Exploring the Efficacy of Platinum and Palladium Nanostructures for Organic Molecule Detection via Raman Spectroscopy

Comparison of Hydrogen Bonded Organic Framework with Reduced Graphene Oxide-Pd Based Nanocatalyst: Which One Is More Efficient for Entrapment of Nitrophenol Pollutants?

In this study, a Pd nanoparticles@hydrogen-bonded organic framework (Pd NPs@HOF) thin film was fabricated at the toluene-water interface. The HOF was formed through the interaction of trimesic acid (TMA) and melamine (Mel) in the water phase, while Pd(0) was produced from the reduction of [PdCl2(cod)] in the organic phase. The as-synthesized Pd NPs@HOF thin film was demonstrated to be an effective catalyst for the selective reduction of p-nitrophenol and o-nitrophenol to p-aminophenol and o-aminophenol. The porous network of the Pd NPs@HOF introduced strong active sites between Mel, TMA, and Pd(0). Kinetic studies showed that the Pd NPs@HOF catalyst exhibited an enhanced rate of p-nitrophenol and o-nitrophenol reduction in comparison with Pd@reduced-graphene oxide (r-GO) with rates that were 1.7 times faster for p-nitrophenol and 1.5 times faster for o-nitrophenol or even 10 times faster than some Pd-based catalysts, with a maximum conversion of 97.1% which was attributed to the higher porosity and greater surface-to-volume ratio of the Pd NPs@HOF material. Furthermore, π-π stacking interactions enhance the catalytic activity of the Pd NPs@HOF catalyst by increasing the active sites, stabilizing the NPs and trapping the nitrophenols, facilitating the electron transfer, and providing the synergistic effect. Also, contributions of hydrogen bonding, van der Waals forces, electrostatic interactions, and π-σ noncovalent interactions are reasons for better performance of Pd NPs@HOF than Pd/r-GO catalyst with the reduced functional groups.

Development of highly sensitive lateral flow immunoassay using PdNPs for detection of Plasmodium species

A lateral flow immunoassay (LFIA) employing palladium nanoparticles (PdNPs) labelled with antibodies has been innovatively designed for the precise detection of Plasmodium falciparum pLDH and HRPII antigen. This study focuses on development of LFIA based on PdNPs detection system to substantially enhance the visual detectability (vLOD), achieving an impressive 12 parasites/microliter (p/µl) vLOD in comparison with conventional system represented 50 p/µl vLOD. The research introduces a novel amplification system that not only heightens the sensitivity of LFIA but also maintains intense coloration. This novel system relies on direct detection of the malaria pLDH and HRPII antigen. In this innovative assay, HRPII antigen interacts with PdNP-conjugated Anti-HRPII detector antibodies, forming an immune complex with Anti-HRPII capture antibodies. The detection limit for HRPII antigen was found to be 8 times higher than that of conventional systems. Moreover, the novel approach for synthesis of PdNPs and their conjugation with antibodies makes this system robust and universally applicable and also extends its potential use to detect various other compounds, including antigens or antibodies from different diseases. This sensitive LFIA detection system presents itself as an efficient screening tool for medical monitoring and point-of-care (POC) settings, offering promising prospects for enhancing disease diagnosis and surveillance.

Synthesis Methods and Optical Sensing Applications of Plasmonic Metal Nanoparticles Made from Rhodium, Platinum, Gold, or Silver

The purpose of this paper is to provide an in-depth review of plasmonic metal nanoparticles made from rhodium, platinum, gold, or silver. We describe fundamental concepts, synthesis methods, and optical sensing applications of these nanoparticles. Plasmonic metal nanoparticles have received a lot of interest due to various applications, such as optical sensors, single-molecule detection, single-cell detection, pathogen detection, environmental contaminant monitoring, cancer diagnostics, biomedicine, and food and health safety monitoring. They provide a promising platform for highly sensitive detection of various analytes. Due to strongly localized optical fields in the hot-spot region near metal nanoparticles, they have the potential for plasmon-enhanced optical sensing applications, including metal-enhanced fluorescence (MEF), surface-enhanced Raman scattering (SERS), and biomedical imaging. We explain the plasmonic enhancement through electromagnetic theory and confirm it with finite-difference time-domain numerical simulations. Moreover, we examine how the localized surface plasmon resonance effects of gold and silver nanoparticles have been utilized for the detection and biosensing of various analytes. Specifically, we discuss the syntheses and applications of rhodium and platinum nanoparticles for the UV plasmonics such as UV-MEF and UV-SERS. Finally, we provide an overview of chemical, physical, and green methods for synthesizing these nanoparticles. We hope that this paper will promote further interest in the optical sensing applications of plasmonic metal nanoparticles in the UV and visible ranges.

Rapid Fabrication of Fe and Pd Thin Films as SERS-Active Substrates via Dynamic Hydrogen Bubble Template Method

Fe and Pd thin film samples have been fabricated in a rapid fashion utilizing the versatile technique of dynamic hydrogen bubble template (DHBT) method via potentiostatic electrodeposition over a copper substrate. The morphology of the samples is dendritic, with the composition being directly proportional to the deposition time. All the samples have been tested as SERS substrates for the detection of Rhodamine 6G (R6G) dye. The samples perform very well, with the best performance shown by the Pd samples. The lowest detectable R6G concentration was found to be 10^-6 M (479 μgL^-1) by one of the Pd samples with the deposition time of 180 s. The highest enhancement of signals noticed in this sample can be attributed to its morphology, which is more nanostructured compared to other samples, which is extremely conducive to the phenomenon of localized surface plasmon resonance (LSPR). Overall, these samples are cheaper, easy to prepare with a rapid fabrication method, and show appreciable SERS performance.

Trends in Application of SERS Substrates beyond Ag and Au, and Their Role in Bioanalysis

This article compares the applications of traditional gold and silver-based SERS substrates and less conventional (Pd/Pt, Cu, Al, Si-based) SERS substrates, focusing on sensing, biosensing, and clinical analysis. In recent decades plethora of new biosensing and clinical SERS applications have fueled the search for more cost-effective, scalable, and stable substrates since traditional gold and silver-based substrates are quite expensive, prone to corrosion, contamination and non-specific binding, particularly by S-containing compounds. Following that, we briefly described our experimental experience with Si and Al-based SERS substrates and systematically analyzed the literature on SERS on substrate materials such as Pd/Pt, Cu, Al, and Si. We tabulated and discussed figures of merit such as enhancement factor (EF) and limit of detection (LOD) from analytical applications of these substrates. The results of the comparison showed that Pd/Pt substrates are not practical due to their high cost; Cu-based substrates are less stable and produce lower signal enhancement. Si and Al-based substrates showed promising results, particularly in combination with gold and silver nanostructures since they could produce comparable EFs and LODs as conventional substrates. In addition, their stability and relatively low cost make them viable alternatives for gold and silver-based substrates. Finally, this review highlighted and compared the clinical performance of non-traditional SERS substrates and traditional gold and silver SERS substrates. We discovered that if we take the average sensitivity, specificity, and accuracy of clinical SERS assays reported in the literature, those parameters, particularly accuracy (93-94%), are similar for SERS bioassays on AgNP@Al, Si-based, Au-based, and Ag-based substrates. We hope that this review will encourage research into SERS biosensing on aluminum, silicon, and some other substrates. These Al and Si based substrates may respond efficiently to the major challenges to the SERS practical application. For instance, they may be not only less expensive, e.g., Al foil, but also in some cases more selective and sometimes more reproducible, when compared to gold-only or silver-only based SERS substrates. Overall, it may result in a greater diversity of applicable SERS substrates, allowing for better optimization and selection of the SERS substrate for a specific sensing/biosensing or clinical application.

High-Throughput Fabrication of Triangular Nanogap Arrays for Surface-Enhanced Raman Spectroscopy

Squeezing light into nanometer-sized metallic nanogaps can generate extremely high near-field intensities, resulting in dramatically enhanced absorption, emission, and Raman scattering of target molecules embedded within the gaps. However, the scarcity of low-cost, high-throughput, and reproducible nanogap fabrication methods offering precise control over the gap size is a continuing obstacle to practical applications. Using a combination of molecular self-assembly, colloidal nanosphere lithography, and physical peeling, we report here a high-throughput method for fabricating large-area arrays of triangular nanogaps that allow the gap width to be tuned from ∼10 to ∼3 nm. The nanogap arrays function as high-performance substrates for surface-enhanced Raman spectroscopy (SERS), with measured enhancement factors as high as 10⁸ relative to a thin gold film. Using the nanogap arrays, methylene blue dye molecules can be detected at concentrations as low as 1 pM, while adenine biomolecules can be detected down to 100 pM. We further show that it is possible to achieve sensitive SERS detection on binary-metal nanogap arrays containing gold and platinum, potentially extending SERS detection to the investigation of reactive species at platinum-based catalytic and electrochemical surfaces.

An environmental approach for the photodegradation of toxic pollutants from wastewater using Pt-Pd nanoparticles: Antioxidant, antibacterial and lipid peroxidation inhibition applications

BACKGROUND

Green synthesis is an effective and friendly method for the environment, especially in recent years has been used in many areas. It finds application opportunities in many fields such as physics, chemistry, electronics, food, and especially health and is the subject of intensive studies in this field.

OBJECTIVES

The synthesized Pt-Pd NPs were aimed to be used as a bio-based photocatalyst under sunlight to prevent wastewater pollution. In addition, it is aimed to use Pt-Pd NPs as biological agents in different applications in the future.

METHODS

In this study, the platinum-palladium nanoparticles were synthesized by the extract of Hibiscus sabdariffa, the characterization of the nanoparticles was carried out by different methods (ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), infrared transform spectroscopy atomic force microscopy (AFM), and ray diffraction (XRD) analysis). And we discussed several different parameters related to human health by obtaining platinum-palladium bimetallic nanoparticles (Pt-Pd NPs) with a green synthesis method. These parameters are antioxidant properties (total phenolic, flavonoid, and DPPH scavenging activity), antibacterial activity, and lipid peroxidation inhibition activity. Gallic acid was used as standard phenolic, and quercetin was used as standard flavonoid reagents. The newly synthesized Hibiscus sabdariffa mediated green synthesized Pt-Pd NPs were compared with gram-positive and gram-negative bacteria, the high antibacterial activity was shown by gram-positive bacteria. The photodegradation of Pt-Pd NPs was carried out against MB dye for 180 min.

RESULTS

TEM results show that the average size of Pt-Pd NPs is around 4.40 nm. The total amount of phenolic compounds contained in 0.2 mg/ml of Pt-Pd NPs was equivalent to 14.962 ± 7.890 μg/ml gallic acid and the total amount of flavonoid component was found to be equal to 28.9986 ± 0.204 μg/ml quercetin. Hibiscus sabdariffa mediated green synthesized Pt-Pd NPs was found to have very effective for lipid peroxidation inhibition activity in the FeCl2-H2O2 system. The maximum DPPH scavenging activity was determined as 97.35% at 200 μg/ml. The photocatalytic activity of Pt-Pd NPs was analysed against Methylene blue (MB) and the maximum degradation percentage was observed to be 83.46% at 180 min.

CONCLUSIONS

The biogenic Pt-Pd NPs showed a high effective photocatalytic and biological activity.

Surface Plasmon Resonances in Silver Nanostars

The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced sensing and spectroscopy, which may be further exploited if the mechanisms behind the excitation of localized surface plasmon resonances (LSPRs) are identified. Here, we show that LSPRs in Ag-NSs can be obtained with finite-difference time-domain (FDTD) calculations by considering the nanostars as combination of crossed nanorods (Ag-NRs). In particular, we demonstrate that an apparent tail at large wavelengths (λ≳700 nm) observed in the extinction spectra of Ag-NSs is due to a strong dipolar plasmon resonance, with no need to invoke heterogeneity (different number of arms) effects as is normally done in the literature. Our description also indicates a way to tune the strongest LSPR at desired wavelengths, which is useful for sensing applications.

Recent Advances of Plasmonic Nanoparticles and their Applications

In the past half-century, surface plasmon resonance in noble metallic nanoparticles has been an important research subject. Recent advances in the synthesis, assembly, characterization, and theories of traditional and non-traditional metal nanostructures open a new pathway to the kaleidoscopic applications of plasmonics. However, accurate and precise models of plasmon resonance are still challenging, as its characteristics can be affected by multiple factors. We herein summarize the recent advances of plasmonic nanoparticles and their applications, particularly regarding the fundamentals and applications of surface plasmon resonance (SPR) in Au nanoparticles, plasmon-enhanced upconversion luminescence, and plasmonic chiral metasurfaces.

Utilization of Inexpensive Carbon-Based Substrates as Platforms for Sensing

Gold (Au) has been widely used as a material for Surface Enhanced Raman Spectroscopy (SERS) due to its plasmonic properties, stability and biocompatibility. Conventionally for SERS application, Au is deposited on a rigid substrate such as glass or silicon. The rigid substrates severely limit analyte collection efficiency as well as portability. Here, flexible substrates like carbon cloth and carbon paper were investigated as potential substrate candidates for SERS application. The flexible substrates were coated with Au nanostructures by electrodeposition. Model analyte, Rhodamine 6G was utilized to demonstrate the capabilities of the flexible SERS substrates. Additionally, the pesticide paraoxon was also detected on the flexible SERS substrates as well as on a real sample like the apple fruit.

Probe of Alcohol Structures in the Gas and Liquid States Using C⁻H Stretching Raman Spectroscopy

Vibrational spectroscopy is a powerful tool for probing molecular structures and dynamics since it offers a unique fingerprint that allows molecular identification. One of important aspects of applying vibrational spectroscopy is to develop the probes that can characterize the related properties of molecules such as the conformation and intermolecular interaction. Many examples of vibrational probes have appeared in the literature, including the azide group (⁻N₃), amide group (⁻CONH₂), nitrile groups (⁻CN), hydroxyl group (⁻OH), ⁻CH group and so on. Among these probes, the ⁻CH group is an excellent one since it is ubiquitous in organic and biological molecules and the C⁻H stretching vibrational spectrum is extraordinarily sensitive to the local molecular environment. However, one challenge encountered in the application of C⁻H probes arises from the difficulty in the accurate assignment due to spectral congestion in the C⁻H stretching region. In this paper, recent advances in the complete assignment of C⁻H stretching spectra of aliphatic alcohols and the utility of C⁻H vibration as a probe of the conformation and weak intermolecular interaction are outlined. These results fully demonstrated the potential of the ⁻CH chemical group as a molecular probe.