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Designing a theranostic probe for noninvasive bone imaging and bone disease therapy is both challenging and desirable. Herein, an ultrasmall Au nanocluster (NC, <2 nm)‐based theranostic probe is developed to achieve highly temporospatial in vivo bone‐targeted photoluminescence (PL) imaging in the second near‐infrared window (NIR‐II) and enhanced rheumatoid arthritis (RA) therapy. The key design of the probe involves the surface phosphorylation of atomically precise NIR‐II emitting Au44 NCs. This phosphorylation enhances the bone‐targeting ability of the probe due to the highly concentrated phosphate groups, allowing the probe to realize in vivo bone‐targeted NIR‐II PL imaging. Moreover, benefiting from the enhanced bone‐targeting ability, ultrasmall hydrodynamic diameter, and excellent anti‐inflammation and immunomodulatory effects, the probe not only demonstrates superior therapeutic efficacy for RA rats, effectively restoring the destructed cartilage to nearly normal but also exhibits good renal clearance and benign biocompatibility. These favorable attributes cannot be achieved by commercial methotrexate used for RA treatment. This study presents a new design paradigm for metal NC‐based theranostic probes, offering the potential for high‐resolution bone‐targeted PL imaging and improved RA therapy. [ABSTRACT FROM AUTHOR]

The control of nanoparticle morphology can effectively change their properties. Adjusting the aggregation state of bovine serum albumin-coated gold nanoclusters (BSA-Au NCs) can regulate the enzyme-mimicking catalytic activity. Hyaluronic acid (HA) induces the aggregation of BSA-Au NCs, leading to the shielding of the catalytic active sites and a decrease in activity; this feature has been utilized to design a multicolor biosensor for hyaluronidase (HAase). The presence of HAase can hydrolyze the glycosidic bonds in HA, causing the aggregated BSA-Au NCs to disperse and express their catalytic activity, which in turn catalyzes the etching of Au nanobipyramids (Au-NBPs) in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB), resulting in a morphological transition from bipyramidal to ellipsoidal and spherical shapes, while the solution displays a variety of colors. Visual recognition of these multicolor changes establishes a relationship between the enzyme activity and color. Based on the controlled aggregation and dispersion of BSA-Au NCs and the etching of Au-NBPs, a simple multicolor HAase biosensor was designed. The proposed biosensor shows a linear response to HAase concentrations in the range of 5–80 U/mL, with clear color changes under optimized conditions. The limit of detection (LOD) of the sensor was determined to be 1.98 U/mL (LOD = 3s/k). This method successfully applies the changing of enzyme-mimicking catalytic activity nanoparticles for colorimetric analysis detection. [ABSTRACT FROM AUTHOR]

[Display omitted] Monitoring blood glucose level is critical, since its abnormality leads to diabetes and causes death, even though glucose is essential for human living. Herein, the sensing study was performed on electrochemical nonenzymatic glucose sensors, which are composed of an Au nanocluster (AuNC) catalyst deposited on a metallic nanotube array (MeNTA) and polypyrrole nanowire (PPyNW). The AuNC was produced by irradiating a femtosecond pulse laser to the Au precursor solution, and it is a simple and facile method. The successful deposition of AuNC on both MeNTA and PPyNW was confirmed by means of the surface morphology and the Au content increase. On the exploration by cyclic voltammetry in alkaline condition, AuNC/MeNTA electrodes showed better performance than AuNC/PPyNW electrodes: The former was a remarkable electrocatalytic detector towards glucose oxidation with better sensitivity, lower detection limit, wider linear range, and longer-term stability without interference from potential interfering agents such as ascorbic acid, urea, NaCl, KCl, etc. Moreover, nonenzymatic AuNC/MeNTA electrodes exhibited high precision and accuracy in real human blood samples and, thus, can be a promising candidate in glucose sensing applications. [ABSTRACT FROM AUTHOR]

Abstract Designing a theranostic probe for noninvasive bone imaging and bone disease therapy is both challenging and desirable. Herein, an ultrasmall Au nanocluster (NC,

Abstract The understanding of the endocytosis process of internalized nanomedicines through membrane biomarker is essential for the development of molecular-specific nanomedicines. In various recent reports, the metalloproteases have been identified as important markers during the metastasis of cancer cells. In particular, MT1-MMP has provoked concern due to its protease activity in the degradation of the extracellular matrix adjacent to tumors. Thus, in the current work, we have applied fluorescent Au nanoclusters which present strong resistance to chemical quenching to the investigation of MT1-MMP-mediated endocytosis. We synthesized protein-based Au nanocluster (PAuNC) and MT1-MMP-specific peptide was conjugated with PAuNC (pPAuNC) for monitoring protease-mediated endocytosis. The fluorescence capacity of pPAuNC was investigated and MT1-MMP-mediated intracellular uptake of pPAuNC was subsequently confirmed by a co-localization analysis using confocal microscopy and molecular competition test. Furthermore, we confirmed a change in the intracellular lipophilic network after an endocytosis event of pPAuNC. The identical lipophilic network change did not occur with the endocytosis of bare PAuNC. By classification of the branched network between the lipophilic organelles at the nanoscale, the image-based analysis of cell organelle networking allowed the evaluation of nanoparticle internalization and impaired cellular components after intracellular accumulation at a single-cell level. Our analyses suggest a methodology to achieve a better understanding of the mechanism by which nanoparticles enter cells.

The understanding of the endocytosis process of internalized nanomedicines through membrane biomarker is essential for the development of molecular-specific nanomedicines. In various recent reports, the metalloproteases have been identified as important markers during the metastasis of cancer cells. In particular, MT1-MMP has provoked concern due to its protease activity in the degradation of the extracellular matrix adjacent to tumors. Thus, in the current work, we have applied fluorescent Au nanoclusters which present strong resistance to chemical quenching to the investigation of MT1-MMP-mediated endocytosis. We synthesized protein-based Au nanocluster (PAuNC) and MT1-MMP-specific peptide was conjugated with PAuNC (pPAuNC) for monitoring protease-mediated endocytosis. The fluorescence capacity of pPAuNC was investigated and MT1-MMP-mediated intracellular uptake of pPAuNC was subsequently confirmed by a co-localization analysis using confocal microscopy and molecular competition test. Furthermore, we confirmed a change in the intracellular lipophilic network after an endocytosis event of pPAuNC. The identical lipophilic network change did not occur with the endocytosis of bare PAuNC. By classification of the branched network between the lipophilic organelles at the nanoscale, the image-based analysis of cell organelle networking allowed the evaluation of nanoparticle internalization and impaired cellular components after intracellular accumulation at a single-cell level. Our analyses suggest a methodology to achieve a better understanding of the mechanism by which nanoparticles enter cells. [ABSTRACT FROM AUTHOR]

11-Mercaptoundecanoic acid-protected gold nanoclusters (Au@MUA NCs) were synthesized and investigated as a model to understand the photoluminescence (PL) properties of water-soluble, structurally unknown Au NCs. Surface engineering, including ligand exchange where the length of the alkane chain was changed, ligand conjugation where the charged terminal carboxyl group of the ligands was blocked, and effects of external chemical reducing and oxidizing agents, was carried out. PL profiles were monitored to reveal the impact of surface engineering on the PL. We found that surface ligands, especially the ligand's length and ligand functionalities, play a significant role in the PL properties of Au@MUA NCs. The results also show interesting properties of these NCs as a tunable PL sensor. [ABSTRACT FROM AUTHOR]

The heterogeneity of perovskite film crystallization along the vertical direction leads to voids and traps at the buried interfaces, hampering both efficiency and stability of perovskite solar cells. Here, bovine serum albumin-functionalized Au nanoclusters (ABSA), combined with heavy gravity, high surface charge density, and strong interactions with the electron transport layer, are designed to reconstruct the buried interfaces for not only high-quality crystallization, but also improved carrier transfer. The ABSA macromolecules with amine function groups and larger surface charge density interact with the perovskite to improve the crystallinity, and gradually migrate towards the buried interface, healing the defective voids, hence suppressing surface recombination velocity from 3075 to 452 cm s -1 . The healed buried interface and the higher surface potential of ABSA-modified TiO 2 lead to improved carrier extraction at the interface. The resulting solar cell attains a power conversion efficiency of 25.0% with negligible hysteresis and remarkable stability, maintaining 92.9% of their initial efficiency after 3200 h of exposure to the ambient atmosphere, they also exhibit better continuous irradiation stability compared to control devices. These findings provide a new metal-protein complex to eliminate the deleterious voids and defects at the buried interface for improved photovoltaic performance and stability., (© 2023 Wiley-VCH GmbH.)

To understand the origin of the irreproducibility of the hole injection barrier at the interface between Au top-contact electrodes and organic semiconductors, we performed a systematic study by focusing on the deposition rate of Au. As a benchmarking material system, we fabricated field-effect transistors with pentacene active layers and Au top-contact electrodes evaporated with the deposition rate from 0.5 to 10 Å/s. From the contact potential differences (Δ CPDs) between Au and pentacene measured with Kelvin-probe force microscopy, cross-sectional structures with scanning transmission electron microscopy, crystallographic structures with X-ray diffraction, and Au depth profiles with secondary ion mass spectrometry, we concluded that the variation of Δ CPD is due to embedded Au nanoclusters in pentacene with the average diameter of 4–6 nm. These Au nanoclusters, of which depth significantly varies by the Au deposition rate, modulate the Δ CPD and interfere with the reproducibility of hole injection barrier. As a result, gate threshold voltage and field-effect mobility also become irreproducible. Image 100 • Band alignment between Au electrodes and pentacene was studied to understand the variation of the hole injection barrier. • Diffusion of Au atoms into the pentacene layer and cluster formation is sensitive to the Au deposition rate. • Variation of the contact potential difference is concluded to be due to the Au clusters embedded in the pentacene layer. [ABSTRACT FROM AUTHOR]

Abstract Nonhydrogenated Diamond-like Carbon-gold (DLC-Au) nanocomposite thin films with various Au contents and cluster size (<10 nm) have been engineered using Excimer Pulsed Laser Deposition (PLD) on silicon (100) substrates with an aim to achieve reduced coefficient of friction (CoF). Structure, microstructure, chemical bonding and chemical composition of these films were comprehensively investigated using X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS), respectively. It is observed that the DLC matrix with lowest Au content sustained higher sp 3 content due to enhanced interaction of carbon and smaller Au nano-cluster formed in these films. DLC-Au Nanocomposite formation takes place due to the low compatibility between carbon and gold which resulted in ultra-smaller Au crystallites in DLC matrix at lowest Au content. This enhanced the sp 3 content in DLC films and induces tribofilm nucleation on the ball counter body with large amount of sp 2 phase fraction which significantly reduced the CoF. [ABSTRACT FROM AUTHOR]

Fluorescent gold nanoclusters (AuNCs) are envisaged as a novel type of fluorophores. This work reports on the first comparative study investigating the effect of presence/absence/abundance of fatty acids (namely palmitic acid, PA) or other substances (like glycoproteins and globulins) in the protein (bovine serum albumin, BSA) on synthesis and properties of the final AuNCs. The most popular template (BSA) and microwave (MW)-assisted synthesis of AuNCs have been intentionally chosen. Our results clearly demonstrate that the fluorescent characteristics (i.e., fluorescence lifetime and quantum yield) are affected by the fatty acids and/or other substances. Importantly, the as-prepared AuNCs are biocompatible, as determined by Alamar Blue assay performed on Hep G2 cell line.

A kind of novel hybrid membrane for the detection and separation of mercury ion (Hg 2+ ) was fabricated by filtrating gold nanocluster embedded bovine serum albumin (AuNCs@BSA) nanofibers and graphene oxide (GO). With the help of N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, the BSA nanofiber and graphene oxide (GO) can be covalently binded due to the reaction between amino and carboxyl groups. The separation mechanism of the hybrid membrane are attributed to the high-affinity metallophilic Hg 2+ -Au + interactions, Hg 2+ -cysteine residue binding as well as electrostatic interaction. The experimental results indicated that the created GO-AuNCs@BSA hybrid membrane exhibits excellent performance for removing Hg 2+ pollutants from water. The adsorbing efficiency of Hg 2+ can reach up to 90.45% at the first cycle and the separation process can be repeated numerous times without damaging the membrane structure. [ABSTRACT FROM AUTHOR]

Au nanoclusters (NCs) bring new opportunities for constructing visible-light photocatalysts for solar-driven CO 2 conversion, whereas the agglomeration under illumination and lack of catalytic sites severely hinder their application. One promising approach to address the limitations is the confinement of Au NCs on a heterogeneous substrate with efficient catalytic sites, in which a concomitant bottleneck originates from the electron transfer between Au NCs and catalytic sites determining the charge transfer dynamics. Herein, we develop an effective strategy for grafting Au NCs onto ultrathin layered double hydroxide (LDH) nanosheets via engineering bridging ligands. The bridging ligands function as both surface anchors and electron mediators, which confine and stabilize Au NCs on LDH, as well as facilitate electron transfer from Au NCs to catalytic sites. As a result, the durability and efficiency for photocatalytic CO 2 reduction is significantly enhanced. This work provides a fresh hint for stabilizing ultrasmall nanoclusters and facilitating the electron transfer between light-harvesting nanoclusters and catalytic sites through bridging ligands. [Display omitted] • A strategy for grafting Au nanoclusters (NCs) on layered double hydroxide (LDH) nanosheets via bridging ligands is developed. • A binary Au NCs/LDH photocatalytic system is constructed for efficient CO 2 reduction. • Bridging ligands function as surface anchors to confine and stabilize Au NCs on LDH. • Bridging ligands serve as electron mediators to facilitate electron transfer. • The activity and selectivity of photocatalytic CO 2 reduction can be tuned by altering bridge ligands and grafting substrates. [ABSTRACT FROM AUTHOR]

Immunotherapy is an advanced therapeutic strategy of cancer treatment but suffers from the issues of off-target adverse effects, lack of real-time monitoring techniques, and unsustainable response. Herein, an ultrasmall Au nanocluster (NC)-based theranostic probe is designed for second near-infrared window (NIR-II) photoluminescence (PL) imaging-guided phototherapies and photoactivatable cancer immunotherapy. The probe (Au 44 MBA 26 -NLG for short) is composed of atomically precise and NIR-II emitting Au 44 MBA 26 NCs (here MBA denotes water-soluble 4-mercaptobenzoic acid) conjugated with immune checkpoint inhibitor 1-cyclohexyl-2-(5H-imidazo[5,1- a ]isoindol-5-yl)ethanol (NLG919) via a singlet oxygen ( 1 O 2 )-cleavable linker. Upon NIR photoirradiation, the Au 44 MBA 26 -NLG not only enables NIR-II PL imaging of tumors in deep tissues for guiding tumor therapy but also allows the leverage of photothermal property for cancer photothermal therapy (PTT) and the photogenerated 1 O 2 for photodynamic therapy (PDT) and releasing NLG919 for cancer immunotherapy. Such a multiple effect modulated by Au 44 MBA 26 -NLG prompts the proliferation and activation of effector T cells, upshifts systemic antitumor T-lymphocyte (T cell) immunity, and finally suppresses the growth of both primary and distant tumors in living mice. Overall, this study may provide a promising theranostic nanoplatform toward NIR-II PL imaging-guided phototherapies and photoactivatable cancer immunotherapy.

High sensitivity, good signal repeatability, and facile fabrication of flexible surface enhanced Raman scattering (SERS) substrates are common pursuits of researchers for the detection of probe molecules in a complex environment. However, fragile adhesion between the noble-metal nanoparticles and substrate material, low selectivity, and complex fabrication process on a large scale limit SERS technology for wide-ranging applications. Herein, we propose a scalable and cost-effective strategy to a fabricate sensitive and mechanically stable flexible Ti 3 C 2 T x MXene@graphene oxide/Au nanoclusters (MG/AuNCs) fiber SERS substrate from wet spinning and subsequent in situ reduction processes. The use of MG fiber provides good flexibility (114 MPa) and charge transfer enhancement (chemical mechanism, CM) for a SERS sensor and allows further in situ growth of AuNCs on its surface to build highly sensitive hot spots (electromagnetic mechanism, EM), promoting the durability and SERS performance of the substrate in complex environments. Therefore, the formed flexible MG/AuNCs-1 fiber exhibits a low detection limit of 1 × 10 -11 M with a 2.01 × 10 9 enhancement factor (EF exp ), signal repeatability (RSD = 9.80%), and time retention (remains 75% after 90 days of storage) for R6G molecules. Furthermore, the l-cysteine-modified MG/AuNCs-1 fiber realized the trace and selective detection of trinitrotoluene (TNT) molecules (0.1 μM) via Meisenheimer complex formation, even by sampling the TNT molecules at a fingerprint or sample bag. These findings fill the gap in the large-scale fabrication of high-performance 2D materials/precious-metal particle composite SERS substrates, with the expectation of pushing flexible SERS sensors toward wider applications.

Structural and energetic properties of nanoclusters of Au, Li, and LiAu ( n = 1-6) were studied employing MP2, M062X, and B3LYP computational methods. The planar (2D) isomers were the most stable structures of the Au clusters. Binding energy per atom ( E) for the Au clusters increased with increase in the cluster size and were in the range of 0.9-1.7 eV. The Li clusters were more unstable, and their E values were about 0.4-0.6 eV. Lithium-doping of Au clusters resulted in an increase of E values and more stable clusters. Also, Li-doping led to stability of the 3D clusters so that the bipyramidal AuLi isomer became more stable than the planar clusters. It was observed that the electron affinities of the Au, Li, and LiAu clusters increased with cluster sizes. Ionization energies and electron affinities of the Li-doped gold clusters were smaller than those for pure Au clusters. [ABSTRACT FROM AUTHOR]

To determine the intrinsic effects of body elements on the electrochemiluminescence (ECL) of metal nanoclusters (NCs), herein, a valence-state engineering strategy is developed to adjust the NCs' ECL with bovine serum albumin (BSA)-stabilized AuNCs as a model, in which engineering the valence state of the Au body element, i.e., Au(0) and Au(I), is performed via successively reducing the precursor AuCl 4 - to Au(I) and Au(0) with BSA. The obtained BSA-AuNCs/N 2 H 4 system leads to three anodic ECL processes at 0.37 (ECL-1), 0.85 (ECL-2), and 1.45 V (ECL-3). ECL-1 is generated from the BSA-Au(0) section of BSA-AuNCs in a surface-defect-involved route and is much stronger and red-shifted compared to ECL-2 and ECL-3, which are generated from the BSA-Au(I) section of BSA-AuNCs in the band-gap-engineered route. Each of the anodic ECL processes can be selectively generated and/or suppressed via adjusting the Au(I)/Au(0) ratio of BSA-AuNCs, tunable ECL generation route, and triggering potential, and the emission intensity and waveband of metal NCs are conveniently achieved in body-element-involved valence-state engineering.

Taking Au as a prototype, hollow cages with different arrangements and those stuffed by a different number of atoms have been studied by using the scalar relativistic density functional theory. The global minimum structures of Au ( i = 0, ±1) are found to exhibit low symmetry core-shell structures: Au and Au feature a four-atom tetrahedral core and Au possesses a six-atom octahedron core. For the neutral Au, the tube-like structure has the highest chemical stability. The obtained information forms the basis for future chemisorption studies to unravel the catalytic effects of gold nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a linker-free connected graphene oxide/Au nanocluster (GO–Au NCs) composite was prepared under sonication through electrostatic interactions, and characterized by transmission electron microscope (TEM), atomic force microscope (AFM), ultraviolet–visible (UV–vis) and FT-IR spectrum. The morphological and structural characterizations evidence that the Au NCs can be efficiently decorated on the GO. The electrochemical investigations indicated that GO–Au NCs composite has an important role in the electrocatalytic activity towards the oxidation of l-cysteine (CySH). The GO–Au NCs composite modified electrode shows a large determination range from 0.05 to 20.0μmol/L, a remarkably low detection limit is 0.02μmol/L and low oxidation potential (+0.387). It was found that metal ions, carbohydrates, nucleotide acids and amino acids had no distinct effect on the determination of l-cysteine. In addition, the sensor has some important advantages such as simple preparation, fast response, good stability and high reproducibility. The direct determination of free reduced and total CySH in human urine samples has been successfully carried out without the assistance of any separation techniques. [Copyright &y& Elsevier]

Seawater electrolysis offers a promising technology for environmental remediation and mass production of sustainable hydrogen. However, intricated synthetic routes, limited oxygen selectivity, and electrode corrosion severely hamper the practical viability of this technology. Here, we designed an effective strategy to assemble interface-rich, Au NCs decorated Gd-Co 2 B nanoflakes embedded in TiO 2 nanosheets grown on Ti foil (Au-Gd-Co 2 B@TiO 2) to meet the multiple needs of electrodes for seawater electrolysis. Benefiting from the high electrical conductivity, superior intrinsic activity, and improved transfer coefficient, this free-standing, Au-Gd-Co 2 B@TiO 2 electrocatalyst demonstrates outstanding performance towards overall seawater splitting needing a small overpotential of 510 mV to attain a geometric activity of 1000 mAcm−2 in alkaline seawater. The higher activity and specificity of Au-Gd- Co 2 B@TiO 2 are credited to the oxygen vacancies and the presence of the Co-Au surface. Furthermore, its super hydrophilic-aerophobic features, improved corrosion resistance, and impressive durability reveal its practical viability for actual seawater electrolysis. In this work, 3D free-standing Au-Gd-Co 2 B@TiO 2 is fabricated as an efficient bifunctional electrocatalyst for sea water electrolysis. [Display omitted] • Au NCs loaded Gd-Co 2 B@TiO 2 was synthesized via facile and scalable approach. • Microwave treatment creates strong interaction between Au NCs and Gd-Co 2 B@TiO 2. • TiO 2 nanosheets with high corrosion resistance serve as a stable skeleton. • Au-GdCo 2 B interface suppresses the hypochlorite formation. • Au-Gd-Co 2 B@TiO 2 has an excellent performance in sea water electrolysis. [ABSTRACT FROM AUTHOR]

Nanocluster films are modeled as a network of tunnel junctions in which random voids have been introduced. The effects of network size and void distribution on electron transport are studied using Monte Carlo simulations of the Coulomb blockade mediated transport. The random void distributions of the model networks are systematically varied by randomly deleting junctions along each row and between the different rows. The nonlinearity and voltage threshold of the I-V curves are calculated for different void topologies and network sizes. Both the threshold voltage and nonlinearity are sensitive to lateral fluctuations of the conduction paths due to the random voids. The nonlinearity is found to be maximized for network aspect ratios of unity or larger and for particular network topologies. Both the nonlinearity and voltage threshold scale with network size. The behaviors seen in simulation are found to correspond well to Au nanocluster I-V measurements. [ABSTRACT FROM PUBLISHER]

Persistent high-risk human papillomavirus (HPV) infection is the leading cause of cervical cancer. Efficient detection of HPV16 E7 is necessary for early diagnosis and cure of the disease. Here, a novel and high-performance Au nanocluster (AuNC) probe-based split-type electrochemiluminescent (ECL) assay platform has been established to detect these oncogenes, in which the nucleic acid hybridization assay and the ECL measurements are performed independently. The proposed approach combines superior magnetic nanobead enrichment and separation technology, specific nucleic acid hybridization technology, and high-efficiency AuNC probe ECL strategy, and shows excellent advantages. First, the split-type ECL sensing platform can effectively avoid interference from biological samples and adequately uses the ECL efficiency of the AuNC probe. Furthermore, the ultrahigh sensitivity assay of HPV DNA can be achieved without any complex nucleic acid amplification technique. Taking advantage of the above merits of split-type detection, the ECL DNA sensor achieved ideal low detection of 6.8 aM and a wide dynamic range bridging 10 orders of magnitude HPV16 E7. Furthermore, together with its favorable and powerful specificity, high sensitivity, and good selectivity, this strategy could detect HPV16 E7 DNA in human samples, which showed great consistency with the FDA-approved approach (Hybrid capture 2, HC2). Therefore, this work proposes a facile and reliable split-type ECL platform for HPV diagnosis and shows great potential for the early diagnosis of other diseases. This study programs a novel split-type ECL assay platform based on high-performance AuNCs probe for HPV diagnosis. Even in the absence of any complex signal amplification techniques, the ECL sensor for HPV16 E7 detection showed an unprecedentedly LOD of 6.8 aM and a wide dynamic range bridging 10 orders of magnitude. Thus, this work proposes a facile and reliable ECL platform for HPV diagnosis and shows great potential for the early diagnosis of other diseases. Image 1 • A novel split-type electrochemiluminescent assay platform for HPV diagnosis. • Combination of MB technique, nucleic acid hybridization technology and high-efficiency AuNC probe ECL technology. • An unprecedentedly LOD of 6.8 aM and a wide dynamic range bridging 10 orders of magnitude for HPV16 E7 detection. • Without any complex nucleic acid amplification strategy. [ABSTRACT FROM AUTHOR]

• A highly selective ratiometric fluorescent sensor N-CQDs/AuNCs for carbendaizm was developed. • The sensor has good selectivity and sensitivity to carbendazim with wide dynamic response range. • Sensor avoids the influences caused by probe concentration and drifts of optoelectronic system. • The ratiometric fluorescent sensor is a promising candidate for carbendazim detection. A novel fluorescence "turn on" ratiometric fluorescent sensor was employed to determine carbendazim. The sensing process was achieved through the strong fluorescence resonance energy transfer (FRET) between nitrogen doped carbon quantum dots (N-CQDs) and gold nanocluster (AuNCs). The photoluminescence intensity of N-CQDs can be deactivated by AuNCs through FRET effect and recovered by the addition of carbendazim. The ratiometric detection of carbendazim is achieved by recording the photoluminescence and second-order Rayleigh scattering (SRS) signal of N-CQDs/AuNCs system. With the introduction of carbendazim to the sensing platform resulted in the photoluminescence and SRS signal of N-CQDS/AuNCs enhancing. UV–vis absorption, Zeta potential and fluorescence lifetime analyses indicate that the fluorescence turn on process can be attributed to the aggregation of AuNCs breaks the FRET process and increases SRS intensity. N-CQDs/AuNCs probe present a good sensitivity and selectivity for carbendazim detection, with two linear response ranges (1−100 μM, 150−1000 μM), low detection limit of 0.83 μM and 37.25 μM. Furthermore, real sample analyses indicate that the as-presented sensor has potentials in carbendazim determination in real sample analyses. [ABSTRACT FROM AUTHOR]

Fluorescent gold nanoclusters (AuNCs) are envisaged as a novel type of fluorophores. This work reports on the first comparative study investigating the effect of presence/absence/abundance of fatty acids (namely palmitic acid, PA) or other substances (like glycoproteins and globulins) in the protein (bovine serum albumin, BSA) on synthesis and properties of the final AuNCs. The most popular template (BSA) and microwave (MW)-assisted synthesis of AuNCs have been intentionally chosen. Our results clearly demonstrate that the fluorescent characteristics (i.e., fluorescence lifetime and quantum yield) are affected by the fatty acids and/or other substances. Importantly, the as-prepared AuNCs are biocompatible, as determined by Alamar Blue assay performed on Hep G2 cell line. [ABSTRACT FROM AUTHOR]

Tetracycline (TC), a widely-used antibiotic to treat bacterial infections, combines with Eu3+ to form a stable EuTC complex that has a low fluorescence (FL) yield because of Eu3+ coordination with water molecules. We report a simple, label-free ratiometric fluorescent platform for sensitively and selectively sensing of TC, using L-histidine caped gold nanoclusters (His-AuNCs) as a FL indicator and an enhancer of Eu3+ FL. The His-AuNCs were prepared via chemical reduction of Au(III) by L-histidine, which was a reducer and a protecting agent. The His-AuNCs exhibited good photostability, outstanding stability toward high ionic strengths, storage stability, and favorable optical properties. In the absence of TC, the AuNCs-Eu3+ system displays strong FL emission at 475 nm (F 475) from the His-AuNCs and weak FL at 620 nm from Eu3+ (F 620) with excitation at 375 nm. TC quenches the His-AuNC FL and greatly enhances the Eu3+ emission. This is attributed to an enhancement of the EuTC complex fluorescence by the His-AuNCs. Thus, a ratiometric F 620 / F 475 FL signal can be used for TC detection by simply mixing AuNCs and Eu3+. Under the optimized conditions, the linear range from 10 nM to 60 μM and a detection limit of 4 nM (S/N = 3) for TC were obtained. The application of the assay platform for the detection of TC in environmental and biological samples was demonstrated. The sensing platform has advantages of easy preparation, rapid response, high sensitivity, and good selectivity. Eu3+ causes quenching of fluorescent emission of His-AuNCs at 475 nm. In the presence of TC, F 475 is further quenched through IFE, while the characteristic emission of Eu3+ at 620 nm was enhanced dramatically. This finding resulted in a new ratiometric fluorescence sensor for TC in water and biological samples. Image 1 • We reported a ratiometric fluorescent system for tetracycline (TC). • The sensor system is constructed by simply mixing AuNCs and Eu3+. • This strategy exhibit excellent selectivity to TC. • Successfully applied to the detection of TC in real samples. [ABSTRACT FROM AUTHOR]

Noble metals or oxide catalysts have traditionally been loaded or doped to enhance the gas sensing properties of oxide semiconductor chemiresistors. However, the selective detection of various chemicals for a wide range of new applications remains a challenging problem. In this paper, we propose a novel bilayer design with an oxide chemiresistor sensing layer and nanoscale catalytic Au overlayer to provide high controllability for gas sensing characteristics. The Au nanocluster overlayer significantly enhances the methylbenzene response of a SnO 2 thick film sensor by reforming gases into more reactive species and suppresses the responses to reactive interference gases through oxidative filtering, leading to excellent selectivity to methylbenzene. Gas sensing characteristics can be tuned by controlling the morphology, amount, and number density of Au nanoclusters through the variation in the Au coating thickness (0.5-3 nm) and thermal annealing conditions (0.5-4 h at 550 °C). Furthermore, the general validity of the proposed Au-coated bilayer sensor design was confirmed through the enhancement of response and selectivity toward methylbenzenes by coating Au nanoclusters onto ZnO and Co 3 O 4 sensors. The sensing mechanism, advantages, and potential applications of bilayer sensors are discussed from the perspective of the separation of sensing and catalytic reactions, as well as the reforming and oxidation of analyte gases in association with the configuration of the sensing layer and Au catalytic overlayer.

This report outlines a versatile high-performance electrochemiluminescence (ECL) enzyme-linked immunosorbent assay (ELISA) platform, which combines the merits of high-quantum-yield Au nanocluster (AuNC) probe-based ECL technology, the efficient ECL-resonance energy-transfer (ECL-RET) strategy, and highly sensitive and specific ELISA technology. The ECL detection procedure was performed on a recyclable MnO 2 /AuNC-modified glassy carbon electrode interface by taking advantage of the ECL-RET between the AuNC probe and MnO 2 nanomaterials (NMs) to quench the ECL intensity. The etching of MnO 2 NMs by the product of ALP-based ELISA recovers the ECL signal. Notably, the ELISA process and the ECL detection procedure in this system are independent. Thus, the ECL-ELISA system can effectively avoid the influence of complex biological samples, and the ECL efficiency of the AuNC probe can be used readily. As demonstrated on TNF-α, because of the abovementioned characteristics, the ECL-ELISA platform presented an extremely wide dynamic range, with a detection limit of 2 orders lower than ELISA. Moreover, the system was also applicable for ultrahigh sensitive detection of various disease-related proteins and able to detect trace biomarkers in real serum samples. Therefore, this multifunctional ECL assay platform is versatile, facile, ultrasensitive, recyclable, and sufficiently straightforward for trace biomarker detection in complex biological samples. This approach not only enriches the foundational study of ECL devices but also greatly expands the potential application of ECL sensors in biological testing and clinical high-throughput diagnosis.

Semiconductor-metal nanocomposites prepared with well-defined gold nanoclusters, such as Au25, Au144, and Au807, showed size-dependent photocatalytic activities for the reduction of nile blue and azobenzene. Whereas the photoreduction of nile blue was directly related with the charge separation and transfer rate from the photoexcited ZnO to gold nanoclusters, the photoreaction of azobenzene showed unexpected size effect with a clear threshold. Mechanistic investigations revealed that the photoreduction of azobenzene proceeded via a proton-coupled electron transfer process. The photocatalytic activity of the ZnO-Au nanocomposites was also dependent on the excitation intensity, demonstrating that the multielectron/multiproton process was controlled by the charge separation and transfer in the nanocomposites.