Linear and nonlinear optical characteristics of CsPbBr3 perovskite quantum dots-doped borosilicate glasses

CsPbBr₃ perovskite QDs are precipitated in a borosilicate glass matrix, while protects efficiently the QD from photo-induced and chemical degradation. We show that the CsPbBr₃ QD doped glasses exhibit strong visible photoluminescence (PL), which is dependence on the concentration that can be controlled by heat treatment conditions. Due to the stabilization by the glass matrix, we are able to determine the nonlinear optical (NLO) properties with a Z-scan technique. We observe a cross-over from saturated absorption (SA) to reverse saturated absorption (RSA) by either increase the pumping intensity or the QD size, reminiscent of quantum size effect in the NLO response. The RSA is associated with two-photon absorption (TPA) that induces strong upconversion luminescence of QD doped glass samples. Our results imply that the glasses containing CsPbBr₃ QDs may find potential applications from solid state lighting to ultrafast optical switches.     

Preparation and properties of Ag modified Tb-doped ZrO2 nanotube arrays

Tb-doped ZrO₂ nanotube arrays were first prepared by anodizing the Zr-Tb alloys, and then Ag modified Tb-doped ZrO₂ nanotube arrays were obtained by loading Ag onto the Tb-doped ZrO₂ nanotube arrays through a thermal decomposition and formaldehyde reduction method. The influences of modification of Ag nanoparticles and AgNO₃ concentrations (0.0001, 0.001, 0.01?M) on the light absorption and photoluminescence (PL) properties were determined. Results show that Ag modified samples prepared by the thermal decomposition method exhibited a significant surface plasmon resonance(SPR) effect, and that the absorption and PL emission peaks were markedly enhanced. Compared to the Tb-doped ZrO₂ nanotube arrays, the PL intensity of the sample prepared using the thermal decomposition method in 0.001?M AgNO₃ solution was enhanced by 45.8%. The samples prepared by the formaldehyde reduction method displayed excessive deposition and oversizing of Ag particles, resulting in worsening of the properties of samples.     

Preparation and photoluminescence properties of perovskite Cs4PbBr6/CsPbBr3 quantum dots integrated into lithium-borosilicate glass

Quantum dots (QDs), like all inorganic perovskite cesium lead bromide Cs₄PbBr₆ and CsPbBr_3, have shown potential as multifunctional optoelectronic materials. However, their lack of stability precludes any further practical uses from being developed. Glass as a carrier can effectively resolve these problems while retaining excellent luminescent properties. Herein, a novel perovskite Cs₄PbBr₆/CsPbBr₃ QDs embedded in lithium borosilicate glass was prepared. The phase transition mechanism of Cs₄PbBr₆/CsPbBr₃-based QDs in lithium-borosilicate glass with varying concentrations of Li₂O was investigated. Increases in the size and quantity of QDs with increasing contents of Li₂O were analyzed using transmission electron microscopy (TEM). A narrow photoluminescence (PL) emission band was observed, with a substantial emission intensity shift and a red-shifted luminescence peak. After 30 days of immersion in water, the QDs maintained approximately 84% of their luminescence intensity. According to the results, the perovskite Cs₄PbBr₆/CsPbBr₃ QDs embedded into lithium borosilicate glass have promising future applications in display technology.     

Photoluminescence Enhancement of SiO2‐Coated LaPO4:Eu3+ Inverse Opals by Surface Plasmon Resonance of Ag Nanoparticles

The surface plasmon resonance of Ag nanoparticles (NPs) and SiO₂ coating had been extensively employed to improve the photoluminescence (PL) intensity of nanomaterials. In the article, the LaPO₄:Eu³⁺ inverse opal photonic crystals were fabricated via combining a self‐assembly process with a sol–gel method. The SiO₂ shells were formed on the skeleton surface of LaPO₄:Eu³⁺ inverse opals and the Ag NPs were added into the voids of LaPO₄:Eu³⁺ inverse opals with the SiO₂ shells. The influence of the SiO₂ shells and Ag NPs on the PL of the LaPO₄:Eu³⁺ inverse opals were investigated. About sevenfold luminescence enhancement of LaPO₄:Eu³⁺ inverse opals was obtained by the coordination action of surface plasmon absorption effects of Ag nanoparticle and silica‐coating effects. The luminescence enhancement mechanisms of LaPO₄:Eu³⁺ inverse opals were discussed.     

Strong photoluminescence enhancement of silicon quantum dots by their near-resonant coupling with multi-polar plasmonic hot spots

Localization of quantum dots (QDs) in the vicinity of metal nanoparticles (NPs) is known as one of the most efficient ways to increase their photoluminescence (PL). Despite the important recent advances achieved in II-VI QDs, only a seven-fold plasmon-induced PL enhancement is reported for Si QDs. In our paper we show that the plasmon-induced strong local PL enhancement of Si QDs in an SiN matrix can reach a 60-fold gain level. This important result was achieved on original tunable "nano-Ag/SiN(X)" plasmonic structures. In particular, we show that (i) localization of Si QDs in hot spot regions created by several randomly arranged Ag NPs and (ii) careful tuning of the multi-polar plasmon bands of Ag NPs to match resonant absorption and emission wavelengths of Si QDs, lead to the important enhancement of their PL intensity.     

Engineering the crystallization behavior of CsPbBr3 quantum dots in borosilicate glass through modulating the glass network modifiers for wide-color-gamut displays

The in-situ growth of CsPbBr₃ perovskite quantum dots (QDs) inside glass has been regarded as an alternative approach to improve their stability. Alkaline-earth metal oxides has multiple effects on the structure of the glass network. Herein, four types of alkaline-earth metal oxides are introduced into borosilicate glasses to modulate glass network structure, which has quite different effects on the crystallization behavior of CsPbBr₃ QDs. The reason can be ascribed to the different impacts of alkaline-earth metal on phase separation, nucleation, and growth procedure. Moreover, CsPbBr₃ QDs embedded in glass (CsPbBr₃ QD@glass) exhibit superior thermostability and photostability compared with CsPbBr₃ QDs powder. Finally, a white light-emitting diode achieving 124% of National Television System Committee (NTSC) gamut is fabricated using the CsPbBr₃ QD@glass, K₂SiF₆:Mn⁴⁺ phosphor film, and blue chip-on-board. This work provides a reference for modulating the glass network modifiers to regulate the crystallization behavior of perovskite QDs.     

Au and Co3O4 anchored Bi2WO6 with enhanced electron paramagnetic resonance,surface plasmon resonance,nonlinear and magnetic properties

The combination of surface plasmon resonance (SPR) effect with hetero-p–n structure shows promising benefits to optical linear and nonlinear properties. In this study, Au nanoparticles (NPs) decorated p–n hetero-structured Co₃O₄/Bi₂WO₆ composite was synthesized and characterized in terms of the optical linear and nonlinear and magnetic properties, morphology, electron transition, charge transfer, energy band gap, polarizability, SPR effect, and oxygen vacancies using scanning electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Z-scan, ultraviolet–visible spectra, and vibrating sample magnetometer. The combination of Co₃O₄ provided active 3d electrons transition and charge transfer which increased carriers’ concentration and reduced the energy band gap. Au SPR enhanced the internal polarization and strengthened the built-in electric field, yielding strong nonlinear behavior. In addition, magnetic Co₃O₄ endowed sample with room-temperature ferromagnetism which was obviously strengthened by Au NPs. The obtained sample is promising for laser and photonics applications.     

Polychromatic tunable luminescence of Eu3+ doped CsPbBr3 quantum dot glass ceramic induced by mechanical crystallization

Nowadays, inorganic perovskite quantum dots (QDs) glass has become a hot topic in the field of new optical materials. In this work, the Eu³⁺ doped CsPbBr₃ QDs phosphate glass has been successfully prepared. Different from the traditional heat treatment method, the CsPbBr₃ QDs were prepared by mechanical crystallization. When the QDs glass was ground at different times, due to the synergistic effect of red emission (Eu³⁺) and green emission (CsPbBr₃ QDs), the prepared QDs glass can produce the red-yellow-green polychromatic luminescence phenomenon. Benefit from the dual-emission centers of CsPbBr₃ QDs and Eu³⁺ which do not interfere with each other, the relative sensitivity of the temperature sensing is up to 2.11% K^-1, proving that the prepared Eu³⁺ doped QDs glass has practical application in the field of temperature sensing. The glass material obtained in this way not only has tunability and favorable sensitivity but also provides an effective way for the preparation of QDs.     

Rb+-doped CsPbBr3 quantum dots with multi-color stabilized in borosilicate glass via crystallization

All-inorganic lead halide quantum dots (QDs) have attracted immense interest because of their excellent photoelectric properties. By virtue of a similar ionic radius and the same valence state, Rb⁺/Cs⁺ mixed-cation have become a novel mechanism to adjust multi-color emission. However, their poor stability remains a serious problem that has not been solved satisfactorily. Interestingly, QDs glass shows good thermostability and moisture susceptibility. Herein, CsPbBr₃: xRb (x = 0, 0.4, 0.6, 0.8) QD glasses which yield tunable emission spectra (475–523 nm) were synthesized successfully via glass crystallization. Most importantly, the as-prepared QDs glasses exhibited ultrastability under various atmospheric, water and heat conditions. Thus, synthesis of a mixed-cation perovskite QDs glass is a new method to achieve stable multi-color emission. They are also expected to become a new generation of photoelectric materials and can be prospectively applied to light-emitting devices.     

Improved photoluminescence quantum yield of CsPbBr3 quantum dots glass ceramics

We have fabricated CsPbBr₃ perovskite quantum dots (QDs) in a multi-component borate glass by melt-quenching technique. Transmission electron microscopy (TEM) reveals a cubic phase CsPbBr₃ crystal for QDs. As the treatment temperature or the treatment time duration increases, the photoluminescence (PL) peak shifts to long wavelength in the range of 510 to 525 nm, and the full width at half-maximum varies in the range of 24 to 18 nm. The absorption edge shifts to low energy side in the range of 2.54 to 2.41 eV. The different photoluminescence excitation spectra (PLE) reflect the change of microstructure for different samples. The PL peak wavelength and line-shape are independent of excitation wavelength. These results of spectra show typical exciton emission characteristics. As treatment conditions strengthens, photoluminescence quantum yield (PLQY) first increases and then decreases, having the best PLQY 86.9%. Bi-exponential fitting curves show that short lifetime τ₁ continuously decreases. Long lifetime τ₂, weight for long lifetime component, and average lifetime τ_avg first increase and then decrease. The PLQY values are affected by both τ₁ and τ₂, which are relative to the crystal quality in the interior and the surface of QDs, respectively. The high PLQY value corresponds to medium treatment condition, which is attributed to a balanced effect of crystal quality in interior and the surface of QDs.     

Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography

Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiN _x layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 10¹⁰ cm^-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH₃ annealing and GaN spacer layer growth for improving the PL intensity of the SiN _x -treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.     

Highly Bright Silica-Coated InP/ZnS Quantum Dot-Embedded Silica Nanoparticles as Biocompatible Nanoprobes

Quantum dots (QDs) have outstanding optical properties such as strong fluorescence, excellent photostability, broad absorption spectra, and narrow emission bands, which make them useful for bioimaging. However, cadmium (Cd)-based QDs, which have been widely studied, have potential toxicity problems. Cd-free QDs have also been studied, but their weak photoluminescence (PL) intensity makes their practical use in bioimaging challenging. In this study, Cd-free QD nanoprobes for bioimaging were fabricated by densely embedding multiple indium phosphide/zinc sulfide (InP/ZnS) QDs onto silica templates and coating them with a silica shell. The fabricated silica-coated InP/ZnS QD-embedded silica nanoparticles (SiO₂@InP QDs@SiO₂ NPs) exhibited hydrophilic properties because of the surface silica shell. The quantum yield (QY), maximum emission peak wavelength, and full-width half-maximum (FWHM) of the final fabricated SiO₂@InP QDs@SiO₂ NPs were 6.61%, 527.01 nm, and 44.62 nm, respectively. Moreover, the brightness of the particles could be easily controlled by adjusting the amount of InP/ZnS QDs in the SiO₂@InP QDs@SiO₂ NPs. When SiO₂@InP QDs@SiO₂ NPs were administered to tumor syngeneic mice, the fluorescence signal was prominently detected in the tumor because of the preferential distribution of the SiO₂@InP QDs@SiO₂ NPs, demonstrating their applicability in bioimaging with NPs. Thus, SiO₂@InP QDs@SiO₂ NPs have the potential to successfully replace Cd-based QDs as highly bright and biocompatible fluorescent nanoprobes.     

Au nanoparticles embedded inverse opal photonic crystals as substrates for upconversion emission enhancement

Photonic crystals (PCs) with periodic dielectric structures are capable to control the propagation of photons when photon energy is in the region of photonic band gap. The upconversion luminescence (UCL) of nanocrystals coated on the PCs surface can be enhanced by the PCs effects. While surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) is being extensively applied to enhance the UCL properties of nanocrystals. However, the PCs or SPR effect are developed separately for the UCL enhancement. In this work, we present a facile preparation method of the Au NPs embedded inverse opals, which was used as substrates to improve the UCL properties of NaYF₄:Yb³⁺, Er³⁺ NPs. The significant luminescence enhancement of NaYF₄:Yb³⁺, Er³⁺ upconverting NPs was obtained by the coupling between the SPR of Au NPs and PCs effects from Au NPs embedded inverse opals substrates. The finding demonstrated that the Au NPs embedded inverse opals as substrates may be useful for the enhanced UCL of other phosphors, producing novel photonic devices.     

Preparation and Characterization of Silica-Coated Magnetic–Fluorescent Bifunctional Microspheres

Bifunctional magnetic–fluorescent composite nanoparticles (MPQDs) with Fe₃O₄ MPs and Mn:ZnS/ZnS core–shell quantum dots (QDs) encapsulated in silica spheres were synthesized through reverse microemulsion method and characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, vibration sample magnetometer, and photoluminescence (PL) spectra. Our strategy could offer the following features: (1) the formation of Mn:ZnS/ZnS core/shell QDs resulted in enhancement of the PL intensity with respect to that of bare Mn:ZnS nanocrystals due to the effective elimination of the surface defects; (2) the magnetic nanoparticles were coated with silica, in order to reduce any detrimental effects on the QD PL by the magnetic cores; and (3) both Fe₃O₄ MPs and Mn:ZnS/ZnS core–shell QDs were encapsulated in silica spheres, and the obtained MPQDs became water soluble. The experimental conditions for the silica coating on the surface of Fe₃O₄ nanoparticles, such as the ratio of water to surfactant (R), the amount of ammonia, and the amount of tetraethoxysilane, on the photoluminescence properties of MPQDs were studied. It was found that the silica coating on the surface of Fe₃O₄ could effectively suppress the interaction between the Fe₃O₄ and the QDs under the most optimal parameters, and the emission intensity of MPQDs showed a maximum. The bifunctional MPQDs prepared under the most optimal parameters have a typical diameter of 35 nm and a saturation magnetization of 4.35 emu/g at room temperature and exhibit strong photoluminescence intensity.     

Robust CsPbBr3 and Zn-Cd-S quantum dots co-doped nano-glass composites with broadly tunable emissions

We report the first study on in-situ co-growth of biphasic CsPbBr₃ and Zn-Cd-S quantum dots (QDs) in borosilicate glass, and provide explicitly evidence of their morphology and nanoscale distribution. Such biphasic QDs co-doped nano-glass composites show unique green and red dual-band emissions. By changing the thermal heating scheme, the fluorescence intensity ratio (FIR) and thus the apparent color can be widely adjusted. The FIR can be also fine-tuned simply by varying the excitation wavelength. Based on the FIR, a self-calibrated X-rays dosimeter is constructed, which also possesses a good thermal stability. Although the X-rays induced scintillation weakening occurs, it can be readily recovered by post-thermal-annealing.     

Doping manganese into CsPb(Cl/Br)3 quantum dots glasses: Dual-color emission and super thermal stability

CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (QDs) represent bright and tunable photoluminescence, it is regrettable that the air instability and poor water resistant properties prevent their application in optoelectronic devices. At the same time, the toxicity of lead is also a major factor restricting its development. As a consequence, we demonstrate the partial replacement of Pb with Mn through conventional melt-quenching and heat-treatment method preparation of Mn-doped CsPb(Cl/Br)₃ QD glass. Mn-doped CsPb(Cl/Br)₃ QD glass exhibits high luminescent intensity like QDs. It is important that Mn-doped CsPb(Cl/Br)₃ QD glass with Dual-Color maintained the same lattice structure like Mn-doped CsPb(Cl/Br)₃ QDs, and highly homogeneous spectral characteristics of Mn luminescence. The intensity and position of this Mn-related emission are also tunable by altering the experimental parameters, such as the Pb-to-Mn feed ratio, annealing temperature. More importantly, the as-prepared orange Mn-doped CsPb(Cl/Br)₃ QD glass was employed to fabricate white LEDs combined with a commercial Ce³⁺:Y₃Al₅O₁₂ phosphor-in-glass (Ce-PiG) on top of a InGaN blue chip. And the constructed WLEDs generate a warm white with an optimal luminous efficacy (LE) of 67.00 lm/W, a high CRI of 81.4, and a low CCT of 4902 K.     

Synthesis and optical properties of novel mixed-metal cation CsPb1−xTixBr3-based perovskite glasses for W-LED

In this report, a mixed-metal cation-based halide perovskite (HP) CsPb_1−xTi_xBr₃ quantum dots (QDs) were first embedded in the B–Si–Zn glasses using a traditional approach of melt quenching and heat treating. A battery of test results such as photoluminescence, X-ray diffraction, and time-resolved attenuation prove that Ti ions do not destroy the properties of CsPbBr₃, and they are successfully doped into CsPbBr₃. At the same time, the doping of Ti ions also reduces the toxicity of lead. By altering the ratio of Pb/Ti, we determined the optimum ratio of CsPb_0.7Ti_0.3Br₃ QDs through experimental data. Due to the excellent optical properties and stability of CsPb_0.7Ti_0.3Br₃ QDs glass, it was designed to construct the white-light emitting diode device with tunable color coordinate, color rendering index, correlated color temperature, and a high luminous efficiency compared with CsPbBr₃ QDs glass, which may be a promising candidate for the field of lighting and displays.     

Plasmon‐Assisted Precipitation of PbS Quantum Dots in Glasses Containing Ag Nanoparticles

PbS QDs of ~ 5nm diameter were precipitated in glasses containing Ag nanoparticles after 3 min of 1.5‐W continuous‐wave laser illumination at λ = 532 nm. Photoluminescence spectra of the PbS QDs recorded in the 1.3~1.6 μm wavelength region revealed conversion of photon energy to thermal energy by surface plasmon resonance. Laser‐assisted local heating around Ag NPs can provide a new method to control the spatial distribution of QDs in glasses.     

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

The use of silicon powder to produce plasmonic Ag nanocomposite phosphate glasses which also exhibit improved transparency in the ultraviolet (UV) is proposed. Ag₂O/Si codoped glasses were prepared in a barium‐phosphate matrix by a simple melt‐quench method in ambient atmosphere. The as‐prepared glasses exhibit enhanced UV transparency, whereby the surface plasmon resonance of Ag nanoparticles (NPs) is manifested for the glasses with higher Ag₂O contents. ³¹P nuclear magnetic resonance spectroscopy is consistent with the formation of P–O–Si bonds, thus suggesting their possible role on the improved UV light transmission. Consequently, a model was presented accounting for the influence of silicon on the polymerization of the phosphate network concomitant with the creation of highly reactive oxygen species. Further exploiting the proposed reactive species, a real‐time spectroscopic study of the plasmonic response of Ag NPs in Ag/Si codoped glass samples was carried out during an in situ thermal processing. The temperature dependence of the Ag particle precipitation was studied in the 400°C–430°C range, from which an Arrhenius‐type plot allowed for estimating the activation energy of the process at 3.42 (±0.38) eV. Ultimately, the vanishing of the luminescence ascribed to Ag⁺ ions was observed in a heat‐treated sample, consistent with the high reactivity acquired by the glass matrix. Silicon thus appears promising for producing UV transparent glasses for high‐performance optics and for the reduction of Ag⁺ ions to produce Ag nanocomposites valuable for photonic (nanoplasmonic) applications.     

Negative thermal quenching CsPbBr3 glass-ceramic based on intrinsic radiation and vacancy defect co-induced dual-emission

Halide perovskite glass-ceramic has recently moved into the center of the attention of perovskite research due to their potential for temperature sensing. However, quantum dots glass-ceramic with excellent luminescence performance still needs to be combined with rare-earth (RE) ions to accurately measure temperature. In this work, a novel non-RE doped dual-emission (460 nm and 512 nm) CsPbBr₃ quantum dots was obtained in telluride glass via the friction crystallization method, where 512 nm was derived from intrinsic luminescence of quantum dots, and 460 nm was originated from thermally induced bromine vacancy, which can be used for temperature sensing. Fluorescence intensity ratio results indicate that the relative sensitivity of dual-emission could reach 5.6 % K^?1 at 323 K. The discovery of non-RE doped CsPbBr₃ QDs glass-ceramic with negative thermal quenching uncovers a new optional sensing glass material that surpass traditional RE-doped QDs glass by their tunability and sensitivity.