Confinement of AuAg NCs in a Pomegranate-Type Silica Architecture for Improved Copper Ion Sensing and Imaging

A label-free and naked-eye fluorescence turn-on assay for one-pot LAMP detection of foodborne pathogens using AuNCs-Cu2+ complex

Loop-mediated isothermal amplification (LAMP) is a rapid and sensitive approach for foodborne pathogen detection; however, a simple, user-friendly, and naked-eye readable readout method remains a challenge. Herein, we synthesized bovine serum albumin stabilized gold nanoclusters (BSA-AuNCs), which exhibit fluorescence quenching upon copper ions (Cu2+) binding and fluorescence recovery in the presence of phosphate ions (PPi). Leveraging this property, we developed a label-free fluorescence turn-on assay for naked-eye LAMP detection by monitoring PPi accumulation under UV light. To mitigate potential cross-contamination risks inherent in LAMP workflows, we integrated the BSA-AuNCs-Cu2+ complex into the reaction lid, enabling a closed, one-pot detection system. This method demonstrated high sensitivity, detecting Salmonella enterica at concentrations as low as 101 CFU/mL within 40 min (excluding nucleic acid extraction process). With its customizable primers and naked-eye visual detection capability, this assay offers a versatile and practical tool for rapid pathogen screening in diverse applications.

Ratiometric fluorescent probe for continuous detection of copper ions and lipoic acid in spinach using gold-silver bimetallic nanoclusters grown in situ on Zn MOF

Accurate monitoring of copper ions (Cu2+) and lipoic acid (LA), essential trace elements and antioxidants in vegetables, is critical for food safety and human health. Here, we developed mercaptopurine-stabilized gold-silver bimetallic nanoclusters (MP-AuAg NCs) as a fluorescence 'turn-off' probe for Cu2+ detection, achieving a linear response of 0.05-20 μM with a detection limit of 23 nM (LOD). To enhance sensitivity, a ratiometric probe (Zn MOF@MP-AuAg NCs) was engineered by in situ growth of zinc metal organic frameworks (Zn MOF) in the nanoclusters, which reduced Cu2+ LOD to 4 nM (linear range: 0.015-0.50 μM). Interestingly, the Cu2+ quenched system functioned as a 'turn on' sensor for LA detection, offering a dual range response: exponential correlation from 0.3 to 80 μM (R2 = 0.997) and linear quantification from 0.3 to 25 μM (LOD = 94 nM, R2 = 0.998). Validated in spinach samples, the method demonstrated exceptional precision (recoveries: 96.5-102 %) and precision (RSD <3.12 %), confirming its reliability for sequential Cu2+-LA analysis in complex food matrices. This work establishes a versatile sensing platform with enhanced sensitivity and practical utility for food quality monitoring.

Surface-Defect-Involved Chemiluminescence Boosted by Gold-Silver Bimetallic Nanoclusters for Bioanalysis

Chemiluminescence (CL) as a powerful analytical tool has garnered increasing interest. However, traditional molecular-based CL luminophores suffer from low emission efficiency due to limited total CL photons emitted per luminophore, driving efforts to explore amplified strategies or novel probes to boost the emission. Although metal nanoclusters (NCs) as luminescent nanoprobes have been extensively studied for electrochemiluminescence and photoluminescence (PL) owing to their intriguing luminescent properties, the CL performance using metal NCs as emitters is often ignored. Herein, based on the synergistic effect within the bimetallic NCs, a series of glutathione-coated Au-Ag bimetallic NCs (GSH-AuAg NCs) were optimized by adjusting precursor ratios and achieved the maximum CL response at a Au:Ag molar ratio of 5:1. To our surprise, CL emission with GSH-AuAg NCs as emitters was triggered with oxidant reagents such as KMnO4, and bimetallic NCs display boosted CL emission (ca. 6.2-fold) compared to monometallic NCs owing to the synergistic effect on enhancing the emission efficiency. Surface-defect-involved CL was revealed by collecting the CL spectra with a maximum emission wavelength of around 750 nm and an obvious red shift of 140 nm compared to PL spectra. The mechanism reveals the KMnO4-injected hole into the valence band through redox reactions with GSH ligands, leading to CL emission by efficient radiative charge recombination with pre-existing electron. A sensing platform based on the GSH-AuAg NCs/oxidant system was constructed for sensing H2O2 and glucose, demonstrating the potential of GSH-AuAg NCs as CL emitters in analytical applications.

Green Emissive Molybdenum Nanoclusters for Selective and Sensitive Detection of Hydroxyl Radical in Water Samples

In this work, Cassia tora (C. tora) have been used as a template to synthesize green fluorescent C. tora molybdenum nanoclusters (C. tora-MoNCs) through a green chemistry approach. These C. tora-MoNCs showed a quantum yield (QY) of 7.72% and exhibited a significant emission peak at 498 nm when excited at 380 nm. The as-prepared C. tora-MoNCs had an average size of 3.48 ± 0.80 nm and showed different surface functionality. The as-synthesized C. tora-MoNCs were successfully identified the hydroxyl radical (•OH) via a fluorescence quenching mechanism. Also, fluorescence lifetime and Stern-Volmer proved that after the addition of •OH radicals it was quenched the fluorescence intensity via a static quenching mechanism. The limit of detection is 9.13 nM, and this approach was successfully utilized for sensing •OH radicals in water samples with a good recovery rate.

Cyanuric chloride-modified dendritic SiO2 nanoparticle for switch-on fluorescence monitoring and dispersive solid-phase extraction of isoquinoline alkaloids

The determination of isoquinoline alkaloids (IQAs) is crucial for maximizing the pharmacological benefits of Rhizoma coptidis (RC). In this study, the dendritic silica sphere (dSiO2) was covalently modified with cyanuric chloride (CNCl) to synthesize a porous dNSiO2-CNCl NP. The fluorescence of berberine (Ber), palmatine (Pal), coptisine (Cop), and jatrorrhizine (Jat) was remarkably enhanced by dNSiO2-CNCl NP for at least 38-fold, inspiring the accurate determination of the isoquinoline total alkaloids (IQTAs) in RC using fluorometry. The method exhibited good linearity within the concentration range of 0.005 to 1 μM, with a limit of detection (LOD) and quantitation (LOQ) of 0.001 and 0.004 μM. Specially, Jat was discovered to form a stable covalent linkage with dNSiO2-CNCl, showing an innovative and enduring fluorescent nanoparticle derived from a natural product. Furthermore, using dNSiO2-CNCl as a substrate for fluorescence enhancement and a dispersive solid-phase extraction (d-SPE) sorbent, a fluorescence-mediated HPLV-UV method was developed to monitor Ber, Pal, and Cop in serum. Rapid qualitative analysis using fluorescence was initially performed. In chromatography analysis, the linear range for Cop was 0.20 to 10 μM, with LOD and LOQ at 0.035 and 0.110 μM, while Pal and Ber showed good linearity in the range of 0.05 to 10 μM, with LODs and LOQs at 0.013 and 0.040 μM. The spiked recovery rates ranged from 90.4 % to 99.8 % for the three IQAs, with intra-day precision below 7.9 % and inter-day precision below 9.9 %. The dual-functional dNSiO2-CNCl NP exhibited promising prospect in fluorescence sensing and separation applications for detecting drugs.

Accurately Tunable AuNC-ZIF Content Architecture Based on Coordination-Dissociation Mechanism Enables Highly Brightness Dual-Site Fluorescent Biosensor

The quantum yield and fluorescence intensity of gold nanocluster (AuNC) nanocarriers are critical parameters for developing ultrasensitive biosensors. In this study, AuNCs-zeolitic-imidazolate-framework (Au-ZIF) nanocomposites are systematically constructed by impregnating AuNCs onto the ZIF-8 surface through a coordination-dissociation mechanism, resulting in a dual-site fluorescence-loaded structure. In this configuration, AuNCs are anchored to the external surface while the integrity of the inner cavity remains intact. The surface of ZIF-8 induces a confinement effect on the configuration and electrons of AuNCs, significantly enhancing luminescence (18-fold increase). The quantum yield of AuNCs exhibits an increase of more than 13-fold, from 2.80% to 38.1%. This approach demonstrates broad applicability and maintains strong fluorescence across different ZIFs. Additionally, a novel nanocomposite, Au-ZIF@carbon-dots (CDs), is synthesized by encapsulating CDs into the inner cavity of Au-ZIF. A ratiometric fluorescence detection platform is subsequently developed and incorporated into hydrogels for the quantitative detection of the pesticide triazophos. By employing an image-processing algorithm, quantitative detection is achieved with a detection limit of 0.07 ng mL⁻1. The findings provide crucial insights into the relationship between the assembly and performance of AuNCs and ZIFs, offering guidance for designing ultrasensitive multifunctional biosensors applicable in the field of biosensing.

A highly sensitive dual-mode detection platform based on the novel copper/molybdenum bimetallic nanoclusters and Co-Fe layered doubled hydroxide nanozyme for butyrylcholinesterase activity sensing

Herein, a novel copper/molybdenum bimetallic nanoclusters (Cu/Mo NCs) with intense blue emission were synthesized by using polyvinylpyrrolidone (PVP) as template and ascorbic acid as reducing agent. Owing to the synergistic effect between Cu and Mo, the fluorescence intensity of Cu/Mo NCs was significantly improved about 6-time than monometallic copper nanoclusters. A novel and sensitive ratiometric fluorescence and colorimetric dual-mode sensing platform for monitoring butyrylcholinesterase (BChE) was strategically constructed by the integration of Cu/Mo NCs with excellent optical properties and Co-Fe layered doubled hydroxide (CoFe-LDH) with superior peroxidase-like activity for the first time. In the presence of H2O2, nonfluorescent and colorless o-phenylenediamine (OPD) was oxidized to fluorescent and yellow 2,3-diaminophenazine (DAP) with maximum fluorescence emission peak at 564 nm and ultraviolet absorption peak at 418 nm by CoFe-LDH with peroxidase-like activity. Simultaneously, the generation of DAP could effectively quench Cu/Mo NCs fluorescence at 444 nm through the inner-filter effect (IFE). The hydrolysis of S-butyrylthiocholine iodide (BTCh) can be catalyzed by butyrylcholinesterase (BChE) to generate thiocholine (TCh) that could hinder the oxidation of OPD, leading to the fluorescence and ultraviolet absorption of DAP decreased, meanwhile, the fluorescence of Cu/Mo NCs recovered. The ratiometric fluorescence signal F564/F444 and colorimetric system both performed a satisfactory response to the concentration of BChE in the range 0.5 to 90 U L-1 and 1 to 100 U L-1 with the LOD of 0.18 U L-1 and 0.36 U L-1, respectively. The dual-mode sensing for BChE exhibited outstanding application potential in biosensing.

Integrating L-Cys-AuNCs in ZIF-8 with Enhanced Fluorescence and Strengthened Stability for Sensitive Detection of Copper Ions

Gold nanoclusters (AuNCs) have been widely investigated because of their unique photoluminescence properties. However, the applications of AuNCs are limited by their poor stability and relatively low fluorescence. In the present work, we developed nanocomposites (L-Cys-AuNCs@ZIF-8) with high fluorescence and stability, which were constructed by encapsulating the water-dispersible L-Cys-AuNCs into a ZIF-8 via Zn2+-triggered growth strategy without high temperature and pressure. The maximum emission wavelength of the L-Cys-AuNCs@ZIF-8 composite was at 868 nm, and the fluorescence intensity of L-Cys-AuNCs@ZIF-8 was nearly nine-fold compared with L-Cys-AuNCs without the ZIF-8 package. The mechanism investigation by fluorescence spectroscopy and X-ray photoelectron spectroscopy showed that L-Cys-AuNCs@ZIF-8 impeded ligand rotation, induced energy dissipation, and diminished the self-quenching effect, attributing to the spatial distribution of L-Cys-AuNCs. Based on the high fluorescence efficiency of L-Cys-AuNCs@ZIF-8, a "signal off" detective platform was proposed with copper ions as a model analyte, achieving a sensitive detection limit of Cu2+ at 16.7 nM. The quenching mechanism was confirmed, showing that the structure of the L-Cys-AuNCs@ZIF-8 nanocomposites was collapsed by the addition of Cu2+. Attributing to the strong adsorption ability between copper ions and pyridyl nitrogen, the as-prepared L-Cys-AuNCs@ZIF-8 was shown to accumulate Cu2+, and the Zn2+ in ZIF-8 was replaced by Cu2+.

A ratiometric fluorescence nanosensor for glutathione detection based on spatially confined dual-emission of α-lipoic acid-modified gold nanoclusters and silicon nanoparticles

The development of dual-emission ratiometric fluorescent probes with aggregation-induced emission enhancement (AIEE) overcomes the limitations of gold nanocluster (Au NC)-based probes, particularly their weak intrinsic fluorescence, in real-world applications. These AIEE probes also exhibit superior detection limits and enhanced sensitivity. A novel combination for the reliable fluorometric detection of glutathione (GSH) was proposed, utilizing aggregation-induced emission enhancement (AIEE) facilitated by electrostatic interaction and spatial confinement. The probe consists of a ratiometric combination of negatively charged α-lipoic acid-modified Au NCs (LA@Au NCs) and positively charged silicon nanoparticles (SiNPs). The addition of SiNPs causes aggregation of LA@Au NCs, enhancing the fluorescence of LA@Au NCs through the AIE effect under electrostatic interaction and spatial confinement. The addition of Cu2+ quenched the emission of LA@Au NCs as a result of charge transfer. The fluorescence emissions of LA@Au NCs were restored upon the addition of GSH due to the interaction between GSH and Cu2+. Simultaneously, the emission signal of SiNPs remains unchanged, serving as an internal reference signal during GSH measurement. It was found that the fluorescence ratio (F680/F465) is directly proportional to the concentration of GSH in the range of 0.05-100 μM, with a detection limit of 1.7 nM (S/N = 3). The proposed system was applied to detect GSH in real samples, including dietary supplements, human serum, and saliva samples. This work opens new avenues for constructing novel sensors based on AIEE for detecting biomolecules.

Enhanced fluorometric detection of histamine using red emissive amino acid-functionalized bimetallic nanoclusters

Lysine-capped gold nanoclusters doped with silver (LYS@Ag/Au NCs) have been developed for the sensitive and selective "turn-off" fluorescence detection of histamine. This fluorescent probe demonstrates excellent stability and a high quantum yield of 9.45%. Upon addition of histamine, a positively charged biogenic amine, to the LYS@Ag/Au NCs fluorescent probe, its fluorescence emission is quenched due to electrostatic interaction, aggregation, and hydrogen bond formation. The probe exhibits good sensitivity for the determination of histamine within the range of 0.003-350 μM, with a detection limit of 0.001 μM based on a signal-to-noise ratio of 3. Furthermore, the probe has been applied to detect biogenic amines in complicated matrices, highlighting its potential for practical applications. However, interference from the analogue histidine was observed during analysis, which can be mitigated by using a Supelclean™ LC-SAX solid-phase extraction column for removal.

A novel competitive fluorescence colorimetric dual-mode immunosensor for detecting ochratoxin A based on the synergistically enhanced peroxidase-like activity of AuAg NCs-SPCN nanocomposite

The sensitive and rapid detection of Ochratoxin A in foods is particularly urgent for ensuring human security due to its larger toxicity to the body. Herein, a novel competitive fluorescence colorimetric dual-mode immunosensor for detecting Ochratoxin A based on AuAg NCs-SPCN nanocomposite was designed and constructed. The synergistic effect of SPCN and AuAg NCs dramatically improved the nanozyme activity. The fluorescence intensity was enhanced due to the aggregation luminescence effect, and a new emission peak appeared at 440 nm to form a fluorescence signal. For colorimetric, H2O2 was effectively decomposed by AuAg NCs-SPCN to form ·OH groups and oxidize 3,3',5,5'-tetramethylbenzidine to blue oxTMB. The dual-mode immunosensor showed a good linear relationship from 0.001 μg/L to 10 μg/L and the detection limits were 0.155 ng/L (fluorescence) and 0.213 ng/L (colorimetric). So, this dual-mode immunosensor would have a potential applicative prospect for sensitive detecting Ochratoxin A and other small molecules.

Complementary imaging of nanoclusters interacting with mitochondria via stimulated emission depletion and scanning transmission electron microscopy

The emerging stress caused by nanomaterials in the environment is of great concern because they can have toxic effects on organisms. However, thorough study of the interactions between cells and diverse nanoparticles (NPs) using a unified approach is challenging. Here, we present a novel approach combining stimulated emission depletion (STED) microscopy and scanning transmission electron microscopy (STEM) for quantitative assessment, real-time tracking, and in situ imaging of the intracellular behavior of gold-silver nanoclusters (AuAgNCs), based on their fluorescence and electron properties. The results revealed an aggregated state of AuAgNCs within the mitochondria and an increase in sulfur content in AuAgNCs, presumably owing to their reaction with thiol-containing molecules inside the mitochondria. Moreover, AuAgNCs (100 μg/mL) induced a 75% decline in mitochondrial membrane potential and a 12-fold increase of mitochondrial reactive oxygen species in comparison to control. This mitochondrial damage may be triggered by the reaction of AuAgNCs with thiol, which provides direct imaging evidence for uncovering the action mechanism of AuAgNCs on the mitochondria. The proposed dual-imaging strategy using STED and STEM is a potential tool to offer valuable insights into cytotoxicity between subcellular structures and diverse NPs, and can serve as a key strategy for nanomaterial biosafety assessment.

Fluorogen-Functionalized Mesoporous Silica Hybrid Sensing Materials: Applications in Cu2+ Detection

Since Cu2+ ions play a pivotal role in both ecosystems and human health, the development of a rapid and sensitive method for Cu2+ detection holds significant importance. Fluorescent mesoporous silica materials (FMSMs) have garnered considerable attention in the realm of chemical sensing, biosensing, and bioimaging due to their distinctive structure and easily functionalized surfaces. As a result, numerous Cu2+ sensors based on FMSMs have been devised and extensively applied in environmental and biological Cu2+ detection over the past few decades. This review centers on the recent advancements in the methodologies for preparing FMSMs, the mechanisms underlying sensing, and the applications of FMSMs-based sensors for Cu2+ detection. Lastly, we present and elucidate pertinent perspectives concerning FMSMs-based Cu2+ sensors.

Engineering GaN/AuNC core-shell nanowire heterojunctions by gold nanoclusters with excitation-dependent behavior for enhancing the responsivity and stability of self-driven photodetectors

Self-driven broadband photodetectors (PDs) with low-power consumption have great potential applications in the wide range of next-generation optoelectronic devices. In this study, a self-driven broadband PD responding to an ultraviolet-visible range based on gallium nitride/gold nanocluster (GaN/AuNC) core-shell nanowire heterojunctions is fabricated for the first time. By introducing the AuNCs onto the GaN nanowire surfaces, the GaN/AuNC core-shell nanowire heterojunctions can be formed efficiently. It is crucial that AuNCs have the functions of light collectors and hole conductors in heterojunctions due to the suitable energy level alignment. Under the optimized conditions of AuNCs, it is found that GaN/AuNC core-shell nanowires can significantly increase the photocurrent and responsivity of PDs, mainly resulting from the light interreflection within the heterojunctions and the effective improvement of carrier transport. Owing to the excitation-dependent emission behavior of AuNCs, the responsivity of PD with GaN/AuNC core-shell nanowire heterojunctions can be enhanced by around 330% compared with that of PD without AuNCs under visible illumination. Furthermore, GaN/AuNC hybrid nanowires with excitation-dependent fluorescence behavior can modulate the enhanced amplitude performance of broadband PDs. Owing to the high stability of AuNCs, the photocurrent of the PD with AuNCs is still quite stable after continuous operation for more than 20 000 s. Therefore, this study provides an effective method for developing new broadband PDs with high performance and low energy consumption.

Remodeling tumor immunosuppression with molecularly imprinted nanoparticles to enhance immunogenic cell death for cancer immunotherapy

Insufficient tumor accumulation and distribution of immunogenic cell death (ICD) inducer as well as low antitumor immunity severely restrict the therapeutic efficacy of tumor immunotherapy. Tumor associated fibroblasts (TAFs) are important in tumor extracellular matrix (ECM) remodeling and immune evasion. Reprogramming tumor immunosuppressive microenvironment via TAFs regulation might present a promising way for enhanced ICD effect and complete tumor elimination. In this study, TAFs derived tryptase imprinted nanoparticles (DMSN@MIPs) are developed to modulate TAFs and improve tumor immunotherapy effect of doxorubicin liposomes (DOX/LIP). Tryptase (TPS), secreted by mast cells, are found to support tumor growth via transcriptionally activating TAFs to an activated state with increased expression of fibroblast activation marker α-smooth muscle actin (α-SMA). DMSN@MIPs canbe used as artificial antibodies, which effectively neutralize TPS, reduce TAFs activation, promote intra-tumor penetration of DOX/LIP and enhance ICD effect induced by DOX/LIP. In addition, the combined administration system remodels immunosuppressive microenvironment, which not only significantly up-regulates immune cells (DC cells, CD8+T cells, NK cells), but also significantly down-regulates immunosuppressive cells (Treg cells, MDSCs cells). Our results support the DMSN@MIPs canbe a promising approach to improve ICD efficacy in cancer immunotherapy.

Chiroptical Nanocellulose Bio-Labels for Independent Multi-Channel Optical Encryption

Advanced multiplexing optical labels with multiple information channels provide a powerful strategy for large-capacity and high-security information encryption. However, current optical labels face challenges of difficulty to realize independent multi-channel encryption, cumbersome design, and environmental pollution. Herein, multiplexing chiroptical bio-labels integrating with multiple optical elements, including structural color, photoluminescence (PL), circular polarized light activity, humidity-responsible color, and micro/nano physical patterns, are constructed in complex design based on host-guest self-assembly of cellulose nanocrystals and bio-gold nanoclusters. The thin nanocellulose labels exhibit tunable circular polarized structural color crossover the entire visible wavelength and circularly polarized PL with the highest-recorded dissymmetry factor up to 1.05 due to the well-ordered chiral organization of templated gold nanoclusters. Most importantly, these elements can independently encode customized anti-counterfeiting information to achieve five independent channels of high-level anti-counterfeiting, which are rarely achieved in traditional materials and design counterparts. Considering the exceptional seamless integration of five independent encryption channels and the recyclable features of labels, the bio-labels have great potential for the next generation anti-counterfeiting materials technology.

Passion fruit-inspired dendritic mesoporous silica nanospheres-enriched quantum dots coupled with magnetism-controllable aptasensor enable sensitive detection of ochratoxin A in food products

Ochratoxin A (OTA) is a powerful mycotoxin present in a variety of food products, and its detection is important for human health. Here, a fluorescent aptasensor is reported for sensitive OTA determination. Specifically, the surface of bio-inspired passion fruit-like dendritic mesoporous silica nanospheres-enriched quantum dots (MSNQs-apt) was first modified with the OTA aptamer as the recognition unit and fluorescence emitter, while the aptamer-complementary DNA (MNPs-cDNA) was linked with the magnetic nanoparticles (MNPs) as the separation element. In the range of 2.56 pg/mL to 8 ng/mL, the proposed aptasensor exhibited satisfactory linearity and a detection limit of 1.402 pg/mL. The developed aptasensor achieved recoveries of 90.98-103.20% and 94.33-107.57 % in red wine and wheat flour samples, respectively. By simply replacing the aptamer, this aptasensor can be easily extended to detection of other analytes, suggesting its potential as a universal detection platform for mycotoxins in food products.

Encapsulating gold nanoclusters into metal-organic frameworks to boost luminescence for sensitive detection of copper ions and organophosphorus pesticides

Gold nanoclusters (Au NCs) with luminescence property are emerging as promising candidates in fluorescent methods for monitoring contaminants, but low luminescence efficiency hampers their extensive applications. Herein, GSH-Au NCs@ZIF-8 was designed by encapsulating GSH-Au NCs with AIE effect into metal-organic frameworks, achieving high luminescence efficiency and good stability through the confinement effect of ZIF-8. Accordingly, a fluorescent sensing platform was constructed for the sensitive detection of copper ions (Cu²⁺) and organophosphorus pesticides (OPs). Firstly, the as-prepared GSH-Au NCs@ZIF-8 could strongly accumulate Cu²⁺ due to the adsorption property of MOFs, accompanied by a significant fluorescence quenching effect with a low detection limit of 0.016 μM for Cu²⁺. Besides, thiocholine (Tch), the hydrolysis product of acetylthiocholine (ATch) by acetylcholinesterase (AchE), could coordinate with Cu²⁺ by sulfhydryl groups (-SH), leading to a significant fluorescence recovery, which was further used for the quantification of OPs owing to its inhibition to AChE activity. Furthermore, a hydrogel sensor was explored to accomplish equipment-free, visual, and quantitative monitoring of Cu²⁺ and OPs by a smartphone sensing platform. Overall, this work provides an effective and universal strategy for enhancing the luminescence efficiency and stability of Au NCs, which would greatly promote their applications in contaminants monitoring.

Recyclable Luminescent Sensor for Detecting Creatinine Based on a Lanthanide-Organic Framework

Creatinine is an important clinical marker for human health, but detecting it by a luminescent sensor based on metal-organic frameworks is rarely investigated. In this work, we synthesized a new lanthanide-organic framework {[Tb(L)(CH₃COO)(H₂O)]·0.5DMF}_n (1) (H₂L = 3,5-bis(4'-carboxy-phenyl)1,2,4-triazole) with good solvent and acid/alkaline stabilities. Experimental results indicate that 1 can be used in the detection of creatinine in an aqueous solution with a wide linear detection range from 3.27 to 371 μM, and the detection limit can reach 1.7 × 10^-6 M based on the 3σ method, which is less than the pathogenic concentration in a real environment. In addition, this luminescent sensor can also monitor the concentration changes of creatinine in diluted serum solutions and can be recycled at least five times, suggesting that it has a potential application for clinical monitoring.

Dual-Mode Immunosensor for Electrochemiluminescence Resonance Energy Transfer and Electrochemical Detection of Rabies Virus Glycoprotein Based on Ru(bpy)32+-Loaded Dendritic Mesoporous Silica Nanoparticles

Rabies is a serious zoonotic disease in almost all warm-blooded animals and causes fatal encephalitis. The detection of rabies virus (RABV) is critical and remains a significant challenge. Herein, an electrochemiluminescence resonance energy transfer (ECL-RET) and electrochemical (EC) dual-mode immunosensor was developed for highly sensitive detection of RABV glycoprotein. Dendritic mesoporous silica nanoparticles (DMSNs) were employed to load Ru(bpy)₃²⁺ and to obtain ECL probes (Ru@DMSNs). Ru@DMSNs were decorated on the electrode surface, followed by the modification of the RABV antibody (Ab₁). RABV was specifically recognized and captured by Ab₁, causing the decline of the ECL signal due to the obstruction of electron transfer. Additionally, manganese oxide nanoparticles (MnO_x) modified with Ab₂ can further quench the ECL signal of Ru@DMSNs via the RET between Ru@DMSNs and MnO_x. Meanwhile, MnO_x can catalyze the oxidation of o-phenylenediamine (o-PD), generating a significant differential pulse voltammetry (DPV) signal as a second signal to monitor RABV glycoprotein concentration. Consequently, an immunosensor was developed to achieve dual-signal detection of RABV and improve reliability. Under the optimal conditions, detection ranges of 0.10 pg·mL^-1 to 10 ng·mL^-1 for ECL (with an 88 fg·mL^-1 detection limit) and 1 pg·mL^-1 to 2 ng·mL^-1 for EC (with a 0.1 pg·mL^-1 detection limit) were obtained for RABV detection. The reliability of this immunoassay was validated by eight brain tissue samples. The results were found to be compatible with the results of the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, indicating the potential applicability of this method for RABV diagnosis.

Synthesis of Copper Nanocluster and Its Application in Pollutant Analysis

Copper nanoclusters (Cu NCs) with their inherent optical and chemical advantages have gained increasing attention as a kind of novel material that possesses great potential, primarily in the use of contaminants sensing and bio-imaging. With a focus on environmental safety, this article comprehensively reviews the recent advances of Cu NCs in the application of various contaminants, including pesticide residues, heavy metal ions, sulfide ions and nitroaromatics. The common preparation methods and sensing mechanisms are summarized. The typical high-quality sensing probes based on Cu NCs towards various target contaminants are presented; additionally, the challenges and future perspectives in the development and application of Cu NCs in monitoring and analyzing environmental pollutants are discussed.

Copper nanocluster composites for analytical (bio)-sensing and imaging: a review

As an ideal substitute for traditional organic fluorescent dyes or up-conversion nanomaterials, copper nanoclusters (CuNCs) have developed rapidly and have been involved in exciting achievements in versatile applications. The emergence of novel CuNCs composites improves the poor stability and fluorescence intensity of CuNCs. With this in mind, great efforts have been made to develop a wide variety of CuNCs composites, and impressive progress has been made in the past few years. In this review, we systematically summarize absorption, fluorescence, electrochemiluminescence, and catalytic properties and focus on the multiple factors that affect the fluorescence properties of CuNCs. The fluorescence properties of CuNCs are discussed from the point of view of core size, surface ligands, self-assembly, metal defects, pH, solvent, ions, metal doping, and confinement effect. Especially, we illustrate the research progress and representative applications of CuNCs composites in bio-related fields, which have received considerable interests in the past years. Additionally, the sensing mechanism of CuNCs composites is highlighted. Finally, we summarize current challenges and look forward to the future development of CuNCs composites. Schematic diagram of the categories, possible sensing mechanisms, and bio-related applications of copper nanoclusters composites.

Titanium dioxide-functionalized dendritic mesoporous silica nanoparticles for highly selective isolation of phosphoproteins

Selective isolation of phosphoproteins is of great significance in biological applications. Herein, titanium dioxide-functionalized dendritic mesoporous silica nanoparticles are prepared via a post-grafting method for selective capture of phosphoproteins. The fabricated nanoparticles possess a unique central-radial pore structure with a surface area of 666.66 m² /g and a pore size of 22.2 nm. The high-binding affinity of TiO₂ with the phosphate groups facilitates the selective adsorption of phosphoproteins. Moreover, the open central-radial pore structure endows the dendritic mesoporous nanoparticles with better adsorption performance toward phosphoproteins with respect to the commercial titanium dioxide nanoparticles and titanium dioxide-functionalized conventional mesoporous silica nanoparticles by providing more accessible affinity sites. At pH 2, an adsorption capacity of 157.2 mg/g is derived for β-casein. The feasibility of the as-prepared dendritic material in real biological sample assay is demonstrated by the selective isolation of phosphoproteins from defatted milk, as illustrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis assay.

Fluorescent carbon dots embedded in mesoporous silica nanospheres: A simple platform for Cr(VI) detection in environmental water

In this work, amino-functionalized mesoporous silica nanospheres (NH₂-mSiO₂) anchored with carbon dots (CDs) have been designed to construct an outstanding fluorescent sensor for heavy metal detection. Uniform mSiO₂ was chosen to provide an optically transparent scaffold for immobilizing CDs. With the help of amino group modification on the surface of silica, benzene-1,4-diboronic acid (BA) was used as raw material to load CDs in the pores of mSiO₂ by one-step solvothermal method. The proposed nanohybrid can solve the problem of aggregation-induced fluorescence quenching, leading to bright blue emission at 450 nm. Meanwhile, the fluorescence of NH₂-mSiO₂@CDs showed high sensitivity to Cr(VI) in acetic acid buffer solution (pH = 4) with detection limit as low as 5 nM by inner filter effect (IFE) and electrostatic interaction (EI). The proposed method can also be extended to other CDs-based detection systems for chemical/biological sensors.

Surface functionalized red fluorescent dual-metallic Au/Ag nanoclusters for endoplasmic reticulum imaging

An efficient method is reported to prepare endoplasmic reticulum-targetable dual-metallic gold-silver nanoclusters, denoted as ER-Au/Ag nanoclusters (NCs), by virtue of a rationally designed molecular ligand. The prepared ER-Au/Ag NCs possesses red-emitting fluorescence with a strong emission at 622 nm and a high fluorescence quantum yield of 5.1%, which could avoid the influence of biological auto-fluorescence. Further investigation results showed that ER-Au/Ag NCs exhibited superior photostability, minimal cytotoxicity, and ER-targeting capability. Enabled by these meritorious features, ER-Au/Ag NCs have been successfully employed for long-term bioimaging of ER in living cells.Graphical abstract A sensitive non-enzymatic fluorescent glucose probe-based ZnO nanorod decorated with Au nanoparticles.

A coumarin-containing Schiff base fluorescent probe with AIE effect for the copper(ii) ion

A novel coumarin-derived Cu²⁺-selective Schiff base fluorescent “turn-off” chemosensor CTPE was successfully obtained, which showed an AIE effect. It could identify Cu²⁺ by quenching its fluorescence. The lower limit of detection was 0.36 μM. CTPE can act as a highly selective and sensitive fluorescence probe for detecting Cu²⁺.

A novel coumarin-derived Schiff base fluorescent “turn-off” chemosensor with AIE effect showed selectivity towards Cu²⁺. The recognition mechanism is presented.

Anchoring copper nanoclusters to Zn-containing hydroxy double salt: construction of 2D surface confinement induced enhanced emission toward bio-enzyme sensing and light-emitting diode fabrication

Surface CIEE based on Zn-HDS as host material and GSH-CuNCs as guest molecules was developed to produce fluorescence composite GSH-CuNCs/Zn-HDS for the first time.

Investigation of the surface confinement effect of copper nanoclusters: construction of an ultrasensitive fluorescence turn-on bio-enzyme sensing platform

Copper nanoclusters (CuNCs) have attracted considerable research interest due to their good physicochemical properties, ease of preparation, and low price. However, the low quantum yield and poor stability in aqueous solutions have greatly limited their applications. In order to improve the fluorescence properties and stability of CuNCs, in this paper, the surface confinement effect of CuNCs based on 2D layered double hydroxide (LDH) was proposed to prepare the fluorescent composites of glutathione protected CuNCs and LDH (GS-CuNCs/LDH) with excellent quantum yield and long fluorescence lifetime. Moreover, a novel, simple, and ultrasensitive fluorescence assay for the detection of hyaluronidase was proposed based on the surface confinement effect. The limit of detection for hyaluronidase was as low as 0.014 U mL-1. For the first time, this work developed a bio-enzyme sensing platform based on the surface confinement effect, which can serve as a promising candidate in biosensing.

Dual-emitting zein-protected gold nanoclusters for ratiometric fluorescence detection of Hg2+/Ag+ ions in both aqueous solution and self-assembled protein film

An abundant plant-sourced protein, zein, is used to prepare fluorescent Au nanoclusters as a promising alternative to animal/microorganism proteins.