reaction is completed within 1 min at room temperature, and short-chain hexanoic acid and hexylamine serve as the binary ligands, which enable us to synthesize highly luminescent NaYF4:Ce3+,Tb3+ nanoparticles at room temperature. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the as-prepared nanocrystals. The results reveal that the NaYF4:Ce3+,Tb3+ nanocrystals exhibit excellent dispersion and have a particle size of 2.7 nm. Our NaYF4:Ce3+,Tb3+ nanocrystals possess the advantages of room-temperature preparation, high PLQY, and ultrasmall particle size. These results reveal that the NaYF4:Ce3+,Tb3+ nanocrystals might have a high potential in the applications of lighting, display devices, and bioimaging.

An Ultrafast and Room-Temperature Strategy for Kilogram-Scale Synthesis of Sub-5 nm Eu3+ -doped CaMO4 Nanocrystals with a Photoluminescence Quantum Yield Exceeding 85.

Rare earth-doped metal oxide nanocrystals have a high potential in display, lighting, and bio-imaging, owing to their excellent emission efficiency, superior chemical, and thermal stability. However, the photoluminescence quantum yields (PLQYs) of rare earth-doped metal oxide nanocrystals have been reported to be much lower than those of the corresponding bulk phosphors, group II-VI, and halide-based perovskite quantum dots because of their poor crystallinity and high-concentration surface defects. Here, an ultrafast and room-temperature strategy for the kilogram-scale synthesis of sub-5 nm Eu3+ -doped CaMoO4 nanocrystals is presented, and this reaction can be finished in 1 min under ambient conditions. The absolute PLQYs for sub-5 nm Eu3+ -doped CaMoO4 nanocrystals can reach over 85%, which are comparable to those of the corresponding bulk phosphors prepared by the high-temperature solid state reaction. Moreover, the as-produced nanocrystals exhibit a superior thermal stability and their emission intensity unexpectedly increases after sintering at 600 °C for 2 h in air. 1.9 kg of Eu3+ -doped CaMoO4 nanocrystals with a PLQY of 85.1% can be obtained in single reaction.

Ionic Liquid-Assisted Ink for Inkjet-Printed Indium Tin Oxide Transparent and Conductive Thin Films.

Drop-on-demand inkjet printing is used to deposit indium tin oxide (ITO) transparent and conductive thin films. ITO printable ink is prepared by dissolving indium hydroxide and tin (IV) chloride into ethanol with the assistance of acetic acid/tert-butylamine ionic liquid. Ionic liquid-assisted ITO ink exhibits a complete wetting behavior on the glass substrate and a tunable viscosity, which makes it particularly suitable for the inkjet printing fabrication of ITO thin films. After annealing at 500 °C in forming gas, ITO thin films with a sheet resistance of 99 Ω/□, a resistivity of 2.28 × 10-3 Ω·cm, and a transmittance of 95.2% in the range of 400-1000 nm can be obtained. The effects of annealing temperature on the resistivity, mobility, carrier concentration, transmittance, and optical band gap are investigated systematically. Compared with commercial ITO thin films made by conventional vacuum-based deposition approaches, these printable ITO thin films have a higher material utilization.

Room-Temperature, Ultrafast, and Aqueous-Phase Synthesis of Ultrasmall LaPO4:Ce3+, Tb3+ Nanoparticles with a Photoluminescence Quantum Yield of 74.

LaPO4:Ce3+, Tb3+ nanoparticles with a particle size of 2.7 nm are prepared by a facile room-temperature ligand-assisted coprecipitation method in an aqueous solution. Short-chain butyric acid and butylamine are used as binary ligands and play a critically important role in the synthesis of highly luminescent LaPO4:Ce3+, Tb3+ nanoparticles. The absolute photoluminescence quantum yield as high as 74% can be achieved for extremely small LaPO4:Ce3+, Tb3+ nanoparticles with an optimal composition of La0.4PO4:Ce0.13+, Tb0.53+, which is different from La0.4PO4:Ce0.453+, Tb0.153+ for bulk phosphor. The energy transfer from Ce3+ ions to Tb3+ ions is investigated in sub-3 nm LaPO4:Ce3+, Tb3+ nanoparticles, and Ce3+ ion emission is almost completely suppressed. This room-temperature, ultrafast, and aqueous-phase synthetic strategy is particularly suitable for the large-scale preparation of highly luminescent LaPO4:Ce3+, Tb3+ nanoparticles. LaPO4:Ce3+, Tb3+ nanoparticles (110 g) can be synthesized in one batch, which is perfectly suited to the needs of industrial production.

Luminescent Thin Films Enabled by CsPbX3 (X=Cl, Br, I) Precursor Solution.

Inorganic cesium lead halide perovskite nanocrystals are candidates for lighting and display materials due to their outstanding optoelectronic properties. However, the dissolution issue of perovskite nanocrystals in polar solvents remains a challenge for practical applications. Herein, we present a newly designed one-step spin-coating strategy to prepare a novel multicolor-tunable CsPbX3 (X=Cl, Br, I) nanocrystal film, where the CsPbX3 precursor solution was formed by dissolving PbO, Cs2 CO3 , and CH3 NH3 X into the ionic liquid n-butylammonium butyrate. The as-designed CsPbX3 nanocrystal films show high color purity with a narrow emission width. Also, the blue CsPb(Cl/Br)3 film demonstrates an absolute photoluminescence quantum yields (PLQY) of 15.6 %, which is higher than 11.7 % of green CsPbBr3 and 8.3 % of red CsPb(Br/I)3 film. This study develops an effective approach to preparing CsPbX3 nanocrystal thin films, opening a new avenue to design perovskite nanocrystals-based devices for lighting and display applications.

Quantum-Sized SnO2 Nanoparticles with Upshifted Conduction Band: A Promising Electron Transportation Material for Quantum Dot Light-Emitting Diodes.

In previous reports of the literature, ZnO nanoparticles were unexceptionally used as the electron transportation material in highly efficient CdSe-based quantum dot light-emitting diodes (QD-LEDs). However, as an amphoteric oxide, ZnO nanoparticles are chemically unstable in air. Here, we utilize quantum-sized SnO2 nanoparticles as the electron transportation layer (ETL) of CdSe-based QD-LEDs. Decreasing the size of SnO2 nanoparticles will upshift the conduction band from -4.50 to -3.84 eV based on the quantum size effect, which is beneficial to facilitate electron injection into the QD emitting layer. Our investigations show that QD-LEDs based on quantum-sized SnO2 nanoparticles exhibit comparable electroluminescence properties and higher stability in contrast to ZnO nanoparticle-based QD-LEDs, demonstrating that small-sized SnO2 nanoparticles have a bright prospect due to the ETL in QD-LEDs.

Electrostatic Interaction Mediates the Formation of Vesicular Structures from Coassembly of PS-b-PAA with Quantum Dots.

Vesicular structures of block copolymers and inorganic nanoparticles with good stability have potential applications in therapeutic drug release and bioimaging. Herein, a block copolymer of polystyrene-b-poly(acrylic acid) (PS48-b-PAA67) and water-soluble AgInS2/ZnS core/shell quantum dots (QDs) capped with gelatin and thioglycolic acid were coassembled in tetrahydrofuran by adding water. The positively charged QDs bind to negatively charged PAA segments through electrostatic interaction. Numerous vesicular structures, such as uniform bilayer vesicles, flowerlike large compound vesicles, onionlike lamellar structures consisting of alternating PS and PAA&QD layers, and multilamellar vesicles with spaces between concentric vesicle layers were obtained from the coassembly of PS48-b-PAA67 with QDs. The binding of the positively charged QDs to the PAA block influenced both the intra-aggregate PAA corona conformation and the interaggregate interactions. The key parameters affecting the formation of these vesicular structures included the QD content, solution pH, and water addition rate. Thus, tunable vesicular structures can be prepared and regulated through this simple but effective coassembly method.

Gram-Scale Synthesis of Hydrophilic PEI-Coated AgInS2 Quantum Dots and Its Application in Hydrogen Peroxide/Glucose Detection and Cell Imaging.

Assisted with polyethylenimine, 4.0 L of water-soluble AgInS2 quantum dots (AIS QDs) were successfully synthesized in an electric pressure cooker. As-prepared QDs exhibit yellow emission with a photoluminescence (PL) quantum yield up to 32%. The QDs also show excellent water/buffer stability. The highly luminescent AIS QDs are used to explore their dual-functional behavior: detection of hydrogen peroxide (H2O2)/glucose and cell imaging. The amino-functionalized AIS QDs show high sensitivity and specificity for H2O2 and glucose with detection limits of 0.42 and 0.90 µM, respectively. A linear correlation was established between PL intensity and concentration of H2O2 in the ranges of 0.5-10 µM and 10-300 µM, while the linear ranges were 1-10 µM and 10-1000 µM for detection of glucose. The AIS QDs reveal negligible cytotoxicity on HeLa cells. Furthermore, the luminescence of AIS QDs gives the function of optical imaging.

Homogeneous Synthesis and Electroluminescence Device of Highly Luminescent CsPbBr3 Perovskite Nanocrystals.

Highly luminescent CsPbBr3 perovskite nanocrystals (PNCs) are homogeneously synthesized by mixing toluene solutions of PbBr2 and cesium oleate at room temperature in open air. We found that PbBr2 can be easily dissolved in nonpolar toluene in the presence of tetraoctylammonium bromide, which allows us to homogeneously prepare CsPbBr3 perovskite quantum dots and prevents the use of harmful polar organic solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Additionally, this method can be extended to synthesize highly luminescent CH3NH3PbBr3 perovskite quantum dots. An electroluminescence device with a maximal luminance of 110 cd/m2 has been fabricated by using high-quality CsPbBr3 PNCs as the emitting layer.

High color rendering index warm white light emitting diodes fabricated from AgInS2/ZnS quantum dot/PVA flexible hybrid films.

Flexible luminescent materials, with the advantages of foldability and crack resistance, have attracted extensive interest owing to their broad application in collapsible optoelectronic devices. In this work, highly luminescent water-soluble green and red AgInS2/ZnS core/shell quantum dots (QDs) are synthesized in an electric pressure cooker. Luminescent and flexible films are fabricated by combining QDs with polyvinyl alcohol (PVA), and the green and red QD/PVA films show a high photoluminescence quantum yield (PLQY) of about 55% and 64% upon 460 nm excitation, respectively. Finally, the green and red QD/PVA films are successfully applied on top of a conventional blue InGaN chip for remote-type warm-white LEDs. As-fabricated warm-white LEDs exhibit a higher color rendering index (CRI) of about 90.2 and a correlated color temperature (CCT) of 3698 K.

Large-scale synthesis of well-dispersed copper nanowires in an electric pressure cooker and their application in transparent and conductive networks.

We present a novel large-scale synthetic method for well-separated copper nanowires (CuNWs) in a commercial electric pressure cooker under mild reaction conditions. CuNWs (∼2.1 g) can be prepared in a batch with the cost of $4.20/g. Well-dispersed polyvinylpyrrolidone-capped CuNWs were obtained via a ligand-exchange method. The transparent and conductive CuNW networks with excellent electrical conductivity and high optical transmittance (30 Ω/□ at 86% transmittance, respectively) were fabricated by a spin-coating process.

Green and facile synthesis of water-soluble Cu-In-S/ZnS core/shell quantum dots.

Water-soluble Cu-In-S/ZnS core/shell quantum dots with a photoluminescence quantum yield up to 38% and an emission peak tunable from 543 to 625 nm have been successfully synthesized. All of the synthetic procedures were conducted in an aqueous solution at 95 °C under open-air conditions. L-Glutathione and sodium citrate were used as the dual stabilizing agents to balance the reactivity between copper and indium ions.

Simple continuous-flow synthesis of Cu-In-Zn-S/ZnS and Ag-In-Zn-S/ZnS core/shell quantum dots.

We present a simple continuous-flow reaction for the synthesis of quaternary Cu-In-Zn-S/ZnS and Ag-In-Zn-S/ZnS core/shell quantum dots (QDs) using inexpensive and low-toxic precursors. The composition and band gap of Cu-In-Zn-S and Ag-In-Zn-S QDs were well controlled by changing the molar ratios of the starting materials. The PL quantum yields of Cu-In-Zn-S/ZnS core/shell quantum dots can reach as high as 40%.

Low-temperature in situ preparation of Eu3+/Tb3+-doped CaMoO4/SrMoO4 nanoparticle thin films and their application in anti-counterfeiting.

Rare earth-doped metal oxide thin films exhibit remarkable potential for application in anti-counterfeiting, owing to their exceptional fluorescent properties. However, the existing fabrication techniques for these rare earth-doped luminescent thin films are predominantly complex and necessitate high-temperature conditions. In light of this issue, we present a low-temperature method for in situ fabrication of luminescent Ca1-xMoO4:Eux3+ and Sr1-xMoO4:Tbx3+ nanocrystal thin films by a solution deposition process. The developed method has the advantages of simple operation, rapid and low-temperature synthesis. The optimal chemical compositions of molybdate-based luminescent films are Ca0.90MoO4:Eu0.103+ and Sr0.90MoO4:Tb0.103+. Moreover, we evaluate the practical feasibility of luminescent nanoparticle films in the field of anti-counterfeiting by combining the unique fluorescent properties of rare earth ions and designing customized fluorescent patterns.

Room-temperature and ultrafast Eu3+ ion doping for highly luminescent and extremely small CaMoO4 nanocrystals.

We developed a room-temperature and ultrafast Eu3+-ion doping approach for the synthesis of highly luminescent Eu-doped CaMoO4 nanoparticles. Firstly, CaMoO4 nanoparticles with a particle size of 3.9 nm are rapidly prepared using a room temperature co-precipitation approach. Subsequently, Eu-doped CaMoO4 nanoparticles with a photoluminescence quantum yield of up to 75% are synthesized by a post-cation exchange reaction at room temperature. This facile and room-temperature synthetic strategy enables us to prepare highly luminescent and extremely small rare earth ion-doped metal oxide nanocrystals.

Alloyed Mn-Cu-In-S nanocrystals: a new type of diluted magnetic semiconductor quantum dots.

A new type of Mn-Cu-In-S diluted magnetic semiconductor quantum dots was synthesized and reported for the first time. The quantum dots, with no highly toxic elements, not only show the same classic diluted magnetic behavior as Mn-doped CdSe, but also exhibit tunable luminescent properties in a relatively large window from 542 to 648 nm. An absolute photoluminescence quantum yield up to 20% was obtained after the shell growth of ZnS. This kind of magnetic/luminescent bi-functional Mn-Cu-In-S/ZnS core/shell quantum dot might serve as promising nanoprobes for use in dual-mode optical and magnetic resonance imaging techniques.

Alloyed (ZnSe)(x)(CuInSe2)(1-x) and CuInSe(x)S(2-x) nanocrystals with a monophase zinc blende structure over the entire composition range.

Metastable zinc blende CuInSe(2) nanocrystals were synthesized by a hot-injection approach. It was found that the lattice mismatches between zinc blende CuInSe(2) and ZnSe as well as CuInSe(2) and CuInS(2) are only 2.0% and 4.6%, respectively. Thus, alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a zinc blende structure have been successfully synthesized over the entire composition range, and the band gaps of alloys can be tuned in the range from 2.82 to 0.96 eV and 1.43 to 0.98 eV, respectively. These alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a broad tunable band gap have a high potential for photovoltaic and photocatalytic applications.

Two-step deposition of Ag nanowires/Zn2SnO4 transparent conductive films for antistatic coatings.

Silver nanowire (AgNW) networks play an important role in the transparent conductive electrodes or antistatic coatings. In this work, we describe a facile two-step method to fabricate AgNWs/Zn2SnO4 composite films. Long AgNWs with a high aspect ratio were prepared through a modified polyol method, in which the organic octylamine hydrochloride rather than the commonly used inorganic chlorides was used as the shape-controlling agent. The AgNW networks were fabricated on the glass substrate, on which the Zn2SnO4 film was deposited, forming robust AgNWs/Zn2SnO4 composite films. The as-prepared composite films have strong adhesion, high thermal stability, low sheet resistance (5-15 ohm sq-1) and high light transmittance (85-80%), indicating a promising application prospect for transparent conductive electrodes and antistatic coatings.

Quantum-dot-decorated robust transductable bioluminescent nanocapsules.

Bioluminescence, due to its high sensitivity, has been exploited in various analytical and imaging applications. In this work, we report a highly stable, cell-transductable, and wavelength-tunable bioluminescence system achieved with an elegant and simple design. Using aqueous in situ polymerization on a bioluminescent enzyme anchored with polymerizable vinyl groups, we obtained nanosized core-shell nanocapsules with the enzyme as the core and a cross-linked thin polymer net as the shell. These nanocapsules possess greatly enhanced stability, retained bioactivity, and a readily engineered surface. In particular, by incorporating polymerizable amines in the polymerization, we endowed the nanocapsules with efficient cell-transduction and sufficient conjugation sites for follow-up modification. Following in situ polymerization, decorating the polymer shell with fluorescent quantum dots allowed us to access a continuous tunable wavelength, which extends the application of such bioluminescent nanocapsules, especially in deep tissue. In addition, the unique core-shell structure and adequate conjugation sites on surface enabled us to maximize the BRET efficiency by adjusting the QD/enzyme conjugation ratio.