Surface modification of Cu nanoparticles coated commercial titanium in the presence of tryptophan: Comprehensive electrochemical and spectroscopic investigations

Simplified Biochemical Analysis Using p‑Block Metals and Their Compounds with SilverSurface Enhancement from the Point of View of Electronic Structure

This mini-review presents recent trends in the field of surface-enhanced spectroscopies, which are increasingly gaining ground for biomolecule detection. The paper discusses the role of electromagnetic and chemical bonding mechanisms for an explanation of Raman scattering and fluorescence enhancement. The charge transfer (CT) effect, which is involved in the chemical mechanism, plays an important role in changing the polarizability and is decisive in enhancing certain Raman scattering bands and fluorescence emission. The CT effect is determined by the band structure and the energy of the excitation radiation by which photoelectrons and holes with different energies are generated. Here we analyze the changes in the band structure of silver by adding p-block metals as well as the possibility to control CT and to enhance specific Raman bands through their engineering.

Streamlined Flow Synthesis of Plasmonic Nanoparticles and SERS Detection of Uremic Toxins with Trace-Level Liquid Volumes in a Microchamber

Rapid detection of uremic toxins is crucial due to their severe health risks, including oxidative stress, inflammation, neurotoxicity, cardiovascular complications, and progression of chronic kidney disease. Surface-enhanced Raman spectroscopy (SERS) may provide sensitive, fast, and clinical-grade real-time monitoring of these toxins, enabling effective management with timely dialysis treatments. This study introduces a 3D-printed microchamber that integrates the fabrication of plasmonic metal nanoparticles for the in-flow detection of biological toxins and pharmaceutical drugs using SERS, making it ideal for on-site diagnostics in clinical settings. The microchamber supports quantitative and highly reproducible detection with liquid volumes under 100 μL, which is crucial for trace-level biomarker detection and minimizing cross-contamination. It employs a tunable solvent exchange method for the in situ synthesis of silver nanoparticles (AgNPs) on flexible PDMS or rigid Si wafer substrates, avoiding costly nanofabrication techniques. Ultralow detection limits were achieved for two model compounds and three pharmaceutical drugs: 10-11 M for rhodamine 6G, 10-7 M for adenine, and 10-6 M for the pharmaceutical drugs. A total of 13 biological toxins, including three neurotransmitters, one neuromodulator, five amino acids, two polyamines, and two urea cycle metabolites, were detected with quantitative limits ranging from 10-3 to 10-6 M, all below permissible levels and aligning with physiological conditions. SERS detection within microchambers facilitates rapid on-site analysis, proving ideal for personalized health monitoring, point-of-care diagnostics, and environmental pollution assessment.

Exploring the nanoscale: AFM-IR visualization of cysteine adsorption on gold nanoparticles

This study focuses on the adsorption process of L-cysteine (Cys), a sulfur-containing amino acid, onto monolayers of gold nanoparticles (AuNPs) prepared through distinct protocols on mica substrates. Two types of AuNPs were prepared using two different methods: the first employed a physical approach, which combined the Inert Gas Condensation (IGC) technique with the magnetron sputtering method, while the second utilized a chemical method involving the reduction of tetrachloroauric acid with trisodium citrate (TC). The characterization of AuNPs was performed using transmission electron microscopy (TEM) and atomic force microscopy (AFM), of up to 5 ± 1.3 nm for bare AuNPs obtained through vacuum techniques, and up to 12 ± 5 nm for negatively charged, citrate-stabilized TCAuNPs(-). The application of spectroscopic techniques based on the surface-enhanced effects allows for describing the adsorption process in both micro- and nanoscale systems: Cys/bare AuNPs and Cys/ TCAuNPs(-). The commonly used surface-enhanced Raman spectroscopy (SERS) technique provided insights into adsorption behaviours at the microscale level. In the case of TCAuNPs(-), an interaction involving the lone electron pair of sulfur (S) atom and metal surface, while on the bare AuNPs, S is adsorbed on the surface, but the cleavage of the SH group is not discernible. Nanoscale analysis was complemented using AFM combined with the surface-enhanced infrared absorption spectroscopy (AFM-SEIRA) technique. AFM-SEIRA map indicated the formation of hot spot which were predominantly located between aggregated TCAuNPs(-) and on specific NPs surfaces (area between NPs and gold-coated tip). Results from the SERS and AFM-SEIRA techniques were in good agreement, underscoring the comprehensive understanding achieved through the chosen experimental approach regarding the Cys interactions with layers of AuNPs.

Ionic Liquid-Modified Copper for the Enhanced Thermal Conductivity and Mechanical Properties of Epoxy Resin/Expanded Graphite Composites

In this study, diglycidylether of bisphenol A (DGEBA)/expanded graphite (EG)/copper (Cu) powder composites with high thermal conductivity were prepared for use as thermal interface materials. To construct an excellent thermally conductive network, the Cu surface was modified using the ionic liquid 1-ethyl-3-methyl imidazolium dicyanamide. In addition, the effect of the Cu content on the thermal conductivity, thermal stability, flexural properties, impact strength, and morphologies of the DGEBA/EG/Cu composites was investigated. The results indicated that the addition of 10 wt % Cu increased the thermal conductivity of the composites from 7.35 to 9.86 W/(m·K). Conversely, the thermal stability of the composites decreased with the addition of Cu. The flexural strength and impact strength of the composites increased from 27.9 MPa and 0.81 kJ/m2 to 39.6 MPa and 0.96 kJ/m2, respectively, as the Cu content increased from 0 to 10 wt %. Moreover, the flexural modulus of the composites increased from 9632 to 11,309 MPa with the addition of 10 wt % Cu. Scanning electron microscopy analysis of the DGEBA/EG/Cu composites revealed sheet-shaped blocks with numerous microcracks on the fracture surfaces.

In Situ and Ex Situ Raman Studies of Cysteine’s Behavior on a Titanium Surface in Buffer Solution

In this paper, surface-enhanced Raman spectroscopy (SERS) was used to investigate the adsorption process of cysteine (Cys). Studies were carried out in the presence of phosphate-buffered saline solution (PBS), at pH 7.4, and acidified to pH 5, 3, and 1, on the surface of Ti for implant application. In situ SERS spectra obtained for the Cys/Ti solution system, after 24 h of immersion time, indicated that the buffer solution strongly influences the adsorption behavior of Cys on the Ti surface. This results in a decrease in Cys adsorption on the Ti surface, in the range of pH 7.4 to 3. The strong interaction between a sulfur atom of Cys and a Ti surface was observed only at pH = 1, under strongly acidic conditions. In contrast, ex situ SERS spectra recorded for the same samples but in a dried Cys/Ti system show a completely different behavior of Cys on the Ti surface. Formation of a disulfide (S-S) bond has occurred as a result of the dimerization or aggregation of Cys molecules on the Ti surface. Detailed analysis of the adsorption behavior of Cys on the Ti surface can be very important in the preparation of bioactive materials (i.e., coated by organic layers).