Nanoscale Advances最新文献

We performed extensive all-atom molecular dynamics simulations to investigate the interaction dynamics and orientation of levofloxacin, a newer fluoroquinolone antibiotic, with anionic (SDS) and cationic (CTAB) micelles. The maximum drug/micelle ratio (loading capacity and entrapment efficiency) was estimated for anionic and cationic micelles. High encapsulation efficiencies were observed for SDS (average: ∼80%). In contrast, for CTAB micelles, the efficiency was ∼8%, indicating that the binding of levofloxacin molecules to SDS micelles is significantly higher than that to CTAB micelles. Tilted orientations were observed for levofloxacin in SDS micelles (∼48-51°) and in CTAB micelles (∼40-42°), where the positively charged piperazine group is anchored to anionic headgroups. In contrast, the negatively charged carboxylic group is close to cationic headgroups. Calculating the relative binding energies, we found that levofloxacin binds more strongly to SDS than CTAB. Due to π-π interactions and hydrogen bonding, the formation of concerted columnar stacks of levofloxacin was also recorded for both anionic and cationic micelles.

In this study, gallium-doped zinc oxide (GZO) nanoparticles were synthesized via a sol-gel approach followed by controlled thermal treatment, yielding nanocrystalline semiconductors with tunable Ga concentrations for advanced plasmonic applications. Structural and morphological analyses using transmission electron microscopy (TEM) revealed uniform grain distribution with particle sizes of ∼60-80 nm and the preservation of the wurtzite crystal framework. It further confirmed the successful substitution of Zn²⁺ by Ga³⁺ ions (2.5% doping), demonstrating effective doping without disrupting the lattice integrity. The analysis of the complex dielectric function, including the real (ε ₁) and imaginary (ε ₂) components, exhibited a crossover of ε ₁ from negative to positive values and a corresponding peak in ε ₂ within the near-infrared region, indicative of strong plasmonic resonance. Complementary electron energy loss spectroscopy (EELS) revealed a sharp, intense peak near ∼0 eV, confirming the presence of collective free-carrier oscillations. To rationalize these observations, first-principles density functional theory (DFT) calculations were performed, revealing an energy gap of 3.1 eV. We have observed an upward shift of the Fermi level toward the conduction band, consistent with enhanced free-carrier density due to Ga incorporation. The emergence of partially occupied conduction states, spanning -1.3 to -1.7 eV for GZO2.5 and GZO6.25, promotes intraband transitions, leading to a pronounced low-energy optical response and a robust epsilon-near-zero (ENZ) effect. Collectively, these results highlight the coexistence of semiconducting and plasmonic behavior in GZO nanoparticles, underscoring their potential for tunable optoelectronic devices, low-loss infrared plasmonics, and ENZ-enabled photonic applications.

Magnetic nanoparticles (MNPs) can be functionalized with targeting ligands to give them an affinity for a biomolecule of interest. Functionalized MNPs (fMNPs) can aggregate in the presence of a multivalent target, causing a change in their magnetization. The 3rd harmonic phase of the fMNP magnetization signal can be proportional to the multivalent target concentration. When fMNPs are suspended in protein rich media (like biological fluids), off-target proteins tend to non-specifically adsorb to them, potentially masking their targeting ligands, and leading to a change in fMNP target affinity. The layer of adsorbed off-target proteins is commonly referred to as a protein corona. We used a model system consisting of biotinylated MNPs that target streptavidin to study the impact of protein corona formation on fMNP-based biosensing. Interestingly, the resolution of our biotinylated MNP-based aggregation assay changed from 64.43 nM streptavidin in the absence of off-target serum proteins, to 3.22 nM streptavidin in the presence of off-target serum proteins. Therefore, biotinylated MNP streptavidin sensitivity increased in the presence of off-target serum proteins. We attribute the increase in biotinylated MNP streptavidin sensitivity to competition between streptavidin and off-target serum proteins with a low biotin binding affinity. In contrast, competition between streptavidin and an off-target protein with a high biotin binding affinity decreased biotinylated MNP streptavidin sensitivity. Our results can be leveraged to inform the design optimization of an in vivo fMNP-based biosensor. Additionally, our results can also be leveraged to design an in vitro fMNP-based biosensor with a diluent off-target protein concentration and binding affinity optimal for target quantification in a tailored range.

A microfluidic enzymatic sensor based on cross-linked crystals of an ancestral β-lactamase (βLa-CLECs) was developed for the detection of β-lactam antibiotics under continuous flow conditions. The sensor is presented in a modular configuration, consisting of a separated microprobe for enzymatic catalysis, allowing for precise enzyme loading, and a photonic lab-on-a-chip (PhLoC) platform for detection by in-line spectrophotometric measurements. The exceptional thermal stability of the reconstructed Precambrian β-lactamase made it suitable for the steps required in device fabrication and carrier-free immobilization treatment, while its inherent promiscuity, i.e., its capability to degrade a variety of lactam antibiotics, including man-made third-generation antibiotics, broadens its potential application. Full catalytic activity of the ancestral enzyme was retained after immobilization, and inhibition by antibiotics such as ampicillin and sulbactam was detected at concentrations as low as parts per billion. These results support the use of ancient enzymes as stable and responsive biorecognition elements in cost-effective, high-throughput analytical systems targeting environmental pollutants and pharmaceutical compounds.

Methane must undergo complete catalytic oxidation to reduce the emission of unburned methane from power plants and natural gas engines. However, the poor temperature stability of carbon-based supports frequently restricts their usage in methane oxidation. This limitation can be addressed by modifying the carbon structure to enable the development of thermally resilient catalysts. This study utilises onion-like carbon (OLC), a support material made from nanodiamonds by high-temperature calcination, to disperse palladium (Pd) nanoparticles (Pd/OLC). The choice of OLC as the support is based on its distinct physicochemical merits (i.e., enhanced graphitization, a more ordered but defect-rich architecture, better thermal transport and porosity, gas-accessible active sites, improved electrical conductivity and structural stability). The resultant OLC promoted exceptional catalytic activity in the Pd/OLC by offering increased graphitisation, superior gas transport, accessible active sites, and exceptional temperature stability. The effect of adding nickel oxide (NiO) to Pd/OLC in PdNiO/OLC was also investigated, and the results show increased catalytic effectiveness through improved surface area, refined metal dispersion, and reduced particle size. PdNiO/OLC achieves full methane oxidation (T ₁₀₀) at a lower temperature (400 °C) than Pd/OLC (450 °C) and commercial Pd/C (650 °C). These results demonstrate the potential of OLC as a strong carbon support for gas-phase catalytic processes at high temperatures, which extends beyond methane combustion.

In situ monitoring of chemical reactions, specifically reactions leading to the formation of plasmonic nanomaterials within droplets, has become a necessity for several applications in nanotechnology and sensing. In this study, we use a custom-designed optical transmission spectroscopy setup that can detect signals from a single anisotropic droplet over the entire visible spectral range (400-900 nm) without the use of external additives as reporters. We use data obtained from light scattered by the droplets to differentiate the 'drop only' regions from the 'oil only' regions and to extract information from within single droplets. We then load the droplets with anisotropic gold nanoparticles of different concentrations and show the variations in the optical signals based on their concentrations from single droplets and compare the data to the averaged data from several droplets, to demonstrate the validity of our technique. Finally, we employ the developed platform for monitoring in situ synthesis of gold nanoparticles within a microfluidic chip in real-time. Measurement at different locations along the channel enables us to track the reaction within a droplet at different time points, providing insights into the reaction kinetics. We also measure spectral data to understand the influence of reagent concentration on the synthesis. The developed technique can thus be employed for in situ monitoring of any chemical reaction within a single anisotropic droplet, provided it has absorption/transmission signatures, and will find wide applicability in the development of single-droplet analysis platforms.

Sulphur incorporation plays a crucial role in the formation of Mo-S-I nanostructures, but its effect on phase stability and morphology has remained unclear. Here, we show that trace sulphur stabilizes a metastable MoI_2-x S _x phase that grows as high-aspect-ratio nanowires (NWs), in contrast to the low-aspect-ratio prisms of pure MoI₂. These intermediate NWs subsequently transform into Mo₆S₂I₈ NWs, revealing a sulphur-promoted growth pathway. Structural and electronic characterization using XRD, TEM, SEM, UV-Vis, Raman, UHV AFM/KPFM, and STM/STS clarifies the ambiguous role of MoI₂. The MoI_2-x S _x NWs show diameters of 100-300 nm, lengths up to 20 µm, and a nominal composition of 7.5% S, 38% Mo, and 54.5% I. Work function measurements indicate a progressive shift from 4.6 ± 0.1 eV in the intermediate phase to 5.0 ± 0.1 eV in the final Mo₆S₂I₈ NWs, while density-of-states analysis reveals a U-shaped band gap of ∼1.2 eV in the NW cores. Our results establish a general concept: minor compositional tuning can stabilize metastable intermediates as templates for controlled nanowire morphology and function, opening pathways for optoelectronic, nanoelectronic, and composite applications.

Rechargeable calcium-ion batteries offer a promising solution for energy storage due to calcium's natural abundance, high deposition potential, and superior energy density compared to magnesium-ion systems. Their divalent nature further enhances their appeal for next-generation battery technologies. In this study, we present a DFT analysis focusing on Janus transition metal dichalcogenides (TMDs) as potential anode materials for Ca ion batteries utilizing the GGA-PBE exchange-correlation functional. The research explores the structural, electronic, and adsorption characteristics of nanosheets such as ScSeS, ScTeS and TiSeS. All investigated TMDs show favorable Ca adsorption with negative adsorption energies that preserve structural integrity without notable distortion, thus confirming structural stability. Band structure analysis further reveals that ScSeS, ScTeS, and TiSeS display metallic behavior, as evidenced by conduction bands that cross the Fermi level. In addition, cohesive energy calculations provide values of -1.28, -2.17, and -2.06 eV per atom for ScSeS, ScTeS, and TiSeS, respectively, underscoring their energetic stability. Low diffusion barriers have been found for the three nanosheets. Furthermore, ScSeS and TiSeS nanosheets demonstrate high theoretical specific capacities of approximately 436.73 mAh g^-1 and 428.84 mAh g^-1, with low OCVs of 0.64 V and 0.23 V, respectively. These combined properties position ScSeS and TiSeS as promising anode materials for calcium-ion batteries.

Squeezing optical fields into resonant modes with deep-subwavelength volumes is crucial for advancing quantum optics and nanoscale sensing. A promising approach is to harness surface plasmon modes in resonators composed of stacked metal-insulator-metal cylindrical layers, where optical fields in the visible and infrared ranges are transformed into strongly confined gap modes. In a structure with cylindrical symmetry, whispering gallery modes form a family of eigenmodes with a high azimuthal order, which are typically inaccessible in plasmonic sandwich configurations under plane wave illumination, and their excitation usually requires carefully positioned focused electron probes. Here, we propose an efficient method for exciting whispering gallery modes in gap-surface plasmon resonators using plane wave excitation. The introduction of a nanoscale through-split in the top metal layer enables the formation of a rich set of WGMs in the near-infrared spectrum, resulting in 2-3 orders of magnitude enhancement in total electromagnetic energy accumulated in the spacer. This strategy offers a practical pathway to unveil hidden modal families in plasmonic sandwich resonators to control light-matter interactions at the nanoscale and to drive the further miniaturization of plasmonic devices.

The co-occurrence of per- and polyfluoroalkyl substances (PFAS) and nanoplastics (NPs) poses a synergistic threat to environmental and human health, yet the molecular mechanisms governing PFAS-NP complexation and membrane interactions remain unclear. Using atomistic molecular dynamics simulations, we investigated the adsorption of neutral polytetrafluoroethylene (PTFE) and anionic perfluorinated compounds (perfluorooctanoic acid, PFOA, and perfluorooctanesulfonic acid, PFOS) on polystyrene NPs (3.1 and 6.7 nm) and their interactions with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. Polystyrene NPs act as carriers, transporting PFAS molecules to the lipid/water interface, where PFAS attachment modifies NP interfacial behavior. PFAS adsorption on the NP surface is driven by hydrophobic and fluorophilic interactions. Neutral PTFE exhibits inhomogeneous, partially penetrated adsorption, while anionic PFOS and PFOA form relatively homogeneous adsorption layers due to electrostatic repulsion among their anionic headgroups. In the POPC membrane, the exposed trimethylammonium groups with non-hydrogen-bonded water prevail over phosphate groups with hydrogen-bonded water, reducing the zwitterionic membrane's resistance to NP adsorption. Consequently, surface hydration hinders the attachment of neutral bare and PTFE-coated NPs, while anionic PFOS-coated NPs rapidly adsorb via electrostatic attraction to the positively charged POPC trimethylammonium groups, overcoming the hydration barrier. PFOA-coated NPs adsorb transiently; however, PFOA detachment exposes the NP core, weakening NP-lipid interactions and leading to NP desorption and insertion of detached PFOA molecules. The addition of 0.1 M KCl does not significantly alter the interfacial behavior of small PFAS-NP complexes.