Exploring Plasmonic Standalone Surface-Enhanced Raman Scattering Nanoprobes for Multifaceted Applications in Biomedical, Food, and Environmental Fields.

Surface-enhanced Raman scattering (SERS) is an innovative spectroscopic technique that amplifies the Raman signals of molecules adsorbed on rough metal surfaces, making it pivotal for single-molecule detection in complex biological and environmental matrices. This review aims to elucidate the design strategies and recent advancements in the application of standalone SERS nanoprobes, with a special focus on quantifiable SERS tags. We conducted a comprehensive analysis of the recent literature, focusing on the development of SERS nanoprobes that employ novel nanostructuring techniques to enhance signal reliability and quantification.

A MOF-Templated Double-Shelled CoO/NiCoO Nanocomposite for Electrochemical Detection of Alfuzosin.

We developed a novel electrochemical sensor for the detection of alfuzosin (AFZ), a drug used to treat benign prostatic hyperplasia, using a double-shelled CoO/NiCoO nanocomposite-modified electrode. The nanocomposites were synthesized using a template-assisted approach, with zeolitic imidazole framework-67 (ZIF-67) as the sacrificial template, involving the formation of uniform ZIF-67/Ni-Co layered double hydroxide (LDH) hollow structures followed by calcination to achieve the final nanocomposite. The nanocomposite was characterized by various techniques and showed high porosity, large surface area, and good conductivity.

Polysorbate- and DNA-Mediated Synthesis and Strong, Stable, and Tunable Near-Infrared Photoluminescence of Plasmonic Long-Body Nanosnowmen.

Direct photoluminescence (PL) from metal nanoparticles (NPs) without chemical dyes is promising for sensing and imaging applications since this offers a highly tunable platform for controlling and enhancing the signals in various conditions and does not suffer from photobleaching or photoblinking. It is, however, difficult to synthesize metal NPs with a high quantum yield (QY), particularly in the near-infrared (NIR) region where deep penetration and reduced light scattering are advantageous for bioimaging. Herein, we designed and synthesized Au-Ag long-body nanosnowman structures (LNSs), facilitated by polysorbate 20 (Tween 20).

Nontrivial, Unconventional Electrochromic Behaviors of Plasmonic Nanocubes.

Plasmonic electrochromism, a change in the localized surface plasmon resonance (LSPR) with an applied electric potential, has been attracting increasing attention for the development of spectroscopic tools or optoelectronic systems. There is a consensus on the mechanism of plasmonic electrochromism based on the classical capacitor and the Drude model. However, the electrochromic behaviors of metallic nanoparticles in narrow optical windows have been demonstrated only with small monotonic LSPR shifts, which limits the use of the electrochromism.

Electrochromic response and control of plasmonic metal nanoparticles.

Plasmonic electrochromism, the dependence of the colour of plasmonic materials on the applied electrical potential, has been under the spotlight recently as a key element for the development of optoelectronic devices and spectroscopic tools. In this review, we focus on the electrochromic behaviour and underlying mechanistic principles of plasmonic metal nanoparticles, whose localised surface plasmon resonance occurs in the visible part of the electromagnetic spectrum, and present a comprehensive review on the recent progress in understanding and controlling plasmonic electrochromism. The mechanisms underlying the electrochromism of plasmonic metal nanoparticles could be divided into four categories, based on the origin of the LSPR shift: (1) capacitive charging model accompanying variation in the Fermi level, (2) faradaic reactions, (3) non-faradaic reactions, and (4) electrochemically active functional molecule-mediated mechanism.

Development of a Tough, Self-Healing Polyampholyte Terpolymer Hydrogel Patch with Enhanced Skin Adhesion via Tuning the Density and Strength of Ion-Pair Associations.

Polyampholyte (PA) hydrogels have great potential for biomedical applications, owing to their high toughness and good self-recovery and self-healing (SELF) behavior in addition to their physical properties similar to human tissue. However, their implementation as practical biomedical skin patches or wearable devices has so far been limited by their insufficient transdermal adhesion strength. In this work, a new polyampholytic terpolymer (PAT) hydrogel with enhanced skin adhesion was developed using a novel and simple strategy that tunes the structure of ion-pair associations (IPAs), acting as cross-links, in the hydrogel via adding an extra neutral monomer component into the network without changing the total charge balance.

One-Pot Heterointerfacial Metamorphosis for Synthesis and Control of Widely Varying Heterostructured Nanoparticles.

Despite remarkable facileness and potential in forming a wide variety of heterostructured nanoparticles with extraordinary compositional and structural complexity, one-pot synthesis of multicomponent heterostructures is largely limited by the lack of fundamental mechanistic understanding, designing principles, and well-established, generally applicable chemical methods. Herein, we developed a one-pot heterointerfacial metamorphosis (1HIM) method that allows heterointerfaces inside a particle to undergo multiple equilibrium stages to form a variety of highly crystalline heterostructured nanoparticles at a relatively low temperature (<100 °C). As proof-of-concept experiments, it was shown that widely different single-crystalline semiconductor-metal anisotropic nanoparticles with synergistic chemical, spectroscopic, and band-gap-engineering properties, including a series of metal-semiconductor nanoframes with high structural and compositional tunability, can be formed by using the 1HIM approach.

Direct observation and catalytic role of mediator atom in 2D materials.

The structural transformations of graphene defects have been extensively researched through aberration-corrected transmission electron microscopy (AC-TEM) and theoretical calculations. For a long time, a core concept in understanding the structural evolution of graphene defects has been the Stone-Thrower-Wales (STW)-type bond rotation. In this study, we show that undercoordinated atoms induce bond formation and breaking, with much lower energy barriers than the STW-type bond rotation.

Surface-enhanced Raman scattering-based detection of hazardous chemicals in various phases and matrices with plasmonic nanostructures.

Surface-enhanced Raman scattering (SERS)-based sensors utilize the electromagnetic-field enhancement of plasmonic substrates with the chemical specificity of vibrational Raman spectroscopy to identify trace amounts of a wide variety of different target analytes while being minimally affected by photobleaching. However, despite many advantageous features of this method, SERS sensors, particularly for detecting hazardous chemicals, suffer from several limitations such as requirement of gigantic signal enhancement that is often poorly controllable, subtle change and degradation of the SERS substrate, consecutive fluctuation of the signal, the lack of reliable receptors for capturing targets of interest and the absence of general principles for detecting various chemicals in different phases and matrices. To overcome these limitations and for SERS sensors to find practical use, one must (1) acknowledge the characteristics of the matrices of target systems, (2) finely engineer and tune the receptors of the SERS sensor to properly extract the target analyte from the phase, and (3) implement additional mechanistic modifications to enhance the plasmonic signal.

Plasmonic Nanoparticle-Interfaced Lipid Bilayer Membranes.

Plasmonic nanoparticles are widely exploited in diverse bioapplications ranging from therapeutics to biosensing and biocomputing because of their strong and tunable light-matter interactions, facile and versatile chemical/biological ligand modifications, and biocompatibility. With the rapid growth of nanobiotechnology, understanding dynamic interactions between nanoparticles and biological systems at the molecular or single-particle level is becoming increasingly important for interrogating biological systems with functional nanostructures and for developing nanoparticle-based biosensors and therapeutic agents. Therefore, significant efforts have been devoted to precisely design and create nano-bio interfaces by manipulating the nanoparticles' size, shape, and surface ligand interactions with complex biological systems to maximize their performance and avoid unwanted responses, such as their agglomeration and cytotoxicity.

Transformative Heterointerface Evolution and Plasmonic Tuning of Anisotropic Trimetallic Nanoparticles.

Multicomponent nanoparticles that incorporate multiple nanocrystal domains into a single particle represent an important class of material with highly tailorable structures and properties. The controlled synthesis of multicomponent NPs with 3 or more components in the desired structure, particularly anisotropic structure, and property is, however, challenging. Here, we developed a polymer and galvanic replacement reaction-based transformative heterointerface evolution (THE) method to form and tune gold-copper-silver multimetallic anisotropic nanoparticles (MAPs) with well-defined configurations, including structural order, particle and junction geometry, giving rise to extraordinarily high tunability in the structural design, synthesis and optical property of trimetallic plasmonic nanoantenna structures.

Associating and Dissociating Nanodimer Analysis for Quantifying Ultrasmall Amounts of DNA.

The amplification- and enzyme-free quantification of DNA at ultralow concentrations, on the order of 10-1000 targets, is highly beneficial but extremely challenging. To address this challenge, true detection signals must be reliably discriminated from false or noise signals. Herein, we describe the development of associating and dissociating nanodimer analysis (ADNA) as a method that enables a maximum number of detection signals to be collected from true target-binding events while keeping nonspecific signals at a minimum level.

Plasmonic Nanogap-Enhanced Raman Scattering with Nanoparticles.

Plasmonic coupling-based electromagnetic field localization and enhancement are becoming increasingly important in chemistry, nanoscience, materials science, physics, and engineering over the past decade, generating a number of new concepts and applications. Among the plasmonically coupled nanostructures, metal nanostructures with nanogaps have been of special interest due to their ultrastrong electromagnetic fields and controllable optical properties that can be useful for a variety of signal enhancements such as surface-enhanced Raman scattering (SERS). The Raman scattering process is highly inefficient, with a very small cross-section, and Raman signals are often poorly reproducible, meaning that very strong, controllable SERS is needed to obtain reliable Raman signals with metallic nanostructures and thus open up new avenues for a variety of Raman-based applications.

Synthesis, Optical Properties, and Multiplexed Raman Bio-Imaging of Surface Roughness-Controlled Nanobridged Nanogap Particles.

Plasmonic nanostructures are widely studied and used because of their useful size, shape, composition and assembled structure-based plasmonic properties. It is, however, highly challenging to precisely design, reproducibly synthesize and reliably utilize plasmonic nanostructures with enhanced optical properties. Here, we devise a facile synthetic method to generate Au surface roughness-controlled nanobridged nanogap particles (Au-RNNPs) with ultrasmall (≈1 nm) interior gap and tunable surface roughness in a highly controllable manner.

Electrochemical detection of nanomolar dopamine in the presence of neurophysiological concentration of ascorbic acid and uric acid using charge-coated carbon nanotubes via facile and green preparation.

Negatively charged multi-walled carbon nanotubes (MWCNTs) were prepared using simple sonication technique with non-toxic citric acid (CA) for the electrochemical detection of dopamine (DA). CA/MWCNTs were placed on glassy carbon (GC) electrodes by drop-casting method and then electrochemical determinations of DA were performed in the presence of highly concentrated ascorbic acid (AA). For the comparison of the charge effect on MWCNTs surface, positively charged polyethyleneimine (PEI)/MWCNT/GC electrode and pristine MWCNT/GC electrode were also prepared.

Controlled Co-Assembly of Nanoparticles and Polymer into Ultralong and Continuous One-Dimensional Nanochains.

We report a robust one-dimensional (1D) nanoparticle-assembly strategy that uses the self-assembly of nanoparticles with ligand and thermal controls, polyethylene glycol (PEG) with thiol and carboxyl groups, and nanoparticle oligomer and polymer codewetting process to form ultralong and continuous 1D nanochains. The 1D nanochains were assembled with closely packed 1D nanoparticle oligomer building blocks, elongated and buttressed by dynamic 1D PEG templates formed on a hydrophobic surface via anisotropic spinodal dewetting. Using this strategy, nanoparticle-packed 1D nanochains (∼1 nm interparticle spacing) were fabricated with ∼60 nm-width and a few to >10 μm-length (nearly 20 μm in some cases) from 20 nm gold nanoparticles.

Thiolated DNA-based chemistry and control in the structure and optical properties of plasmonic nanoparticles with ultrasmall interior nanogap.

The design, synthesis and control of plasmonic nanostructures, especially with ultrasmall plasmonically coupled nanogap (∼1 nm or smaller), are of significant interest and importance in chemistry, nanoscience, materials science, optics and nanobiotechnology. Here, we studied and established the thiolated DNA-based synthetic principles and methods in forming and controlling Au core-nanogap-Au shell structures [Au-nanobridged nanogap particles (Au-NNPs)] with various interior nanogap and Au shell structures. We found that differences in the binding affinities and modes among four different bases to Au core, DNA sequence, DNA grafting density and chemical reagents alter Au shell growth mechanism and interior nanogap-forming process on thiolated DNA-modified Au core.

Massively parallel and highly quantitative single-particle analysis on interactions between nanoparticles on supported lipid bilayer.

Observation of individual single-nanoparticle reactions provides direct information and insight for many complex chemical, physical, and biological processes, but this is utterly challenging with conventional high-resolution imaging techniques on conventional platforms. Here, we developed a photostable plasmonic nanoparticle-modified supported lipid bilayer (PNP-SLB) platform that allows for massively parallel in situ analysis of the interactions between nanoparticles with single-particle resolution on a two-dimensional (2D) fluidic surface. Each particle-by-particle PNP clustering process was monitored in real time and quantified via analysis of individual particle diffusion trajectories and single-particle-level plasmonic coupling.

Chiral gold nanoparticle-based electrochemical sensor for enantioselective recognition of 3,4-dihydroxyphenylalanine.

The enantioselective recognition of 3,4-dihydroxyphenylalanine using penicillamine-modified gold nanoparticles has been investigated. Smaller gold nanoparticles with one enantiomeric ligand facilitate the redox reaction of only one enantiomer of 3,4-dihydroxyphenylalanine, with cross inversion for the gold nanoparticles with the other enantiomeric ligand.

Enhanced electrogenerated chemiluminescence of a ruthenium tris(2,2')bipyridyl/tripropylamine system on a boron-doped diamond nanograss array.

Significant enhancement of the ECL signals from the Ru(bpy)(3)(2+)/TPA system was achieved when using a BDD nanograss array, mainly because of the highly facile oxidation of TPA. The facile oxidation of TPA is due to the superior properties of the BDD nanograss array, such as improved electrocatalytic activity and accelerated electron transfer.

Highly sensitive detection of DNA by electrogenerated chemiluminescence amplification using dendritic Ru(bpy)(3)(2+)-doped silica nanoparticles.

This study describes the development and characterization of a novel dendritic signal amplification strategy. It relies on the use of two different Ru(bpy)(3)(2+)-doped silica nanoparticles (Probe(1,2)RSNP and Probe(2c)RSNP) coated with complementary DNAs, which can be simply and conveniently self-assembled to build sandwich-type dendritic architectures on a gold grid. The performance of this dendritic amplification route was demonstrated in conjunction with the electrogenerated chemiluminescent (ECL) detection of the target DNA.

A regenerative electrochemical sensor based on oligonucleotide for the selective determination of mercury(II).

We have developed a selective, sensitive, and re-usable electrochemical sensor for Hg2+ ion detection. This sensor is based on the Hg2+-induced conformational change of a single-stranded DNA (ssDNA) which involves an electroactive, ferrocene-labeled DNA hairpin structure and provides strategically the selective binding of a thymine-thymine mismatch for the Hg2+ ion. The ferrocene-labeled DNA is self-assembled through S-Au bonding on a polycrystalline gold electrode surface and the surface blocked with 3-mercapto-1-propanol to form a mixed monolayer.

Enhancement of electrogenerated chemiluminescence and radical stability by peripheral multidonors on alkynylpyrene derivatives.

A very generous donor: The electrochemiluminescence (ECL) efficiency and radical stability of pyrene, a poor ECL luminophore, are markedly improved as the number of peripheral multidonor units increased in a series of compounds (see picture). Photophysical and electrochemical studies and theoretical calculations have contributed to the understanding of the ECL enhancement, which is a step forward in the development of new light-emitting materials.