CsPbBr3 perovskite quantum dots-based Janus membrane with multifunction of luminescence, magnetism and aeolotropic electroconductivity

Lead halide perovskite quantum dots (QDs) are promising semiconductors for next-generation photoelectric devices. However, the development of perovskite QDs-based multifunctional materials still needs to be addressed in order to further advance the application of perovskite QDs. Herein, a successful synthesis of Janus microfibers array Janus membrane (JMAJM) with up-down structure and multifunction of luminescence, magnetism and electroconductivity is firstly achieved based on CsPbBr3 QDs through a parallel electrospinning. JMAJM comprises up-down two layers tightly bonded together. The up-layer of JMAJM is luminescence/magnetism Janus microfibers array (L/M-JMAJM) constructed by [CsPbBr3/polymethyl methacrylate (PMMA)]//[CoFe2O4/PMMA] Janus microfibers as building elements. The down-layer of JMAJM is luminescence/electroconductivity Janus microfibers array (L/E-JMAJM) fabricated by [CsPbBr3/PMMA]//[polyaniline (PANI)/PMMA] Janus microfibers as building elements. Two independent microcosmic regions are designed and realized in a Janus microfiber, confining luminescence with magnetic or conductive substances into their respective regions, thus minimizing adverse effects of other dark-colored functional substances on the fluorescence of CsPbBr3 QDs. This peculiar Janus microfiber enables the effective separation and high integration of CsPbBr3 QDs with other functional substances. The up-down structure of JMAJM ensures a high integration of luminescence, magnetism and conductivity. Meanwhile, JMAJM addresses the environmental instability of CsPbBr3 QDs while simultaneously endows perovskite QDs-based materials with additional functions to realize multifunction. Under ultraviolet excitation, fluorescence characteristics of the CsPbBr3 QDs in JMAJM are maintained, exhibiting a vibrant green emission at 517 nm. Meanwhile, JMAJM achieves a maximum saturation magnetization of 20.32 emu·g-1, high conductance of 10-2 S and aeolotropic electroconductivity degree of 107. The combination of micro-partition with macro-partition in JMAJM receives superior concurrent luminescence-magnetic-conductive multifunction. This work provides a novel idea and strategy for advancing perovskite QDs-based multifunctional materials.

Ligand-mediated exciton dissociation and interparticle energy transfer on CsPbBr3 perovskite quantum dots for efficient CO2-to-CO photoreduction

Perovskite quantum dots (PQDs) hold immense potential as photocatalysts for CO2 reduction due to their remarkable quantum properties, which facilitates the generation of multiple excitons, providing the necessary high-energy electrons for CO2 photoreduction. However, harnessing multi-excitons in PQDs for superior photocatalysis remains challenging, as achieving the concurrent dissociation of excitons and interparticle energy transfer proves elusive. This study introduces a ligand density-controlled strategy to enhance both exciton dissociation and interparticle energy transfer in CsPbBr3 PQDs. Optimized CsPbBr3 PQDs with the regulated ligand density exhibit efficient photocatalytic conversion of CO2 to CO, achieving a 2.26-fold improvement over unoptimized counterparts while maintaining chemical integrity. Multiple analytical techniques, including Kelvin probe force microscopy, temperature-dependent photoluminescence, femtosecond transient absorption spectroscopy, and density functional theory calculations, collectively affirm that the proper ligand termination promotes the charge separation and the interparticle transfer through ligand-mediated interfacial electron coupling and electronic interactions. This work reveals ligand density-dependent variations in the gas-solid photocatalytic CO2 reduction performance of CsPbBr3 PQDs, underscoring the importance of ligand engineering for enhancing quantum dot photocatalysis.

Visual and rapid fluorescence sensing for hexavalent chromium by hydroxypropyl chitosan passivated bismuth-based perovskite quantum dots

Hydroxypropyl chitosan-Cs3Bi2Cl9 perovskite quantum dots (HPCS-PQDs) were synthesized by a simple ligand-assisted reprecipitation method via green hydroxypropyl chitosan as the ligand and used as the specific signal of a fluorescence probe to achieve the highly sensitive detection of hexavalent chromium (Cr(VI)) and compared with chitosan-Cs3Bi2Cl9 QDs (CS-PQDs). HPCS-PQDs with multiple active hydroxyl passivations were found to enhance the photoluminescence quantum yield (PLQY) by 90%. After being placed in aqueous solution and irradiated with ultraviolet light for 96 h the fluorescence intensity of HPCS-PQDs remained above 60%. The blue emission of HPCS-PQDs has a good selectivity and short response time (30 s) for Cr(VI). A good linear relationship is established between the fluorescence quenching rate of the HPCS-PQDs and concentration of Cr(VI) from 0.8 to 400 µM, with a limit of detection (LOD) of 0.27 µM. The fluorescence quenching mechanism is the static quenching and internal filtration effect caused by HPCS-PQDs forming a non-fluorescent ground-state complex with Cr(VI). The sensor can not only be used to detect Cr(VI) in water samples with high accuracy but can also be prepared as a test paper for the detection for Cr(VI).

Operando spectroscopic characterization of formamidinium lead iodide perovskite quantum dots for tracking electrochemical reactions

Multidimensional ABX3 hybrid perovskites three-dimensionally confined dot-shaped structure demonstrate versatile potential to photoelectrochemical cells for water splitting, hydrogen generation, solar cells, and light-emitting diodes. To apply perovskite quantum dots (PQDs) to solar-driven chemistry and optoelectronic devices, understanding the photoinduced charge carrier dynamics of PQDs under electrochemical conditions or applied bias are important. In this study, the detailed transformation mechanism of formamidinium lead iodide perovskite quantum dots under electrochemical conditions was studied by tracking the products of the reaction through cyclic voltammetry, X-ray photoemission spectroscopy, in-situ UV-visible spectroelectrochemistry, etc. Through comprehensive characterizations, the mechanism of irreversible oxidative transformation of perovskite quantum dots was presented. This study provides deeper insight into the electrochemical behavior of PQDs for successful solar-driven chemistry and optoelectronic device applications.

Surface crafting and entrapment of CsPbBr3 perovskite QDs in ZIF-8 for ammonia recognition

The substantial optical features of perovskite quantum dots (PQD) lead to rapid growth in the investigation of their surface and lattice doping for optoelectronic and biochemical sensor advancements. Herein, we have used the surface ligand crafting model of PQD by ammonia and its optimum response to recognise ammonia in the sensing cellulose paper. The PQD with acetyl amine and octanoic acid capped were synthesized and entrapped in zeolites imidazole framework to delay the instant quenching and envisaged response to ammonia with high sensitivity. The hybrid perovskite quantum dots and Zeolite imidazolate framework-8 (PQD@ZIF-8) materials were further immersed in cellulose paper for solid-state sensor fabrication for the detection of ammonia by naked-eye and a Xiaomi Note-5 mobile camera. The ammonia was measured with high sensitivity at ambient conditions, with a detection limit of 16 ppm and a linear detection range of 1 to 500 ppm. This research provides a new platform for designing sensor selectivity and sensitivity, which could be used to further develop fluorescent nanomaterials-based sensors for small molecule detection.

A molecularly imprinted photopolymer based on mesh TpPa-2 embedded with perovskite CsPbBr3 quantum dots for the sensitive solid fluorescence sensing of patulin in apple products

Here, a novel molecularly imprinted photopolymer was prepared using CsPbBr₃ quantum dots as the fluorescence source, TpPa-2 as substrate for selective solid fluorescence detection of patulin (PAT). TpPa-2 can promote efficient recognition of PAT due to its unique structure and significantly improve the fluorescence stability and sensitivity. The test results showed that the photopolymer exhibited large adsorption capacity (131.75 mg/g), fast adsorption ability (12 mins), superior reusability and high selectivity. The sensor proposed had good linearity for PAT in the range of 0.2-20 ng/mL and was applied to the analysis of PAT in apple juice and apple jam with a limit of detection as low as 0.027 ng/mL. Therefore it maybe a promising method for solid fluorescence detection of trace PAT in food analysis.

Tuning optical properties of CsPbBr3by mixing Nd3+trivalent lanthanide halide cations for blue light emitting devices

In recent years, significant progress has been made in the red and green perovskite quantum dots (PQDs) based light-emitting devices. However, a scarcity of blue-emitting devices that are extremely efficient precludes their research and development for optoelectronic applications. Taking advantage of tunable bandgaps of PQDs over the entire visible spectrum, herein we tune optical properties of CSPbBr₃by mixing Nd³⁺trivalent lanthanide halide cations for blue light-emitting devices. The CsPbBr₃PQDs doped with Nd³⁺trivalent lanthanide halide cations emitted strong photoemission from green into the blue region. By adjusting their doping concentration, a tunable wavelength from (515 nm) to (450 nm) was achieved with FWHM from (37.83 nm) to (16.6 nm). We simultaneously observed PL linewidth broadening thermal quenching of PL and the blue shift of the optical bandgap from temperature-dependent PL studies. The Nd³⁺cations into CsPbBr₃PQDs more efficiently reduced non-radiative recombination. As a result of the efficient removal of defects from PQDs, the photoluminescence quantum yield (PLQY) has been significantly increased to 91% in the blue-emitting region. Significantly, Nd³⁺PQDs exhibit excellent long-term stability against the external environment, including water, temperature, and ultraviolet light irradiation. Moreover, we successfully transformed Nd³⁺doped PQDs into highly fluorescent nanocomposites. Incorporating these findings, we fabricate and test a stable blue light-emitting LED with EL emission at (462 nm), (475 nm), and successfully produce white light emission from Nd³⁺doped nanocomposites with a CIE at (0.32, 0.34), respectively. The findings imply that low-cost Nd³⁺doped perovskites may be attractive as light converters in LCDs with a broad color gamut.

Brightly luminescent (NH4)xCs1-xPbBr3 quantum dots for in vitro imaging and efficient photothermal ablation therapy

Herein, we report for the first time a facile strategy for the highly efficient (NH₄)_xCs_1-xPbBr₃ quantum dots (QDs). By modulating the amount of ammonium, (NH₄)_xCs_1-xPbBr₃ QDs with different photoluminescence (PL) quantum yields (QY) were synthesized. The results of X-ray diffraction and X-ray photoelectron spectroscopy showed that the crystal structure of (NH₄)_xCs_1-xPbBr₃ was altered by incorporation of NH₄⁺ cations into the CsPbBr₃ lattice. The (NH₄)_xCs_1-xPbBr₃ QDs showed enhanced PL QY, higher photostability, and long-term storage stability compared to CsPbBr₃ QDs. Furthermore, (NH₄)_xCs_1-xPbBr₃ QDs could be conjugated with a photothermal dye (IR780) via a one-pot reaction using poly(styrene-co-maleic anhydride) and IR780-MPTS. To the best of our knowledge, the present work is the first attempt integrating perovskite QDs and phototherapeutic molecules into one system (abbreviated as PQD-IR780), demonstrating good water dispersibility and high photothermal conversion efficiency of 57.85%. In vitro experiments performed to examine subcellular uptake showed high fluorescence brightness was observed in HeLa, B16F1, and HepG2 cancer cells cultured with PQD-IR780. The results indicate that the internalization mechanism for uptaking of PQD-IR780 inside HeLa cells is energy-dependent and caveolin-mediated endocytosis. The in vitro cell viability assays and photothermal therapy revealed that PQD-IR780 showed good biocompatibility and can induce hyperthermia upon laser irradiation.

Supersensitive and reusable perovskite nanocomposite fiber paper for time-resolved single-droplet detection

Traditional test paper cannot be reusable and needs much sample solution. In this study, a reusable perovskite nanocomposite fiber paper consisting of CsPbBr₃ quantum dots in-situ growing in the solid polymer fibers with high concentration is fabricated via microwave and electrospinning methods. RhoB is used as the sample solution because it is a hazardous matter but often occurs in printing and dyeing wastewater or appears in food as additives, and traditional detection system generally requires much sample solution (>1 ml) to concentrate for higher concentrations due to the low detection sensitivity. Just need a droplet of sample solution (<25 μl) can this perovskite fiber paper achieve 0.01 ppm of supersensitive detection, which is superior to a majority of reported detection limit. Different from traditional detection based on luminescence intensity, this detection is a new kind of time-resolved method, so that it gets rid of complex and time-consuming calibration (>1 h) usually in traditional detection, and this time-resolved detection can be achieved within ~3 min. Moreover, this perovskite fiber paper is endowed with recyclable property without losing advantages of supersensitive detection (~0.01 ppm), rapid measuring speed (<3 min), and tiny dosage (<25 μl), which is another advantage than conventional detection systems.

Water-stable perovskite-on-polymer fluorescent microspheres for simultaneous monitoring of pH, urea, and urease

Perovskite materials have attracted attention due to their excellent optical and electrical properties; however, their unsatisfactory stability limits their application in biochemical detection. In this paper, CsPbBr₃ perovskite quantum dots were successfully encapsulated in poly(styrene/acrylamide) microspheres, using a swelling-shrinking method. The manufactured perovskite microspheres (PDPS composites) not only maintained strong photoluminescence (PL) stability but also demonstrated great water solubility. Additionally, a real-time pH monitoring platform was constructed based on the prepared PDPS composites and dopamine, and the system showed a good linear relationship in a pH range of 4-12. Furthermore, urea could be hydrolyzed to produce hydroxyl groups, thereby increasing the pH of the solution. Therefore, this system was then extended for urea and urease detection. As a result, the detection limits of urea and urease were recorded as 1.67 μM and 2.1 mU/mL, respectively. This development provides an interesting demonstration of the expanding list of applications of perovskite materials.

Remote Tracking Gas Molecular via the Standalone-Like Nanosensor-Based Tele-Monitoring System

HIGHLIGHTS

A standalone-like smart device that can remotely track the variation of air pollutants in a power-saving way is created; Metal–organic framework-derived hollow polyhedral ZnO was successfully synthesized, allowing the created smart device to be highly selective and to sensitively track the variation of NO₂ concentration; A novel photoluminescence-enhanced Li-Fi telecommunication technique is proposed, offering the created smart device with the capability of long distance wireless communication.

ABSTRACT

Remote tracking the variation of air quality in an effective way will be highly helpful to decrease the health risk of human short- and long-term exposures to air pollution. However, high power consumption and poor sensing performance remain the concerned issues, thereby limiting the scale-up in deploying air quality tracking networks. Herein, we report a standalone-like smart device that can remotely track the variation of air pollutants in a power-saving way. Brevity, the created smart device demonstrated satisfactory selectivity (against six kinds of representative exhaust gases or air pollutants), desirable response magnitude (164–100 ppm), and acceptable response/recovery rate (52.0/50.5 s), as well as linear response relationship to NO₂. After aging for 2 weeks, the created device exhibited relatively stable sensing performance more than 3 months. Moreover, a photoluminescence-enhanced light fidelity (Li-Fi) telecommunication technique is proposed and the Li-Fi communication distance is significantly extended. Conclusively, our reported standalone-like smart device would sever as a powerful sensing platform to construct high-performance and low-power consumption air quality wireless sensor networks and to prevent air pollutant-induced diseases via a more effective and low-cost approach. [Image: see text]

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s40820-020-00551-w) contains supplementary material, which is available to authorized users.

Optical and structural properties of CsPbBr3 perovskite quantum dots/PFO polymer composite thin films

The aim of this study is to investigate the optical and structural properties of polymer/perovskite quantum dots (QDs) composite thin films and estimate the applicability of using these blends as active materials in photonic devices. A solution has been utilized, which is processed based on conjugated polymer and perovskite QDs composite films. The incorporation of CsPbBr₃ QDs, with various weight ratios, influences the structure of the thin films, as proven by several techniques. The results of the study showed that the surface of the poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO)/CsPbBr₃ thin films improved, when compared to that of the pristine CsPbBr₃ thin film. The increase in the steepness parameter and decrease in both the energy gaps and Urbach tail, upon the increment of CsPbBr₃ QDs, can be attributed to the decrease in the localized density of electronic states within the forbidden band gap of the hybrids. The overlap between the absorption spectrum of PFO and emission spectrum of CsPbBr₃ QDs, and the enhancement in the emission peak of CsPbBr₃ in the blends, confirmed the efficient non-radiative energy transfer between them.