Nucleation and growth are critical steps in crystallization, which plays an important role in determining crystal structure, size, morphology, and purity. Therefore, understanding the mechanisms of ...nucleation and growth is crucial to realize the controllable fabrication of crystalline products with desired and reproducible properties. Based on classical models, the initial crystal nucleus is formed by the spontaneous aggregation of ions, atoms, or molecules, and crystal growth is dependent on the monomer’s diffusion and the surface reaction. Recently, numerous in situ investigations on crystallization dynamics have uncovered the existence of nonclassical mechanisms. This review provides a summary and highlights the in situ studies of crystal nucleation and growth, with a particular emphasis on the state-of-the-art research progress since the year 2016, and includes technological advances, atomic-scale observations, substrate- and temperature-dependent nucleation and growth, and the progress achieved in the various materials: metals, alloys, metallic compounds, colloids, and proteins. Finally, the forthcoming opportunities and challenges in this fascinating field are discussed.
Phytochemicals offer immense promise for sustainable development and production of nanotechnology-enabled products. In the present study,
Olax nana
Wall. ex Benth. (family:
Olacaceae
) aqueous ...extract was used as an effective stabilizing agent to produce biogenic silver (ON-AgNPs) and gold nanoparticles (ON-AuNPs), which were investigated for biocompatibility and prospective biomedical applications (antibacterial, anticancer, antileishmanial, enzyme inhibition, antinociceptive, and anti-inflammatory activities). Various characterization techniques (XRD, FTIR, SEM, TEM, DLS, EDX, and SAED) revealed efficient biosynthesis of ON-AgNPs (26 nm) and ON-AuNPs (47 nm). In the toxicological assessment, ON-AgNPs and ON-AuNPs were found biocompatible towards human RBCs and macrophages (IC
50
>
200 μg/mL
)
. In a concentration range of 62.5–2000 μg/mL, a strong antibacterial effect was produced by ON-AgNPs against
Staphylococcus epidermidis
(MIC = 7.14 μg/mL) and
Escherichia coli
(8.25 μg/mL), while ON-AuNPs was only active against
Staphylococcus aureus
(9.14 μg/mL). At a concentration of 3.9–500 μg/mL, a dose-dependant inhibition of HepG2 cancer cells was produced by ON-AgNPs (IC
50
= 14.93 μg/mL) and ON-AuNPs (2.97 μg/mL). Both ON-AgNPs and ON-AuNPs were found active against
Leishmania tropica
(KMH23) promastigotes (IC
50
= 12.56 and 21.52 μg/mL) and amastigotes (17.44 and 42.20 μg/mL), respectively, after exposure to a concentration range of 1–200 μg/mL for 72 h. Preferential enzyme inhibition against urease and carbonic anhydrase II were noted for ON-AgNPs (39.23 and 8.89%) and ON-AuNPs (31.34 and 6.34%), respectively; however, these were found inactive against xanthine oxidase at 0.2 mg/mL. In the in vivo antinociceptive (acetic acid-induced abdominal constrictions) and anti-inflammatory (carrageenan-induced paw edema) activities, ON-AgNPs and ON-AuNPs at doses of 40 and 80 mg/kg, significantly attenuated the tonic nociception (
P
< 0.001) and ameliorated the carrageenan-induced inflammation (
P
< 0.01,
P
< 0.001). The results of in vitro and in vivo activities indicated that the biogenic nanoparticles can be used as valuable theranostic agents for further exploration of diverse biomedical applications.
Hybrid halide perovskites are now superstar materials leading the field of low-cost thin film photovoltaics technologies. Following the surge for more efficient and stable 3D bulk alloys, ...multilayered halide perovskites and colloidal perovskite nanostructures appeared in 2016 as viable alternative solutions to this challenge, largely exceeding the original proof of concept made in 2009 and 2014, respectively. This triggered renewed interest in lower-dimensional hybrid halide perovskites and at the same time increasingly more numerous and differentiated applications. The present paper is a review of the past and present literature on both colloidal nanostructures and multilayered compounds, emphasizing that availability of accurate structural information is of dramatic importance to reach a fair understanding of quantum and dielectric confinement effects. Layered halide perovskites occupy a special place in the history of halide perovskites, with a large number of seminal papers in the 1980s and 1990s. In recent years, the rationalization of structure–properties relationship has greatly benefited from new theoretical approaches dedicated to their electronic structures and optoelectronic properties, as well as a growing number of contributions based on modern experimental techniques. This is a necessary step to provide in-depth tools to decipher their extensive chemical engineering possibilities which surpass the ones of their 3D bulk counterparts. Comparisons to classical semiconductor nanostructures and 2D van der Waals heterostructures are also stressed. Since 2015, colloidal nanostructures have undergone a quick development for applications based on light emission. Although intensively studied in the last two years by various spectroscopy techniques, the description of quantum and dielectric confinement effects on their optoelectronic properties is still in its infancy.
Recent developments in the electrokinetic determination of particle, protein and polyelectrolyte monolayers at solid/electrolyte interfaces, are reviewed. Illustrative theoretical results ...characterizing particle transport to interfaces are presented, especially analytical formulae for the limiting flux under various deposition regimes and expressions for diffusion coefficients of various particle shapes. Then, blocking effects appearing for higher surface coverage of particles are characterized in terms of the random sequential adsorption model. These theoretical predictions are used for interpretation of experimental results obtained for colloid particles and proteins under convection and diffusion transport conditions. The kinetics of particle deposition and the structure of monolayers are analyzed quantitatively in terms of the generalized random sequential adsorption (RSA) model, considering the coupling of the bulk and surface transport steps. Experimental results are also discussed, showing the dependence of the jamming coverage of monolayers on the ionic strength of particle suspensions. In the next section, theoretical and experimental results pertaining to electrokinetics of particle covered surfaces are presented. Theoretical models are discussed, enabling a quantitative evaluation of the streaming current and the streaming potential as a function of particle coverage and their surface properties (zeta potential). Experimental data related to electrokinetic characteristics of particle monolayers, mostly streaming potential measurements, are presented and interpreted in terms of the above theoretical approaches. These results, obtained for model systems of monodisperse colloid particles are used as reference data for discussion of experiments performed for polyelectrolyte and protein covered surfaces. The utility of the electrokinetic measurements for a precise,
in situ determination of particle and protein monolayers at various interfaces is pointed out.
This simple strategy is propitious to the formation of silver nanowires in high-yield, and the diameters of these nanowires can be controlled by adjusting the concentration of sodium sulfide (Na
2S).
...Silver nanowires have been successfully synthesized via a simple solvothermal method by adding sodium sulfide (Na
2S) into the solution. The Ag
2S colloids produced in the initial stage help reduce the concentration of free Ag
+ ions in the initial formation of silver seeds and subsequently release Ag
+ ions to the solution. Otherwise, there is no oxidative etching owing to the absence of oxygen. In these cases, silver nanowires are grown preferentially. Furthermore, silver nanowires with adjustable diameters can be obtained by adjusting the concentration of Na
2S. Electron microscopy, X-ray diffraction, and absorption spectra have been used to investigate the products, and a mechanism is proposed to interpret the controlled synthesis of silver nanowires. Finally, our results indicate that this approach provides a versatile route to prepare silver nanowires with controllable diameters.
Crystallization is one of the major challenges in using glassy solids for technological applications. Considering pharmaceutical drugs, maintaining a stable amorphous form is highly desirable for ...improved solubility. Glasses prepared by the physical vapor deposition technique got attention because they possess very high stability, taking thousands of years for an ordinary glass to achieve. In this work, we have investigated the effect of reducing film thickness on the α-relaxation dynamics and crystallization tendency of vapor-deposited films of celecoxib (CXB), a pharmaceutical substance. We have scrutinized its crystallization behavior above and below the glass-transition temperature (T g). Even though vapor deposition of CXB cannot inhibit crystallization completely, we found a significant decrease in the crystallization rate with decreasing film thickness. Finally, we have observed striking differences in relaxation dynamics of vapor-deposited thin films above the T g compared to spin-coated counterparts of the same thickness.
Cleaning with Bulk Nanobubbles Zhu, Jie; An, Hongjie; Alheshibri, Muidh ...
Langmuir,
11/2016, Letnik:
32, Številka:
43
Journal Article
Recenzirano
The electrolysis of aqueous solutions produces solutions that are supersaturated in oxygen and hydrogen gas. This results in the formation of gas bubbles, including nanobubbles ∼100 nm in size that ...are stable for ∼24 h. These aqueous solutions containing bubbles have been evaluated for cleaning efficacy in the removal of model contaminants bovine serum albumin and lysozyme from surfaces and in the prevention of the fouling of surfaces by these same proteins. Hydrophilic and hydrophobic surfaces were investigated. It is shown that nanobubbles can prevent the fouling of surfaces and that they can also clean already fouled surfaces. It is also argued that in practical applications where cleaning is carried out rapidly using a high degree of mechanical agitation the role of cleaning agents is not primarily in assisting the removal of soil but in suspending the soil that is removed by mechanical action and preventing it from redepositing onto surfaces. This may also be the primary mode of action of nanobubbles during cleaning.
Present work deals with studies of ninhydrin (N) and phenylalanine (Phe) in cationic gemini micellar system by spectrophotometer under diverge kinetic environments. The results of the current study ...follow fractional-order in N and first-order in Phe. The study is intensely catalyzed by gemini surfactant (GS) system and rate constants (kψ) are enriched even though at GS lower than critical micelle concentration (cmc). The noticed enhancement in rates between reactant molecules and gemini is attributed to hydrophobic and electrostatic interactions. To interpret the influence of various GS, ranging from (1–3000) x 10−5 mol dm−3, on kψ, a model so-called pseudo-phase originally proposed by Berezin et al. and improved by Bunton was applied. Various parameters and constants (like binding constants, thermodynamic parameters and micellar rate constants) have been evaluated. Under the present kinetic condition, a probable reaction mechanism between N and Phe is recommended. The conductivities of pure gemini and the presence of reactants at two temperatures, i.e., at 303 K and 343 K were measured using a conductivity instrument. The cmc of pure geminis in the current case determined at 303 K is consistent with those data reported, earlier.
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The increasing need for drug delivery systems that improve specificity and activity and at the same time reduce toxicity to ensure maximum treatment safety has led to the development of a great ...variety of drug vectors. Carriers based on soft matter have particularly interesting characteristics. Herein we present the current standing of the research in this area, and focus on two main families, namely matrix systems and vesicles. We outline the structure, properties, and potential applications of these vectors, and discuss their main advantages and drawbacks in their synthesis.
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