SERS-Based Aptamer Sensing Strategy for Diabetes Biomarker Detection.

Accurate detection of glucose and insulin is crucial for early diagnosis, classification, and timely prevention of diabetes. In this study, we present a novel surface-enhanced Raman scattering (SERS) aptasensor for glucose and insulin detection. The SERS aptasensor is composed of gold bipyramidal nanoparticles (Au BPs), SH-aptamer-methylene blue (MB), and thiolated polyethylene glycol (SH-PEG).

SERS Sensor for Acetylcholine Detection Based on Covalent Organic Framework Hybridized Gold Nanoparticles As Nanozymes.

An innovative and potent nanozyme with reductase-like activity was developed by integrating the in situ synthesis of gold nanoparticles (Au NPs) onto the surface of a covalent organic framework (COF). Based on the reductase-like activity of the COF-hybridized Au NPs, this nanozyme could efficiently catalyze the reduction of 4-nitrophenol (4-NPH). Moreover, the prepared nanohybrid was utilized as an excellent surface-enhanced Raman scattering (SERS) substrate for highly sensitive SERS detection by combining the excellent adsorption properties of COFs and the large number of Raman hotspots between the high-density Au NPs.

Three-dimensional NTF-Ag composites for ultrasensitive SERS-based detection of malachite green on crucian carp skin.

Three-dimensional (3D) NaTiO flower (NTF) systems were synthesized, followed by sputter coating with silver (Ag) nanoparticles to increase surface-enhanced Raman scattering (SERS) activity. By varying the sputtering time, SERS activity of the Ag-decorated NTF (NTF-Ag) structures was optimized. Furthermore, the theoretical evidence from finite difference time domain (FDTD) simulations confirmed that an appropriate density of Ag particles increased the electromagnetic field contribution.

Configurational Isomerization-Induced Orientation Switching: Non-Fused Ring Dipodal Phosphonic Acids as Hole-Extraction Layers for Efficient Organic Solar Cells.

Phosphonic acid (PA) self-assembled molecules have recently emerged as efficient hole-extraction layers (HELs) for organic solar cells (OSCs). However, the structural effects of PAs on their self-assembly behaviors on indium tin oxide (ITO) and thus photovoltaic performance remain obscure. Herein, we present a novel class of PAs, namely "non-fused ring dipodal phosphonic acids" (NFR-DPAs), featuring simple and malleable non-fused ring backbones and dipodal phosphonic acid anchoring groups.

Covalent organic framework-hybridized Ag nanoparticles as SERS substrate for highly sensitive detection of DNA bases.

Currently, research in the development of high-performance sensing platforms has increased to fulfill the needs of analysis and detection. In this study, we developed a novel type of surface-enhanced Raman scattering (SERS) chip composed of a covalent organic framework (COF)-silver nanoparticles (AgNPs) nanocomposite, and this nanocomposite was fabricated by a one-step method of ultrasonically mixing the obtained COF and AgNPs. The fabricated chip exhibited high sensitivity and repeatable SERS effects.

Novel Developments and Progress in Two-Dimensional Correlation Spectroscopy (2D-COS).

This first of the two-part series of the comprehensive survey review on the progress of the two-dimensional correlation spectroscopy (2D-COS) field during the period 2021-2022, covers books, reviews, tutorials, novel concepts and theories, and patent applications that appeared in the last two years, as well as some inappropriate use or citations of 2D-COS. The overall trend clearly shows that 2D-COS is continually growing and evolving with notable new developments. The technique is well recognized as a powerful analytical tool that provides deep insights into systems in many science fields.

Diverse Applications of Two-Dimensional Correlation Spectroscopy (2D-COS).

This second of the two-part series of a comprehensive survey review provides the diverse applications of two-dimensional correlation spectroscopy (2D-COS) covering different probes, perturbations, and systems in the last two years. Infrared spectroscopy has maintained its top popularity in 2D-COS over the past two years. Fluorescence spectroscopy is the second most frequently used analytical method, which has been heavily applied to the analysis of heavy metal binding, environmental, and solution systems.

Decoration of Ag nanoparticle on MXene sheets for SERS studies.

MXene sheets with the unique electrical and optical properties show the excellent potential for surface-enhanced Raman spectroscopy (SERS) applications. In this study, we chose TiCT, a type of MXene, to decorate silver nanoparticles (Ag NPs) on the ultrathin two-dimensional (2D) MXene sheets. The designed Ag-MXene substrates with SERS activity showed high sensitivity, high stability, and reproducibility.

SERS monitoring of methylene blue degradation by Au-Ag@CuO-rGO nanocomposite.

A combination of multiple materials effectively improves and enhances the performance of the materials. Thus, a gold-silver@cuprous oxide (Au-Ag@CuO)-reduced graphene oxide (rGO) structure was designed and fabricated. We decorated the Au nanoparticles (NPs) on the Ag@CuO-rGO composite surface by a redox reaction to form a Au-Ag@CuO-rGO structure with two noble metals attached to a CuO semiconductor.

Investigation of selective SERS enhancement mechanism of Au nanospheres and Au nanorods based on 2T2D-SERS correlation spectroscopy.

The selective enhancement mechanism in surface-enhanced Raman scattering (SERS) is demonstrated. Two different types of single nanoparticles (Au nanosphere and Au nanorod) were used to investigate the role of the localized surface plasmon resonance (LSPR) in SERS spectra by using the two-trace two-dimensional (2T2D) correlation spectroscopy. The SERS intensities of three probe molecules, 4-mercaptobenzoic acid (4-MBA), 4-aminothiophenol (4-ATP), and 4-bromobenzenethiol (4-BBT), respectively, were enhanced but slightly different when adsorbed on Au nanospheres and Au nanorods.

Effect of a Ag-rGO structure on the SERS activity of PEDOT:PSS films.

π-Conjugated organic semiconductors with tunable electronic structures are new prospective active substrate materials for surface-enhanced Raman scattering (SERS). However, observing higher SERS activity when using organic semiconductors as substrates could be difficult because there is no plasmonic effect of hot electrons. Here, we designed a Ag-reduced graphene oxide (rGO) structure, introduced it into a poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) solution, and spin-coated the solution to obtain a Ag-rGO/PEDOT:PSS (ARPP) film.

Self-Healable Adhesive Hydrogel with a Preserved Underwater Adhesive Ability Based on Histidine-Zinc Coordination and a Bioengineered Hybrid Mussel Protein.

Mussels are marine organisms that are capable of constructing an underwater adhesion between their bodies and rigid structures. It is well known that mussels achieve underwater adhesion through the presence of mussel adhesive proteins (MAPs) that contain high levels of 3,4-dihydroxyphenylalanine (DOPA). Although the extraordinary underwater adhesive properties of mussels are attributed to DOPA, its capacity to play a dual role in surface adhesion and internal cohesion is inherently limited.

Investigation of Minerals Extracted during Seawater Desalination Using Two-Dimensional Correlation Spectroscopy.

In this study, mineral components extracted during the desalination process were concentrated and dried, and then identified using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), infrared (IR), and Raman spectroscopy. For detailed identification, two-dimensional correlation spectroscopy (2D-COS) was also applied to the XRD patterns, IR spectra, and Raman spectra of the minerals obtained from each desalination step. The EDS results confirm the presence of seawater minerals rich in Na ions in the first and second extracts, Ca ions are present only in these stages, and Mg ions are abundant in the third and final extracts.

Noble metal-free SERS: mechanisms and applications.

Surface-enhanced Raman scattering (SERS) is a very important tool in vibrational spectroscopy. The coupling of nanomaterials induces local surface plasmon resonance (LSPR), which contributes greatly to SERS. Due to its remarkable sensitivity in trace detection, SERS has gained prominence in the fields of catalysis, biosensors, drug tracking, and optoelectronic devices.

Ag decoration on NaTiO nanowires for improved SERS and PHE performance.

NaTiO (NTO) is recognized as an authenticated promising photocatalyst and surface-enhanced Raman scattering (SERS) active material, although its performance is limited by its high carrier recombination rate, wide band gap and inadequate utilization of visible light. In this study, to solve these issues, sea urchin-shaped NTO nanowires directly grown on a substrate were fabricated, and then Ag nanoparticles were decorated on NTO nanowires using sputtering equipment. The as-prepared Ag-NTO substrates exhibited different morphologies and high SERS activity, which was confirmed by finite-difference time-domain (FDTD) simulations, showing that appropriate Ag decoration can bring more nanogaps and thus enhance the electromagnetic field (EM) contribution.

Reactive oxygen species-responsive clicked assembly of gold nanoparticles to enhance photothermal therapy.

To enhance the efficacy of photothermal therapy (PTT) at tumor sites, we designed a reactive oxygen species (ROS)-responsive gold nanoparticle (AuNP)-based nanosystem in which azide-decorated AuNPs (N@AuNPs) and diselenide-coated alkyne-decorated AuNPs (Se/Ak@AuNPs) were separately prepared for selective clicking into nanoclusters when exposed to ROS. Se/Ak@AuNPs were dual-functionalized with alkyne moieties and diselenide linkers embedded in a long chain of polyethylene glycol (PEG) to enable the alkyne moieties of Se/Ak@AuNPs to be inaccessible to the azide moieties of N@AuNPs owing to steric hindrance. At tumor sites where the ROS level is elevated due to the increased metabolic activity, cellular receptor signaling, mitochondrial dysfunction, and oncogene activity, the diselenide linkers were cleaved, leading to the liberation of the long PEG chains tethered to AuNPs, and the alkyne moieties could be recognized by the surrounding azide moieties to generate a click reaction.

Molecular-Orbital Delocalization Enhances Charge Transfer in π-Conjugated Organic Semiconductors.

π-Conjugated organic semiconductors are promising materials for surface-enhanced Raman scattering (SERS)-active substrates based on the tunability of electronic structures and molecular orbitals. Herein, we investigate the effect of the temperature-mediated resonance-structure transitions of poly(3,4-ethylenedioxythiophene) (PEDOT) in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT : PSS) films on the interactions between substrate and probe molecules, thereby affecting the SERS activity. Absorption spectroscopy and density functional theory calculations show that this effect occurs mainly due to delocalization of the electron distribution in molecular orbitals, effectively promoting the charge transfer between the semiconductor and probe molecules.

Interface Design of 3D Flower-like Ag@ZnSe Composites: SERS and Photocatalytic Performance.

In this work, we cosputtered Ag and ZnSe on a polystyrene template to form a three-dimensional (3D) Ag@ZnSe (x) structure. The 3D surface morphology and material composition that provided abundant "hot spots" were controlled by adjusting the sputtering power of the ZnSe, which was confirmed by finite-difference time-domain (FDTD) simulation. The introduction of ZnSe into the noble metal Ag also introduced a charge-transfer (CT) effect into the system, and the CT path was proven with the two-dimensional correlation spectroscopy (2D-COS)-surface-enhanced Raman scattering (SERS) technique.

One Carbon Ring Expansion of Bipyrrole to Bipyridine Enables Access to a π-Extended, Non-innocent, Corrole-like Ligand.

A π-extended, diaza-triphenylene embedded, mono-anionic corrole analogue and its Ni complex were synthesized from a diaza-triphenylene precursor, which was obtained from a double one-carbon insertion into a naphthobipyrrole diester. Following conversion to the corresponding activated diol and acid-catalyzed condensation with pyrrole, subsequent reaction with pentafluorobenzaldehyde afforded mono-anionic, π-extended bipyricorrole-like macrocycle. Attempted Ni insertion with Ni(OAc)  ⋅ 4H O resulted an ESR active, Ni bipyricorrole radical complex, which was converted to a stable cationic Ni complex upon treatment with [(Et O) (SbCl ) ].

Probe-Free Identification of RNA Virus Variants with Point Mutations by Surface-Enhanced Raman Spectroscopy.

As observed in the COVID-19 pandemic, RNA viruses continue to rapidly evolve through mutations. In the absence of effective therapeutics, early detection of new severely pathogenic viruses and quarantine of infected people are critical for reducing the spread of the viral infections. However, conventional detection methods require a substantial amount of time to develop probes specific to new viruses, thereby impeding immediate response to the emergence of viral pathogens.

Electrospun Nanofibrils Surface-Decorated with Photo-Cross-Linked Hyaluronic Acid for Cell-Directed Assembly.

Hyaluronic acid (HA) was chemically immobilized on the surface of electrospun nanofibrils to form a cell/NF complex. Poly(caprolactone) (PCL) was electrospun into nanofibrous mats that were subsequently aminolyzed into nanofibrils. The aminolyzed nanofibrils were surface-decorated with methacrylated HA via Michael type addtion and by photo-cross-linking.

Signal amplification surface-enhanced Raman scattering immunosorbent assay of human chorionic gonadotrophin based on repeated enzyme biocatalytic precipitation.

A novel surface-enhanced Raman scattering (SERS) immunoassay method based on tyramine signal amplification (TSA) technology triggering the formation of enzyme repeats on an enzyme-linked immunosorbent assay (ELISA) was designed for highly sensitive detection of human chorionic gonadotropin (hCG) using enzymatic biocatalytic precipitation toward -phenylenediamine (OPD). Initially, a horseradish peroxidase (HRP)-labeled hCG antibody was fixed by the double antibody sandwich method, and then a tyramine-HRP conjugate was used to form HRP repeats by triggering the immobilized HRP on ELISA with the aid of HO. In the presence of the target hCG, the HRP repeats carried by the sandwich immune complex catalyzed the oxidation of OPD to produce product molecules with different structures, resulting in changes in the SERS fingerprint spectrum.

Controllable hot electron transfer in the Ag/MoO layer by layer system: Thickness-dependent MoO layer.

The Ag and MoO layer-by-layer sputtering method was employed to fabricate Ag/MoO coated on a polystyrene (PS) array (Ag/MoO@PS), which exhibited excellent surface-enhanced Raman scattering (SERS) activity. The thickness of the MoO layer was controlled by changing the sputtering power. The SERS intensity of 4-aminothiophenol (PATP) on Ag/MoO@PS with a 2 nm thickness of the MoO layer was comparable to that on pure Ag coated on the PS array (Ag@PS).