Carbogenically coated silica nanoparticles and their forensic applications

Abstract

Carbogenically coated silica nanoparticles (C-SiO2) exhibit color-tunability and carry great promise for two important forensic applications. First, the C-SiO2 nanopowders are ideal for fingerprint development, yielding strong contrast against multicoloured and patterned backgrounds. Second, spontaneous nanoparticle aggregation leads to non-duplicable, inexpensive nanotags that can support sustainable technologies to combat counterfeiting.

Dramatic photoluminescence quenching in carbon dots induced by cyclic voltammetry

“…Owing to this unique combination of promising properties, C-dots are systematically explored in optoelectronics 11 , solar photovoltaics 12 , bio-imaging 13 , cancer therapy 13 , photocatalysis 14 and chemical sensing 15 . In addition, interest lies on the development of a new generation of antimicrobials 16 , forensic materials 17,18 and nanothermometers 19 . Although, the PL mechanism is not fully understood, four contributions have been recognised associated to edge and surface defects, quantum confinement of sp 2 islands, crosslink enhanced emission and the presence of organic chromophores, respectively 20 .…”

Carbon Dots for Forensic Applications: A Critical Review

“…The working principle for security nano-barcodes based on C-dots is based on their unique optical properties, which can give rise to a potentially unlimited range of unclonable motifs and prints that are nearly impossible to decode and reverse-engineer. Fernandes et al [42] demonstrated that their previously mentioned C-SiO 2 nanoparticles lost colloidal stability when the pH of their medium dropped below 8.5, thereafter undergoing spontaneous aggregation as their aqueous medium evaporated and generating complex superstructures ( Figure 7) in a nondeterministic manner. These structures would be impossible to duplicate and are therefore ideal for identification and authentication labelling [56].…”

“…The working principle for C-dot-based compositions for fingerprint recovery lies in the fact that they adopt different colours when illuminated by different light sources, enabling background-free images and maximising the reliability of fingerprint analysis. While C-dots in the solid state have a tendency to self-quench [39], several strategies have been proposed to overcome this effect, including the use of a diluent matrix [40,41], the development of core-shell nanostructures [42], the incorporation of heteroatom doping [43,44], exploitation of effects such as resonance energy transfer [RET] and π-π interactions [45] and the use of molecular spacers [46]. C-dot-based powders for fluorescent visualisation of latent fingerprints were first demonstrated by Fernandes et al [40], who showed that the incorporation of 0.7 wt.…”

“…Further work by Fernandes and colleagues [42] was focused on carbogenically-coated silica nanoparticles (C-SiO 2 ) prepared by treating silica nanoparticles with dimethyloctadecyl [3-(trimethoxysilyl)propyl]ammonium chloride, followed by pyrolysis, surface oxidation with nitric acid, amine functionalisation and, ultimately, dialysis against water. The nanoparticles had an average diameter of 22 nm and contained C (26%), H (4%) and N (5%).…”

Construction of core-shell hybrid nanoparticles templated by virus-like particles

“…Organic-inorganic hybrid nanoparticles (NPs) with combined functionalities have attracted great interest in recent years. [1][2][3][4][5][6][7][8] In particular, environmentally friendly and low-cost plant virus based hybrid materials have been widely studied [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] due to their promising applications in biomedicine, electronic devices and vaccine storage. [28][29][30][31][32][33][34][35][36][37][38][39][40][41] The advantages of using viruses as templates are: (i) these are monodisperse NPs with a high level of symmetry, which is suitable for the construction of uniform nanoparticles; and (ii) many of the virus NPs are stable over wide pH and temperature ranges, which makes them applicable for the synthesis of hybrid NPs.…”