Highly luminescent biocompatible CsPbBr3@SiO2 core-shell nanoprobes for bioimaging and drug delivery

Biocompatible Perovskite Nanocrystals with Enhanced Stability for White Light-Emitting Diodes

Recently emerged lead halide perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals (PNCs) have attracted tremendous attention due to their excellent optical properties. However, the poor water stability, unsatisfactory luminescence efficiency, disappointing lead leakage, and toxicity have restricted their practical applications in photoelectronics and biomedical fields. Herein, a controllable encapsulated strategy is investigated to realize CsPbX3 PNCs/PVP @PMMA composites with superior luminescence properties and excellent biocompatibility. Additionally, the synthesized CsPbBr3 and CsPbBr0.6I2.4 PNCs/PVP@PMMA structures exhibit green and red emissions with a maximal photoluminescence quantum yield (PLQY) of about 70.24% and 98.26%, respectively. These CsPbX3 PNCs/PVP@PMMA structures show high emission efficiency, excellent stability after water storage for 18 months, and low cytotoxicity at the PNC concentration at 500 μg mL-1. Moreover, white light-emitting diode (WLED) devices based on mixtures of CsPbBr3 and CsPbBr0.6I2.4 PNCs/PVP@PMMA perovskite structures are investigated, which exhibit excellent warm-white light emissions at room temperature. A flexible manipulation method is used to fabricate the white light emitters based on these perovskite composites, providing a fantastic platform for fabricating solid-state white light sources and full-color displays.

Dual Passivation Strategy for Highly Stable Blue-Luminescent CsPbBr3 Nanoplatelets

Blue-emitting colloidal CsPbX3 (X = Br, Cl, or I) perovskite nanocrystals have emerged as one of the most fascinating materials for optoelectronic applications. However, their applicability is hindered by poor stability and a low photoluminescence efficiency. Herein, highly stable CsPbBr3 nanoplatelets exhibiting intense blue luminescence are fabricated by employing a strategy in which the morphology is regulated and the surface is subjected to dual passivation through the incorporation of zirconium acetylacetonate [Zr(acac)4]. The passivated CsPbBr3 nanocrystals exhibit adjustable light emission from green to dark blue and a controllable morphology from nanocubes (NCs) to nanoplatelets (NPLs) and nanorods accomplished by varying the content of Zr(acac)4. The optimized NPLs are characterized by a bright blue emission with a central wavelength of 459 nm and a high photoluminescence quantum yield of 90%. The addition of Zr(acac)4 in the synthesis of CsPbBr3 induces oriented growth with a two-dimensional morphology. The Zr(acac)4 can repair the surface defects of the nanocrystal surface, and the surface is also capped with the Zr(OH)4 cluster layer. Therefore, the passivated blue-emitting NPLs exhibit outstanding stability compared to that of pristine NPLs during long-term storage and exposure to light. This work provides a novel strategy for fabricating highly stable PNCs with deep-blue emission and widens their potential applications in blue-emitting optoelectronic devices.

Dual-emission CPB@SMSO@SiO2 composites with tunable afterglow through energy transfer

Afterglow materials face limitations in color variety, low luminosity, and stability. Thus, developing materials with adjustable afterglow color, increased photoluminescence (PL) intensity, and enhanced stability is crucial. This paper reports the fabrication of a series of core-shell composites, CPB@SMSO@SiO2, which combine Sr2MgSi2O7: Eu2+, Dy3+ (SMSO) and lead halide perovskite quantum dots (CsPbBr3/CPB PeQDs) through a process involving in-situ growth and hydrolytic coating. The SMSO in the composite can absorb 365 nm UV light and then emit 470 nm light, which can be absorbed by the CsPbBr3 PeQDs, resulting in an overall increase in the PL intensity of the composite. The afterglow color can be turned from green to blue by adjusting the ratio of SMSO and CsPbBr3. Furthermore, the stability of the composites is improved by the SiO2 shell layer formed by hydrolysis of tetramethyl orthosilicate (TMOS). This study presents an opportunity to develop innovative afterglow materials.

Ultra-stable and highly-bright CsPbBr3 perovskite/silica nanocomposites for miRNA detection based on digital single-nanoparticle counting

Single-nanoparticle counting (SNPC) based on fluorescent tag (FT) stands out for its capacity to achieve amplification-free and sensitive detection of biomarkers. The stability and luminescence of FT are important to the sensitivity and reliability of SPNC. In this work, we developed novel perovskite/silica nanocomposites by in-situ nanoconfined growth of CsPbBr3 nanocrystals inside mesoporous structure of silica nanoparticles. PbBr(OH) was formed in an alkaline-assisted reaction triggered by water on the surface of CsPbBr3 nanocrystals. The as-obtained nanocomposites, featuring dual protection from silica matrix and PbBr(OH), exhibited high absolute photoluminescence quantum yield (PLQY) of 86.5% and demonstrated outstanding PL stability confronting with water, heat, ultrasound and UV-irradiation, which is desired by SNPC-based biosensor. Thereafter, these nanocomposites were used to construct an operationally friendly SNPC assay for the amplification-free quantification of cancer-associated miRNA. Quantitative detection of miRNA could be accomplished by directly counting the number of nanocomposites using a flow cytometer in this assay. This strategy did not ask for multiple washing steps and demonstrated specific and sensitive detection of miRNA 21, which exhibited a dynamic range of 1-1000 pM and limit of detection of 79 amol. The employment of highly stable perovskite/silica nanocomposites improved the test reliability and stability of SNPC, revealing the vast potential of perovskites in biosensing.

Biocompatible Silica-Coated Europium-Doped CsPbBr3 Nanoparticles with Luminescence in Water for Zebrafish Bioimaging

Cesium lead halide (CsPbX3, X = Br, Cl, and I) nanocrystals (NCs) are widely concerned and applied in many fields due to the excellent photoelectric performance. However, the toxicity of Pb and the loss of luminescence in water limit its application in vivo. A stable perovskite nanomaterial with good bioimaging properties is developed by incorporating europium (Eu) in CsPbX3 NCs followed with the surface coating of silica (SiO2) shell (CsPbX3:Eu@SiO2). Through the surface coating of SiO2, the luminescence stability of CsPbBr3 in water is improved and the leakage of Pb2+ is significantly reduced. In particular, Eu doping inhibits the photoluminescence quantum yield reduction of CsPbBr3 caused by SiO2 coating, and further reduces the release of Pb2+. CsPbBr3:Eu@SiO2 nanoparticles (NPs) show efficient luminescence in water and good biocompatibility to achieve cell imaging. More importantly, CsPb(ClBr)3:Eu@SiO2 NPs are obtained by adjusting the halogen components, and green light and blue light are realized in zebrafish imaging, showing good imaging effect and biosafety. The work provides a strategy for advanced perovskite nanomaterials toward biological practical application.

Exploiting halide perovskites for heavy metal ion detection

Heavy metal ions such as mercury (Hg), copper (Cu), and cadmium (Cd) pose significant threats to ecosystems and human health due to their toxicity and bioaccumulation potential. With growing environmental concerns over heavy metal ion pollution, there is an urgent need to develop efficient detection methods for safeguarding public health and the environment. Various materials, including polymers, nanomaterials, and porous substances, have been used for heavy metal ion detection and have shown promising performance for different scenarios. However, each of these materials has certain limitations as probes. Metal halide perovskites (MHPs), known for their exceptional optoelectronic properties and high structural and chemical tunability, have gained great attention in applications such as photovoltaics and LEDs. Yet, their potential as metal ion probes remains rarely explored. This review assesses MHPs as prospective materials for heavy metal ion detection, taking their structure, chemical properties, and responses to external stimuli into consideration. Three key detection mechanisms-cation exchange (CE), electron transfer (ET), and fluorescence resonance energy transfer (FRET), are explored to understand how metal ions trigger fluorescence changes on perovskites, enabling their detection. Finally, current avenues of developing perovskite probes are discussed, which include exploration of lead-free perovskites to mitigate environmental concerns arising from lead leakage and the pursuit of achieving high-sensitivity and stable detection in aqueous media, summarizing the existing and promising strategies in this field.

Acetic acid-driven synthesis of environmentally stable MAPb0.5Sn0.5Br3 nano-assembly for anti-counterfeiting

In mixed Sn-Pb perovskites, the synergistic properties of tin (Sn) and lead (Pb) are leveraged, effectively combining the merits of Pb-based perovskites while simultaneously reducing Pb-associated toxicity. However, the propensity for Sn to undergo facile oxidation from Sn2+ to Sn4+ poses a significant challenge to the stability of these mixed perovskites, limiting their advancement. This study proposes an innovative acetic acid (HAc)-driven synthesis approach to obtain a stable chain-like MAPb0.5Sn0.5Br3 nano-assembly. Leveraging the acidic properties of HAc serves a dual purpose. Primarily, it curtails the oxidation of Sn2+ to Sn4+. Secondly, it orchestrates nanocrystals (NCs) into a more uniform and ordered chain-like assembly, a consequence of hydrogen bonding and coordination interactions facilitated by the HAc. Additionally, HAc demonstrates its capability to passivate MAPb0.5Sn0.5Br3 surface through coordination bonding with unsaturated sites (i.e., Sn2+ or Pb2+), thus effectively compensating for bromide vacancies. Introducing HAc during the synthesis process yields perovskite NCs with enhanced thermal resilience, optical and water stability. Drawing upon the different stimulus responses of synthesized perovskite NCs when exposed to external environment, the optical anti-counterfeiting labels are prepared. The findings provide a potent strategy for augmenting the stability of perovskite NCs, suggesting their potential applicability in anti-counterfeiting endeavors.

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.

Covalent Coupling Assisted Hydrophilic Perovskite Spheres for Ratiometric Fluorescent Visual Multichannel Immunoassay

Quantitative fluorescence immunoassay is essential for the construction of biosensing mechanisms and the quantification of trace markers. But the interference problems caused by low fluorescence efficiency and broad fluorescence spectrum of fluorescent probes have hindered the continued development of ratiometric fluorescence sensing in biosensing. Perovskite materials, with ultra-high color purity (FWHM < 30 nm) and photoluminescence quantum yield (PLQY) (close to 100%), are expected to be next-generation fluorescent probes. However, poor water stability and biocompatibility are still non-negligible in biosensor applications. In this work, hyperstatic perovskite fluorescent microspheres prepared by swelling-shrinking method can be used as ratiometric fluorescence signals and biological immunoassay platforms. Meanwhile, inspired by p-aminophenol (AP) controlled synthesis and the catalytic reaction of 4-aminophenol phosphate (APP) triggered by alkaline phosphatase (ALP), a strategy to prepare fluorescent nanoparticles as fluorescence signals for ALP detection is proposed. Most importantly, it is proposed for the first time to combine this enzymatic fluorescence with perovskite materials using covalent linkage to create a novel cascade immunoassay and use it for quantitative and visualization determination of hepatitis B surface antigen (HBsAg) for application verification. These results indicate the biosensing potential of perovskite materials and provide a pathway for high sensitivity enzyme detection and enzyme triggered immune detection.

Highly luminescent and stable CsPbBr3 perovskite nanocrystals coated with polyethersulfone for white light-emitting diode applications

Simultaneously improving the stability and photoluminescence quantum yield (PLQY) of all inorganic perovskite nanocrystals (NCs) is crucial for their practical utilization in various optoelectronic devices. Here, CsPbBr3 NCs coated with polyethersulfone (PES) were prepared via an in-situ co-precipitation method. The sulfone groups in PES bind to undercoordinated lead ion (Pb2+) on the CsPbBr3 NCs, resulting in significant reduction of surface defects, thus enhancing the PLQY from 74.2% to 88.3%. Meanwhile, the PES-coated NCs exhibit high water resistance and excellent heat and light stability, maintaining over 85% of the initial PL intensity under thermal aging (70°C, 4 h) and continuous 365 nm ultraviolet (UV) light irradiation (24 W, 8 h) conditions. By contrast, the PL intensity of the control NCs dramatically dropped to less than 40%. Finally, a diode emitting bright white light was fabricated utilizing the PES-coated CsPbBr3 NCs, which exhibits a color gamut of ~110% NTSC standard.

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.

Improving the stability of perovskite nanocrystals via SiO2 coating and their applications

Lead halide perovskite nanocrystals (LHP NCs) with outstanding optical properties have been regarded as promising alternatives to traditional phosphors for lighting and next-generation display technology. However, the practical applications of LHP NCs are seriously hindered by their poor stability upon exposure to moisture, oxygen, light, and heat. Hence, various strategies have been proposed to solve this issue. In this review, we have focused our attention on improving the stability of LHP NCs via SiO2 coating because it has the advantages of simple operation, less toxicity, and easy repetition. SiO2 coating is classified into four types: (a) in situ hydrolytic coating, (b) mesoporous silica loading, (c) mediated anchoring, and (d) double coating. The potential applications of SiO2-coated LHP NCs in the field of optoelectronics, biology, and catalysis are presented to elucidate the reliability and availability of SiO2 coating. Finally, the future development and challenges in the preparation of SiO2-coated LHP NCs are analyzed in order to promote the commercialization process of LHP NC-related commodities.

Comprehensive Neurotoxicity of Lead Halide Perovskite Nanocrystals in Nematode Caenorhabditis elegans

To date, all-inorganic lead halide perovskite quantum dots have emerged as promising materials for photonic, optoelectronic devices, and biological applications, especially in solar cells, raising numerous concerns about their biosafety. Most of the studies related to the toxicity of perovskite quantum dots (PeQDs) have focused on the potential risks of hybrid perovskites by using zebrafish or human cells. So far, the neurotoxic effects and fundamental mechanisms of PeQDs remain unknown. Herein, a comprehensive methodology is designed to investigate the neurotoxicity of PeQDs by using Caenorhabditis elegans as a model organism. The results show that the accumulation of PeQDs mainly focuses on the alimentary system and head region. Acute exposure to PeQDs results in a decrease in locomotor behaviors and pharyngeal pumping, whereas chronic exposure to PeQDs causes brood decline and shortens lifespan. In addition, some abnormal issues occur in the uterus during reproduction assays, such as vulva protrusion, impaired eggs left in the vulva, and egg hatching inside the mother. Excessive reactive oxygen species formation is also observed. The neurotoxicity of PeQDs is explained by gene expression. This study provides a complete insight into the neurotoxicity of PeQD and encourages the development of novel nontoxic PeQDs.

Multifunctional mesoporous silica nanoparticles for biomedical applications

Mesoporous silica nanoparticles (MSNs) are recognized as a prime example of nanotechnology applied in the biomedical field, due to their easily tunable structure and composition, diverse surface functionalization properties, and excellent biocompatibility. Over the past two decades, researchers have developed a wide variety of MSNs-based nanoplatforms through careful design and controlled preparation techniques, demonstrating their adaptability to various biomedical application scenarios. With the continuous breakthroughs of MSNs in the fields of biosensing, disease diagnosis and treatment, tissue engineering, etc., MSNs are gradually moving from basic research to clinical trials. In this review, we provide a detailed summary of MSNs in the biomedical field, beginning with a comprehensive overview of their development history. We then discuss the types of MSNs-based nanostructured architectures, as well as the classification of MSNs-based nanocomposites according to the elements existed in various inorganic functional components. Subsequently, we summarize the primary purposes of surface-functionalized modifications of MSNs. In the following, we discuss the biomedical applications of MSNs, and highlight the MSNs-based targeted therapeutic modalities currently developed. Given the importance of clinical translation, we also summarize the progress of MSNs in clinical trials. Finally, we take a perspective on the future direction and remaining challenges of MSNs in the biomedical field.

Carriers, Quasi-particles, and Collective Excitations in Halide Perovskites

Halide perovskites (HPs) are potential game-changing materials for a broad spectrum of optoelectronic applications ranging from photovoltaics, light-emitting devices, lasers to radiation detectors, ferroelectrics, thermoelectrics, etc. Underpinning this spectacular expansion is their fascinating photophysics involving a complex interplay of carrier, lattice, and quasi-particle interactions spanning several temporal orders that give rise to their remarkable optical and electronic properties. Herein, we critically examine and distill their dynamical behavior, collective interactions, and underlying mechanisms in conjunction with the experimental approaches. This review aims to provide a unified photophysical picture fundamental to understanding the outstanding light-harvesting and light-emitting properties of HPs. The hotbed of carrier and quasi-particle interactions uncovered in HPs underscores the critical role of ultrafast spectroscopy and fundamental photophysics studies in advancing perovskite optoelectronics.

Study on myocardial toxicity induced by lead halide perovskites nanoparticles

Lead halide perovskites (LHPs) are outstanding candidates for next-generation optoelectronic materials, with considerable prospects of use and commercial value. However, knowledge about their toxicity is scarce, which may limit their commercialization. Here, for the first time, we studied the cardiotoxicity and molecular mechanisms of representative CsPbBr3 nanoparticles in LHPs. After their intranasal administration to Institute of Cancer Research (ICR) mice, using advanced synchrotron radiation, mass spectrometry, and ultrasound imaging, we revealed that CsPbBr3 nanoparticles can severely affect cardiac systolic function by accumulating in the myocardial tissue. RNA sequencing and Western blotting demonstrated that CsPbBr3 nanoparticles induced excessive oxidative stress in cardiomyocytes, thereby provoking endoplasmic reticulum stress, disturbing calcium homeostasis, and ultimately leading to apoptosis. Our findings highlight the cardiotoxic effects of LHPs and provide crucial toxicological data for the product.

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.

Polaron states of the full-configuration defects in metal halide perovskites

The systematical analysis for varieties of defects with different depths and lattice relaxation strengths in metal halide perovskites (MHPs) is a challenging task. Here, we study the energy shifts of the full-configuration defects due to the polaron effect based on the all-coupling variational method in MHPs, where these polaron states are formed stemming from different defect species coupling with the longitudinal optical phonon modes via Fro¨hlich mechanism. We find that the polaron effect results in defect levels varying from tens to several hundreds of meV, which are very close to the correction of defect levels due to the defect-polaron effect, especially for these defects migration proved in the recent experiments in MHPs. These results provide the significant enlightenment not only for analyzing the radiation and non-radiation processes of carriers mediated by defects, but also for optimizing defect effect in the photovoltaic and photoelectric devices based on MHPs materials.

Mesoporous Silica Nanoparticles-Based Nanoplatforms: Basic Construction, Current State, and Emerging Applications in Anticancer Therapeutics

In recent years, researchers are developing novel nanoparticles for diagnostic applications using imaging techniques and for therapeutic purposes through drug delivery techniques. The unique physical and chemical properties of mesoporous silica nanoparticles (MSNs) make it possible to integrate a variety of commonly used therapeutic and imaging agents to construct a multimodal synergistic anticancer drug delivery system. Herein, recent advances in MSNs synthesis for drug delivery and smart response applications are reviewed. First, synthetic strategies for the fabrication of ordered MSNs, hollow MSNs, core-shell structured MSNs, dendritic MSNs, and biodegradable MSNs are outlined. Then, the recent research progress in designing functional MSN materials with various controlled release mechanisms in anticancer therapy is discussed, and new properties are introduced to suggest the latest design requirements as drug delivery materials. The review also highlights significant achievements in bioimaging using MSNs and their multifunctional counterparts as delivery vehicles. Finally, personal views on key directions for future work in this area are presented.

Highly luminescent dual-phase CsPbBr3/Cs4PbBr6 microcrystals for a wide color gamut for backlight displays

Cesium lead bromide perovskite nanocrystals (NCs) embedded in Cs₄PbBr₆ or CsPb₂Br₅ matrices forming core/shell structures are promising luminescent materials that exhibit remarkable photoluminescence properties meeting the need in a wide range of applications while overcoming stability challenges. Here, we report the large-scale, ligand-free synthesis of dual-phase Cs₄PbBr₆/CsPbBr₃ microcrystals (MCs) using ultrasonication at room temperature, exhibiting a high photoluminescence quantum yield (PLQY) of 82.7% and good stability. High-resolution transmission electron microscopy and X-ray photoelectron characterization confirm that CsPbBr₃ NCs are embedded in the Cs₄PbBr₆ matrix-forming CsPbBr₃/Cs₄PbBr₆ dual-phase structure. The evolution of the luminescence properties with temperature suggests that the strong green emission results from direct exciton recombination in the isolated [PbBr₆]^4- octahedra, which possess a large exciton binding energy of 283.6 meV. As revealed from their emission intensities, the dual-phase CsPbBr₃/Cs₄PbBr₆ MCs demonstrate excellent stability against ultraviolet irradiation (76%), good moisture resistance (42.7%), and good thermal tolerance (51%). It is understood that such excellent PLQY and stability are due to the surface passivation of the CsPbBr₃ NCs attributed to the large bandgap as well as the isolated [PbBr₆]^4- octahedra separated by Cs⁺ ions in the Cs₄PbBr₆ crystal lattice. Finally, the suitability of the green-emitting CsPbBr₃/Cs₄PbBr₆ material for achieving white-light emission and a wide color gamut is evaluated by constructing a prototype white light-emitting diode (w-LED) using CsPbBr₃/Cs₄PbBr₆ and red-emitting K₂SiF₆:Mn⁴⁺ materials taken in different weight ratios and combined with a blue light-emitting InGaN LED chip (λ = 455 nm). The constructed w-LED device exhibits the color coordinates (0.3315, 0.3289), an efficacy of 68 lm W^-1, a color rendering index of 87%, a color temperature of 5564 K, and a wide color gamut of ∼118.78% (NTSC) and ∼88.69% (Rec. 2020) with RGB color filters in the CIE 1931 color space. Therefore, based on our present findings, we strongly believe that the dual-phase CsPbBr₃/Cs₄PbBr₆ material is a promising green-emitting phosphor for use in w-LEDs as the backlight of display systems.

Highly Emitting Perovskite Nanocrystals with 2-Year Stability in Water through an Automated Polymer Encapsulation for Bioimaging

Lead-based halide perovskite nanocrystals are highly luminescent materials, but their sensitivity to humid environments and their biotoxicity are still important challenges to solve. Here, we develop a stepwise approach to encapsulate representative CsPbBr₃ nanocrystals into water-soluble polymer capsules. We show that our protocol can be extended to nanocrystals coated with different ligands, enabling an outstanding high photoluminescence quantum yield of ∼60% that is preserved over two years in capsules dispersed in water. We demonstrate that this on-bench strategy can be implemented on an automated platform with slight modifications, granting access to a faster and more reproducible fabrication process. Also, we reveal that the capsules can be exploited as photoluminescent probes for cell imaging at a dose as low as 0.3 μg_Pb/mL that is well below the toxicity threshold for Pb and Cs ions. Our approach contributes to expanding significantly the fields of applications of these luminescent materials including biology and biomedicine.

Application of perovskites in bioimaging: the state-of-the-art and future developments

BACKGROUND

Recently, the development of perovskite-based nanocrystals for sustainable applications in bioimaging and clinical diagnostics have become a very active area of research. From 2D hybrid to zero-dimensional quantum dots (QDs), perovskites along with a variety of characteristic features, specifically non-linear optoelectronics properties, have attracted enormous research attention. These characteristics can be tuned by the type of cations or anions and their ratio used in host perovskites. Carrier doping and chemical modifications are additional alternatives to control optical and magnetism in radiodiagnostics.

AREA COVERED

This review begins by explaining the physical phenomena associated with luminescence or optical features of novel perovskites in diagnostic applications. Moreover, reported oxide, halide, doped, and QDs-based nanoprobes were elaborated. At last, the need for novel perovskite development, for example, persistent luminescent and low cytotoxicity is discussed, and the futuristic perspective of perovskites in clinical diagnostics with real-time demonstration is explained.

EXPERT OPINION

Our article concludes that hybrid perovskites, including metal-free, core-shell nanocomposites-based, and alloy-based perovskites, exhibit tunable bandgap and high photoluminescence quantum yields which ultimately result in high optical features. However, given limited understanding of ion transport mechanisms and dependency on environmental conditions of the perovskites, more research is needed.

Incorporation of Perovskite Nanocrystals into Polymer Matrix for Enhanced Stability in Biological Media: In Vitro and In Vivo Studies

The outstanding optical properties and multiphoton absorption of lead halide perovskites make them promising for use as fluorescence tags in bioimaging applications. However, their poor stability in aqueous media and biological fluids significantly limits their further use for in vitro and in vivo applications. In this work, we have developed a universal approach for the encapsulation of lead halide perovskite nanocrystals (PNCs) (CsPbBr₃ and CsPbI₃) as water-resistant fluorescent markers, which are suitable for fluorescence bioimaging. The obtained encapsulated PNCs demonstrate bright green emission at 510 nm (CsPbBr₃) and red emission at 688 nm (CsPbI₃) under one- and two-photon excitation, and they possess an enhanced stability in water and biological fluids (PBS, human serum) for a prolonged period of time (1 week). Further in vitro and in vivo experiments revealed enhanced stability of PNCs even after their introduction directly into the biological microenvironment (CT26 cells and DBA mice). The developed approach allows making a step toward stable, low-cost, and highly efficient bioimaging platforms that are spectrally tunable and have narrow emission.

Highly Luminescent, Stable, and Red-Emitting CsMgxPb1-xI3 Quantum Dots for Dual-Modal Imaging-Guided Photodynamic Therapy and Photocatalytic Activity

In this study, for the first time, red-emitting CsMg_xPb_1-xI₃ quantum dots (QDs) are prepared by doping with magnesium (Mg) ions via the one-pot microwave pyrolysis technique. The X-ray diffraction and X-ray photoelectron spectroscopy results have confirmed partial substitution of Pb²⁺ by Mg²⁺ inside the CsPbI₃ framework. The as-synthesized CsMg_xPb_1-xI₃ QDs have exhibited excellent morphology, higher quantum yield (upto ∼89%), better photostability and storage stability than undoped CsPbI₃. Next, the bioavailability of as-synthesized hydrophobic CsMg_xPb_1-xI₃ QDs is improved by encapsulating them into gadolinium-conjugated pluronic 127 (PF127-Gd) micelles through hydrophobic interactions (PQD@Gd). The optical properties of perovskite quantum dots (PQDs) and the presence of Gd could endow the PQD@Gd with fluorescence imaging, magnetic resonance imaging (MRI), and phototherapeutic properties. Accordingly, the MRI contrasting effects of PQD@Gd nanoagents are demonstrated by employing T₁ and T₂ studies, which validated that PQD@Gd nanoagents had superior MR contrasting effect with a r₂/r₁ ratio of 1.38. In vitro MRI and fluorescence imaging analyses have shown that the PQD@Gd nanoagents are internalized into the cancer cells via a caveolae-mediated endocytosis pathway. The PQD@Gd nanoagents have exhibited excellent biocompatibility even at concentrations as high as 450 ppm. Interestingly, the as-prepared PQD@Gd nanoagents have efficiently produced cytotoxic reactive oxygen species in the cancer cells under 671 nm laser illumination and thereby induced cell death. Moreover, the PQD@Gd nanoagent also demonstrated excellent photocatalytic activity toward organic pollutants under visible light irradiation. The organic pollutants rhodamine b, methyl orange, and methylene blue were degraded by 92.11, 89.21, and 76.21%, respectively, under 60, 80, and 100 min, respectively, irradiation time. The plausible mechanism for the photocatalytic activity is also elucidated. Overall, this work proposes a novel strategy to enhance the optical properties, stability, and bioapplicability of PQDs. The multifunctional PQD@Gd nanoagents developed in this study could be the potential choice of components not only for cancer therapy due to dual-modal imaging and photodynamic therapeutic properties but also for organic pollutant or bacterial removal due to excellent photocatalytic properties.

Encapsulation of lead halide perovskite nanocrystals (NCs) at the single-particle level: strategies and properties

Lead halide perovskite NCs (APbX₃, A = formamidinium (FA), methylammonium (MA) or Cs; X = Cl, Br, I or their mixture) have attracted unprecedented attention due to their excellent photophysical properties and wide application prospects. However, the inherent ionic structure of APbX₃ NCs makes them very sensitive to external conditions such as water and oxygen, resulting in poor stability. As a feasible strategy, encapsulation is considered to be effective in improving the stability. In this minireview, we focus on single-particle-level coating, which not only can improve the stability but also maintain the nano effect of the original NCs. This review summarizes the fundamental information on APbX₃ NCs and the necessity of single-particle-level coating. Subsequently, a variety of heterostructures at the single-particle level are introduced in detail. Then, their applications are summarized. Moreover, we discuss the challenges and prospects of the single-particle-level heterostructures based on APbX₃ NCs.

Biomimetic amphiphilic FAAP NPs nanoparticles: Synthesis, characterization and antivirus activity

Antiviral agents based on natural products have attracted substantial attention in clinical applications for their distinct biological activities,molecular structuralmultiformities, and low biotoxicities. Ferulic acid (FA) with apigenin propaneto form an esterified FA derivative (FAAP).Herein, we designed a CsPbBr3-modified chitosan oligosaccharide, a biomimetic nanoplatform that could load with FAAP. After self-assembly by combining FAAP with CsPbBr3-modified chitosan oligosaccharide (FAAP NPs), the resulting nanoparticles (FAAP NPs) showed high antioxidant and anti-inflammatory activities for enhancing the inhibition of porcineparvovirus.FAAP NPs exhibited no signs of acute toxicity in vitro or in vivo. DPPH and ABST are widely used for quantitative determination of antioxidant capacity. FAAP NPs exhibited excellent DPPH and ABTS radical scavenging abilities. In addition, we found that FAAP NPs inhibited PPV infection-induced PK-15 cell apoptosis, which was associated with regulating antioxidant and anti-inflammatory signaling pathways. Importantly, we showed that FAAP NPs blocked PPV infection-induced mitochondrial apoptosis in PK-15 cells via a p53/BH3 domain molecular-dependent mechanism.

Targeted delivery of paclitaxel by NL2 peptide-functionalized on core-shell LaVO4: Eu3@ poly (levodopa) luminescent nanoparticles

Targeted drug delivery enhances drug efficiency and selectivity without affecting normal cells. Luminescent nanoparticles can be used for tumor imaging as well as selective tumor targeting for drug delivery. In this research, LaVO4 :Eu3+ was synthesized, the luminescent nanocrystal was coated by surface polymerization of levodopa in the presence of Paclitaxel (PTX), and then NL2 peptide was coupled on the surface of polymer-coated luminescent nanoparticles. Next, the capability of the modified drug was examined by in vitro and in vivo experiments. MTT assay on SK-BR-3 cell line (as breast cancer cells) and fluorescent microscopy results indicate that this modification decreases significantly drug toxicity and increases its selectivity. In addition, in vivo experiments confirm more capability of the NL2-functionalized nanocomposite for reducing tumor size, drug distribution in the body, and more aggregation of PTX in tumor tissue. Overall, it is concluded that tumor imaging is possible using luminescent LaVO4 :Eu3+ core and NL2 peptide increases significantly the specificity of PTX in combination with a functionalized luminescent polymeric carrier.

Substrate-independent three-dimensional polymer nanosheets induced by solution casting

Nanosheets are important structures usually composed of inorganic materials, such as metals, metal oxides, and carbon. Their creation typically involves hydrothermal, electrochemical or microwave processes. In this study, we report a novel formation mechanism of 3D polymer nanosheets via facile solution casting using a comb copolymer consisting of poly(ethylene glycol) behenyl ether methacrylate and poly(oxyethylene) methacrylate (PEGBEM–POEM). Controlling the composition of comb copolymer yielded nanosheets with different packing density and surface coverage. Interestingly, the structure exhibits substrate independence as confirmed by glass, inorganic wafer, organic filter paper, and porous membrane. The formation of 3D nanosheets was investigated in detail using coarse-grained molecular dynamics simulations. The obtained polymer nanosheets were further utilized as templates for inorganic nanosheets, which exhibit high conductivity owing to interconnectivity, and hence have promising electronic and electrochemical applications.

Unprecedented substrate-independent polymeric 3D nanosheets were induced via simple solution casting using PEGBEM–POEM comb copolymer. A possible mechanism is the change in the polymer–solvent interactions on the surface.

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.

Synthesis of Chemically Stable Ultrathin SiO2-Coated Core-Shell Perovskite QDs via Modulation of Ligand Binding Energy for All-Solution-Processed Light-Emitting Diodes

Recently, perovskite quantum dots (QDs) have attracted intensive interest due to their outstanding optical properties, but their extremely poor chemical stability hinders the development of the high-performance perovskite QD-based light-emitting diodes (PeLEDs). In this study, chemically stable SiO₂-coated core-shell perovskite QDs are prepared to fabricate all-solution-processed PeLEDs. When the SiO₂ shell thickness increases, the chemical stability of perovskite QDs is dramatically improved, while the charge injection efficiency is significantly decreased, which becomes the biggest obstacle for PeLED applications. Thus, controlling the SiO₂ thickness is essential to obtain core-shell perovskite QDs optimal for PeLEDs in an aspect of chemical and optoelectrical properties. The 3-aminopropyl-triethoxysilane (APTES)/oleylamine (OAm) volume ratio is found to be a critical factor for obtaining an ultrathin SiO₂ shell. Optimization of the APTES/OAm ratio affords A-site-doped CsPbBr₃ QDs with an ultrathin SiO₂ shell (A-CsPbBr₃@SiO₂ QDs) that exhibit longer radiative lifetimes and smaller shallow trap fraction than those without A-site doping, resulting in a higher photoluminescence quantum yield. A-CsPbBr₃@SiO₂ QDs also demonstrate long-term superior chemical stability in polar solvents without loss of optical properties due to passivation by the SiO₂ shell and less defects via A-site doping. Consequently, all-solution-processed PeLED is successfully fabricated under ambient conditions, facilitating perovskite QD utilization in low-cost, large-area, flexible next-generation displays.