Bimetallic Core-shell Nanoparticles Research Articles

Hetero-epitaxial grown Pt@Au core-shell bimetallic nanoparticles on reduced graphene oxide (RGO) as electrocatalyst for oxygen reduction reaction in alkaline media

The core-shell structured Pt@Aubimetallic nanoparticles (NPs) were decorated on the reduced graphene oxide (RGO) surface by a heteroepitaxial growth method. The morphological details of Pt@Au/RGO core/shell bimetallic NPs were assessed by high-resolution transmission electron microscopy (HR-TEM), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). Electron microscopy results revealed that Pt@Au particles of 3.4 nm were firmly attached to RGO sheets. The electrochemical response of Pt@Au/RGO nanostructured electrocatalyst was measured through cyclic voltammetry (CV) at room temperature in 0.1 M KOH solution. Oxygen reduction reaction (ORR) efficacies of Pt@Au/RGO were evaluated by linear sweep voltammetry (LSV) by rotating catalyst-coated glassy carbon (GC) electrode at different rotation speeds in oxygen saturated 0.1 M KOH solution. The electrochemical activity descriptors (half-wave potential, onset potential, limiting current density) were assessed from ORR polarisation curves. The results revealed that Pt@Au/RGO bimetallic NPs showed enhanced higher catalytic activity towards ORR compared to commercial Pt/C catalyst as well as similarly synthesised Pt/RGO and Au/RGO. The enhanced catalytic activity of Pt@Au/RGO electrocatalyst might result from the core/shell structure with a tiny Pt core and a thin Au shell, as well as the synergistic effects of Au and Pt.

Theoretical optical characterization of one-dimensional ternary photonic crystal embedded with nanocomposite of bimetallic core-shell nanoparticles

Theoretical optical characterization of one-dimensional ternary photonic crystal embedded with nanocomposite of bimetallic core-shell nanoparticles

Atomistic investigation of pressure effects on sintering of bimetallic core–shell nanoparticles

Pressure-assisted sintering (PAS) utilizing bimetallic core–shell nanoparticles (CS NPs) has garnered widespread attention for its ability to produce advanced components with excellent thermal and electrical conductivities, even at low temperatures. This study presents the first investigation into the PAS of bimetallic CS NPs, using Ag-coated Cu material as a representative system, through all-atom molecular dynamics (MD) simulations. The study provides detailed insights into the atomic-scale processes and mechanisms that govern pressure-assisted sintering, elucidating the coalescence phenomena and revealing the significant influence of external pressure. By comparing atomistic behaviors, such as diffusion, migration, and microstructure evolution, between PAS and thermal sintering, a deeper understanding of the underlying mechanisms is achieved. Furthermore, the results highlight the importance of considering microstructural characteristics in addition to void fraction assessment for accurately estimating mechanical properties. This study enhances our understanding of sintering methods and offers a new perspective on designing process conditions in the PAS process.

Ameliorative and Neuroprotective Effect of Core-Shell Type Se@Au Conjugated Hesperidin Nanoparticles in Diabetes-Induced Cognitive Impairment.

Diabetes mellitus is the most chronic metabolic ailment characterized by insulin deficiency leading to aberrant cognitive dysfunction in later stages. Hesperidin is a bioflavonoid, having different pharmacological activities, but its poor water solubility and short plasma half-life restrict its applications in the clinical field. So, the hesperidin was conjugated with gold, selenium, and core-shell bimetallic nanoparticles of gold and selenium. Different spectroscopic methods characterized the synthesized monometallic and bimetallic nanoparticles. The rats were injected with streptozotocin to induce cognitive dysfunction, followed by administering HSP, HSP-Au NPs, HSP-Se NPs, and Se@Au-HSP NPs daily for 21 days. Then, the neurobehavioral studies, oxidative stress parameters, AChE and nitrite levels, the content of amyloid-β42, and inflammatory mediators were accessed to evaluate the effect of the nanoparticles against the STZ rat model. The results showed a significant increase in oxidative stress, AChE activity, amyloid-β42, nitrite levels, and neuroinflammation by upregulating the inflammatory cytokines in the streptozotocin-administered rat brain. The HSP, HSP-Au NPs, HSP-Se NPs, and Se@Au-HSP NPs effectively reversed all these effects of streptozotocin. However, the bimetallic nanoparticle Se@Au-HSP NPs revealed better neuroprotective action than HSP-Au NPs and HSP-Se NPs. Hesperidin-conjugated bimetallic nanoparticles improved learning and memory in the STZ rat model and may be an alternative approach for neurodegenerative diseases, including Alzheimer's disease.

Barbican-inspired bimetallic core–shell nanoparticles for fabricating natural leather-based radiation protective materials with enhanced X-ray shielding capability

With the wide application of X-rays, the development of flexible and efficient radiation protective materials to reduce the hazards of radiation is in great demand. Inspired by the Barbican defense system, the bimetallic nanocomposites were designed and assembled to trap X-rays photons to experience ordered and cyclic attenuation behavior, where two high-atomic-number elements with different absorption edges, Bismuth (Bi) and Tin (Sn), are assembled into a core–shell nanostructure (Bi@Sn) and were then evenly dispersed into natural leather (NL) to fabricated a high-efficiency wearable radiation protective material (Bi@Sn/NL). Benefiting from the well-defined Barbican-effect mechanism of the core–shell nanostructure, Bi@Sn nanoparticle features more efficient X-ray shielding capability than Bi+Sn nanoparticles mixtures which directly mixed Bi and Sn, and a 2.0 mm-thick Bi2.31@Sn2.43/NL could achieve a comparable attenuation efficiency to a 0.25 mm lead plate and averagely exceeded ∼10.4% than Bi2.31+Sn2.43/NL. Furthermore, Bi2.31@Sn2.43/NL also displays superior physiomechanical properties to the requirements of the Chinese National Standard and features an ultralow density of 1.2876 g cm−3. This work is expected to provide a promising strategy for the design and development of lightweight and high-efficiency wearable radiation protective materials.

Structural Analysis of PtPd Core‐Shell Bimetallic Nanoparticles and their Enhanced Catalytic Performance for Ethanol Oxidation Reaction

AbstractDirect alcohol fuel cells are claiming to be one of the primary clean power sources to attain a sustainable future. In the present study, PtPd core‐shell bimetallic nanoparticles (CSNPs) were synthesized by the polyol method. The shell was adjusted by adding an increased amount of Pd precursor on pre‐synthesized Pt nanoparticles. The morphology and atomic structure of the PtPd CSNPs were characterized by X‐ray diffraction and high‐resolution scanning transmission electron microscopy. PtPd CSNPs were successfully supported on Vulcan XC‐72 carbon and verified by scanning electron microscopy. The electrocatalysts were tested by cyclic voltammetry in an alkaline medium for the activity performance to ethanol oxidation reaction. The stability along with the presence of poisoning carbonaceous species was investigated by chronoamperometry and voltammetry cycles. Also, the cyclic durability was analysed. The results confirmed that the catalytic performance depends on the elemental composition of PtPd CSNPs, showing the optimum catalytic properties to PtPd (1 : 0.5)/C than commercial Pt/C.

Synthesis and Catalytic Study of NiAg Bimetallic Core-Shell Nanoparticles.

This publication presents the synthesis of core-shell nanoparticles, where the core was Ni, and the shell was a Ag-Ni nano alloy. The synthesis was based on the reduction of Ni and Ag ions with sodium borohydride in the presence of trisodium citrate as a stabilizer. In order to determine the phase composition of the obtained nanoparticles, an XRD study was performed, and in order to identify the oxidation states of the nanoparticle components, an XPS spectroscopic study was performed. The composition and shape of the particles were determined using the HR-TEM EDS test. The obtained nanoparticles had a size of 11 nm. The research on catalytic properties was carried out in the model methylene blue reduction system. The investigation of the catalytic activity of colloids was carried out with the use of UV-Vis spectrophotometry. The Ag-Ni alloy was about ten times more active than were pure silver nanoparticles of a similar size.

Barbican-Inspired Bimetallic Core–Shell Nanoparticles with Enhanced X-Ray Shielding Capability for Fabricating High-Efficiency Radiation Protective Materials

Barbican-Inspired Bimetallic Core–Shell Nanoparticles with Enhanced X-Ray Shielding Capability for Fabricating High-Efficiency Radiation Protective Materials

Bimetallic core-shell nanoparticle arrays at liquid-liquid interface for the degradation and monitoring of dye pollutants in situ by surface-enhanced Raman spectroscopy.

In situ monitoring of chemical reactions has attracted great attention in many fields. Herein, we successfully in situ track the degradation reaction process of a dye pollutant, methylene blue (MB), on the liquid-liquid interface (LLI) of bimetallic gold core-silver shell nanoparticles (Au@AgNPs) by surface-enhanced Raman spectroscopy (SERS). The optimized LLI bimetallic array of Au50@Ag10NPs exhibits ultrahigh SERS enhancement and excellent catalytic activity. Results evidenced a detection limit of MB down to 1 ppb, and the degradation rate of Au@AgNPs was as high as 85.2% in 30 s, relying on the excellent self-healing properties of nanoarrays. Furthermore, as a practical SERS analyzer, the LLI bimetallic array was used to detect trace amounts of other harmful dyes, including Rhodamine 6G (R6G) and crystal violet (CV) in pure or complex media. Our LLI bimetallic array exhibits a new orientation for monitoring catalytic reactions involving highly toxic, hazardous, or costly targets in food security fields in the future.

Mesoporous silica coated core-shell nanoparticles substrate for size-selective SERS detection of chloramphenicol

With the growing popularity of the non-destructive technique, surface-enhanced Raman spectroscopy (SERS) demands a highly sensitive and reproducible plasmonic nanoparticles substrate. In this study, a novel bimetallic core–shell nanoparticles (Au@Ag@mSiO2NP) substrate consisting of a gold core, silver shell, and a mesoporous silica coating was synthesized. The mesoporous coating structure was created by employing template molecules such as surfactant and their subsequent removal allowing selective screening based on the size of analyte molecules. Results showed that the plasmonic substrate could selectively enhance small molecules by preventing large macromolecules to reach the exciting zone of the substrate core, achieving the detection of chloramphenicol in milk samples with a detection limit of 6.68 × 10−8 M. Moreover, the mesoporous coating provided additional stability to the Au@Ag nanoparticles, leading to the reusability of the substrate. Thus, this work offered a simple and smart Au@Ag@mSiO2NP substrate for effective SERS detection of analytes.

Exploring bimetallic Au–Ag core shell nanoparticles reduced using leaf extract of Ocimum tenuiflorum as a potential antibacterial and nanocatalytic agent

Biosynthesis of bimetallic Au–Ag core shell nanoparticle under ambient condition using Ocimum tenuiflorum (Krishna Tulsi) leaf extract is being reported for the first time. For the biosynthesized bimetallic core shell nanoparticles (OTAuAgNPs) visual and spectrophotometric analysis was performed. Development of a deep purple color suggested the creation of OTAuAgNPs. It was then validated by UV–Vis spectrophotometry within 4 h of incubation showing a surface plasmon resonance peak at 560 nm. FESEM-EDAX, FT-IR, particle analyzer and XRD were the analytical techniques employed to characterize the biosynthesized OTAuAgNPs. Using a known antibiotic as a control, OTAuAgNPs (10 mg/ml) had a substantial bacteriostatic effect against Gram + ve (Bacillus subtilis) and Gram −ve (E.coli, Pseudomonas aeruginosa) bacteria. The OTAuAgNPs (6.5 mg) showed good catalytic action for the adsorption of Coomassie brilliant blue R250 dye (CBB) (50 mg/L, 25 mL), confirmed by the reduction in absorbance maxima that is time dependent. A remarkable adsorption of CBB (94.79%) was attained within 120 min, and the results were best-suited PSO and Elovich models with adsorption kinetic constant of 5.96E−04 g/mg.min and 37.81 mg/g.min, respectively. Further the toxicity studies of brilliant blue R250 dye and metabolite of CBB (post nano-remediated dye solution) was carried out on Vigna radiata (green gram) germination and growth. OTAuAgNPs as nanocatalyst remediated water revealed that it was nontoxic. Thus an ecofriendly and cost-effective approach for bimetallic nanoparticle synthesis could be further explored for removal of CBB from wastewater effluents.

Probing Optical Nonlinearities of Unconventional Glass Nanocomposites Made of Ionic Liquid Crystals and Bimetallic Nanoparticles.

In this paper, we report the synthesis and characterization of unconventional nanocomposites made of bimetallic nanoparticles dispersed in a liquid crystal glass. Core-shell bimetallic nanoparticles (Ag/Au or Au/Ag) and Ag-Au bimetallic nanoalloys are synthesized using cadmium alkanoate glass-forming liquid crystals as nanoreactors. Optical spectra of the produced glassy nanocomposites exhibit a distinctive absorption peak due to a surface plasmon resonance. In addition, these unusual materials demonstrate a strong nonlinear–optical response probed by means of the Z-scan technique. The use of near-infrared (1064 nm) and visible (532 nm) nanosecond laser pulses reveal a variety of nonlinear–optical mechanisms that depend on the composition of the studied nanocomposites. Our results indicate that metal alkanoate-based glass-forming ionic liquid crystals with embedded plasmonic nanoparticles are promising, yet they are overlooked photonic nanomaterials suitable for optical and nonlinear-optical applications.

Restructuring in bimetallic core-shell nanoparticles: Real-time observation

The formation process of core-shell bimetallic nanoparticles synthesized by sputtering onto a substrate is observed in real time using an originally developed acoustic technique. The technique enables us to evaluate the structural change of nanoparticles at room temperature without contacting the nanoparticles or substrate. In the experiments, the sputtering of metal A followed by metal B tended to form B-shell/A-core nanoparticles. However, in Pd-Au alloy system, notable restructuring occurred during synthesis, resulting in the formation of A-shell/B-core nanoparticles. The formation process is analyzed using the molecular dynamics simulation, revealing that this restructuring occurs on a short timescale, and high diffusivity of Au plays an important role.

Rationalization of the sub-surface segregation in nanoalloys of weakly miscible metals.

The origin of the stability of sub-surface precipitates in core-shell bimetallic nanoparticles is investigated from the perspective of atomic-size effects for systems where the core atoms have a size equal to, or lower than, the shell atoms. With the aim of providing more general assessments, a systematic study is proposed by considering three model systems combining weakly miscible metals: IrPd (negligible lattice mismatch, Δr/rPd = -1%), AuRh (moderate lattice mismatch, Δr/rAu = -7%) and AuCo (large lattice mismatch, Δr/rAu = -13%). The main driving forces for sub-surface segregation and the characteristic core morphologies are quantified from the combination of Monte Carlo and quenched molecular dynamics simulations. The preferential occupation of the sub-surface shell by an impurity of Ir or (Co or Rh) in a Pd or Au nanoparticle, respectively, in particular at the sub-vertex sites, is found to be a common feature in these dilute nanosystems. With the help of a model of the decomposition of the segregation enthalpies, it is shown that the dominant driving forces leading to the preferential sub-surface segregation at the vertex sites can be very different from one system to another: atomic size (AuCo, large lattice mismatch), coupled alloy-size-cohesion (AuRh, moderate lattice mismatch) or coupled alloy-cohesion (IrPd, negligible lattice mismatch) effects. As a consequence, in the core-shell nanoalloys, in the first stage of enrichment of an Au nanoparticle with Co or Rh core atoms, or a Pd nanoparticle with Ir core atoms, all the equilibrium structures consist of similar off-center solute clusters anchored at sub-vertex sites, and this is regardless of the lattice mismatch.

Discrete sources method for modeling of the influence of the non-local effect on the absorption of bimetallic core-shell non-spherical plasmonic nanoparticles

Core-shell bimetallic particles are of great interest, since their plasmonic properties can differ significantly from the properties of their constituent components. In chemistry, they are widely used to improve various photovoltaic energy conversion processes, because they have good absorption and heat transfer properties. In this paper, the generalized non-local optical response theory is used in conjunction with the discrete sources method to examine the impact of spatial nonlocality on the absorption properties of spheroidal core-shell particles composed of two plasmonic metals. It is demonstrated that variation of the core diameter and the thickness of the shell, as well as, as the particle elongation increases the absorption and shifts its maximum to longer wavelengths. Besides, it was found that accounting for spatial dispersion in both metals will reduce the absorption to 65 % of its value without including the nonlocal effect and the corresponding blue shift can exceed 15 nm.

Coal mine gases sensors with dual selectivity at variable temperatures based on a W18O49 ultra-fine nanowires/Pd@Au bimetallic nanoparticles composite

In spite of protecting the safety of miners has been valued by departments, it is still a severe technical challenge to monitor coal mine gases which are generally explosive or poisonous. In this work, Pd@Au core-shell bimetallic nanoparticles (BNPs) are employed to decorate ultra-fine W18O49 nanowires (NWs), which are consequently used to detect coal mine gases. The W18O49 NWs were synthesized by a facile solvothermal method. And different noble metals including Pd and different BNPs were prepared for constructing metal oxide semiconducting gas sensors (MOS). Their structures and morphologies were characterized in detail, and the gas sensing mechanism was discussed in depth. It has been found that W18O49 NWs decorated with Pd@Au BNPs own enhanced gas sensing properties toward H2S and CH4. More importantly, W18O49 NWs/BNPs-2 has dual selectivity at different temperatures. At 100 ℃, the response of the optimized sensor to 50 ppm H2S is 55.5, accordingly, it has only little response to CH4. While at 320 ℃, the response to 1000 ppm CH4 is 7.8, and exhibits good selectivity. This work is of significance for the detection of coal mine gases, and has an application potential in ensuring the safety of mine work.

Bimetallic core-shell nanoparticles to improve the absorption of P3HT: PCBM organic solar cell.

In this paper, we have theoretically studied a poly (3-hexylthiophene): 6,6-phenyl C61-butyric acid methyl ester (P3HT: PCBM) organic solar cell with randomly dispersed bimetallic nanoparticles. We have considered bimetallic core-shell Ag-Au nanoparticles as scattering centers randomly distributed among the active layer of a P3HT: PCBM solar cell. To study the role of Ag-Au nanoparticles, we have used the effective medium theory. The extinction and scattering cross sections of core-shells have been calculated based on the extended Mie theory. The scattering cross section of the active layer has been calculated by combining the extended Mie theory with the effective medium theory. The calculated current-voltage curve of solar cells has been compared with the experimental data of similar works to check the model's validity. In the optimized situation, it shows good agreement with experimental data, and we have obtained about 59% enhancement in the short circuit current of the solar cell.

Towards an understanding of the localized surface plasmon resonance decay pathways in bimetallic core–shell nanoparticles

Exploring the energy transfer mechanisms and understanding the localized surface plasmon resonance (LSPR) decay pathways of plasmas are of great importance for realizing effective composition adjustment and optimization of these novel solar energy materials. In this work, the absorption, scattering, and extinction decay channels of bimetallic core–shell nanostructures were calculated using the finite difference time domain method. Moreover, we separated the energy absorbed in the core and shell of the bimetallic nanoparticles to get a better understanding of the decay pathways of LSPR excited energy. Results indicated that the availability of fast inter-band electron transitions in shell metals is the way to preferentially dissipate the surface electric field energy of nanoparticles. It was supported in essence that the larger imaginary part of the permittivity value of the metal shell is crucial for accelerating the decay channel via the surface of the nanoparticle. This work provided a basic physical framework and transparent design principles for material selection of multifunctional LSPR nanoparticles in practical applications.

The Influence of Size, Shape, and Twin Boundaries on Heat‐Induced Alloying in Individual Au@Ag Core–Shell Nanoparticles

Environmental conditions during real-world application of bimetallic core-shell nanoparticles (NPs) often include the use of elevated temperatures, which are known to cause elemental redistribution, in turn significantly altering the properties of these nanomaterials. Therefore, a thorough understanding of such processes is of great importance. The recently developed combination of fast electron tomography with in situ heating holders is a powerful approach to investigate heat-induced processes at the single NP level, with high spatial resolution in 3D. In combination with 3D finite-difference diffusion simulations, this method can be used to disclose the influence of various NP parameters on the diffusion dynamics in Au@Ag core-shell systems. A detailed study of the influence of heating on atomic diffusion and alloying for Au@Ag NPs with varying core morphology and crystallographic details is carried out. Whereas the core shape and aspect ratio of the NPs play a minor role, twin boundaries are found to have a strong influence on the elemental diffusion.

Gold and Silver Bimetallic Core-shell Nanoparticles with a Polydopamine Interface as an Ideal Catalytic Nanosystem

Çekirdek-kabuk nanopartikül sistemler esnek ve sıradışı özellikleri ile başta katalitik dönüşüm olmak üzere farklı alanlarda kullanılmaktadır. Fakat, bu nanosistemleri üretmek için basit, düşük maliyetli ve yenilikçi stratejiler sınırlı sayıda olup, etkin çekirdek-kabuk nanoyapılar yüksek oranda talep görmektedir. Bu çalışmada ince bir polidopamin (PDOP) tabakası ile oluşturulan bimetalik altın ve gümüş çekirdek-kabuk nanosistemin üretimini önermekteyim. PDOP tabakası bir ara tabaka olarak indirgeme ve stabilize ajan olarak etkin bir performans sunmuştur. Bimetalik çekirdek-kabuk sistemin üretimi elektron mikroskop görüntüleri ve UV-vis absorpsiyon spektrası ile doğrulanmıştır. Nanoyapıların katalitik aktivite testleri, 4-nitrofenolün (4-NP) 4-aminofenole (4-AP) indirgenmesi, çekirdek-kabuk sisteminin tepkimenin ilerlemesini arttırdığı gösterilmiştir. Ayrıca, gümüş indirgeme süresinin önerilen nanosistemin katalitik performansı üzerinde önemli etkiye sahip olduğu gözlenmiştir. 60 dakika gümüş indirgeme süresi için 4-NP’nin 4-AP’ye tamamen dönüşümünün sadece 20 dakikada gerçekleştiği görülmüştür.