Free-Standing Monolayered Metallic Nanoparticle Networks as Building Blocks for Plasmonic Nanoelectronic Junctions

Plasmon-Boosted Cu-Doped TiO2 Oxygen Vacancy-Rich Luminol Electrochemiluminescence for Highly Sensitive Detection of Alkaline Phosphatase

In this study, an effective oxygen vacancy (O_v)-involved luminol-dissolved oxygen (O₂) electrochemiluminescence (luminol-DO ECL) system was developed and exploited for ECL sensing applications through significant plasmon enhancement of the O_v-involved weak luminol-DO ECL signals by the combined use of Cu-doped TiO₂ oxygen vacancy and a Au@SiO₂ nanomembrane. The results disclosed that the ECL response of the corresponding system could be synergistically boosted, and the plausible underlying mechanism has been discussed. Furthermore, for the first time, the developed system has been successfully applied for the highly sensitive detection of alkaline phosphatase with a low limit of detection of 0.005 U/L, with an excellent linear range from 0.005 to 10 U/L, as well as good stability and reproducibility.

Two-Dimensional-Plasmon-Boosted Iron Single-Atom Electrochemiluminescence for the Ultrasensitive Detection of Dopamine, Hemin, and Mercury

Single-atom catalysts (SACs) have recently been exploited for luminol-dissolved oxygen electrochemiluminescence (ECL); however, they still suffer from low sensitivity and narrow detection range for a real sample assay. In this work, we boost markedly the ECL response of the iron SAC (Fe-SAC)-based system, for the first time, by the excitation of two-dimensional plasmons derived from the Au@SiO₂ nanomembrane. The plausible mechanism of plasmon enhancement in the Fe-SAC ECL system has been discussed. The constructed Fe-SAC ECL system has been applied for the ECL detection of dopamine, hemin, and mercury (Hg²⁺), with pretty low limits of detection of 0.1, 0.7, and 0.13 nM and wider linear ranges of 0.001-1.0, 0.001-10, and 0.01-0.5 nM, respectively, under optimal conditions.

Unprecedented efficient electron transport across Au nanoparticles with up to 25-nm insulating SiO2-shells

Quantum tunneling is the basis of molecular electronics, but often its electron transport range is too short to overcome technical defects caused by downscaling of electronic devices, which limits the development of molecular-/nano-electronics. Marrying electronics with plasmonics may well present a revolutionary way to meet this challenge as it can manipulate electron flow with plasmonics at the nanoscale. Here we report on unusually efficient temperature-independent electron transport, with some photoconductivity, across a new type of junction with active plasmonics. The junction is made by assembly of SiO₂ shell-insulated Au nanoparticles (Au@SiO₂ NPs) into dense nanomembranes of a few Au@SiO₂ layers thick and transport is measured across these membranes. We propose that the mechanism is plasmon-enabled transport, possibly tunneling (as it is temperature-independent). Unprecedentedly ultra-long-range transport across one, up to even three layers of Au@SiO₂ in the junction, with a cumulative insulating (silica) gap up to 29 nm/NP layer was achieved, well beyond the measurable limit for normal quantum mechanical tunneling across insulators (~2.5 nm at 0.5–1 V). This finding opens up a new interdisciplinary field of exploration in nanoelectronics with wide potential impact on such areas as electronic information transfer.

Plasmonics Yields Efficient Electron Transport via Assembly of Shell-Insulated Au Nanoparticles

Junctions built from metallic nanoparticles (NPs) can circumvent the diffraction limit and combine molecular/nanoelectronics with plasmonics. However, experimental advances in plasmon-assisted electron transport at the nanoscale have been limited. We construct junctions of a robust, molecule-free, suspended film, built solely from AuNPs, capped by SiO₂ shells (Au@SiO₂), which give insulating tunneling gaps up to 3.6 nm between the NPs. Current measured across monolayers of such AuNPs shows ultra-long-range, plasmon-enabled electron transport (P-transport), beyond the range of normal electron tunneling across insulators. This finding challenges the present understanding of electron transport in such systems and opens possibilities for future combinations of plasmonics and nanoelectronics.

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A robust, molecule-free Au@SiO₂ nanofilm-based plasmonic circuit is fabricated

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It shows unusual long-range electron transport across AuNPs with 3.6-nm silica gap

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LSPR coupling plays a crucial role on the ultra-long-range electron transport

Free-standing monolayer films of ordered colloidal particles

We report a novel method for the fabrication of large area, free standing monolayer films of close-packed colloidal particles. The method involves creating a free-standing, wet film of colloidal dispersion containing mono-dispersed hard particles (such as polystyrene or silica) mixed with smaller and softer polymer particles. During drying, hard particles present in the free standing film arrange in a hexagonal close-packed structure in a monolayer while the softer particles fill the interstices, and deform and coalesce to produce a continuous matrix around the hard particles. The deformation of the soft particles dissipates the stress generated during drying thereby preventing rupture of the monolayer film. The method is facile and very general, applicable to a large variety of colloidal particles. The monolayer films exhibit strong iridescence indicating potential application in photonic devices.

Silver-functionalized g-C3N4 nanohybrids as signal-transduction tags for electrochemical immunoassay of human carbohydrate antigen 19-9

A simple and feasible electrochemical immunosensing platform was developed for highly efficient screening of a disease-related protein (human carbohydrate antigen 19-9, CA 19-9 used in this case) using silver-functionalized g-C3N4 nanosheets (Ag/g-C3N4) as signal-transduction tags. Initially, Ag/g-C3N4 nanohybrids were synthesized by combining thermal polymerization of the melamine precursor with the photo-assisted reduction method. Thereafter, the as-synthesized Ag/g-C3N4 nanohybrids were utilized for the labeling of the anti-CA 19-9 detection antibody by using a typical carbodiimide coupling method. The assay was carried out on a capture antibody-modified glassy carbon electrode in a sandwich-type detection mode. The detectable signal mainly derived from the voltammetric characteristics of the immobilized nanosilver particles on the g-C3N4 nanosheets within the applied potentials. Under the optimal conditions, the voltammetric peak currents increased with the increasing amount of target CA 19-9, and exhibited a wide linear range from 5.0 mU mL(-1) to 50 U mL(-1) with a detection limit of 1.2 mU mL(-1). Our strategy also displayed good reproducibility, precision and specificity. The results of the analysis of clinical serum specimens were in good accordance with the results obtained by an enzyme-linked immunosorbent assay (ELISA) method. The newly developed immunosensing system is promising for enzyme-free and cost-effective analysis of low-abundance proteins.