Unraveling the Formation Mechanism of Dendritic Fibrous Nanosilica

We studied the formation mechanism of dendritic fibrous nanosilica (DFNS) that involves several intriguing dynamical steps. Through electron microscopy and real-time small-angle X-ray scattering studies, it has been demonstrated that the structural evolution of bicontinuous microemulsion droplets (BMDs) and their subsequent coalescence, yielding nanoreactor template, is responsible for to the formation of complex DFNS morphology. The role of cosurfactant has been found to be quite crucial, which allowed the understanding of this intricate mechanism involving the complex interplay of self-assembly, dynamics of BMDs formation, and coalescence. The role of BMDs in formation of DFNS has not been reported so far and the present work allows a deeper molecular-level understanding of DFNS formation

Palladium Nanoparticles Hosted in Poly(ethylenimine) and Poly(ethylene glycol methacrylate phosphate) Anchored Membranes for Catalyzing Uranyl Ions Reduction and Mizoroki–Heck Coupling Reaction

The poly­(ethylenimine) (PEI) and poly­(ethylene glycol methacrylate phosphate) (poly­(EGMP)) functionalized microporous poly­(propylene) membrane have been developed to host the palladium (Pd) nanoparticles (NPs) for catalyzing the inorganic and organic reactions. These functionalized membranes are characterized for their porosities and pore-size distributions. Field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-rays spectrometry (EDX) attached to FE-SEM, and small-angle X-rays scattering (SAXS) have been used to study the Pd NPs size distributions and homogeneous distributions in the membrane matrixes. The average size of Pd NPs has been found to be ≈2 nm in all the membranes by SAXS experiments, and elemental mappings by EDX suggest uniform distributions of Pd NPs. However, a very small number of bigger particles have been formed in the membrane having lowered pore-filling due to lower network elasticity in some region that allowed agglomeration to some extent. The in situ generated H₂ during the decomposition of formic acid on Pd surface is used for the reduction of UO₂²⁺ to U⁴⁺. It has been observed that the primary, secondary, and tertiary amine groups on PEI facilitate the formic acid decomposition preferentially to form H₂. However, the Pd NPs hosted in the poly­(EGMP) seem to be less efficient in reducing uranyl ions that bind strongly with the phosphate groups. The effect of physical structure of membrane matrix on catalyzing the uranyl ion reduction is also studied. The Pd²⁺ and Pd NP-loaded PEI and poly­(EGMP) membranes are also studied for their catalytic activities in the representative Mizoroki–Heck cross-coupling reaction of iodobenzene with ethyl acrylate in the presence of base at 100 °C without any solvent. In this case also, the Pd NPs embedded PEI-membrane has given better yield (76%) in comparison with the poly­(EGMP) membrane (65%) with the same amount of Pd NPs and under similar conditions. However, there have been also marginally higher catalytic activities of the Pd NP-loaded membranes as compared to Pd²⁺ ions loaded in the same host membrane. It has been observed from X-ray photoelectron spectroscopy (XPS) that Pd²⁺ ions are reduced to Pd⁰ that actually catalyze the Mizoroki–Heck cross-coupling reaction

Exclusion from Hexagonal Mesophase Surfactant Domains Drives End-to-End Enchainment of Rod-Like Particles

Anisotropic rod-like particles assemble end-to-end when the surfactant/water matrix in which they are dispersed is cooled from the isotropic to the lyotropic hexagonal phase. We demonstrate the formation of such end-to-end assemblies for gold nanorods, which are tens of nanometers in size, as well as for micrometer-sized ellipsoidal polystyrene particles. In both cases, the particles are well-dispersed in the low-viscosity surfactant/water phase above the isotropic-H₁ transition temperature. On cooling into the H₁ phase, mesophase domains form and the particles are expelled to the isotropic phase. As the H₁ domains grow and finally impinge, the particles are localized at the domain boundaries where they reorient and assemble end-to-end. Remarkably, we observe the formation of end-to-end assemblies of gold nanorods even for volume fractions as low as 2 × 10^–6 in the initially dispersed state. The extent of particle “enchainment” increases with the particle concentration and with the aspect ratio of the particles

Redox Decomposition of Silver Citrate Complex in Nanoscale Confinement: An Unusual Mechanism of Formation and Growth of Silver Nanoparticles

We demonstrate for the first time the intrinsic role of nanoconfinement in facilitating the chemical reduction of metal ion precursors with a suitable reductant for the synthesis of metal nanoparticles, when the identical reaction does not occur in bulk solution. Taking the case of citrate reduction of silver ions under the unusual condition of [citrate]/[Ag⁺] ≫ 1, it has been observed that the silver citrate complex, stable in bulk solution, decomposes readily in confined nanodomains of charged and neutral matrices (ion-exchange film and porous polystyrene beads), leading to the formation of silver nanoparticles. The evolution of growth of silver nanoparticles in the ion-exchange films has been studied using a combination of ^110mAg radiotracer, small-angle X-ray scattering (SAXS) experiments, and transmission electron microscopy (TEM). It has been observed that the nanoconfined redox decomposition of silver citrate complex is responsible for the formation of Ag seeds, which thereafter catalyze oxidation of citrate and act as electron sink for subsequent reduction of silver ions. Because of these parallel processes, the particle sizes are in the bimodal distribution at some stages of the reaction. A continuous seeding with parallel growth mechanism has been revealed. Based on the SAXS data and radiotracer kinetics, the growth mechanism has been elucidated as a combination of continuous autoreduction of silver ions on the nanoparticle surfaces and a sudden coalescence of nanoparticles at a critical number density. However, for a fixed period of reduction, the size, size distribution, and number density of thus-formed Ag nanoparticles have been found to be dependent on physical architecture and chemical composition of the matrix

Mesoporous Alumina (MA) Based Double Column Approach for Development of a Clinical Scale ⁹⁹Mo/^99mTc Generator Using (n,γ)⁹⁹Mo: An Enticing Application of Nanomaterial

This paper describes the utility of mesoporous alumina (MA), a high capacity nanomaterial based sorbent, for the development of a clinical grade ⁹⁹Mo/^99mTc generator using (n,γ)⁹⁹Mo. Synthesis of MA was performed using a glucose template in an aqueous system. Structural characterization of the nanosorbent was carried out by analytical techniques such as X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron miscroscopy (SEM), transmission electron microscopy (TEM), thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. The material synthesized was mesoporous and nanocrystalline, with average crystallite size of 2–3 nm with a large surface area of 230 ± 10 m² g^–1. In order to evaluate the surface charge of MA in aqueous solution, the zeta potential was determined at different pH environments. Adsorption characteristics of the sorbent such as time course of the adsorption, distribution ratios of ⁹⁹Mo and ^99mTc ions, Mo sorption capacity under static and dynamic conditions, ⁹⁹Mo adsorption pattern and ^99mTc elution pattern were determined to assess its effectiveness in the preparation of ⁹⁹Mo/^99mTc generator. The measured distribution ratio values indicate that ⁹⁹Mo is both strongly and selectively retained by MA at acidic pH and ^99mTc could be readily eluted from it, using 0.9% NaCl solution. The static sorption capacity and practical sorption capacity under dynamic conditions of MA was determined to be 225 ± 20 and 168 ± 12 mg Mo per gram of sorbent, respectively. With a view to realize the scope of developing clinical scale generator, a novel tandem column generator concept was used in which two ⁹⁹Mo loaded columns were connected in series. In this method ^99mTc eluted from the first column was fed to the second column to achieve higher radioactive concentration (RAC) as well as purity of ^99mTc. A 26 GBq (700 mCi) ⁹⁹Mo/^99mTc generator was developed using (n,γ)⁹⁹Mo having specific activity of ∼18.5 GBq (500 mCi)/g of Mo. The ^99mTc eluted from the generator possessed high radionuclidic, radiochemical, and chemical purity and was amenable for the preparation of ^99mTc-labeled radiopharmaceuticals. The technology can be adapted by those countries having research reactors with flux >1 × 10¹⁴ n·cm^–2·s^–1 to produce ⁹⁹Mo by (n,γ) route. The capacity of the generator can be scaled up to 260 GBq (7 Ci) using (n,γ)⁹⁹Mo produced from a reactor with flux >1 × 10¹⁵ n·cm^–2·s^–1

Size and Chemistry Controlled Cobalt-Ferrite Nanoparticles and Their Anti-proliferative Effect against the MCF‑7 Breast Cancer Cells

Engineering cobalt ferrites for application in health and biomedical science poses a challenge in terms of nanoscale morphology with a controlled size, shape, and thermochemical stability coupled with controlled properties for biocompatibility. Here, we report a simple one-step, low temperature approach to produce crystalline, nanosized cobalt ferrites (CFO) with a size ∼4.7 nm and demonstrate their applicability in breast cancer treatment. Inherent physiochemical and magnetic properties, which are quite important for biomedical applications, along with cytotoxicity of CFO nanoparticles (NPs) are investigated in detail. X-ray diffraction analyses confirm the cubic spinel phase with the tensile strain in crystalline CFO NPs. Chemical bonding analyses using infrared and Raman spectroscopic studies also support the cubic spinel phase. Electron microscopy and small-angle X-ray scattering revealed the narrow particle-size distribution and spherical-shape morphology. The as-synthesized CFO NPs exhibit superparamagnetic character. Unsaturated magnetization behavior suggests the existence of disordered spins in the surface layers. The temperature dependence of the magnetic parameters, namely, saturation magnetization, coercivity, retentivity, and squareness ratio, also supports the surface-localized spins. Cytotoxic activity of the as-synthesized CFO NPs against the human breast cancer (MCF-7) cell line and normal human peripheral blood mononuclear cells (PBMC) has been evaluated. The mild response of CFO NPs in terms of their antiproliferative nature against cancer cells and negligible Cytotoxicity reflecting their human-safe-and-friendly nature makes them suitable for bioapplications. Moreover, assessment of toxicity toward human red blood cells (RBC) revealed (<3%) hemolysis as compared to the positive control, suggesting potential applications of CFO NPs for human cells