Mixed Nanoclusters Research Articles

Cluster-Assisted Mesoplasma Chemical Vapor Deposition for Fast Epitaxial Growth of SiGe/Si Heterostructures: A Molecular Dynamics Simulation Study.

Co-condensation of mixed SiGe nanoclusters and impingement of SiGe nanoclusters on a Si substrate were applied using molecular dynamics (MD) simulation in this study to mimic the fast epitaxial growth of SiGe/Si heterostructures under mesoplasma chemical vapor deposition (CVD) conditions. The condensation dynamics and properties of the SiGe nanoclusters during the simulations were investigated first, and then the impingement of transient SiGe nanoclusters on both Si smooth and trench substrate surfaces under varying conditions was studied theoretically. The results show that the mixed nanoclusters as precursors demonstrate potential for enhancing epitaxial SiGe film growth at a high growth rate, owing to their loosely bound atomic structures and high mobility on the substrate surface. By varying cluster sizes and substrate temperatures, this study also reveals that smaller clusters and higher substrate temperatures contribute to faster structural ordering and smoother surface morphologies. Furthermore, the formed layers display a consistent SiGe composition, closely aligning with nominal values, and the cluster-assisted deposition method achieves the epitaxial bridging of heterostructures during cluster impingement, highlighting its additional distinctive characteristics. The implications of this work make it clear that the mechanism of fast alloyed epitaxial film growth by cluster-assisted mesoplasma CVD is critical for extending it as a versatile platform for synthesizing various epitaxial films.

Adsorption of melphalan anticancer drug on C24, B12N12, B12C6N6, B6C12N12 and B6C6N12 nanocages: A comparative DFT study

Anticancer drug delivery is becoming a central scientific defy since it allows locating drug release near the tumor cell and circumventing secondary side effects. Based on density functional theory (DFT) calculations, adsorption of most abundant melphalan anticancer drug specie at physiological pH on a series of small 24 atoms nanoclusters (C24, B12N12 and carbon doped boron nitride molecules: B12C6N6, B6C12N6 and B6C6N12), was carried out both in vacuum and solvent (water) environment conditions at B3LYP-D3(BJ)/6-31G(d,p) level of theory. The most stable chemisorption state for melphalan was through oxygen atom onto all nanocluster under study, in comparison with chlorine and nitrogen atoms and comparing both environments, the computed results indicate that the adsorption of melphalan in the solvent environment is in general more stable. According to our results, boron nitride and some of its mixed nanoclusters may serve as potential drug delivery nanovehicles for melphalan drug. The results from this work are expected to motivate further inquiries concerning these systems, using both theoretical and experimental approaches, in order to validate their versatility as nanovehicles.

Unexpected trend for thermodynamic stability of Au@void@AgAu yolk-shell nanoparticles: A molecular dynamics study

In this study, Au@void@AgAu yolk-shell nanoparticles with different shell compositions were investigated by molecular dynamics simulation. Various Ag mole fractions in the shell of nanoclusters were considered. The results indicated that sizes of these nanoparticles play the key role in their thermodynamic stability, in such a way that the ratio of external radius to the thickness of the shell region should be decreased enough to reach a thermodynamic stability at room temperature. For small nanoparticles with large ratio of external radius to the thickness of the shell region, collapse of the shell leads to complete filling of the void space and creation of the more stable Au@AgAu core-shell or mixed nanoclusters. Hence, they are not stable at room temperature.

Specifics of luminescence of nanoclusters consisting of InP@ZnS colloidal quantum dots stabilized by oleylamine

Spectral, luminescent, and kinetic characteristics of nanoclusters of hydrophobic colloidal quantum dots (CQDs) of the core@shell type InP@ZnS stabilized by oleylamine have been studied, with the nanoclusters consisting of CQDs of two average sizes: with core diameters of 2.1 and 3.0 nm. For the nanoclusters consisting of the particles of any of these kinds, the experimental data indicate the occurrence of Forster resonance energy transfer with an efficiency of about 50%. For the mixed nanoclusters, energy transfer has not been observed within the experimental error.

Valence band of Co/Cu thin film studied with synchrotron radiation photoemission spectroscopy

The electronic structure of Co (100 Å)/Cu (50 Å) bilayer film on Si(100) has been investigated using valence band photoemission at 50 eV. The aim is to understand the Co/Cu interface and the nature of intermixing in Co and Cu layers. The valence band of Co/Cu interface shows three features at −0.3, −1.17 and −1.9 eV binding energy. The experimental observations are explained with the help of calculations based on projected augmented wave pseudopotential method using density functional theory. The origin of −0.3 eV feature is mainly due to the Co 3d minority spin states while the features at −1.17 and −1.9 eV are due to the formation of Co and Co–Cu mixed nanoclusters at the interface.

Nanoporous Membranes with Mixed Nanoclusters for Raman-Based Label-Free Monitoring of Peroxide Compounds

Monitoring trace amounts of peroxide-based molecules is challenging because of the lack of common optical signatures (fluorescence or absorption in UV-vis range) or chemical functionality easily detectable with common routines. To overcome this issue, we suggest a photochemical decomposition approach followed by the analysis of chemical fragments by a fast, sensitive, and reliable Raman spectroscopic method. To facilitate this approach, we employed a novel design of surface-enhanced Raman scattering (SERS)-active nanoporous substrate based on porous alumina membranes decorated with mixed nanoclusters composed of gold nanorods and nanoparticles. The detectable amount of HMTD below 2 pg demonstrated here is about 3 orders of magnitude lower than the current limit of detection. We suggest that laser-induced photocatalytic decomposition onto nanoparticle clusters is critical for achieving label-free detection of unstable and nonresonant organic molecules.

Light Energy Conversion Using Mixed Molecular Nanoclusters. Porphyrin and C60Cluster Films for Efficient Photocurrent Generation

Composite molecular nanoclusters of fullerene and porphyrin prepared in acetonitrile/toluene mixed solvent absorb light over the entire spectrum of visible light. Upon slow evaporation of the solvent on the copper grid, these mixed nanoclusters undergo close-packed stacking to produce either tubular- or square-shaped microcrystallites and differ from those obtained from single-component clusters. The highly colored composite clusters can be assembled as 3-dimensional arrays onto nanostructured SnO2 films using an electrophoretic deposition approach. The composite cluster films exhibit an incident photon-to-photocurrent efficiency (IPCE) as high as 17% at an applied potential of 0.2 V vs SCE, which is significantly higher than the additive effect observed from either porphyrin (IPCE = 1.6%) or fullerene clusters (IPCE = 5.0%) under similar photoelectrochemical conditions. The high IPCE values observed with porphyrin and C60 clusters demonstrate the synergy of these systems toward yielding efficient photoinduced charge separation within these composite nanoclusters.

Combinatorial Design of Copper‐Based Mixed Nanoclusters: New Catalysts for Suzuki Cross‐Coupling

AbstractQuantum dots (2–5 nm) of copper and copper/palladium mixtures are found to be good catalysts for Suzuki cross‐coupling. The catalysts are applicable to a wide range of iodo‐ and bromoaryl substrates, and give moderate yields using chloroaryl substrates. Cluster activity and stability is found to depend strongly on the preparation method and the reaction conditions. The mechanism of cluster deactivation and the sensitivity of the cluster‐catalysed reaction to substituent effects are studied and discussed.