Single Nanoparticle-Based Heteronanojunction as a Plasmon Ruler for Measuring Dielectric Thin Films

Abstract

Nondestructive, noninvasive and accurate measurement of thin film thicknesses on dielectric substrates is challenging. In this work a ruler for measuring thin film thicknesses utilizes the heteronanojunction construct formed between a plasmonic nanoparticle and a high refractive index nonplasmonic substrate. The high near-field sensitivity in the nanojunction renders it suitable for measuring the thickness of intervening dielectric thin films. We demonstrate this by controlling the thickness of dielectric spacer layers created by overgrowing SiO2 thin films on commercially available silicon substrates. While Rayleigh (using dark-field) scattering measurements show that the spectral response is well correlated to the thickness of SiO2 spacer layers the distance-dependence is much steeper with surface-enhanced Raman scattering (SERS). Good agreement between 3D simulations and experimental results confirm the plasmon ruler construct’s sensitivity to the dielectric thin film spacing. Thus, we postulate that this single nanoparticle based heteronanojunction configuration can serve as a convenient and simple ruler in metrology of thin films as well as a platform for SERS-based detection even in cases where plasmonically active films are not a suitable substrate.

Construction of a Graphene/Au‐Nanoparticles/Cucurbit[7]uril‐Based Sensor for Pb2+ Sensing

“…[4] Such NPOM configuration not only serves as ah ighly sensitiveS ERS sensor that permits single-molecule detection [5] and monitoring of interfacial reactions, [6] but also is very useful for metrology applications. [7] Despite these versatile applications, the NPOM-based SERS platform lacks the selectivity that is particularly critical for real sample analysis. The cucurbit[n]urils (CB[n]), af amily of supramolecular hosts with rich host-guest chemistry,h ave been recently employedi nc onstructing selectivem olecular-recognition-based SERS assay.F or example, Mahajan et al [8] reported CB-mediated assembly of AuNPs,i nw hichC Bn ot only functioned as ap recise rigid molecular spacer that produced highly-controllable hot spot nanojunctions, but it also acted as aS ERS reporter for as elf-calibrated in situ SERS sensor.…”

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The development of highly sensitive and selective methods fort he detection of lead ion (Pb 2 + )i so fg reat scientific importance.I nt his work, we developan ew surfaceenhanced Raman scattering (SERS)-baseds ensor for the selective trace measurement of Pb 2 + .T he SERS-based sensor is assembled from gold nanoparticles (AuNPs)a nd graphene using cucurbit[7]uril( CB[7]) as ap recise molecular glue and al ocal SERS reporter.U pon the addition of Pb 2 + ,C B [7] forms stronger complexes with Pb 2 + and desorbs from AuNPs, resulting in as ensitive "turn-off"o fS ERS signals. This SERS-based assay shows al imit of detection( LOD) of 0.3nm and al inear detection range from 1nm to 0.3 mm for Pb 2 + .

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Single-Particle Plasmon Voltammetry (spPV) for Detecting Anion Adsorption

“…23 In the case of nanoparticle plasmon probes, anion adsorption on single nanoparticle surfaces has been detected through changes in nanoparticle plasmon resonances. 4,5,14 Based on previous work on the role of substrates in the engineering of plasmonic nanoparticles [24][25][26][27] (through interaction of multiple nanoparticles and substrate material) and plasmonic sensing applications, [28][29][30][31] we hypothesize that the optoelectronic and electrochemical properties of the substrate may also play an important role in single-nanoparticle plasmonic electrochemical sensing.…”

Bio-surface engineering with DNA scaffolds for theranostic applications

“…AuNPs have unique optical and electronic properties, and therefore have shown great potential as a building block for an extensive range of applications that include diagnostics [98], drug delivery [99], and plasmonics [100][101][102][103]. It is therefore of great interest to create effective DNA recognition layers on the AuNP surface for various applications.…”