Synthesis and characterization of MoSe2 nanoscrolls via pulsed laser ablation in deep eutectic solvents.

There is ongoing interest in the rapid, reproducible production of 2-dimensional (2-D) transition metal dichalcogenides (TMD), such as molybdenum-based TMD (MoX2), where X is a chalcogen atom such as sulphur (S), selenium (Se) or tellurium (Te), driven by their unique optical and electronic properties. Once fabricated into an atomically thin layer structure, these materials have a direct-indirect bandgap transition, strong spin-orbit coupling, and favourable electronic and mechanical strain-dependent properties which are attractive for electronics. Pulsed laser ablation in liquid (PLAL) is an economic, green alternative for synthesis of TMD. It has been shown that in the case of MoX2, the chemical processes during the plasma phase of the ablation can yield the formation of multispecies, including MoOx quantum dots when oxygen-containing solvents are used. Here, we introduce the formation of MoSe2 nanoscrolls with low oxygen content synthesized via pulsed laser ablation in deep eutectic solvents (PLADES). Our results suggest that the synthesis produces a stable colloidal solution of large 2-D structures with tuneable surface charge by replacing the deep eutectic solvent (DES) with DI water. Nuclear Magnetic Resonance (NMR) results suggest that irradiating the solvent at near infrared NIR energy does not affect its chemical composition. NMR also proves that serial washing can completely remove solvent from the nanostructures. Raman shifts suggest the formation of large, thin MoSe2 nanosheets aided by the solvent confinement resulting from van der Waal forces and hydrogen bonds interactions between MoSe2 and urea. Binding energies measured by X-ray photoelectron spectroscopy (XPS) confirm MoSe2-DES preference to form 1T-MoSe2versus molybdenum oxides and 2H MoSe2 in DI-water. Raman and XPS findings were validated by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Results of this work validate the use of PLADES for the synthesis of stable, crystalline, low-surface-oxygen-content colloidal MoSe2 nanoscrolls in scalable quantities.

Synergistic antifungal effect of chitosan-stabilized selenium nanoparticles synthesized by pulsed laser ablation in liquids against Candida albicans biofilms.

BACKGROUND: Candida albicans is a major opportunistic fungal pathogen. One of the most important virulence factors that contribute to the pathogenesis of candidiasis is its ability to form biofilms. A key characteristic of Candida biofilms is their resistance to antifungal agents. Due to significant morbidity and mortality rates related to biofilm-associated drug resistance, there is an urgency to develop novel nanotechnology-based approaches preventing biofilm-related infections. METHODS: In this study, we report, for the first time, the synthesis of selenium nanoparticles by irradiating selenium pellets by nanosecond pulsed laser ablation in liquid chitosan as a capping agent. Synergy of the fungicidal effect of selenium nanoparticles and chitosan was quantified by the combination index theorem of Chou-Talalay. RESULTS: This drug combination resulted in a potent fungicidal effect against a preformed C. albicans biofilm in a dose-response manner. By advanced electron microscopy techniques, we documented the adhesive and permeabilizing properties of chitosan, therefore allowing selenium nanoparticles to enter as the cell wall of the yeast became disrupted and distorted. Most importantly, we demonstrated a potent quantitative synergistic effect when compounds such as selenium and chitosan are combined. CONCLUSION: These chitosan-stabilized selenium nanoparticles could be used for ex vivo applications such as sterilizers for surfaces and biomedical devices.

Inhibition of Candida albicans biofilm by pure selenium nanoparticles synthesized by pulsed laser ablation in liquids.

Selenoproteins play an important role in the human body by accomplishing essential biological functions like oxido-reductions, antioxidant defense, thyroid hormone metabolism and immune response; therefore, the possibility to synthesize selenium nanoparticles free of any contaminants is exciting for future nano-medical applications. This paper reports the first synthesis of selenium nanoparticles by femtosecond pulsed laser ablation in de-ionized water. Those pure nanoparticles have been successfully used to inhibit the formation of Candida albicans biofilms. Advanced electron microscopy images showed that selenium nanoparticles easily adhere on the biofilm, then penetrate into the pathogen, and consequently damage the cell structure by substituting with sulfur. 50% inhibition of Candida albicans biofilm was obtained at only 25 ppm. Finally, the two physical parameters proved to affect strongly the viability of Candida albicans are the crystallinity and particle size.

Ion-ion correlation, solvent excluded volume and pH effects on physicochemical properties of spherical oxide nanoparticles.

One major source of complexity in the implementation of nanoparticles in aqueous electrolytes arises from the strong influence that biological environments has on their physicochemical properties. A key parameter for understanding the molecular mechanisms governing the physicochemical properties of nanoparticles is the formation of the surface charge density. In this article, we present an efficient and accurate approach that combines a recently introduced classical solvation density functional theory for spherical electrical double layers with a surface complexation model to account for ion-ion correlation and excluded volume effects on the surface titration of spherical nanoparticles. We apply the proposed computational approach to account for the charge-regulated mechanisms on the surface chemistry of spherical silica (SiO2) nanoparticles. We analyze the effects of the nanoparticle size, as well as pH level and electrolyte concentration of the aqueous solution on the nanoparticle's surface charge density and Zeta potential. We validate our predictions for 580Å and 200Å nanoparticles immersed in acid, neutral and alkaline mono-valent aqueous electrolyte solutions against experimental data. Our results on mono-valent electrolyte show that the excluded volume and ion-ion correlations contribute significantly to the surface charge density and Zeta potential of the nanoparticle at high electrolyte concentration and pH levels, where the solvent crowding effects and electrostatic screening have shown a profound influence on the protonation/deprotonation reactions at the liquid/solute interface. The success of this approach in describing physicochemical properties of silica nanoparticles supports its broader application to study other spherical metal oxide nanoparticles.

In vitro monitoring of oxidative processes with self-aggregating gold nanoparticles using all-optical photoacoustic spectroscopy.

In this work, the assembly of gold nanoparticles of (AuNPs) is used to detect the presence of the biomolecule glutathione (GSH) using a novel technique called "all-optical photoacoustic spectroscopy" (AOPAS). The AOPAS technique coupled with AuNPs forms the basis of a biosensing technique capable of probing the dynamic evolution of nano-bio interfaces within a microscopic volume. Dynamic Light Scattering (DLS) and ultraviolet-visible (UV-vis) spectra were measured to describe the kinetics governing the interparticle interactions by monitoring the AuNPs assembly and evolution of the surface plasmon resonance (SPR) band. A comparison of the same dynamic evolution of AuNPs assembly was performed using the AOPAS technique to confirm the validity of this method. The fundamental study is complemented by a demonstration of the performance of this biosensing technique in the presence of cell culture medium containing fetal bovine serum (FBS), which forms a protein corona on the surface of the AuNPs. This work demonstrates that the in vitro monitoring capabilities of the AOPAS provides sensitive measurement at the microscopic level and low nanoparticle concentrations without the artifacts limiting the use of conventional biosensing methods, such as fluorescent indicators. The AOPAS technique not only provides a facile approach for in vitro biosensing, but also shed a light on the real-time detection of thiol containing oxidative stress biomarkers in live systems using AuNPs.

Optical and spectroscopic properties of human whole blood and plasma with and without Y2O3 and Nd³âº:Y2O3 nanoparticles.

The optical properties of human whole blood and blood plasma with and without Y2O3 and Nd³âº:Y2O3 nanoparticles are characterized in the near infrared region at 808 nm using a double integrating sphere technique. Using experimentally measured quantities of diffuse reflectance and diffuse transmittance, a computational analysis was conducted utilizing the Kubelka-Munk, the Inverse Adding Doubling, and Magic Light Kubelka-Munk and Monte Carlo Methods to determine optical properties of the absorption and scattering coefficients. Room temperature absorption and emission spectra were also acquired of Nd³âº:Y2O3 nanoparticles elucidating their utility as biological markers. The emission spectra of Nd³âº:Y2O3 were taken by exciting the nanoparticles before and after entering the whole blood sample. The emission from the 4F(3/2) → 4I(11/2) manifold transition of Nd³âº:Y2O3 nanoparticles readily propagates through the blood sample at excitation of 808 nm and exhibits a shift in relative intensities of the peaks due to differences in scattering. At 808 nm, in both whole blood and plasma samples, a direct relationship was found with absorption coefficient and Y2O3 nanoparticle concentration. Results for the whole blood indicate a small inverse relationship with Y2O3 nanoparticle concentration and scattering coefficient and in contrast a direct relation for the plasma.