Hotspot generation for unique identification with nanomaterials

Abstract

Nanoscale variations in the structure and composition of an object are an enticing basis for verifying its identity, due to the physical complexity of attempting to reproduce such a system. The biggest practical challenge for nanoscale authentication lies in producing a system that can be assessed with a facile measurement. Here, a system is presented in which InP/ZnS quantum dots (QDs) are randomly distributed on a surface of an aluminium-coated substrate with gold nanoparticles (Au NPs). Variations in the local arrangement of the QDs and NPs is shown to lead to interactions between them, which can suppress or enhance fluorescence from the QDs. This position-dependent interaction can be mapped, allowing intensity, emission dynamics, and/or wavelength variations to be used to uniquely identify a specific sample at the nanoscale with a far-field optical measurement. This demonstration could pave the way to producing robust anti-counterfeiting devices.

Encapsulation of Cadmium‐Free InP‐based Quantum Dots in Cross‐Linked Core‐Shell Microparticles via Coaxial Electrospraying

“…The majority of recent publications on QD encapsulation via electrohydrodynamic atomization techniques have predominately focused on Cd-based QDs, and mainly either on the deposition of films containing QDs or electrospinning of QD-infiber composites. [30][31][32][33][34][35][36][37][38][39][40][41][42][43] Only a few studies investigated the incorporation of Cd-based QDs into polymer microparticles via electrospraying, using poly(styrene-acrylate) or a triblock copolymer polystyrene-b-poly(ethylene-butylene)-b-polystyrene (Kraton or SEBS) as host materials. [44,45] To the authors' knowledge, protection of InP-based QDs by electrospraying remains underexplored in general, only recently the first papers on this topic have started to get published, for example by Ahn et al who embedded InP/ZnSeS/ZnS QDs in alumina Al 2 O 3 microbeads.…”

Tattoo‐Like Multi‐Color Physically Unclonable Functions

“…The unique excitation and emission wavelengths together with the other characteristics, e.g., fluorescence lifetime, offer a variety of options in the design and manufacture of unclonable surfaces. PUFs based on organic semiconductors, [4][5][6] photonic polymeric nanospheres, [7,8] metal nanodisks, [9] carbon dots, [10,11] lanthanide-doped zeolites, [12] organic molecules, [13][14][15][16] genetically engineered silk, [17,18] and semiconductor nanocrystals [19][20][21][22][23][24][25][26][27] have been reported recently. Colloidal semiconductors are especially appealing because their optical response is determined by quantum confinement and can be fine-tuned with modulation of their composition and size.…”

“…Fluorescent PUFs have been developed by ink-jet printing of quantum dots on surfaces with stochastic pinning points. [20][21][22][23] Highlighted by these studies, semiconductor nanocrystals are suitable materials for fabricating PUFs. Practical PUF applications require the ability to directly deposit multiple semiconductor nanocrystals over large surfaces with spatial positions determined in a stochastic process.…”

Unclonable Features via Electrospraying of Bulk Polymers

“…Thanks to the acting Coulomb repulsion to the droplets during electrospraying, these droplets can self-separate without being agglomerated, and the positions on the surfaces are random due to the chaotic trajectories they follow. , Inspired by the inherently stochastic nature, we propose electrospraying as a universally applicable fabrication method for the generation of unclonable features for PUF applications. In one example, Young and co-workers used electrospraying as a form of deposition of quantum dots over a drop-cast layer of gold nanoparticles coated with titanium dioxide films to study the formation of hot-spots for PUF applications. To the best of our knowledge, electrospraying of bulk polymers to fabricate PUFs has not been reported.…”