Controlling NIR-II emitting gold organic/inorganic nanohybrids with tunable morphology and surface PEG density for dynamic visualization of vascular dysfunction.

Luminescent Au nanoparticles (AuNPs) and their organic/inorganic nanohybrids are of interest due to their favorable properties and promising biomedical applications. However, most existing AuNP-based hybrid nanostructures cannot satisfy high efficiency in synthesis, deep tissue penetration, and long blood circulation simultaneously, thus cannot be employed in dynamic monitoring of biomedical applications. In this paper, using Pluronic F127 as a template, we report a robust approach for one-pot synthesis of AuNP-based organic/inorganic nanohybrids (AuNHs) with bright luminescence in the second near-infrared (NIR-II) window, tunable shape, and controllable surface polyethylene glycol (PEG) density. The nanohybrids could be controlled from a necklace-like shape with a dense brush PEG configuration to a spherical structure with a brush PEG coating, which greatly impacts the in vivo biological behavior. Compared to spherical AuNHs, the necklace-shaped AuNHs present a higher quantum yield and longer blood circulation, which are superior to most of the individual AuNPs. With these outstanding features, the necklace-shaped AuNHs could achieve real-time, dynamic visualization of vascular dysfunction, capable of directing the precise administration of thrombolytics (a medicine for the breakdown of blood clots). These findings could provide a powerful guide for designing novel NIR-II nanoprobes toward in vivo dynamic information visualization.

Modulating luminescence and assembled shapes of ultrasmall Au nanoparticles towards hierarchical information encryption.

Because of their intriguing luminescence performances, ultrasmall Au nanoparticles (AuNPs) and their assemblies hold great potential in diverse applications, including information security. However, modulating luminescence and assembled shapes of ultrasmall AuNPs to achieve a high-security level of stored information is an enduring and significant challenge. Herein, we report a facile strategy using Pluronic F127 as an adaptive template for preparing Au nanoassemblies (AuNAs) with controllable structures and tunable luminescence to realize hierarchical information encryption through modulating excitation light. The template guided ultrasmall AuNP in situ growth in the inner core and assembled these ultrasmall AuNPs into intriguing necklace-like or spherical nanoarchitectures. By regulating the type of ligand and reductant, their emission was also tunable, ranging from green to the second near-infrared (NIR-II) region. The excitation-dependent emission could be shifted from red to NIR-II, and this significant shift was considerably distinct from the small range variation of conventional nanomaterials in the visible region. In virtue of tunable luminescence and controllable structures, we expanded their potential utility to hierarchical information encryption, and the true information could be decrypted in a two-step sequential manner by regulating excitation light. These findings provided a novel pathway for creating uniform nanomaterials with desired functions for potential applications in information security.

Ligand-regulated self-assembly of luminescent Au nanoparticles towards diverse controllable superstructures.

Only using one type of amphiphilic block copolymers as a template, we present a facile and robust approach to in situ fabricate a series of brightly emitting Au nano-assemblies with high controllability and tunability. Simply by altering thiol ligands, the Au nano-assemblies display diverse superstructures including fibers, vesicles, and honeycombs.

Self-Assembly of Luminescent Gold Nanoparticles with Sensitive pH-Stimulated Structure Transformation and Emission Response toward Lysosome Escape and Intracellular Imaging.

Ultrasmall luminescent gold nanoparticles (AuNPs, d < 3.0 nm) with distinct optical properties and good biocompatibilities hold enormous promise for advanced disease theranostics. However, ultrasmall AuNPs generally show low cellular interaction and are hardly ever transported into the specific subcellular compartments, hampering their further biomedical use in cellular delivery and intracellular tracking. Using a conventional cationic polymer chitosan (CS) with the isoelectric point of 6.5 as a template, ultrasmall luminescent AuNPs can be easily formed into self-assembled nanostructures (AuNPs@CS) with significantly enhanced cellular interaction capability and sensitive emission response toward subcellular location. The self-assembled AuNPs@CS become compacted nanostructures (∼23.5 nm) with high luminescence at low pH values (e.g., pH < 6.5) but reversibly transform to swelled structures with weak luminescence at high pH values (e.g., pH 7.4). The self-assembly of AuNPs not only improves the emission properties but also alters the surface charge and assembly size, resulting in both enhanced cellular internalization and effective endosomal escape capability. More importantly, the sensitive luminescence response of the AuNPs@CS from the acidic organelle lysosome to the neutral cytoplasm demonstrates the great potential in optical intracellular tracking.

Amphiphilic Block Copolymer-Guided in Situ Fabrication of Stable and Highly Controlled Luminescent Copper Nanoassemblies.

Assembling instable ultrasmall nanoparticles (NPs) into uniform nanoarchitectures with excellent stability and controllability in aqueous solution is still challenging. Herein, taking the advantage of controllable size and shape of amphiphilic triblock copolymer template, we report a facile and robust strategy for in situ fabrication of highly luminescent Cu nanoassemblies with uniform morphology and remarkable stability. The dominant number of encapsulated CuNPs in an assembly can be controlled through regulating hydrophobic core size by varying block segments of the template. The cross-linking by a multidentate thiol ligand largely enhances the emission and stability of the Cu nanoassemblies in physiological environment. By virtue of their intriguing features, the Cu nanoassemblies can be applied to possible biomedical applications. These findings establish our approach as a facile and feasible method for preparing stable and well-controlled ultrasmall metal NP-based assemblies.

Transformation from gold nanoclusters to plasmonic nanoparticles: A general strategy towards selective detection of organophosphorothioate pesticides.

Luminescent gold nanoclusters (AuNCs) synthesized using non-thiolate DNA ligands were reported to show both optical and structure responses toward diethyposphorthioate (DEP) derived from the hydrolysis of chlorpyrifos (CP). After incubation of AuNCs with DEP, the non-thiolate DNA ligands were immediately replaced and the tiny AuNCs with ultrasmall size transformed gradually to plasmonic nanoparticles, which resulted in significant luminescence quenching of the AuNCs, offering a new possibility to selectively detect organophosphorothioate pesticides that could be easily hydrolyzed to form the special structures such as DEP containing two binding sites (e.g. S and O atoms). Therefore, selecting CP as a model analyte, we here developed a general strategy for the construction of a novel chemosensor for the determination of CP using the non-thiolate DNA coated AuNCs as an optical probe. Based on aggregation-induced luminescence quenching, this strategy exhibited highly sensitive and selective responses towards CP with a limit of detection (LOD) of 0.50µM, and was applied successfully to the analysis of CP in real sample. More interestingly, this facile strategy could easily distinguish CP from other thiol reagents through solution color change in spite of the existence of the coordination between Au and S atom for both of them, and the response mechanisms for them were studied in detail. In additional, it could be extended to detect the other organophosphorothioate pesticides with the similar structure as CP, which exploits a new platform for the construction of chemosensor and application.

One-pot synthesis of fluorescent DHLA-stabilized Cu nanoclusters for the determination of H2O2.

A facile one-pot approach has been developed to prepare orange-emitting Cu nanoclusters (NCs) using tetrakis(hydroxymethyl)phosphonium chloride as a reducing agent and lipoic acid as a capping agent under an alkaline medium at room temperature. The as-prepared Cu NCs exhibited excellent water solubility, large Stokes shift, long lifetime and good dispersion. After the addition of polyvinyl pyrrolidone, the fluorescence intensity of dihydrolipoic acid-stabilized Cu NCs (DHLA-Cu NCs) was greatly enhanced, and their fluorescence signal remained stable for 5 weeks storage in the dark at room temperature. Based on H2O2-induced fluorescence quenching, DHLA-Cu NCs showed high sensitivity and selectivity for the detection of H2O2 in aqueous solution with a detection limit of 0.3µM, and were applied successfully to the detection of H2O2 in human urine samples.

Metal nanoclusters: applications in environmental monitoring and cancer therapy.

Metal nanoclusters (NCs), with dimensions between metal atoms and nanoparticles, have attracted more and more attention due to their unique physical and chemical properties. With their size approaching the Fermi wavelength of electrons, metal NCs possess molecule-like properties and excellent fluorescence emission. Owing to their ultrasmall size, strong fluorescence, and excellent biocompatibility, they have been widely studied in environmental and biological fields concerning their applications. In this review, we will introduce the properties of metal NCs, mainly focusing on the synthesis of metal alloy NCs and the recent progress in their applications in environmental monitoring and cancer therapy.

Highly fluorescent copper nanoclusters as a probe for the determination of pH.

A simple, one-pot synthetic route was developed for the preparation of green-emitting and pH-responsive Cu nanoclusters (NCs). The Cu NCs were obtained using cysteine (Cys) as both the reducing agent and the capping agent under alkaline conditions at room temperature. The Cu NCs were characterized using spectroscopic and microscopic techniques and exhibited excellent water solubility, ultrasmall size, good dispersion, bright fluorescence and good photostability. Moreover, the Cu NCs were stable even in a high ionic strength medium such as 1M NaCl. Interestingly, the Cys-Cu NCs showed an intrinsically reversible response toward pH change in the range 4-10, and thus can be utilized as an effective and reversible pH indicator.

A colorimetric agarose gel for formaldehyde measurement based on nanotechnology involving Tollens reaction.

Gold nanoparticles (Au NPs) coupled with Tollens reagent were used for measuring formaldehyde. Au@Ag core-shell NPs were formed along with distinct color changes from pink to deep yellow. This colorimetric system was further immobilized into an agarose gel, which was used for monitoring of gaseous formaldehyde.

Silver-gold alloy nanoclusters as a fluorescence-enhanced probe for aluminum ion sensing.

In this paper, the development of a simple method is described for preparing highly red fluorescent mercaptosuccinic acid stabilized AgAu alloy nanoclusters (MSA-AgAu NCs) through the core etching of Ag nanoparticles (NPs) and a galvanic exchange reaction using nonorganic solvent and no multistep centrifuge washing. The as-prepared MSA-AgAu NCs were characterized using spectroscopic and microscopic techniques. After covalently attaching methoxy-poly(ethylene glycol)-NH2 (m-PEG-NH2), PEGylated MSA-AgAu NCs were still stable even in 1 M NaCl. Probably based on the deposition of Al(3+)-enhanced fluorescence, the PEGylated MSA-AgAu NCs offered highly selective and sensitive sensing of Al(3+) in aqueous solution with a detection limit of 0.8 µM.

A novel solid-state electrochemiluminescence sensor for the determination of hydrogen peroxide based on an Au nanocluster-silica nanoparticle nanocomposite.

A gold nanocluster@bovine serum albumin-silica nanoparticle composite has been synthesized and used for the solid-state electrochemiluminescence (ECL) sensing of hydrogen peroxide. The ECL characteristics have also been studied.

Facile synthesis of red-emitting lysozyme-stabilized Ag nanoclusters.

A facile approach was developed to prepare positively charged and red-emitting lysozyme-stabilized Ag nanoclusters (Lys-AgNCs) using NaBH4 as a reducing agent at room temperature. The Lys-AgNCs can be applied in the highly selective detection of Hg²âº.

Sonochemical synthesis of highly fluorescent glutathione-stabilized Ag nanoclusters and S2- sensing.

A facile one-pot sonochemical approach is presented to prepare highly blue-emitting Ag nanoclusters (AgNCs) using glutathione as a stabilizing agent in aqueous solution. The as-prepared AgNCs can be applied in the selective detection of S(2-) with a limit of detection of 2 nM based on fluorescence quenching.

A dissolved oxygen sensor based on composite fluorinated xerogel doped with platinum porphyrin dye.

A new functional fluorinated material taking n-propyltrimethoxysilicane (n-propyl-TriMOS) and 3,3,3-trifluoropropyltrimethoxysilicane (TFP-TriMOS) as precursors was applied to construct a novel dissolved oxygen sensing film. The sensing film was fabricated by dip-coating the functional fluorinated material-doped [meso-tetrakis(pentafluorophenyl) porphyinato] platinum(II) (PtF(20) TPP) onto a glass slide. The oxygen sensing film exhibited a good linear relationship, fast response time, long stability and high sensitivity to dissolved oxygen. In the developed optical oxygen sensor, an LED and a photodiode were composed to construct a back-detection optical system not needing an optical fiber based on fluorescence intensity detection. The smart optical oxygen sensor based on the PtF(20) TPP fluorescence quenching possesses the advantages of portability and low cost and can be applied to the dissolved oxygen in situ monitoring in seawater.

Optical colorimetric sensor strip for direct readout glucose measurement.

A novel direct readout colorimetric optical glucose sensor strip was constructed based on a three-layer film, including a green-emitted CdTe/CdS quantum dots (QDs) layer as a stable color background, a red-fluorescent platinum-porphyrin oxygen-sensing layer and a glucose oxidase layer. The sensor achieved high resolution (up to 0.2 mmol L(-1)) glucose determination with a detection range from 0 to 3.0 mmol L(-1). A "glucose ruler" which acts as a glucose standard colorimetric card was obtained. Glucose concentration could easily be directly readout using the "glucose ruler", which made the glucose determination rapid, convenient and easy. The effects of pH, salinity and temperature were systematically investigated. The prepared sensor was finally applied for glucose sample analysis, compared with the "glucose ruler", accurate results could be directly readout.