Viewing Aggregation-Induced Emission of Metal Nanoclusters from Design Strategies to Applications

Layer by Layer Spraying Fabrication of Aggregation-Induced Emission Metal-Organic Frameworks Thin Film

The development of new metal-organic frameworks (MOFs) thin films is important for expanding their functions and applications. Herein, we first report a new kind of MOF thin film by using aggregation-induced emission (AIE) dicarboxyl ligand through a liquid-phase epitaxial (LPE) layer-by-layer (LBL) spraying method (named AIE surface-coordinated metal-organic frameworks thin film, AIE-SURMOF). The obtained AIE-SURMOF Zn4O(TPE)3 (ZnTPE) has highly growth orientation and homogeneous thin film, showing strong fluorescent property. Furthermore, by loading chiral guest in the MOF pore, the formed chiral encapsulated AIE-SURMOF can clearly indicate obvious circularly polarized luminescence performance with glum of 0.01. This study provides new MOF thin film and new strategy for expanding function and application of MOF materials.

Self-Assembly of Atomically Precise Nanoclusters: From Irregular Assembly to Crystalline Assembly

The persistent efforts toward achieving superior properties for assembled nanoscale particles have been held back due to the resulting polydispersity associated with colloidal routes of synthesis [...].

Detection and imaging of bacterial biofilms with glutathione-stabilized gold nanoclusters

Bacterial biofilms colonize chronic wounds and surfaces of medical devices, thus making the development of reliable methods for imaging and detection of biofilms crucial. Although fluorescent identification of bacteria is sensitive and non-destructive, the lack of biofilm-specific fluorescent dyes limits the application of this technique to biofilm detection. Here, we demonstrate, for the first time, that fluorescent glutathione-stabilized gold nanoclusters (GSH-AuNCs) without targeting ligands can specifically interact with extracellular matrix components of Gram-negative and Gram-positive bacterial biofilms resulting in fluorescent staining of bacterial biofilms. By contrast, fluorescent bovine serum albumin-stabilized gold nanoclusters and 11-mercaptoundecanoic acid - stabilized gold nanoclusters do not stain the extracellular matrix of biofilms. According to molecular docking studies, GSH-AuNCs show affinity to several targets in extracellular matrix, including amyloid-anchoring proteins, matrix proteins and polysaccharides. Some experimental evidence was obtained for the interaction of GSH-AuNCs with the lipopolysaccharide (LPS) that was isolated from the matrix of Azospirillum baldaniorum biofilms. Based on GSH-AuNCs properties, we propose a new fluorescent method for the measurement of biofilm biomass with a limit of detection 1.7 × 10⁵ CFU/mL. The sensitivity of the method is 10-fold higher than the standard biofilm quantification with the crystal violet assay. There is a good linear relationship between the fluorescence intensity from the biofilms and the number of CFU from the biofilms in the range from 2.6 × 10⁵ to 6.7 × 10⁷ CFU/mL. The developed nanocluster-mediated method of biofilm staining was successfully applied for quantitative detection of biofilm formation on urinary catheter surface. The presented data suggest that fluorescent GSH-AuNCs can be used to diagnose medical device-associated infections.

Periodic Surface Structuring of Copper with Spherical and Cylindrical Lenses

The use of a cylindrical lens in femtosecond laser surface structuring is receiving attention to improve the processing efficiency. Here, we investigate the structures produced on a copper target, in air, by exploiting both spherical and cylindrical lenses for beam focusing, aiming at elucidating similarities and differences of the two approaches. The morphological features of the surface structures generated by ≈180 fs laser pulses at 1030 nm over areas of 8 × 8 mm² were analyzed. For the spherical lens, micron-sized parallel channels are formed on the target surface, which is covered by subwavelength ripples and nanoparticles. Instead, the cylindrical lens leads to a surface decorated with ripples and nanoparticles with a negligible presence of micro-channels. Moreover, the morphological features achieved by focusing ≈180 fs laser pulses at 515 nm with the cylindrical lens and varying the scanning parameters were also studied. The experimental results evidence a direct effect of the hatch distance used in the scanning process on the target surface that contains dark and bright bands corresponding to regions where the rippled surface contains a richer decoration or a negligible redeposition of nanoparticles. Our findings can be of interest in large area surface structuring for the selection of the more appropriate focusing configuration according to the final application of the structured surface.