Aqueous, Non-Polymer-Based Perovskite Quantum Dots for Bioimaging: Conserving Fluorescence and Long-Term Stability via Simple and Robust Synthesis

Eco-friendly synthesis of Cs3Bi2Br9 perovskite quantum dots using castor oil as solvent and ligand for leather anti-counterfeiting

All-inorganic cesium bismuth bromide perovskite quantum dots(Cs3Bi2Br9 PQDs) have emerged as promising alternatives to lead-based perovskite quantum dots with excellent performance due to their low toxicity, drawing extensive attention over recent decades. However, challenges remain in terms of their stability and the reliance on organic solvents during the preparation process. Herein, a novel synthesis method for Cs3Bi2Br9 PQDs is introduced, utilizing eco-friendly castor oil as both the solvent and ligand (CO-Cs3Bi2Br9). These PQDs display a vivid blue emission at 430 nm, with an impressive photoluminescence quantum yield (PLQY) of 21.2%. Furthermore, they maintain 97.3% of their fluorescence intensity after 72 h of environmental exposure. The effects of various components of castor oil, including ricinoleic, oleic and linoleic acid, on crystal growth and properties of the Cs3Bi2Br9 are investigated. Significantly, the presence of conjugated double bonds in linoleic acid, when used as a solvent, results in a PLQY of up to 53% for the synthesized Cs3Bi2Br9 PQDs. Moreover, CO-Cs3Bi2Br9 PQDs are introduced into leather by a layer-by-layer self-assembly method, the bright blue fluorescent pattern can be observed in the CO-Cs3Bi2Br9/leather under ultraviolet irradiation, indicating the leather anti-counterfeiting potential of CO-Cs3Bi2Br9 PQDs. This study opens a novel pathway for the sustainable synthesis of PQDs through the utilization of castor oil-derived natural green solvents.

Synergistic Integration of Halide Perovskite and Rare-Earth Ions toward Photonics

Halide perovskites (HPs), emerging as a noteworthy class of semiconductors, hold great promise for an array of optoelectronic applications, including anti-counterfeiting, light-emitting diodes (LEDs), solar cells (SCs), and photodetectors, primarily due to their large absorption cross section, high fluorescence efficiency, tunable emission spectrum within the visible region, and high tolerance for lattice defects, as well as their adaptability for solution-based fabrication processes. Unlike luminescent HPs with band-edge emission, trivalent rare-earth (RE) ions typically emit low-energy light through intra-4f optical transitions, characterized by narrow emission spectra and long emission lifetimes. When fused, the cooperative interactions between HPs and REs endow the resulting binary composites not only with optoelectronic properties inherited from their parent materials but also introduce new attributes unattainable by either component alone. This review begins with the fundamental optoelectronic characteristics of HPs and REs, followed by a particular focus on the impact of REs on the electronic structures of HPs and the associated energy transfer processes. The advanced synthesis methods utilized to prepare HPs, RE-doped compounds, and their binary composites are overviewed. Furthermore, potential applications are summarized across diverse domains, including high-fidelity anticounterfeiting, bioimaging, LEDs, photovoltaics, photodetection, and photocatalysis, and conclude with remaining challenges and future research prospects.

Machine learning-driven fluorescent sensor array using aqueous CsPbBr3 perovskite quantum dots for rapid detection and sterilization of foodborne pathogens

With the growing global concern over food safety, the rapid detection and disinfection of foodborne pathogens have become critical in public health. This study presents a novel machine learning-driven fluorescent sensor array utilizing aqueous CsPbBr3 perovskite quantum dots (PQDs) for the rapid identification and eradication of foodborne pathogens. The relative signal intensity changes (ΔRGB) generated by the sensor array were analyzed using the machine learning algorithm-Support Vector Machine (SVM). The study achieved the identification and recognition of five pathogens and their mixtures within a concentration range of 1.0 × 103 to 1.0 × 107 CFU/mL with an accuracy rate of 100 %, and the limits of detection (LOD) for the pathogens were found to be low. Additionally, the array also showed excellent performance in the identification of pathogens in tap water, achieving an accuracy rate of 100 %. Furthermore, the fluorescent sensor array was capable of inactivating the pathogens with an efficiency of over 99 % within 30 min post-detection. This development provides an efficient and reliable tool for the field of food safety detection.

Synthesis, characterization, and practical applications of perovskite quantum dots: recent update

This review paper provides an in-depth analysis of Perovskite quantum dots (PQDs), a class of nanomaterials with unique optical and electronic properties that hold immense potential for various technological applications. The paper delves into the structural characteristics, synthesis methods, and characterization techniques of PQDs, highlighting their distinct advantages over other Quantum Dots (QDs). Various applications of PQDs in fields such as solar cells, LEDs, bioimaging, photocatalysis, and sensors are discussed, showcasing their versatility and promising capabilities. The ongoing advancements in PQD research and development point towards a bright future for these nanostructures in revolutionizing diverse industries and technologies.

Double Layer SiO2-Coated Water-Stable Halide Perovskite as a Promising Antimicrobial Photocatalyst under Visible Light

Halide perovskite nanocrystals (HPNCs) have emerged as promising materials for various light harvesting applications due to their exceptional optical and electronic properties. However, their inherent instability in water and biological fluids has limited their use as photocatalysts in the aqueous phase. In this study, we present highly water-stable SiO2-coated HPNCs as efficient photocatalysts for antimicrobial applications. The double SiO2 layer coating method confers long-term structural and optical stability to HPNCs in water, while the in situ synthesis of lead- and bismuth-based perovskite NCs into the SiO2 shell enhances their versatility and tunability. We demonstrate that the substantial generation of singlet oxygen via energy transfer from HPNCs enables efficient photoinduced antibacterial efficacy under aqueous conditions. More than 90% of Escherichia coli was inactivated under mild visible light irradiation for 6 h. The excellent photocatalytic antibacterial performance suggests that SiO2-coated HPNCs hold great potential for various aqueous phase photocatalytic applications.

Aqueous-phase dual-functional chiral perovskites for hydrogen sulfide (H2S) detection and antibacterial applications in Escherichia coli

Perovskite nanocrystals (PNCs) have attracted extensive attention for their potential applications in biology. However, only a handful of PNCs have been scrutinized in the biological domain due to issues such as instability, poor dispersion, and size inhomogeneity in polar solvents. The development of dual-functional perovskite nanomaterials with hydrogen sulfide (H2S) sensing and antibacterial capabilities is particularly intriguing. In this study, we prepared chiral quasi-two-dimensional (quasi-2D) perovskite nanomaterials, Bio(S-PEA)2CsPb2Br7 and Bio(R-PEA)2CsPb2Br7, that were uniformly dispersed in aqueous media. The effective encapsulation of methoxypolyethylene glycol amine (mPEG-NH2) improved water stability and uniformity of particle size. Circular dichroism (CD) signals were created by the successful insertion of chiral cations. These perovskites as probes showed a rapid and sensitive fluorescence quenching response to H2S, and the effect of imaging detection was observed at the Escherichia coli (E. coli) level. As antibacterial agents, their pronounced positive charge properties facilitated membrane lysis and subsequent E. coli death, indicating a significant antibacterial effect. This work has preliminary explored the application of chiral perovskites in biology and provides insight into the development of bifunctional perovskite nanomaterials for biological applications.

Exploiting the Photo-Physical Properties of Metal Halide Perovskite Nanocrystals for Bioimaging

Perovskite nanomaterials have recently been exploited for bioimaging applications due to their unique photo-physical properties, including high absorbance, good photostability, narrow emissions, and nonlinear optical properties. These attributes outperform conventional fluorescent materials such as organic dyes and metal chalcogenide quantum dots and endow them with the potential to reshape a wide array of bioimaging modalities. Yet, their full potential necessitates a deep grasp of their structure-attribute relationship and strategies for enhancing water stability through surface engineering for meeting the stringent and unique requirements of each individual imaging modality. This review delves into this evolving frontier, highlighting how their distinctive photo-physical properties can be leveraged and optimized for various bioimaging modalities, including visible light imaging, near-infrared imaging, and super-resolution imaging.

A perovskite-based electrochemiluminescence aptasensor for tetracycline screening

Tetracyclines are currently the most commonly used class of antibiotics, and their residue issue significantly impacts public health safety. In this study, a surface modification of perovskite with cetyltrimethylammonium bromide led to the generation of stable electrochemiluminescence (ECL) emitters in aqueous systems and improved the biocompatibility of perovskite. A perovskite quantum dot-based ECL sensing strategy was developed. Utilizing the corresponding aptamer of the antibiotics, strain displacement reactions were triggered, disrupting the ECL quenching system composed of perovskite and Ag nanoclusters (Ag NCs) on the electrode surface, generating a signal to achieve quantitative detection of several common tetracycline antibiotics. The perovskite quantum dot provided a strong and stable initial signal, while the efficient catalytic activity of the silver cluster enhanced the recognition sensitivity. Tetracycline, chlortetracycline, and oxytetracycline were used as examples to demonstrate the differentiation and quantitative detection through this method. In addition, the aptasensor exhibited analytical performance with the linear range (0.1-10 μM OTC) and good recovery rates of 94.7% to 101.6% in real samples. This approach has the potential to become a sensitive and practical approach for assessing antibiotic residues.

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.

Phase transferred and non-coated, water soluble perovskite quantum dots for biocompatibility and sensing

Despite the excellent optoelectronic properties exhibited by CsPbBr₃ QDs (PQDs) for sensing applications, their poor resistance to water does not allow their utilization as probes to detect analytes in aqueous media. The present work provides water soluble PQDs (dispersed in water) prepared by an appropriate phase engineering of the ligand. The dicarboxylate functional ligands at a particular pH allow the protonated state to form solvated carboxyl dimers, which interconnects PQDs, thus avoiding Ostwald ripening and enhancing the photoluminescence quantum yield (PLQY). As a proof of concept, this probe was applied to detect bioamines in water, namely histamine, hexamethylenediamine, phenethylamine, dopamine and thiamine. The probe is highly selective to histamine at concentrations below 500 nM and this selectivity of histamine over dopamine is very interesting and rarely reported. More importantly, this work offers a standard protocol for transferring PQDs from the organic to aqueous phase, for the detection of such biomolecules in water.

Biomolecules incorporated in halide perovskite nanocrystals: synthesis, optical properties, and applications

Halide perovskite nanocrystals (HPNCs) have emerged at the forefront of nanomaterials research over the past two decades. The physicochemical and optoelectronic properties of these inorganic semiconductor nanoparticles can be modulated through the introduction of various ligands. The use of biomolecules as ligands has been demonstrated to improve the stability, luminescence, conductivity and biocompatibility of HPNCs. The rapid advancement of this field relies on a strong understanding of how the structure and properties of biomolecules influences their interactions with HPNCs, as well as their potential to extend applications of HPNCs towards biological applications. This review addresses the role of several classes of biomolecules (amino acids, proteins, carbohydrates, nucleotides, etc.) that have shown promise for improving the performance of HPNCs and their potential applications. Specifically, we have reviewed the recent advances on incorporating biomolecules with HP nanomaterials on the formation, physicochemical properties, and stability of HP compounds. We have also shed light on the potential for using HPs in biological and environmental applications by compiling some recent of proof-of-concept demonstrations. Overall, this review aims to guide the field towards incorporating biomolecules into the next-generation of high-performance HPNCs for biological and environmental applications.