Plasmon Peak Research Articles

First-principles approach to the structural, physical, electronic, magnetic and optical properties of honeycomb ordered antimonates Na3Fe2SbO6

The search for new magnetic materials, electrochemical sensors and storage devices has ignited the study of layered honeycomb oxides in the past few years. We have performed a first-principles density functional theory (DFT) based investigation on the structural, elastic and associated thermophysical, mechanical, electronic, and optical properties of Na3Fe2SbO6 honeycomb ordered antimonates. The obtained lattice parameters as well as volume of the geometrically optimized structure were consistent with the available experimental data in the circumstance of ferromagnetic ordering. A comprehensive study of elastic constants implies a low to intermediate level of structure anisotropy, good machinability, mechanically brittle and hard. A large Debye temperature of 442.567 K and melting temperature of 2061.88 ± 300K implies high temperature application. The density of states suggests that the compound possesses a metallic character with a high magnetic moment. Furthermore, Na3Fe2SbO6 possesses excellent absorption characteristics in the spectral range in ultraviolet regions. It has low reflectivity and a high refractive index in the visible range of photon energy, and the plasmon peak found at 17.65 eV. The frequency-dependent optical conductivity confirms a metallic feature and agrees with the electronic density of states observations.

Ab-initio study of the optical properties of 2D Yn+1Cn (n = 1, 2, and 3) MXenes and bulk of YC

Calculations are accomplished in the framework of density functional theory and pseudopotential method with local density approximation (LDA) and QUANTUM-ESPRESSO/PWSCF computational code. Large negative values of ε1ω represent that materials exhibit Drude-like behavior while at higher energies, interband transitions occur. According to the results of the imaginary part of the dielectric functionε2ω, it can be stated that the absorption starts from small energies, which indicates that the bulk of YC and Yn+1Cn (n = 1, 2, and 3) monolayers have no energy bandgap and show a metallic nature. The sharp plasmonic energy peak for the YC structure in the x-direction can be seen at 18.61 eV; also the values of sharp plasmonic energy peaks for the Y2C, Y3C2, and Y4C3 in the x-direction are 13.40 eV, 11.98 eV, and 10.14 eV respectively. The results of the reflection spectrum show that the bulk of YC and 2D Yn+1Cn (n = 1, 2, and 3) MXenes have large values due to the presence of free electrons and plasma fluctuations, and confirm the metallic nature of the mentioned compounds. For the bulk of YC, the refractive index prominent peaks approach zero within the photon energy range of 13 eV up to 16 eV, while the corresponding range for the 2D Yn+1Cn MXenes is narrower and equal to 6 eV up to 7 eV. Also, the absorption spectrum in the bulk structure of YC and Yn+1Cn MXenes starts from zero photon energy which verifies the metallic behavior of the studied structures.

Synthesis and Characterization of Magnetoplasmonic Air-Stable Au@FeCo

The synthesis of FeCo alloys as highly magnetic nanoparticles has been valuable, as far as applications for magnetic nanoparticles are concerned. However, recently, a field of magnetoplasmonics in which magnetic nanoparticles such as the FeCo alloys doped with plasmonic materials such as Au and Ag to create a hybrid nanostructure with both properties has emerged. These magnetoplasmonic metamaterials have greatly enhanced the limit of detection of analytes in spectroscopic methods, as well as providing a more widely applicable nanoparticle to broaden the use of FeCo alloys even further. Herein, we discuss the synthesis of high-yield and fairly monodisperse spherical FeCo and Au-doped FeCo (Au@FeCo) with varying compositions of Au synthesized via the thermal decomposition of iron pentacarbonyl (Fe(CO)5) and dicobalt octacarbonyl (Co2(CO)8), followed by the addition of Au atoms using triphenylphosphine gold(I) chloride ((Ph3P)AuCl) via both coprecipitation and by delayed addition methods. The products were separated using a hand-held magnet, and then characterized via ultraviolet-visible light (UV-vis), scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), flame atomic absorption spectrometry (F-AAS), and magnetization measurements. Optical studies revealed a plasmonic peak at 550 nm in the Au@FeCo nanoparticles that had a gold content (%Au) of >2% (by weight), determined using F-AAS. Colocation of the Fe, Co, and Au were demonstrated through EDX analysis. Location of the Au atoms in the core were seen through high-resolution bright-field imaging. To understand the use of these nanoparticles for potential application in therapeutics and/or electronics, resistance measurements were performed to assess power loss as a function of frequency. We also achieved magnetization values as high as 150 emu/g and as low as 50 emu/g for gold-loaded samples based on %Au by weight. This paves the way to continue to develop magneto-plasmonic structures chemically using these synthesis strategies.

Pd-Based Hybrid Nanoparticles As Multimodal Theranostic Nanomedicine.

A nanodelivery system based on palladium nanoparticles (PdNP) and cisplatin (CisPt) was developed by physisorption of the drug onto the PdNP synthesized via a green redox process, using d-glucose and polyvinylpyrrolidone (PVP) as reducing and stabilizing/capping agents, respectively. UV-vis analysis and H2-evolution measurements were carried out to prove the nanoparticles' capability to act as bimodal theranostic nanomedicine, i.e., having both plasmonic and photocatalytic properties. XPS, XRD, and TEM allowed light to be shed on the chemical composition and morphology of the PdNP. The analysis of the UV-visible spectra evidenced plasmonic peak changes for the hybrid nanoparticle-drug assembly (Pd@CisPt), which pointed to a significant interaction of CisPt with the NP surface. The drug loading was quantitatively estimated by ICP-OES measurements, while DLS and AFM confirmed the strong association of the drug with the nanoparticle surface. The test of SOD-like activity in a cell-free environment proved the maintenance of the antioxidant capability of PdNP also in the Pd@CisPt systems. Finally, Pd@CisPt tested in prostate cancer cells (PC-3 line) unveiled the antitumoral action of the developed nanomedicine, related to reactive oxygen species (ROS) generation, with a condition of protein misfolding/unfolding and DNA damage, as evidenced by cytotoxicity and MitoSOX assays, as well as Raman microspectroscopy, respectively. Cell imaging by confocal microscopy evidenced cellular uptake of the nanoparticles, as well as dynamic processes of copper ion accumulation at the level of subcellular compartments. Finally, cell migration studies upon treatment with Pd@CisPt evidenced a tunable response between the inhibitory effect of CisPt and the enhanced rate of cell migration for the metal NP alone, which pointed out the promising potential of the developed theranostic nanomedicine in tissue regeneration.

Plasmonic Properties of SrVO3 Bulk and Nanostructures

AbstractCorrelated metals, such as SrVO3 (SVO) or SrNbO3, are promising materials for optical devices such as transparent conductors. Here, a real‐space and reciprocal‐space electron‐energy‐loss‐spectroscopy (EELS) investigation of SVO bulk and nanostructures is reported. An intense 1.35 eV excitation with a weak energy dispersion is observed in the loss function and is attributed to a bulk plasmonic excitation from the 3d‐t2g orbitals. Ab initio calculations done within a time‐dependent density functional theory framework reveal that a 1.5 band renormalization is sufficient to reproduce quantitatively this d–d plasmon energy and dispersion. The corresponding localized surface plasmon (LSP) peaks are measured by EELS on various nanostructures and are compared to finite‐difference time‐domain simulations. These LSPs exhibit quality factors above canonical materials (e.g., indium tin oxide) in the near‐infrared regime, demonstrating that SVO is also a material of high interest for plasmonic applications. Finally, by phasing out the surface plasmon contribution with EELS collected at minute off‐dipolar conditions, the bulk‐type plasmonic values are retrieved with nanometrical resolution. Core–shelled electronic structures are then observed for nanorods designed by focused ion beam (FIB), revealing a bandgap opening due to FIB damage. It is envisioned that similar bulk measurement can be feasible for most of the transition metal oxide nanostructures.

Quantifying arsenic and mercury in aqueous media via bio-inspired gold nanoparticles modified by mango leaf extract.

The present study conveys a new method for detecting arsenic(iii) and mercury(ii) in aqueous solution via bio-inspired gold nanoparticles. The process of synthesizing gold nanoparticles involves the utilization of the chemical reduction method. The functionalization of gold nanoparticles' surface is achieved via mango leaf extract. The as-synthesized nanoparticles are characterized by UV-Vis and DLS which reveal a plasmonic peak around ∼520 nm with an average size distribution of ∼44 nm. The modified gold nanoparticles have demonstrated selective detection capabilities towards arsenic(iii) as well as mercury(ii), as evidenced by color changes observed in the presence of ions of arsenic as well as mercury. The addition of mercury and arsenic lead to the overall aggregation-thereby bringing a colorimetric response. The limit of detection was determined to be 1 ppb and 1.5 ppb for arsenic(iii) and mercury(ii) ions, respectively along with exceptional linearity.

Microfluidic device-fabricated spiky nano-burflower shape gold nanomaterials facilitate large biomolecule delivery into cells using infrared light pulses.

Photothermal nanoparticle-sensitised photoporation is an emerging approach, which is considered an efficient tool for the intracellular delivery of biomolecules. Nevertheless, using this method to achieve high transfection efficiency generally compromises cell viability and uneven distribution of nanoparticles results in non-uniform delivery. Here, we show that high aspect ratio gold nano-burflowers, synthesised in a microfluidic device, facilitate highly efficient small to very-large cargo delivery uniformly using infrared light pulses without sacrificing cell viability. By precisely controlling the flow rates of shaping reagent and reducing agent, high-density (24 numbers) sharply branched spikes (∼80 nm tip-to-tip length) of higher aspect ratios (∼6.5) with a small core diameter (∼45 nm) were synthesised. As produced gold burflower-shape nanoparticles are biocompatible, colloidally stable (large surface zeta potential value), and uniform in morphology with a higher plasmonic peak (max. 890 nm). Theoretical analysis revealed that spikes on the nanoparticles generate a higher electromagnetic field enhancement upon interaction with light pulses. It induces plasmonic nanobubbles in the vicinity of the cells, followed by pore formation on the membrane leading to diverse biomolecular delivery into cells. Our platform has been successfully implemented for uniform delivery of small to very large biomolecules, including siRNA (20-24 bp), plasmid DNA expressing green fluorescent protein (6.2 kbp), Cas-9 plasmid (9.3 kbp), and β-galactosidase enzyme (465 kDa) into diverse mammalian cells with high transfection efficiency and cell viability. For very large biomolecules such as enzymes, the best results were achieved as ∼100% transfection efficiency and ∼100% cell viability in SiHa cells. Together, our findings demonstrate that the spiky gold nano-burflower shape nanoparticles manufactured in a microfluidic system exhibited excellent plasmonic behaviour and could serve as an effective tool in manipulating cell physiology.

Sol-Gel Synthesis of Uniform Arrays of Ag and Au Nanoparticles

The obtaining of uniform arrays of silver and gold nanoparticles with a surface density up to 3.3∙109 cm–2 on the zinc oxide buffer layers by sol-gel method is described. The variations of the solution composition and synthesis mode, layers coating and subsequent heat treatment were carried out. The absorption spectra of the obtained samples had a peak near 400–570 nm corresponding to the plasmon resonance in the Ag and Au nanoparticles. Wavelength and shape of Ag and Au nanoparticles plasmon peak varied depending on the synthesis mode: the use of ZnO buffer layers leads to an increase in the intensity of the nanoparticles plasmon peak, the annealing leads to a gradual decrease and broadening of the absorption peak of Ag and mixed Ag and Au nanoparticles arrays, but does not affect the peak of Au nanoparticles.

Acceleration and retrieval of selenium nanoparticles synthesized from Lactobacillus acidophilus

Lactobacillus acidophilus DSMZ20079T was used in this study to effectuate selenium nanoparticles (SeNPs) by transforming toxic soluble selenite oxyanions (SeO32-) into red insoluble elemental selenium (Se0). The strain was able to withstand, tolerate, and grow in the presence of high levels of selenite toxicity at concentrations ranging from 1 mM to 10 mM. Produced SeNPs were purified and subsequently characterized systematically using UV–Vis spectroscopy, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared (FTIR) techniques. The absorbance scan of UV–Vis showed a broad plasmon peak at 260 nm. The TEM microscopy showed spherical-shaped Se0 nanoparticles with a size ranging from 8 to 23 nm. XRD results revealed crystalline shape with a mean size of 13.23 nm. This research focuses on the synthesis of selenium nanoparticles from Lactobacillus acidophilus DSMZ20079T which has the potency to function as a natural manufactory.

Spectroscopic/colorimetric dual-mode rapid and ultrasensitive detection of reactive oxygen species based on shape-dependent silver nanostructures.

Excessive production of reactive oxygen species (ROS) from endogenous and exogenous pathways is linked to oxidative stress and various diseases. Although a variety of ROS probes have been developed, their multistep synthesis strategies and complicated instrumental operating procedures limit their frequent use. In this work, different shaped silver nanostructures including nanoparticles, nanoprisms, and nanocubes were utilized to demonstrate simple spectroscopic and colorimetric techniques for sensitive ROS detection. The nanostructures displayed different sensing behaviours recorded via plasmon tuning with morphological changes upon exposure to ROS. Among the nanostructures, silver nanocubes were found to be extremely efficient in recognising a particular ROS, namely hypochlorite ions. The detection limits of this ROS were calculated to be 23.76 nM, 85.71 nM, and 36.37 nM for silver nanoparticles, nanoprisms, and nanocubes, respectively. A time-dependent microscopic examination was carried out and revealed that the presence of hypochlorite ions deteriorates structural morphologies. The formation of highly reactive chlorite, chlorate, and chloride ions in hypochlorite ion solution was ascribed to the significant spectroscopic and microscopic changes in all the nanostructures. The attenuation of plasmonic peaks and etching of nanostructures by ROS were supported by the increment of the oxidation state of silver. In addition, silver nanocubes were successfully applied to recognize ROS in Spinacia oleracea and real water samples. The results confirm the potentiality of silver nanostructures for sensitive detection of ROS in biological and environmental systems.

Gold Nanoparticles Synthesized Using Various Reducing Agents and the Effect of Aging for DNA Sensing.

Gold nanoparticles (AuNPs) are one of the most commonly used reagents in colloidal science and biosensor technology. In this work, we first compared AuNPs prepared using four different reducing agents including citrate, glucose, ascorbate, and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). At the same absorbance at the surface plasmon peak of 520-530 nm, citrate-AuNPs and glucose-AuNPs adsorbed more DNA and achieved higher affinity to the adsorbed DNA. In addition, citrate-AuNPs had better sensitivity than glucose-AuNPs for label-free DNA detection. Then, using citrate-AuNPs, the effect of aging was studied by incubation of the AuNPs at 22 °C (room temperature) and at 4 °C for up to 6 months. During aging, the colloidal stability and DNA adsorption efficiency gradually decreased. In addition, the DNA sensing sensitivity using a label-free method also dropped around 4-fold after 6 months. Heating at boiling temperature of the aged citrate-AuNPs could not rejuvenate the sensing performance. This study shows that while citrate-AuNPs are initially better than the other three AuNPs in their colloid properties and sensing properties, this edge in performance might gradually decrease due to constantly changing surface properties caused from the aging effect.

Fast and hydrosensitive switching of plasmonic nanocavities via photothermal effect

Metallic nanoplasmonics, due to its extremely small size and ultrafast speed, has been one of the key components for next-generation information technology. It is vital that the highly tunable nanoplasmonic system in the solid state can be achieved for optoelectronic devices, which, still remains elusive for the visible region. Here we sandwich vanadyl oxalate ( VOC 2 O 4 ) thin films in-between gold nanoparticles and gold film to establish thermo-responsive nanoantennas. The thickness of the VOC 2 O 4 composite films remains almost unchanged within the temperature cycles between 15°C and 80°C, while the refractive index of the films decreases with the increase of temperature due to the dehydration, which results in blueshift of the plasmon peak up to 60 nm. The plasmon resonances can be fully recovered when the temperature cools down again. This process is reversible within the temperature range of 15°C–80°C, which can be optically modulated with photothermal effect. Such thermo-responsive plasmonic nanoantenna works in the solid state with hundreds of kilohertz switching speed, which is highly compatible with traditional optoelectronic devices. It can be envisioned that this thermo-responsive optical thin film can be a promising candidate for integrated nanoplasmonic and optoelectronic devices.

Gold Nanostar Characterization by Nanoparticle Tracking Analysis.

We demonstrate the application of nanoparticle tracking analysis (NTA) for the quantitative characterization of gold nanostars (GNSs). GNSs were synthesized by the seed-mediated growth method using triblock copolymer (TBP) gold nanoparticles (GNPs). These GNPs (≈ 10 nm) were synthesized from Au3+ (≈ 1 mM) in aqueous F127 (w/v 5%) containing the co-reductant ascorbic acid (≈ 2 mM). The GNS tip-to-core aspect ratio (AR) decreased when higher concentrations of GNPs were added to the growth solution. The AR dependency of GNSs on Au3+/Au(seed) concentration ratio implies that growth is partly under kinetic control. NTA measured GNS sizes, concentrations, and relative scattering intensities. Molar absorption coefficients ∼ 109-1010 M-1 cm-1 (ε400nm) for each batch of GNSs were determined using the combination of extinction spectra and NTA concentrations for heterogeneous samples. NTA in combination with UV-vis was used to derive the linear relationships: (1) hydrodynamic size versus localized surface plasmon peak maxima; (2) ε400nm versus localized surface plasmon peak maxima; (3) ε400nm versus hydrodynamic size. NTA for quantitative characterization of anisotropic nanoparticles could lead to future applications, including heterogeneous colloidal catalysis.

GREEN SYNTHESIS AND CHARACTERISATION OF ZnO NANOPARTICLES FROM MANIHOT ESCULENTA (CASSAVA) PEEL AND THEIR ANTIBACTERIAL STUDY

<p>A technique for green manufacturing of zinc oxide based nanoparticles utilising cassava peel has been approached in this research for antibacterial investigation. Especially, the cassava peel is an agro waste from starch and food processing industries and the extract of Cassava peel is used for synthesising the zinc oxide nanoparticles (ZnO-NPs). The peel based zinc oxide nanoparticles were synthesized using bioreduction method. The plasmon peak from UV–Visible spectroscopy is observed at 380 nm, while the XRD shows an average crystallite size of 67.31nm with hexagonal structure and also the stability of bio synthesised nanoparticles are confirmed by FTIR study. Additionally, FESEM confirms the structure is found to be spherical whereas Zeta potential analysis has confirmed the nanoparticles have a stable and well-dispersed form. Furthermore, the anti bacterial study against bio synthesized ZnO-NPs is carried out for both gram positive and gram negative bacteria. Therefore, the results proved that the bacteria are found to be more active against the synthesized nanoparticles.</p>

Effective Blue Light-Absorbing AuAg Nanoparticles in InP Quantum Dots-Based Color Conversion.

In typical color-by-blue mode-based quantum dot (QD) display devices, only part of the blue excitation light is absorbed by QD emitters, thus it is accompanied by the leakage of blue light through the devices. To address this issue, we offer, for the first time, the applicability of AuAg alloy nanoparticles (NPs) as effective blue light absorbers in InP QD-based color-by-blue platforms. For this, high-quality fluorescent green and red InP QDs with a double shell scheme of ZnSe/ZnS were synthesized and embedded in a transparent polymer film. Separately, a series of Au/Ag ratio-varied AuAg NPs with tunable plasmonic absorption peaks were synthesized. Among them, AuAg NPs possessing the most appropriate absorption peak with respect to spectral overlap with blue emission are chosen for the subsequent preparation of AuAg NP polymeric films with varied NP concentrations. A stack of AuAg NP polymeric film on top of InP QD film is then placed remotely on a blue light-emitting diode, successfully resulting in systematically progressive suppression of blue light leakage with increasing AuAg NP concentration. Furthermore, the beneficial function of the AuAg NP polymeric overlayer in mitigating undesirable QD excitation upon exposure to ambient lights was further examined.

Evaluate the toxicity of silver nanoparticles by chemical and green synthesis methods

Plant leaf extract of Hibiscus rosa-sinensis was used to make biological silver nanoparticles (Bio-AgNPs) and AgNO3 was used to make chemical silver nanoparticles (CH-AgNPs). The synthesis of nanoparticles was indicated by the appearance of CH-AgNPs (transparent colour change to brownish black) and Bio-AgNPs (pale yellow colour change to blackish brown). The synthesis of AgNPs was primary confirmed using UV–VIS absorption spectroscopy, with plasmon peak maximums at 425 nm and 419 nm for chemical and biological procedures, respectively. The average size (45.55 nm for CH-AgNPs and 25.65 nm for Bio-AgNPs) were determined by using Transmission Electron Microscope (TEM), and they were uniformly dispersed with no apparent aggregation. Toxicity of nanoparticlas was evaluating by calculation the toxic effect value (TEV) of silver nanoparticles as in vitro against Bacillus subtilis. TEV against B. subtilis in CH-AgNPs was reported to be as high as 85.45 % and as low as 55.75 % in Bio-AgNPs. On the other hand, the in vivo toxicity was evaluated by using Drosophila melanogaster. The physiological characteristic (body melanization/pigmentation) was proved by the fact that, in contrast to Bio-AgNPs, CH-AgNPs are incredibly detrimental to insect reproductive traits. On the other hand, Bio-AgNPs synthesised at higher concentrations (50–100 %) are fully capable of removing the pigmentation from the thorax cuticles with some detrimental effects for insect reproductive traits if used for extended periods of time. Bio-AgNPs at lower concentrations (20–50 %) are able to remove the pigmentation from the thorax cuticles without harming for insect reproductive traits.

Understanding the impact of Y2+ (Y[dbnd]Mn, Fe, and Co) cations on physical properties of SrYGe2O6 clinopyroxene: A DFT insight

Pyroxenes are one of the most important minerals in igneous rock with extremely varied compositions. Here, the structural, mechanical, magnetic, thermodynamic, and optoelectronic features of the SrYGe2O6 (Y= Mn, Fe, and Co) in the monoclinic phase is presented by the density functional theory (DFT) investigation. The generated structures using GGA-PBE, GGA-PBSOL, and LDA exchange-correlation functional in a ferromagnetic ordering have lattice parameters that agree with the existing experimental data. All of the three structures are found mechanically stable by Born stability criteria. The most ductile material is SrCoGe2O6, whereas Poisson's ratio (σ) predicts that SrMnGe2O6 is brittle. These have metallic nature for one spin state and semiconducting for another spin state, which confirms the half-metallic or half semiconducting nature. The direct type half-metallic gap for SrCoGe2O6, SrMnGe2O6 and SrFeGe2O6 are found as 1.76 eV, 1.252 eV, and 0.701 eV, respectively. A deep electronic structural configuration is analyzed by the bond population analysis. Effective masses of charge carriers and exciton binding energies revealed insight into the transport properties. The structures exhibit significant UV photon absorption, high visible photon reflectivity, and plasmon peaks of about 13 eV were seen in estimated loss function spectra. These characteristics collectively point to possible applications for these pyroxenes in optoelectronics and spintronics.

A surface-enhanced Raman scattering (SERS) biosensor fabricated using the electrodeposition method for ultrasensitive detection of amino acid histidine

The amino acid histidine is an important bioactive molecule for growth and tissue repair and has an influential role as a neurotransmitter in the human musculoskeletal and central nervous systems. Therefore, excessive deficiency of this amino acid and the proteins induced by it causes many diseases. For this reason, the specific and sensitive detection of the amino acid histidine is very important. Surface-enhanced Raman scattering (SERS) is a sensitive method for detecting low concentrations of various substances, especially biomaterials. The silver nanoparticles (AgNPs)-coated substrates were employed in the present investigation to detect the amino acid histidine to control the diseases caused by it. First, a chemical method named Tollens was applied to fabricate AgNPs, and then, the Fluorine-doped tin oxide (FTO) substrates were coated with AgNPs by applying voltage and through the electrodeposition technique. Therefore, AgNPs were fabricated using the Tollens method, as well as the size distribution of nanoparticles was specified as being equal to 130–150 nm by employing dynamic light scattering. Moreover, UV–Vis spectroscopy was employed for the characterization of prepared substrates and AgNPs. The results show that the plasmonic peak tends toward longer wavelengths following the self-array of AgNPs. In addition, it was proved by the field-emission scanning electron microscope (FE-SEM) images that AgNPs on the surface of FTO substrates were distributed non-uniformly. The limit of detection (LOD) was equal to 10−9 for SERS-active substrates for the purpose of detecting this amino acid. Moreover, for ten repeated calculations, the mean relative standard deviation (RSD) was achieved to be 3.86%. Furthermore, the values for the enhancement factor were obtained to be 1.344 × 105 and 1.389 × 105 via experimental and simulation methods, respectively. Thus, the results obtained from Raman indicate that by applying the developed methods, SERS-active substrates coated with AgNPs for the detection of amino acid histidine show advantageous results for SERS-based investigations and can cause the development of nanosensors.

Ni-doped A-site excess SrTiO3 thin films modified with Au nanoparticles by a thermodynamically-driven restructuring for plasmonic activity

Plasmonically active nanoparticles offer a promising pathway to extend the absorption range of photocatalysts. While not necessarily catalytically active themselves, these particles allow the absorption of lower energy photons in wide band gap photocatalysts. Here, we present A-site excess SrTiO3 thin films, doped with Ni, where through a subsequent exsolution process we created well-socketed Ni nanoparticles in the surface of SrTiO3. These were galvanically replaced by Au, resulting in well-socketed Au nanoparticles with variable size on the surface, depending on the galvanic replacement time. Photoelectrochemical measurements and electron energy loss spectroscopy revealed the improved photoresponse of the thin films by plasmonic activity of the nanoparticles. The energy of the plasmon peak suggests that the main improvement results from the injection of hot charge carriers. Our study opens new avenues for the design and synthesis of the next generation of photocatalytic materials.

Molecular beam epitaxial growth of multilayer 2D-boron nitride on Ni substrates from borazine and plasma-activated nitrogen

2D boron nitride (2D-BN) was synthesized by gas-source molecular beam epitaxy on polycrystalline and monocrystalline Ni substrates using gaseous borazine and active nitrogen generated by a remote plasma source. The excess of nitrogen atoms allows to overcome the thickness self-limitation active on Ni when using borazine alone. The nucleation density and the shape of the 2D-BN domains are clearly related to the Ni substrate preparation and to the growth parameters. Based on spatially-resolved photoemission spectroscopy and on the detection of the π plasmon peak, we discuss the origin of the N1s and B1s components and their relationship with an electronic coupling at the interface. After optimization of the growth parameters, a full 2D-BN coverage is obtained, although the material thickness is not evenly distributed. The 2D-BN presents a granular structure on (111) oriented Ni grains, showing a rather poor cristallographic quality. On the contrary, high quality 2D-BN is found on (101) and (001) Ni grains, where triangular islands are observed whose lateral size is limited to ∼20 μm.