MnII-Doped Cesium Lead Chloride Perovskite Nanocrystals: Demonstration of Oxygen Sensing Capability Based on Luminescent Dopants and Host-Dopant Energy Transfer

A dual emitting CsPbBr3/Eu-BDC composite as a ratiometric photoluminescent turn-on probe for aliphatic amine sensing

The impressive photoluminescence properties of all inorganic cesium lead halide perovskite quantum dots (PeQDs) make them highly intriguing for fluorescence chemosensor applications. Herein, a ratiometric dual emitting perovskite-based sensor was designed by synthesizing fluorescent CsPbBr3 PeQDs in situ within a matrix of Eu-BDC (Eu(III) benzene-1,4-dicarboxylate). The results presented here establish the suggested sensor's quick and selective turn-on PL response to volatile primary aliphatic amine derivatives. In the presence of amines, the designed CsPbBr3/Eu-BDC sensor exhibits an enhancement of the PL signal of CsPbBr3 at 518 nm and the Eu-BDC signal at 615 nm served as a standard for constructing the ratiometric sensing system. Thereby, a visual color change from red to green was observed with the incremental addition of methylamine to the probe. A low detection limit of 0.083 ppm was determined for methylamine. In both the solution and vapor phases, this ratiometric sensor responds to a variety of primary aliphatic amines with very quick and strong fluorescence. Moreover, the sensor was effectively used for monitoring meat spoilage owing to the emission of biogenic amine vapor from meat products.

Sensing Utilities of Cesium Lead Halide Perovskites and Composites: A Comprehensive Review

Recently, the utilization of metal halide perovskites in sensing and their application in environmental studies have reached a new height. Among the different metal halide perovskites, cesium lead halide perovskites (CsPbX3; X = Cl, Br, and I) and composites have attracted great interest in sensing applications owing to their exceptional optoelectronic properties. Most CsPbX3 nanostructures and composites possess great structural stability, luminescence, and electrical properties for developing distinct optical and photonic devices. When exposed to light, heat, and water, CsPbX3 and composites can display stable sensing utilities. Many CsPbX3 and composites have been reported as probes in the detection of diverse analytes, such as metal ions, anions, important chemical species, humidity, temperature, radiation photodetection, and so forth. So far, the sensing studies of metal halide perovskites covering all metallic and organic-inorganic perovskites have already been reviewed in many studies. Nevertheless, a detailed review of the sensing utilities of CsPbX3 and composites could be helpful for researchers who are looking for innovative designs using these nanomaterials. Herein, we deliver a thorough review of the sensing utilities of CsPbX3 and composites, in the quantitation of metal ions, anions, chemicals, explosives, bioanalytes, pesticides, fungicides, cellular imaging, volatile organic compounds (VOCs), toxic gases, humidity, temperature, radiation, and photodetection. Furthermore, this review also covers the synthetic pathways, design requirements, advantages, limitations, and future directions for this material.

Trinity Strategy: Enabling Perovskite as Hydrophilic and Efficient Fluorescent Nanozyme for Constructing Biomarker Reporting Platform

Water instability and sensing homogeneity are the Achilles' heel of CsPbX3 NPs in biological fluids application. This work reports the preparation of Mn2+:CsPbCl3@SiO2 yolk-shell nanoparticles (YSNPs) in aqueous solutions created through the integration of ligand, surface, and crystal engineering strategies. The SN2 reaction between 4-chlorobutyric acid (CBA) and oleylamine (OAm) yields a zwitterionic ligand that facilitates the dispersion of YSNPs in water, while the robust SiO2 shell enhances their overall stability. Besides, Mn2+ doping in YSNPs not only introduces a second emission center but also enables potential postsynthetic designability, leading to the switching from YSNPs to MnO2@YSNPs with excellent oxidase (OXD)-like activity. Theoretical calculations reveal that electron transfer from CsPbCl3 to in situ MnO2 and the adsorption-desorption process of 3,3',5,5'-tetramethylbenzidine (TMB) synergistically amplify the OXD-like activity. In the presence of ascorbic acid (AA), Mn4+ in MnO2@YSNPs (fluorescent nanozyme) is reduced to Mn2+ and dissociated, thereby inhibiting the OXD-like activity and triggering fluorescence "turn-on/off", i.e., dual-mode recognition. Finally, a biomarker reporting platform based on MnO2@YSNPs fluorescent nanozyme is constructed with AA as the reporter molecule, and the accurate detection of human serum alkaline phosphatase (ALP) is realized, demonstrating the vast potential of perovskites in biosensing.

Photostable and high-brightness aggregation-induced emission of iridium luminogen achieving reliable and sensitive continuous luminescent quantification of molecular oxygen

Online continuous luminescent oxygen quantification requires both high-brightness luminescence and superior photobleaching resistance of luminogens to afford the requisite level of sensitivity and operational stability, which remains a challenge. Herein, a fluorine-free design strategy of incremental rotors for preparing iridium luminogens with excellent photobleaching resistance and high-brightness aggregation-induced emission (AIE) is presented. The incremental rotors gradually improve the rotational activity of substituents, efficaciously activating the AIE with synchronously improved aggregation-state luminescence efficiency, which is theoretically confirmed by the variations of dipole moments and experimentally verified by the luminescent lifetimes. Moreover, the introduction of triphenylamine significantly improves the photobleaching resistance of iridium luminogens. Subsequently, by optimizing the loading capacity of the iridium luminogen, the improvement of high-brightness AIE on the oxygen sensitivity of ethocel films is successfully observed. Thickness attenuation of ethocel films dramatically shortens the quenching/recovery response to 4.7 s. Importantly, owing to the exceptional photobleaching resistance of the iridium luminogen, distinguished photo-fatigue resistance with operational stability is exhibited by the ethocel film with no luminescence attenuation during 8000 s continuous oxygen quantification.

Modulating the afterglow time of Mn2+ doped double perovskites by size tuning and its applications in dynamic information display

Mn²⁺ doped lead-free double perovskites are emerging afterglow materials that can avoid the usage of rare earth ions. However, the regulation of the afterglow time is still a challenge. In this work, the Mn doped Cs₂Na_0.2Ag_0.8InCl₆ crystals with afterglow emission at about 600 nm are synthesized by a solvothermal method. Then, the Mn²⁺ doped double perovskite crystals are crushed into different sizes. As the size decreases from 1.7 mm to 0.075 mm, the afterglow time decreases from 2070 s to 196 s. Steady-state photoluminescence (PL) spectra, time resolved PL, thermoluminescence (TL) reveal the afterglow time monotonously decreases due to the enhanced nonradiative surface trapping. The modulation on afterglow time will greatly promote their applications in various fields, such as bioimaging, sensing, encryption, and anti-counterfeiting. As a proof of concept, dynamic display of information is realized based on different afterglow times.

The Challenges of O2 Detection in Biological Fluids: Classical Methods and Translation to Clinical Applications

Dissolved oxygen (DO) is deeply involved in preserving the life of cellular tissues and human beings due to its key role in cellular metabolism: its alterations may reflect important pathophysiological conditions. DO levels are measured to identify pathological conditions, explain pathophysiological mechanisms, and monitor the efficacy of therapeutic approaches. This is particularly relevant when the measurements are performed in vivo but also in contexts where a variety of biological and synthetic media are used, such as ex vivo organ perfusion. A reliable measurement of medium oxygenation ensures a high-quality process. It is crucial to provide a high-accuracy, real-time method for DO quantification, which could be robust towards different medium compositions and temperatures. In fact, biological fluids and synthetic clinical fluids represent a challenging environment where DO interacts with various compounds and can change continuously and dynamically, and further precaution is needed to obtain reliable results. This study aims to present and discuss the main oxygen detection and quantification methods, focusing on the technical needs for their translation to clinical practice. Firstly, we resumed all the main methodologies and advancements concerning dissolved oxygen determination. After identifying the main groups of all the available techniques for DO sensing based on their mechanisms and applicability, we focused on transferring the most promising approaches to a clinical in vivo/ex vivo setting.

Ultraefficient Singlet Oxygen Generation from Manganese-Doped Cesium Lead Chloride Perovskite Quantum Dots

Lead halide perovskites hold promise for photovoltaics, lasers, and light-emitting diode (LED) applications, being known as light-harvesting or -emitting materials. Here we show that colloidal lead halide CsPbCl₃ perovskite quantum dots (PQDs), when incorporating divalent manganese (Mn²⁺) ions, are able to produce spin-paired singlet oxygen molecules with over-unit quantum yield (∼1.08) in air conditions. Our mechanistic studies and atomic-level density functional theory calculations endorse an energy-migration-mediated quantum cutting process favoring multiple singlet oxygen generation (MSOG), in which one exciton-activated bulk Mn²⁺ ion (∼2.0 eV) inside the nanocrystal migrates its energy among the Mn²⁺ sublattice to two surface Mn²⁺ defect states (∼1.0 eV), followed by nonradiative energy transfers to two surrounding oxygen molecules. Moreover, superhydrophobicization of MSOG PQDs through silica-mediated polystyrene encapsulation prevents them from disintegrating in aqueous medium, enabling photodegradation of methyl orange at a rate even higher than that of the canonical titanium oxide photocatalyst. The observation of ultraefficient singlet oxygen generation in PQDs has implications for fields ranging from photodynamic therapy to photocatalytic applications.

Review on Sensing Applications of Perovskite Nanomaterials

Recently, perovskite-based nanomaterials are utilized in diverse sustainable applications. Their unique structural characteristics allow researchers to explore functionalities towards diverse directions, such as solar cells, light emitting devices, transistors, sensors, etc. Many perovskite nanomaterial-based devices have been demonstrated with extraordinary sensing performance to various chemical and biological species in both solid and solution states. In particular, perovskite nanomaterials are capable of detecting small molecules such as O2, NO2, CO2, etc. This review elaborates the sensing applications of those perovskite materials with diverse cations, dopants and composites. Moreover, the underlying mechanisms and electron transport properties, which are important for understanding those sensor performances, will be discussed. Their synthetic tactics, structural information, modifications and real time sensing applications are provided to promote such perovskite nanomaterials-based molecular designs. Lastly, we summarize the perspectives and provide feasible guidelines for future developing of novel perovskite nanostructure-based chemo- and biosensors with real time demonstration.

Cation-doping matters in caesium lead halide perovskite nanocrystals: from physicochemical fundamentals to optoelectronic applications

All-inorganic caesium lead halide perovskite nanocrystals (PeNCs) with different dimensionalities have recently fascinated the research community due to their extraordinary optoelectronic properties including tunable bandgaps over the entire visible spectral region, high photoluminescence quantum yields (PLQYs) close to unity and narrow emission line widths down to 10-20 nm, making them particularly suitable as promising candidates for numerous applications ranging from light-emitting diodes (LEDs), solar cells to scintillators. Despite the considerable progress made in the past six years, the real-world applications of caesium lead halide PeNCs themselves especially in the category of CsPbX₃ (X = Cl, Br and I) are still restricted by their labile crystal lattices and downgraded luminescence when exposed to ambient air conditions. Recent experimental and theoretical studies on cation doping have proven to be an effective way to significantly improve the physicochemical properties of cesium lead halide PeNCs, which would have profound implications for a range of applications. In this review, we provide a brief overview of the most recent advances in cation-doped all-inorganic caesium lead halide PeNCs, aimed at developing high-performance and long-term stable optoelectronic and photovoltaic devices, which covers areas from their fundamental considerations of cation doping, controlled synthesis methodology and novel physicochemical properties to the optoelectronic applications with an emphasis on perovskite-based LEDs and solar cells. And finally, some possible directions of future efforts toward this active research field are also proposed.

TADF-Emitting Zn(II)-Benzoporphyrin: An Indicator for Simultaneous Sensing of Oxygen and Temperature

A new luminescent indicator is presented that enables simultaneous measurement of oxygen and temperature at a single wavelength. The indicator, an alkylsulfone-substituted Zn(II)-meso-tetraphenyltetrabenzoporphyrin, emits prompt and thermally activated delayed fluorescence (TADF). TADF is sensitive toward oxygen and temperature and is referenced against prompt fluorescence (PF) that is not affected by oxygen. The information on both parameters is accessed from the decay time of TADF and the temperature-dependent ratio of TADF and PF. Sensor foils, made from poly(styrene-co-acrylonitrile) and the indicator dye, enable temperature-compensated trace oxygen sensing (0.002-6 hPa pO2) at ambient conditions. Compared to the previously reported dual sensors based on two emitters, the new sensor significantly simplifies the experimental setup and eliminates risks of different leaching or photobleaching rates by utilizing only one indicator dye and operating at a single wavelength.

Unveiling the interfacial electrochemiluminescence behavior of lead halide perovskite nanocrystals

In this study, a three-phase heterostructure interface including glassy carbon (conducting medium), CsPbBr₃ perovskite nanocrystals (PNCs, emitter) and acetonitrile (electrolyte) is constructed for fully investigating the interfacial electrochemiluminescence (ECL) behavior of CsPbBr₃ PNCs. We find that these interfaces serve as bridges for efficient electron-hole transfer during the ECL process. As a proof of concept, the increase of the heterostructure interface area will accordingly enhance the ECL intensity of CsPbBr₃ PNCs. About seven-fold enhancement of the ECL intensity could be achieved when the interface area has triple-fold increase, which provides a new perspective to construct more efficient ECL systems via interface engineering.

Orange to Red, Emission-Tunable Mn-Doped Two-Dimensional Perovskites with High Luminescence and Stability

Lead halide perovskites are emerging as promising candidates for high-efficiency light-emitting diode (LED) applications because of their tunable band gaps and high quantum yield (QY). However, it remains a challenge to obtain stable red emitting materials with high QY. Herein, we report a facile and convenient hot-injection strategy to synthesize Mn-doped two-dimensional (2D) perovskite nanosheets. The emission peak can be tuned from 597 to 658 nm by manipulating the crystal field strength. In particular, a QY as high as 97% for 2D perovskite is achieved. The as-prepared perovskite also possesses excellent stability, whose emission property can be maintained for almost one year. A monochrome LED is further fabricated by employing the as-prepared perovskite as phosphor, which also shows high long-term stability. We believe that these highly efficient and stable perovskites will open up new opportunities in LED applications.

A taurine-functionalized 3D graphene-based foam for electrochemical determination of hydrogen peroxide

We present a synthesis approach of taurine-functionalized graphene foam (a-NSGF) using hydrothermal reduction, freeze-drying and high temperature annealing. The higher temperature in annealing allowed the N/S atoms of taurine enter into the graphene lattice, which improves its electrocatalytic activity greatly. The a-NSGF consisting of taurine that modified into 3D layers of graphene and endow is of the rapid sensitive to hydrogen peroxide (H₂O₂). The electrode using a-NSGF modification reveals highly sensitive and stable towards the concentration change of H₂O₂ due to the stable 3D structure and good electrical conductivity of a-NSGF. A linear correlation between H₂O₂ concentration and the electrochemical signal is found to be in a range from 1.5 to 300 μM and the correlation coefficient is R² = 0.999. The modified electrode has been applied in the determination of H₂O₂ in rain samples and the results have been compared with the China National Standard Method. The recoveries range from 94.6% to 106.7%. These results show that the proposed sensor is promising for the development of novel electrochemical sensing for H₂O₂ determination.

Tuning from Quantum Dots to Magic Sized Clusters of CsPbBr3 Using Novel Planar Ligands Based on the Trivalent Nitrate Coordination Complex

We report the first demonstration of using trivalent metal hydrated nitrate coordination complexes (TMHNCCs) as novel passivation ligands to control the synthesis of magic sized clusters (MSCs) and quantum dots (QDs) of CsPbBr₃ perovskite at room temperature. We can easily tune from QDs to MSCs or produce a mixture of the two by changing the amount of TMHNCC ligands used, with more ligands favoring MSCs. The original TMHNCC introduced, aluminum nitrate nonahydrate [ANN, Al(NO₃)₃·9H₂O], led to the production of aluminum dihydroxide nitrate tetrahydrate {ADNT, [Al(OH)₂(NO₃)]·4H₂O}, with the assistance of oleic acid (OA) and oleylamine (OAm). Through several control experiments, we determined that ADNT is the primary ligand for effectively passivating the MSCs and QDs, with OAm being essential for deprotonating ANN and OA for adjusting the pH of the reaction system. We suggest that ADNT is planar on the surface of the MSCs or QDs with its NO₃^- and OH^- groups binding to the Cs⁺ and Pb²⁺ defect sites and Al³⁺ binding to the Br^- defect sites of the MSCs or QDs.

Ligand-free all-inorganic metal halide nanocubes for fast, ultra-sensitive and self-powered ozone sensors

Ligand-free all-inorganic lead halide nanocubes have been investigated as ozone sensing materials operating at room temperature. It is found that the nanocubes, crystallined in the orthorhombic CsPbBr₃ structure, can operate at room temperature, be self-powered and exhibit high sensitivity and remarkable repeatability. More importantly, they demonstrate higher sensitivity (54% in 187 ppb) and faster response and recovery times compared to hybrid lead mixed halide perovskite (CH₃NH₃PbI_3-x Cl _x ) layers, which is the only lead halide perovskite material tested for ozone sensing, to date. Following the exposure to an ozone environment, the stoichiometry and the morphology of the nanocubes remain unaltered. The facile and easy fabrication process together with the high responsivity and stability to the ozone environment makes the bare CsPbBr₃ nanocubes a promising material for sensing applications. The sensing properties of the nanoparticulate metal halides presented here provide new exciting opportunities towards engineering reliable and cheap sensing elements for room-temperature operated and self-powered sensors.

Formation of disulphide linkages restricts intramolecular motions of a fluorophore: detection of molecular oxygen in food packaging

Reliable and easy detection of oxygen in food packaging without the aid of sophisticated instruments is highly coveted. A tetraphenylethene probe based on oxygen-mediated polymerization via the formation of disulfides causes restricted intramolecular rotation of the TPE phenyls resulting in a >100 fold enhancement of emission and thus detects O2 in food packages.

Molecular assembly-induced charge transfer between a mixed (phthalocyaninato)(porphyrinato) yttrium triple-decker and a fullerene

A close interface of a mixed (phthalocyaninato)(porphyrinato) yttrium triple-decker and a fullerene in cocrystals affords stronger charge transfer than each individual.

High mobility at the interface of the cocrystallized sandwich-type tetrapyrrole metal compound and fullerene layers

Organic field effect transistor (OFET) devices fabricated based on mixed-(phthalocyaninato)(porphyrinato) yttrium(iii) and fullerene cocrystals represent one of the most excellent cocrystal ambipolar OFET devices reported thus far.