Fabrication Of Nanocrystals Research Articles

Top‐Down Fabrication of Stable Methylammonium Lead Halide Perovskite Nanocrystals by Employing a Mixture of Ligands as Coordinating Solvents

AbstractA top‐down method is demonstrated for the fabrication of CH3NH3PbBr3 and CH3NH3PbI3 perovskite nanocrystals, employing a mixture of ligands oleic acid and oleylamine as coordinating solvents. This approach avoids the use of any polar solvents, skips multiple reaction steps by employing a simple ultrasonic treatment of the perovskite precursors, and yields rather monodisperse blue‐, green‐, and red‐emitting methylammonium lead halide nanocrystals with a high photoluminescence quantum yield (up to 72 % for the green‐emitting nanocrystals) and remarkably improved stability. After discussing all relevant reaction parameters, the green‐emitting CH3NH3PbBr3 nanocrystals are employed as a component of down‐conversion white‐light‐emitting devices.

光照射による銀ナノ粒子の形状変化 : 球形粒子から異方性ナノ粒子を作る( 光で成長する結晶)

光照射による銀ナノ粒子の形状変化 : 球形粒子から異方性ナノ粒子を作る( 光で成長する結晶)

Preparation and Fluorescence Properties of Perylenediimide Nanodispersions Having a One‐Dimensional π‐Stacked Structure

AbstractThe inside cover artwork is provided by Dr. Tsuyoshi Asahi and Shino Sasaki. The image shows the fabrication of perylenediimide nanocrystals composed of π‐stacking 1‐D columns by laser fragmentation in liquid and exciton migration in nanocrystals. Read the full text of the article at 10.1002/cphc.201601413.

Controlled fabrication of osmium nanocrystals by electron, laser and microwave irradiation and characterisation by microfocus X-ray absorption spectroscopy.

Osmium nanocrystals can be fabricated by electron (3-50 nm, formed by atom migration), 785-815 nm laser (20-50 nm, in micelle islands), and microwave (ca. 1 nm in arrays, >100 mg scale) irradiation of a polymer-encapsulated OsII carborane; microfocus X-ray absorption studies at the Os LIII-edge show differences between the three preparation methods, suggesting that the electron-beam irradiated materials have a significant support interaction and/or surface oxidation, while the laser and microwave samples are more like metallic osmium.

Facile one-pot fabrication of cellulose nanocrystals and enzymatic synthesis of its esterified derivative in mixed ionic liquids

As an important cellulose derivative, esterified cellulose nanocrystals (E-CNCs) could be applied in biomedical and chemical industries.

Microfluidic Fabrication of Hydrocortisone Nanocrystals Coated with Polymeric Stabilisers.

Hydrocortisone (HC) nanocrystals intended for parenteral administration of HC were produced by anti-solvent crystallisation within coaxial assemblies of pulled borosilicate glass capillaries using either co-current flow of aqueous and organic phases or counter-current flow focusing. The organic phase was composed of 7 mg/mL of HC in a 60:40 (v/v) mixture of ethanol and water and the anti-solvent was milli-Q water. The microfluidic mixers were fabricated with an orifice diameter of the inner capillary ranging from 50 µm to 400 µm and operated at the aqueous to organic phase flow rate ratio ranging from 5 to 25. The size of the nanocrystals decreased with increasing aqueous to organic flow rate ratio. The counter-current flow microfluidic mixers provided smaller nanocrystals than the co-current flow devices under the same conditions and for the same geometry, due to smaller diameter of the organic phase stream in the mixing zone. The Z-average particle size of the drug nanocrystals increased from 210–280 nm to 320–400 nm after coating the nanocrystals with 0.2 wt % aqueous solution of hydroxypropyl methylcellulose (HPMC) in a stirred vial. The differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) analyses carried out on the dried nanocrystals stabilized with HPMC, polyvinyl pyrrolidone (PVP), and sodium lauryl sulfate (SLS) were investigated and reported. The degree of crystallinity for the processed sample was lowest for the sample stabilised with HPMC and the highest for the raw HC powder.

Nanocrystallization: A Unique Approach to Yield Bright Organic Nanocrystals for Biological Applications.

A new bottom-up nanocrystallization method is developed to fabricate highly fluorescent organic nanocrystals in aqueous media using an aggregation-induced emission fluorogen (AIEgen) as an example. The nanocrystallization strategy leads to the fabrication of uniform nanocrystals of 110 ± 10 nm size in aqueous media, which shows over 400% increase in brightness as compared to the amorphous nanoaggregates.

Synthesis, Morphology Control and Deposition of CeO2 Nanocrystals Toward Thin Film

Cerium dioxide (CeO2, ceria) is one of the most important materials toward electrolyte materials of solid oxide fuel cells. Since physicochemical and electrical properties of CeO2 vary with the particle dimension, morphology control of CeO2 on nanometer scale has been the key subject to realize the optimal properties for each application. Fabrication of CeO2 nanocrystals with remarkable morphologies such as nano-cubes is the first step in development of nanometer-scaled SOFC. In this study, CeO2 nanocrystals of around 5 nm in diameter were prepared by a hydrothermal route using potassium oleate as a stabilizing agent in the same manner as described in the previous papers. And then, nanocrystals were dispersed on crystal substrate toward thin film device.

One-pot biogenic fabrication of silver nanocrystals using Quisqualis indica: Effectiveness on malaria and Zika virus mosquito vectors, and impact on non-target aquatic organisms

Currently, mosquito vector control is facing a number of key challenges, including the rapid development of resistance to synthetic pesticides and the recent spread of aggressive arbovirus outbreaks. The biosynthesis of silver nanoparticles (AgNPs) is currently considered an environmental friendly alternative to the employ of pyrethroids, carbamates and microbial agents (e.g. Bacillus thuringiensis var. israelensis), since AgNPs are easy to produce, effective and stable in the aquatic environment. However, their biophysical features showed wide variations according to the botanical agent using for the green synthesis, outlining the importance of screening local floral resources used as reducing and stabilizing agents. In this study, we focused on the biophysical properties and the mosquitocidal action of Quisqualis indica-fabricated AgNPs. AgNPs were characterized using spectroscopic (UV, FTIR, XRD) and microscopic (AFM, SEM, TEM and EDX) techniques. AFM, SEM and TEM confirmed the synthesis of poly-dispersed AgNPs with spherical shape and size ranging from 1 to 30nm. XRD shed light on the crystalline structure of these AgNPs. The acute toxicity of Quisqualis indica extract and AgNPs was evaluated against malaria, arbovirus, and filariasis vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, as well as on three important non-target aquatic organisms. The Q. indica leaf extract showed moderate larvicidal effectiveness on Cx. quinquefasciatus (LC50=220.42), Ae. aegypti (LC50=203.63) and An. stephensi (LC50=185.98). Q. indica-fabricated AgNPs showed high toxicity against Cx. quinquefasciatus (LC50=14.63), Ae. aegypti (LC50=13.55) and An. stephensi (LC50=12.52), respectively. Notably, Q. indica-synthesized AgNPs were moderately toxic to non-target aquatic mosquito predators Anisops bouvieri (LC50=653.05μg/mL), Diplonychus indicus (LC50=860.94μg/mL) and Gambusia affinis (LC50=2183.16μg/mL), if compared to the targeted mosquitoes. Overall, the proposed one-pot biogenic fabrication of AgNPs using Q. indica is a low-cost and eco-friendly tool in the fight against Zika virus, malaria and filariasis vectors, with little impact against non-target aquatic mosquito predators.

One-pot fabrication of silver nanocrystals using Nicandra physalodes: A novel route for mosquito vector control with moderate toxicity on non-target water bugs

Mosquitoes (Diptera: Culicidae) as vectors for important diseases and parasites causing millions of deaths every year. The use of synthetic pesticides against Culicidae leads to resistance and environmental concerns. Therefore, eco-friendly control tools are a priority. In this research, Nicandra physalodes-mediated synthesis of silver nanoparticles (Ag NPs) was conducted, in order to control larval populations of three important mosquito vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. Biofabricated Ag NPs were characterized using UV–vis spectrophotometry, XRD, FTIR spectroscopy, SEM, and TEM analyses. Ag NPs were highly toxic against the three mosquito vectors. Maximum efficacy was detected against A. stephensi (LC50=12.39μg/mL), followed by Ae. aegypti (LC50=13.61μg/mL) and Cx. quinquefasciatus (LC50=14.79μg/mL). Interestingly, Ag NPs were safer for the non-target aquatic organism Diplonychus indicus sharing the same aquatic habitats of mosquito larvae. LC50 and LC90 values were 1032.81 and 19,076.59μg/mL, respectively. Overall, our results highlight that N. physalodes-fabricated Ag NPs are a promising for development of eco-friendly larvicides against mosquito vectors, with negligible toxicity against non-target aquatic water bugs.

Fabrication of CdSe nanocrystals using porous anodic alumina and their optical properties

In this paper, Porous anodic alumina (PAA) template with highly ordered nanopores structure was synthesized on aluminum foils by two step anodization process. PAA template has hexagonal pores with average size between 30 and 180nm. L-cysteine (L-Cys) functionalized cadmium selenide nanocrystals (CdSe NCs) were successfully embedded inside PAA layers by simple immersion in aqueous solution. The effect of pore diameter enlargement on the microstructure of CdSe NCs/PAA films was systematically studied by FE-SEM, XRD, EDX, Raman, UV–VIS absorbance and PL analysis. FE-SEM microscopy was used to investigate the surface morphology of PAA templates before and after CdSe NCs deposition. XRD investigation demonstrates that CdSe NCs into PAA templates were cubic in nature with zinc-blende structure. Raman measurements exhibit the characteristic modes of CdSe on the PAA layers as well as the films crystallinity as function of widening pores diameter. Optical properties of deposited CdSe NCs on PAA templates have been investigated using optical absorption and PL techniques. Photoluminescence spectroscopy has been used to determine the bandgap energy and the average size of CdSe NCs deposited on PAA layer. This method involves fitting the experimental spectra, using a model based on quantum confinement of electrons in CdSe nanocrystals having spherical and cylindrical forms (Quantum Dots (QDs) and Quantum Wires (QWs)). This model allows correlation between the PL spectra and the microstructure of the CdSe/PAA. Both photoluminescence and optical absorption show that the PL peak energy and the optical absorption edge of CdSe NCs/PAA exhibit similar behavior with changes in nanostructure size. The spectral behaviors of optical absorption and PL are consistent with a quantum confinement model throughout the sizes and shapes of the CdSe nanocrystals of the luminescent films. The effective bandgap energies determined from the PL peaks position are in good agreement with those estimated from the optical absorbance spectra.Investigations have shown that optical properties of CdSe/PAA nanostructure were influenced by the pores sizes of PAA. It was observed an increase in CdSe NCs size from 2.22 to 2.56nm when the average pores diameter of PAA increases from 30 to 180nm. This finding indicates an enhancement in PL intensity and a red-shift in PL emission peaks from 2.35 to 2.14eV. By applying the quantum confinement model, we demonstrated that the redshift of PL peak is attributed to the change of CdSe NCs size with the pores diameter and that their spectral behaviors are related to the shape and the size distribution of the nanoparticles.

(Invited) Silicon Nanocrystals: Size Control, Basic Understanding and High Quantum Yields

Controlled fabrication of Si nanocrystals via the SiOx/SiO2 superlattice approach enables size control as well as density control [1]. The resulting layer arranged Si nanocrystals represent a model system to systematically study photonic and electronic properties of indirect gap quantum dots. Hence a deeper understanding can be developed for absorption, recombination, carrier kinetics and transport. As example, the temperature dependence of confined excitons in Si quantum dots and their respective temperature depending band gap will be analyzed for different sizes and will be compared with theory prediction. [2] The interplay of radiative and non-radiative recombination will be studied using recombination kinetics based on detailed time resolved measurements. [3] In addition, the origin of the luminescence in Si2N3embedded Si NCs are discussed. [4] Transport properties will be evaluated as a function of NCs size and distance. [5] Finally, systematic doping experiments with P will be analyzed for doping efficiency, in-cooperation into the Si NCs and self-purification, and electronic transport. [6, 7] [1] M. Zacharias et al. Appl. Phys. Lett. 80 (2002) 661. [2] A. M. Hartel et al. Phys. Rev. B 85, 165306 (2012). [3] A.M. Hartel et al. Rev. B 87 (2013) 035428. [4] A. Zelinina et al. J. Appl. Phys. 114 (2013) 184311. [5] S. Gutsch et al. J. Appl. Phys. 113 (2013) 133703. [6] H. Gnaser et al. J. Appl. Phys.113 (2013) 034304 [7] S. Gutsch et al. Appl. Phys. Lett. 106 (2015) 113103.

Kinetically Controlling Surface Structure to Construct Defect-Rich Intermetallic Nanocrystals: Effective and Stable Catalysts.

Kinetic control of surface defects is achieved, and cubic, concave cubic, and defect-rich cubic intermetallic Pt3 Sn nanocrystals are prepared for the electro-oxidation of formic acid. The generality of this kinetic approach is demonstrated by the fabrication of Pt-Mn nanocrystals with different surface defects. The defect-rich nanocrystals exhibit high catalytic activity and stability concurrently, indicating their potential application in fuel cells.

Fabrication of magnetite nanocrystals in alcohol/water mixed solvents: catalytic and colloid property evaluation

Size tailoring in alcohol–water mixed solvents produces small magnetite nanocrystals with appreciably high catalytic activities that form ultrastable colloids when suspended in water.

Serial Morphological Transformations of Au Nanocrystals via Post-Synthetic Galvanic Dissolution and Recursive Growth

Geometric modification of Au nanostructures is typically achieved in multistep reactions, where synthesis parameters need to be well-controlled. In this work, we report a facile method using IrCl3 to refine morphologically diverse Au nanostructures and trigger their morphological transformations. The synthesis is accomplished at room temperature by an iterative process of galvanic dissolution and recursive growth. Seeds retrieved after the dissolution of different Au nanostructure archetypes served in the structural recovery and morphological transformation via rapid and slow regrowth, respectively. The rapid regrowth was accomplished by adding ascorbic acid (AA), while the slow regrowth occurred spontaneously. In the structural recovery, the nanostructures regrew back to their original morphologies. Improvements in the shape quality and size distributions were observed for the rapid regrowth case. In the spontaneous slow regrowth transformation, the resulting nanostructures were encased by {111} facets, minimizing total surface energy through the more closely packed planes. Transformation of the four nanostructure archetypes showed correlation, trending toward these lower indexed facets and to twinned structures (from RDs to OCTs, OCTs to TPs, and TPs to PSs). Surveying all observations, our work of the metal cation-mediated geometric modulation of Au nanostructures delivers important clues in understanding nanoparticle synthesis and provides a new path for the fabrication of nanocrystals with high-quality size and shape distribution.

Fabrication and Characterization of Rutile TiO2 Nanocrystals by Water Soluble Precursor

In this research, TiO2 nanoparticles were synthesized by a simple wet chemical method. TiCl4 was used as precursor in hydrogen peroxideand ethanol. The TiO2 nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron dispersive spectroscopy (EDS) and UV-Vis spectrophotometer. The particle size of the as-synthesized TiO2 was estimated by XRD and TEM analyses in the range of 5-10 nm. The SEM images showed that the size of sphere-like shaped nanoparticles decrease with increasing annealing temperature. The prepared TiO2 nanoparticles were characterized for phase composition, using X-ray diffractometry. The crystal structure of the nanoparticles after annealing was measured by XRD analysis. It was realized that phase transition from anatase to rutile occurs after heat treatment at 600 °C. The particle size of the annealed sample was also calculated about 20 nm by XRD analysis. The EDS spectrum showed peaks of titanium and oxygen with fewer impurities. The UV-Vis spectrum showed anatase and rutile phase at wavelength about 375 nm (Eg = 3.30 eV) and 470 nm (Eg = 2.63 eV) for as-prepared TiO2 and annealed TiO2 nanoparticles respectively.

Microfluidic‐Spinning‐Directed Microreactors Toward Generation of Multiple Nanocrystals Loaded Anisotropic Fluorescent Microfibers

Anisotropic fluorescent hybrid microfibers with distinct optical properties and delicate architectures have aroused special interest because of their potential applications in tissue engineering, drug delivery, sensors, and functional textiles. Microfluidic systems have provided an ideal microreactor platform to produce anisotropic fibers due to their simplified manipulation, high efficiency, flexible controllability, and environmental‐friendly chemical process. Here a novel microfiber reactor based on a microfluidic spinning technique for in situ fabrication of nanocrystals loaded anisotropic fluorescent hybrid microfibers is demonstrated. Multiple nanocrystal reactions are carried out in coaxial flow‐based microdevices with different geometric features, and various nanocrystals loaded microfibers with solid, string‐of‐beads and Janus topographies are obtained. Moreover, the resulted anisotropic fluorescent hybrid microfibers present multiple optical signals. This strategy contributes a facile and environmental‐friendly route to anisotropic fluorescent hybrid microfibers and might open a promising avenue to multiplex optical sensing materials.

Synthesis and Functions of Ag2S Nanostructures.

The paper presents a review about synthesis and applications of Ag2S nanostructures. As the modern photoelectric and biological materials, Ag2S nanomaterials are potentially useful for both structure and function purposes. Ag2S is a direction narrow band gap semiconductor with special properties. Ag2S nanostructures have been widely researched in chemistry and biochemistry fields because of their unusual optical, electrical, and mechanical properties. It can also be used in many fields, such as photovoltaic cells and infrared detector. In the past few years, Ag2S nanostructures have been synthesized by various methods. The article mainly discusses the four types of preparation methods. Moreover, this article shows a detailed review on the new properties, fabrication, and applications of Ag2S nanocrystals.

Roles of aromatic side chains and template effects of the hydrophobic cavity of a self-assembled peptide nanoarchitecture for anisotropic growth of gold nanocrystals

Gold nanocrystals are promising as catalysts and for use in sensing/imaging systems, photonic/plasmonic devices, electronics, drug delivery systems, and for photothermal therapy due to their unique physical, chemical, and biocompatible properties. The use of various organic templates allows control of the size, shape, structure, surface modification and topology of gold nanocrystals; in particular, currently the synthesis of gold nanorods requires a cytotoxic surfactant to control morphology. To control the shape of gold nanocrystals, we previously demonstrated the de novo design and synthesis of a β-sheet-forming nonapeptide (RU006: Ac-AIAKAXKIA–NH2, X=l-2-naphthylalanine, Nal) and the fabrication of gold nanocrystals by mixing RU006 and HAuCl4 in water. The reaction afforded ultrathin gold nanoribbons 50–100nm wide, several nanometers high, and microns long. To understand the mechanism underlying gold nanoribbon formation by the RU006 system, we here report (i) the effects of replacement of the Nal aromatic side chain in the RU006 sequence with other aromatic moieties, (ii) the electrochemical properties of aromatic side chains in the de novo designed template peptides to estimate the redox potential and number of electrons participating in the gold crystallization process, and (iii) the stoichiometry of the RU006 system for gold nanoribbon synthesis. Interestingly, RU006 bearing a naphthalene moiety (oxidation peak potential of 1.50V vs Ag/Ag+) and an analog [Ant6]-RU006 bearing a bulky anthracene moiety (oxidation peak potential of 1.05V vs Ag/Ag+) allowed the growth of anisotropic (ribbon-like) and isotropic (round) gold nanocrystals, respectively. This trend in morphology of gold nanocrystals was attributed to spatially-arranged hydrophobic cavities sufficiently large to accommodate the gold precursor and to allow directed crystal growth driven by cross-linking reactions among the naphthalene rings. Support for this mechanism was obtained by decreasing the mole fraction of [Ant6]-RU006 against the total concentration of [Ant6]-RU006 and [Phe6]-RU006: absorption spectra similar to that for RU006 were obtained. Differences in the redox properties of the anthracene and naphthalene moieties scarcely affected morphology. We propose that construction of an appropriate hydrophobic cavity is important for templating gold nanocrystal architectures by peptide self-assembly. This mechanism would be applicable for developing simple, low toxicity, mild synthetic methods for constructing metallic nanomaterials for therapeutic use.

Fabrication of aceclofenac nanocrystals for improved dissolution: Process optimization and physicochemical characterization

The purpose of the study is to optimize process variables and fabricate nanocrystals to improve dissolution rate of aceclofenac. Particle engineering was carried out to obtain pure drug nanocrystals of aceclofenac to overcome its poor dissolution behavior using different polymeric stabilizers. A Box-Behnken design was used to study the influence of process variables and further optimization was carried out. The physicochemical properties were evaluated including particle size distribution, powder X-ray diffractometry, scanning electron microscopy and dissolution studies. Preclinical investigation was also carried out in Wistar rats. All the identified process variables influenced the particle size and dissolution velocity of aceclofenac. Methyl cellulose (MC) and hydroxypropyl methyl cellulose (HPMC) were found very effective in preventing growth of crystals and improving the dissolution of aceclofenac. The optimized process variables predicted were 0.47%, 25 °C and 1070 rpm for stabilizer concentration, processing temperature and mixing speed respectively using MC as stabilizer. The optimized aceclofenac nanocrystals showed improved dissolution and reduced particle size (Q = 87.27 ± 0.83% and Mz = 54.23 ± 3.24 nm). Preclinical investigation using Wistar rats revealed statistically significant improvement of efficacy of optimized nanocrystals in terms of percentage inhibition of paw edema induced by carrageenan challenge indicating enhanced bioavailability through improved dissolution of aceclofenac nanocrystals.