Microwave-assisted in situ synthesis of fluorescent gold nanoclusters with BSA/montmorillonite and application on latent fingermark imaging

A method for in situ preparation of fluorescent gold nanoclusters(Au NCs) with bovine serum albumin/montmorillonite composite powder(Au NC-BSA/MMT) was developed, and the products were used to detect latent fingermarks. In this work, Au NCs were "grown" both inside and on the surface of BSA/MMT clay using one-step reduction of HAu Cl4 by BSA. The as-prepared Au NC-BSA/MMT nanocomposites emit intensive red fluorescence under the excitation of UV-visible light and show stable chemical features and low toxicity. The obtained fluorescent powders were characterized by UV-visible absorption spectroscopy,fluorescence spectroscopy, infrared spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction to depict their sizes, structural information and optical features. Given their environmentally friendly preparation, simple operation, low cost, efficient UVvisible radiation-dependent photoluminescence and good affinity with finger residues, the in situ synthesized Au NC-BSA/MMT nanocomposite powders were used as an alternative fluorescent developing reagent for developing latent fingermarks deposited on various object surfaces(such as glass, aluminum foil, painted metal, plastic products and weighing papers) for individual identification. As results, the developed fingermarks with clear patterns and satisfactory level-2(minutiae points) and level-3(sweat pores) ridge details were obtained. Notably, treated prints could be excited by red light and emitted near infrared fluorescence, which was beneficial to avoid background interference and reduce the damage caused by UV light. With the advantages of the simple preparation process and good enhancement performance for latent fingermarks, the proposed method might be used in the preparation of various fluorescent probes for detecting trace evidence in forensic sciences.

Optical Properties of Au Nanoparticles Coated on Surface of Glass or Anodic Aluminum Oxide Template

Au nanoparticles coated on the surface of glass （Sample A） or on anodic aluminum oxide template surface （Sample B） were prepared using titanium dioxide sol-gel doped with chloroauric acid and with a reduction process. FE-SEM, UV-Vis spectrum and Fluorescence spectrum tests show that Au nanoparticles have been distributed randomly on the surface of glass, while deposition occurs on the surface of regular hollows for anodic aluminum oxide template. A sharp absorption peak appears at the wavelength of 536 nm for sample B, while there is a red shift, with a broader peak for sample A. A distinct fluorescence emission at the wavelength of 633 nm is detected for sample A, but no noticeable fluorescence emission has been found for Sample B. The results indicate that the microstructure and optical properties of Au nanoparticles can be modulated by different substrate.

A turn-on fluorescent probe for Au^(3+) based on rodamine derivative and its bioimaging application

A new fluorescent probe RY was synthesized for the detection of Au3+ions based on a rhodamine B derivative.The fluorescent probe showed good selectivity and sensitivity to Au3+ions.Obvious color and fluorescence changes could be observed with the naked eye while the fluorescent probe reacted with the Au3+ions.The detection limit of the probe was determined to be 36 ppb by the fluorescence titration.The excellent linear relationship suggests that the probe is potentially useful for quantitative detection of Au3+in vitro.We also demonstrated its bioimaging application in both living cells and mice.This was the first time that a fluorescent probe was successfully applied to imaging Au3+in living animals.

Theranostic gold cluster nanoassembly for simultaneous enhanced cancer imaging and photodynamic therapy

As one of near-infrared（NIR） fluorescent（FL） nanoprobes, gold nanoclusters（Au NCs） are delicated to passive-targeting tumors for NIR FL imaging, but which easily cleared by the kidneys for the small size（〈1.5 nm）. Herein, the well-defined gold clusters nanoassembly（Au CNA） was synthesized by the selfassembly of Au NCs based on protein cross-linking approach. The as-prepared Au CNA demonstrated highly effective cellular uptake and precise tumor targeting compared to that of Au NCs. Moreover, with the irradiation of 660 nm laser, Au CNA generated largely reactive oxygen species（ROS） for photodynamic therapy（PDT）. In vitro and [39TD$IF]in vivo PDT revealed that Au CNA exhibited largely cell death and significantly tumor removal at a low power density of 0.2 W/cm^2. It could be speculated that the laser-excited Au CNA produced photon energy, which further obtained electron from oxygen to generate radical species.Therefore, Au CNA as a photosensitizer could realize NIR FL imaging and NIR laser induced PDT.

Ovalbumin-stabilized gold nanoclusters with ascorbic acid as reducing agent for detection of serum copper

Ovalbumin-stabilized gold nanoclusters （OVA@AuNCs） were prepared with ascorbic acid as a reducing agent. This strategy could realize the synthesis of water-soluble OVA@AuNCs within 20 min. The asprepared fluorescent probe showed a red fluorescence emission at 630 nm. Moreover, the properties of the OVA@AuNCs were characterized by transmission electron microscope, dynamic light scattering, ultraviolet-visible spectroscopy, fluorescent spectroscopy. Based on the surface electron density decrease-induced fluorescence quenching mechanism, the OVA@AuNCs provided high sensitivity and selectivity for sensing copper ions. A good linear relationship was obtained between the fluorescence intensity of OVA@AuNCs and the concentration of copper ions in the range of 5.0-100.0pumol/L （R2z0.999） with a detection limit of 640 nmol/L. Furthermore, the rat serum copper contents were determined by using the OVA@AuNCs based assay, indicating great potential of fluorescent probes for application in biological and clinical analysis.