Size Of Nanocrystals Research Articles

Octahedral Nanocrystals of Ru-Doped PtFeNiCuW/CNTs High-Entropy Alloy: High Performance Toward pH-Universal Hydrogen Evolution Reaction.

Integrating high-entropy philosophy and nanocrystal-specific orientation into a single catalyst represents a promising strategy in development of high-performance catalysts. Nonetheless, shape-controlled synthesis of high-entropy alloy (HEA) nanocrystals is challenging owing to the distinct redox potentials and growth dynamics of metal elements. Herein, a one-pot co-reduction method is developed to fabricate ruthenium (Ru)-doped PtFeNiCuW octahedral HEA nanocrystals onto carbon nanotubes (Ru-PtFeNiCuW/CNTs). It is demonstrated that Ru dopants and W(CO)6 promote the concurrent reduction and growth of other metal precursors to obtain higher yield and larger size of HEA nanocrystals, despite low Ru content in Ru-PtFeNiCuW/CNTs. As an electrocatalyst toward hydrogen evolution reaction (HER), Ru-PtFeNiCuW/CNTs exhibits low overpotentials of 9, 16, and 34mV at a current density of 10mA cm-2 and Tafel slopes of 19.2, 27.9, and 23.1mV dec-1 in acidic, alkaline, and neutral electrolytes, respectively. As a cathodic catalyst, Ru-PtFeNiCuW/CNTs operates for up to 1500 and 1200 h in acidic and alkaline electrolyte, respectively, at a current density of 50mA cm-2 in a two-electrode system for full water splitting. Theoretical calculations reveal accelerated kinetics of H2O dissociation on W sites and *H desorption on hollow Cu-Cu-Cu and Cu-Cu-Pt sites.

Micelle-mediated growth of gold nanocrystals on a surface

Understanding nanocrystal growth is crucial for several reasons, as it plays a significant role in various scientific, technological, and industrial applications. Knowledge of nanocrystal growth allows scientists and engineers to control the size, shape, and composition of nanocrystals. This control is essential for tailoring the properties of nanomaterials for specific applications, such as electronics, catalysis, sensing and medicine. Nanocrystals are used in various biomedical applications, such as drug delivery, imaging, etc. Understanding their growth is essential for designing nanomaterials with specific functionalities for targeted drug delivery and imaging modalities. A molecular dynamics simulation study has been carried out to investigate the growth of nanocrystals in aqueous solutions in the presence of surfactants. In this study, we investigated the structural and thermodynamic properties of a micelle formed by cetyltrimethylammonium bromide (CTAB) in the aqueous solution and used that to quantify its role in the nucleation process when gold nucleates are in close proximity to another gold nanoparticle or surface. The path through which the nucleate gets fused with other entities, such as gold nanoparticles or surfaces, in the presence of a micelle in solution needs an explanation. We have shown the path and quantified energy required for the gold nucleate to get infused into the gold surface. Well-dispersed sets of gold atoms in solution were subjected to a series of steered molecular dynamics simulations, and it revealed that gold atoms, individually, must overcome an energy barrier of 10.52 ± 0.3 kcal/mol to start nucleating on the substrate. Due to this energy barrier, atoms form aggregate or nucleate inside the micelle. To control the release of the engulfed nucleate into the micelle onto the substrate, one needs to understand the mechanism of its release and quantify the energy requirement for the process. Here, we have used an enhanced sampling technique (umbrella sampling) to calculate the free energy required for the process mentioned above. A gold nucleate would require an additional energy of ∼10.36 kcal/mol to break the strong layering of micelle and water on the substrate. The radius of gyration and order parameter calculations show the extent of deformation of the micelle while releasing the engulfed nucleate on the substrate, and it gives us a recipe to alter the shape of the micelle and easier release of the nucleate on the surface. This study summarizes the path of nucleation of nucleates in the micellar solution and the recipe for the easier release of nucleates on the substrate.

Lead-free metal–halide perovskite nanocrystals: synthesis and optical properties [Review

Subject of study. Lead-free perovskite nanocrystals (LFPNCs), their main characteristics, synthesis methods, and optical properties are examined. Aim of study. The aim is to analyze the state-of-the-art research data on the synthesis methods and optical properties of LFPNCs. In addition, the formation processes of LFPNCs, their main synthesis methods, and the dependence of nanocrystal size and photoluminescence quantum yield (PLQY) on synthesis parameters (such as method, temperature, and ligand type) are determined. Main results. The formation of LFPNCs is analyzed based on the LaMer and cluster growth models. According to the research data, the primary methods for preparing these nanocrystals (NCs) are hot-injection and ligand-assisted reprecipitation (LARP). Evidently, the average size of LFPNCs increases with increasing reaction temperature. For NCs synthesized by LARP, increasing the reaction temperature to 100°C leads to a slight decrease in the quantum yield. However, for the NCs prepared by hot-injection, the PLQY remains independent of the temperature. Additionally, using oleic acid as a ligand results in a narrow size distribution of NCs, whereas using a mixture of ligands results in NCs exhibiting the highest PLQY. Practical significance. The literature analysis results show that the LARP method is the most promising for synthesizing LFPNCs owing to its ease of implementation, energy efficiency, and scalability. The LFPNCs produced using this method can be applied as active materials in sensor technologies, photovoltaics, and optoelectronic devices.

Spectral properties of Yb-doped AgBiS2 and AgInS2 nanocrystals

Subject of study. The spectral features of nanocrystals with ternary compositions I-V-VI2 and I-III-VI2 doped with the rare earth metal ytterbium are investigated and described. Purpose of the study. The aim of this work is to develop a novel synthesis method for these nanocrystals to further examine their optical and morphological properties. Method. The average sizes of AgInS2:Yb and AgBiS2:Yb nanocrystals are analyzed using atomic force microscopy and dynamic light scattering, and the results are compared. Spectrophotometry and spectrofluorimetry are employed to record the absorption and photoluminescence spectra, respectively. Additionally, the photoluminescence decay kinetics are recorded using a laser scanning luminescence microscope for a deeper exploration of the electronic structure of the synthesized materials. Main results. Morphological analysis reveals that single-stage synthesis produced nanocrystals based on the AgInS2 matrix are smaller than the reference sample, while two-stage synthesis results in average nanocrystal sizes 1.5 times larger than the reference sample. The absorption spectra of the AgInS2:Yb and AgBiS2:Yb samples, as well as their reference samples, correspond to typical absorption spectra of semiconductor nanocrystals of ternary compounds. The absorption spectrum of AgBiS2:Yb nanocrystals, unlike AgInS2:Yb, spans a broad range from 300 nm to 1300 nm. In the photoluminescence spectra of AgInS2 and AgInS2:Yb nanocrystals, no significant shift of the band maximum is observed, and photoluminescence typical of Yb ions is absent. It is found that the weighted average photoluminescence lifetime in AgInS2:Yb nanocrystals can be modulated by ytterbium doping. Photoluminescence in AgBiS2 and AgBiS2:Yb samples is not detected in the red and near-infrared regions. Practical significance. These materials may be used in the fabrication of absorber layers for solar cells, as well as sensitizers for photodynamic and photothermal therapy. Further studies of isotropic samples of these nanocrystals could not only expand their potential applications but also enhance the physical properties of nanoparticles in the long term.

Tungsten Nanoparticles Generated in an Atmospheric Pressure Plasma Jet

AbstractThe atmospheric pressure plasma source HelixJet has been used to generate tungsten nanocrystals with narrow size distributions, well defined size control and with a considerably good particle yield. Tungsten particles are produced as the result of an evaporation process of a tungsten wire inserted on the middle axis of the jet after the wire is heated by interaction with the plasma. Temperature measurements using a thermocouple and by optical emission spectroscopy showed that, while the overall temperature of the wire is very high, it is not in the range of the melting temperature of tungsten; however, it can reach values needed for sublimation. Additionally, the wire is heated selectively while the temperature of the jet components reaches only a few hundred degrees Celsius. The particles cluster into agglomerates and their formation has been analyzed in relation to the reliability of a commercial scanning mobility particle sizer spectrometer. The dependence of the particle morphology and crystal structure on the plasma parameters such as power and gas flow was studied via transmission electron microscopy and the average size of the tungsten nanocrystals could be tuned between 12 and 25 nm.

Evolution of structural dynamics in cesium lead halide perovskite colloidal nanocrystals from temperature-controlled synthesis.

Halide perovskite nanocrystals are at the forefront of materials research due to their remarkable optoelectronic properties and versatile applications. While their lattice structure and optical properties have been extensively investigated for the structure-property correlation, their lattice dynamics, the physical link between the lattice structure and optoelectronic properties, has been much less visited. We report the evolution of structural dynamics of a series of cesium lead halide perovskite nanocrystals whose size and morphology are systematically varied by synthesis temperature. Low-frequency Raman spectroscopy uncovers the nanocrystals' structural dynamics, including a relaxational spectral continuum from ligand librations and a phonon spectrum evolving with nanocrystal size. As the size of nanocrystals increases, their phonon spectrum becomes more intense, and their spectral weights redistribute with new first- and second-order modes being activated. The linewidth of the observed phonon modes generally broadens as the nanocrystal grows larger, an interesting deviation from the established phonon confinement model. We suggest that strong confinement and truncation of the lattice and ligands anchoring on the surface might lead to pinning of the lattice dynamics at nanoscale. These findings offer new insights into the bulk-nano-transition in halide perovskite soft semiconductors.

Effect of striae on the high temperature dielectric and electrical properties of lithium aluminosilicate glass-ceramics

Lithium Aluminosilicate glass-ceramics with striae (LAS-WS) and without striae (LAS-WoS) were processed using melt casting technique. LAS-WS and LAS-WoS samples were characterized and found stress birefringence >10 nm/cm and <10 nm/cm, respectively. LAS-WS and LAS-WoS samples were subjected to structural, microstructural, high temperature dielectric and electrical characterization. The presence of striation did not significantly affected the formation of β-spondumene structure during crystallization heat treatment. TEM image confirms the formation of nanocrystals in the glass matrix of lithium aluminosilicate glass-ceramics. The homogeneous distribution of LAS nanocrystals of average size of 3–6 nm is evident from TEM results. Stress birefringence distribution in lithium aluminosilicate glass-ceramic clearly shows the striae formation. Shadowgraphy images confirmed the striae free and striae containing regions in the glass-ceramic. The effect of striae on dielectric properties and AC conductivity was analysed using impedance spectroscopy and it was found that the value of the relative permittivity decreased from 415 (1.2 Hz) to 9.76 (1.2 MHz) for LAS-WoS and from 401 (1.2 Hz) to 10.3 (1.2 MHz) for LAS-WS, respectively. It was found that striae in LAS glass-ceramics influence the electrical impedance and AC conductivity relaxation process rather than relative permittivity. The effect of striae on crystallization and morphology are presented. Both the samples have shown crystallinity of more than 75 %. The electrical conductivity of σ = 2.0 × 10−3 S/cm for LAS-WoS and 2.7 × 10−3 S/cm for LAS-WS at 300 °C as well as σ = 4.6 × 10−3 S/cm for LAS-WoS and 6.9 × 10−3 S/cm for LAS-WS at 700 °C are found to be in good agreement due to increase in the electrical conductivity with temperature. The ionic conductivity of the material due to Li-ion mobility with respect to temperature and electric field and possible mechanism of AC conductivity are discussed. The results presented indicates the potential application of this material that demands high temperature operation of lithium aluminosilicate glass-ceramics.

Inverse design of nano-sized FGM phononic crystals with anticipated band gaps using probabilistic generation based deep-learning network

Current research on the inverse design of phononic crystals, which aim to retrieve optimal structures according to given band gaps, is limited to controlling elastic waves at the macro-scale. This work extends the concept to nano-scale and implements this concept with phononic nanobeam made up of functionally graded materials by applying the nonlocal strain gradient theory and the probabilistic tandem network (PTN), which is responsible for detecting size effects and unveiling implicit relationships between band gaps and nanostructures. An analytical model that has not been published before is proposed based on the plane wave expansion method to predict band structures within size, thickness and porosity effects, enabling quick preparation for composing a dataset to train the network. Acting as an auto-encoder-like framework, the component of PTN in the reverse path allows to effectively encode required band gaps into a latent space, while the network in the forward path serves as a surrogate model to map the candidates from the latent space to band gaps. Numerical results not only show the influences of size effects on band gaps but also verify the accuracy, diversity, and generalization ability to meet different requirements of the inverse design. The proposed PTN can fulfill the on-demand design by generating multiple phononic nanobeams possessing same man-made band gaps. Undoubtedly, the framework proposed in the present work makes it a promising approach to provide flexible and diversified solutions, paving the way to discovering innovative phononic crystals at nano-scale.

Fine-Tuning Crystal Structures of Lead Bromide Perovskite Nanocrystals through Trace Cadmium(II) Doping for Efficient Color-Saturated Green LEDs.

Decreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers of electroluminescent devices. Here, we overcome this trade-off by increasing the exciton effective mass without affecting the size, which is realized through the trace Cd2+ doping of formamidinium lead bromide perovskite nanocrystals. We observe an ~2.7 times increase in the exciton binding energy benefiting from a slight distortion of the [BX6]4- octahedra caused by doping in the case of that the Auger recombination rate is almost unchanged. As a result, bright color-saturated green emitting perovskite nanocrystals with a photoluminescence quantum yield of 96 % are obtained. Cd2+ doping also shifts up the energy levels of the nanocrystals, relative to the Fermi level so that heavily n-doped emitters convert into only slightly n-doped ones; this boosts the charge injection efficiency of the corresponding light-emitting diodes. The light-emitting devices based on those nanocrystals reached a high external quantum efficiency of 29.4 % corresponding to a current efficiency of 123 cd A-1, and showed dramatically improved device lifetime, with a narrow bandwidth of 22 nm and Commission Internationale de I'Eclairage coordinates of (0.20, 0.76) for color-saturated green emission for the electroluminescence peak centered at 534 nm, thus being fully compliant with the latest standard for wide color gamut displays.

Fine‐Tuning Crystal Structures of Lead Bromide Perovskite Nanocrystals through Trace Cadmium(II) Doping for Efficient Color‐Saturated Green LEDs

AbstractDecreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers of electroluminescent devices. Here, we overcome this trade‐off by increasing the exciton effective mass without affecting the size, which is realized through the trace Cd2+ doping of formamidinium lead bromide perovskite nanocrystals. We observe an ~2.7 times increase in the exciton binding energy benefiting from a slight distortion of the [BX6]4− octahedra caused by doping in the case of that the Auger recombination rate is almost unchanged. As a result, bright color‐saturated green emitting perovskite nanocrystals with a photoluminescence quantum yield of 96 % are obtained. Cd2+ doping also shifts up the energy levels of the nanocrystals, relative to the Fermi level so that heavily n‐doped emitters convert into only slightly n‐doped ones; this boosts the charge injection efficiency of the corresponding light‐emitting diodes. The light‐emitting devices based on those nanocrystals reached a high external quantum efficiency of 29.4 % corresponding to a current efficiency of 123 cd A−1, and showed dramatically improved device lifetime, with a narrow bandwidth of 22 nm and Commission Internationale de I'Eclairage coordinates of (0.20, 0.76) for color‐saturated green emission for the electroluminescence peak centered at 534 nm, thus being fully compliant with the latest standard for wide color gamut displays.

High-Resolution X-ray Image from Copper-Based Perovskite Hybrid Polymer.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency, lack of lead toxicity, and X-ray responsiveness. However, during the crystallization process, NCs are prone to agglomeration and exhibit uneven size distribution, resulting in several light scattering that severely affect their imaging resolution. Herein, we successfully developed a high-resolution scintillator film by growing copper-based perovskite NCs within a hybrid polymer matrix. By leveraging the ingenious integration of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA), the size and distribution uniformity of Cs3Cu2I5 NCs can be effectively controlled. Consequently, a high spatial resolution of 14.3 lp mm-1 and a low detection limit of 105 nGy s-1 are achieved, and the scintillator film has excellent flexibility and stability. These results highlight the promising application of Cs3Cu2I5 scintillator films in low-cost, flexible, and high-performance medical imaging.

DEVELOPMENT, OPTIMIZATION AND IN VITRO CHARACTERIZATION OF HALOPERIDOL NANOCRYSTALS USING 32 FACTORIAL DESIGN

Objective: The main aim of the present study was to improve the dissolution rate of Haloperidol nanocrystals and thereby increase their bioavailability. Haloperidol is a typical antipsychotic drug and it is used to treat schizophrenia as well as acute mania and mixed states associated with bipolar disorder. Haloperidol falls into the Biopharmaceutics Classification System (BCS-II) class of drugs (poorly soluble aqueous and highly permeable) and has poor bioavailability. Methods: The present study involves the preparation and optimization of Haloperidol nanocrystals by the anti-solvent precipitation method using Polaxomer407 and polyvinyl pyrrolidone K30 (PVP K30). The prepared nanocrystals were evaluated for various parameters like particle size, zeta potential, % drug content, % yield, surface morphology, drug-excipient compatibility studies (Fourier-transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC)), and in vitro dissolution studies. Results: Nine preparations were done and the best preparation amongst them was selected for further studies. F7 preparation containingpolaxomer407 and PVP K30 was selected as optimized preparation based on their evaluation parameters. 32 factorial design was used in the preparation. The particle size of the F7 nanocrystals was 300.2±2.7 nm and the zeta potential-36.3±3.2 mV. The % yield was in the range of 63.62±0.3%-98.21±0.8 %. The drug content of various preparations was found to be in the range of 58.46±0.8%-93.54±0.5 %. In vitro dissolution studies showed the highest % drug release for F7(91.54±0.03%) in 10 h. Conclusion: F7 preparation was found to be having acceptable characteristics and thus selected as optimized preparation.

Confirmation of the presence of edge dislocations in the prepared FCC ZnTe nanocrystals from the study of structural analysis through the MWH method with added Fourier analysis (W-A method) of diffraction peaks

Nanocrystalline ZnTe with cubic mono-phase has been synthesized by a wet-chemical synthesis process for the study of the presence of dislocations through X-ray diffraction peak profile analysis. The average size of the ZnTe nanocrystals has been determined from the High-Resolution Transmission Electron Microscopic (HRTEM) analysis as 21.9 nm. In the XRD pattern, (111), (200), (220), (311), and (400) diffraction planes have been observed, which confirms the formation of cubic mono-phase of ZnTe. For the extraction of microstructural details, the Rietveld refinement has been performed using Fullprof software and from this refinement, the lattice constant has been obtained as 6.17 Å under the space group of f-43. Here, X-ray diffraction peak has been analyzed through the Williamson-Hall (W–H) analysis method and the Warren-Averbach (W-A) analysis method. Williamson-Hall approach is based on the full-width at half-maxima analysis, whereas the Warren-Averbach method is related to the analysis of the Fourier transform of the broadened X-ray diffraction peaks. For considering and analyzing the anisotropic broadening of the peak, modified Williamson-Hall and modified Warren-Averbach methods have been used for the calculation of size, strain, and dislocation density. The presence of prominent edge dislocation of about 71 % has been confirmed from the anisotropic peak broadening study. In addition, the HRTEM image directly verifies the presence of edge dislocations in both the lattice planes of (111) and (220).

KBiFe2O5 triggered-phase transition of Bi2Fe4O9 and Fe3O4 in tellurite glass with huge nonlinear and magnetic properties

In the quest for glass materials with high nonlinearity and strong magnetism to meet the demands of advancing technology, magnetic nanocrystal (NC) doping emerges as a promising approach. The paper investigates the phase transition from KBiFe2O5 to Bi2Fe4O9 and Fe3O4 NCs within a TeO2–Bi2O3–B2O3 glass matrix. The novelty of this study lies in leveraging the coexistence of multiple phases to amplify both the polarization and magnetic moment of glass. Various techniques, including X-ray diffraction, transition transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and vibrational sample magnetometer were employed to analyze the impact of NCs content and heat treatment temperature on crystallization, structure modification, and properties. KBiFe2O5 NCs doping induces changes in crystal phases and modifies the glass network structure by forming multi-valence states and altering coordination numbers, such as FeO4→FeO6, TeO4→TeO3, and BO4→BO3. Concurrently, appropriate temperature conditions result in reduced NC size, preserving glass transparency and thermal stability. Spinel Fe3O4 NCs formation at higher temperatures enhances magnetic behavior. A glass sample containing 1 mol% KBiFe2O5 NCs, heat-treated at 410 °C, exhibits a narrow bandgap (Eg) of 1.82 eV, high nonlinear parameters (α3 = 3.98 × 10−10 m/W, χ(3) = 8.65 × 10−11 esu), and a low limiting threshold (1.01 × 1012 W/m2). Additionally, owing to the incorporation of high spin states and active magnetic exchange interactions, the same glass demonstrates robust ferromagnetic behavior (Ms = 2.3 emu/g and Hc = 850 G). The approach developed in this study has been demonstrated to be highly effective in producing transparent glass with promising nonlinearity and magnetic performance suitable for photonics applications.

Gram-scale microwave-assisted synthesis of high-quality CsPbBr3 nanocrystals for optoelectronic applications

Fully inorganic halide perovskite nanocrystals (NCs) are promising candidates for optoelectronic applications due to their beneficial properties such as their amenability to solution processing, high absorption coefficients, and high quantum yields. Various methods have been developed to prepare perovskite CsPbX3 (X = Cl, Br, and I) NCs; however, large-scale synthesis with high-quality CsPbX3 NCs remains challenging. In the study, we report an advanced method for the gram-scale synthesis of all-inorganic perovskite NCs via specially designed microwave-assisted synthesis, which offers uniform reaction energy transfer, excellent reproducibility, and flexible parameter tuning. The composition, size and uniformity of the CsPbBr3 NCs have been optimized by controlling the surfactant ratio, precursor ratio, and reaction time. This systematic optimization leads to the production of gram-scale (> 0.165 g per a 100 ml reaction mixture for a single synthesis cycle) high-quality, phase-pure CsPbBr3 NCs with a uniform size of ∼ 10 nm. These optimized NCs exhibit a sharp photoluminescence peak centered at 515 nm with a photoluminescence quantum yield of 94 % and produce excellent radioluminescence under X-ray irradiation. To test the feasibility of these NCs for use in real optoelectronic devices, a photodetector consisting of CsPbBr3 NCs and monolayer MoS2 was fabricated, demonstrating enhanced photosensitivity and a faster response time compared with a pure MoS2-based photodetector. The proposed gram-scale microwave-assisted synthesis method thus has the potential to promote the commercialization of metal halide perovskite NCs through cost-effective mass production for use in many optoelectronic applications.

Peat water purification using nanohydroxyapatite synthesized from Carbon Negative Precipitated Calcium Carbonate precursor

Peatlands covers a vast area globally and used as drinking water source in some parts of Indonesia. Peat water, commonly found in swampy areas, stands out for its striking color intensity, acidic pH levels, and its high affinity for metal binding. Developing various peat water treatment techniques can help provide clean water for local communities. This study reported the preparation of hydroxyapatite (HAp) via hydrothermal method using Carbon Negative Precipitated Calcium Carbonate (PCC) as precursor, obtained from PT. Pertamina, a leading energy company of Indonesia, for treating peat water. HAps were synthesized from precursors that were calcined at 900 °C (HAp 900) and 1000 °C (HAp 1000). Its potential as an adsorbent for peat water purification was evaluated. X-ray diffraction (XRD) revealed good crystallinity in HAp 900 and HAp 1000, with values of 82.33 % and 86.90 %, respectively. These samples also displayed nano-sized crystals, measuring 14.2 ± 0.3 nm and 23.80 ± 0.2 nm. The Ca/P molar ratios were 1.6 for HAp 900 and 1.57 for HAp 1000, which was close to the the theoretical hydroxyapatite ratio of 1.67. FTIR analysis detected the presence of carbonate groups at 1450.42 cm−1 for HAp 900 and 1426 cm−1 for HAp 1000, indicating the formation of carbonated hydroxyapatite. Scanning electron microscopy (SEM) revealed agglomerations and irregularly shaped particles in both HAp samples. Optimal conditions for peat water purification experiment, determined through UV-Vis spectrophotometry, were pH 2, 1 h contact time, and 1 g adsorbent mass for both HAp 900 and HAp 1000.

Fabrication of nanocrystal forms of ᴅ-cycloserine and their application for transdermal and enteric drug delivery systems.

ᴅ-cycloserine (DCS), an FDA-approved medicine for the treatment of tuberculosis, is also a partial agonist at the glycine recognition site of N-methyl-ᴅ-aspartate (NMDA) receptor and has shown significant treatment efficacy for central nervous system (CNS) disorders including depression, schizophrenia, Alzheimer's disease, and post-traumatic stress disorder. The physicochemical properties of DCS, however, limit the options of formulation and medicinal applications of DCS, and warrants further investigation for the development of CNS therapeutics. Nanocrystals play an important role in pharmaceutic design and development. The properties of nanocrystals are remarkably different from their bulk material counterpart, attributed to the large surface-area-to-volume ratio which can improve the bioavailability. In this study, for the first time, DCS, a highly water-soluble compound, has formed nanocrystals and this was confirmed by scanning electronic microscopy and X-ray powder diffraction. Furthermore, DCS nanocrystals were applied to several formulations to test their stability and then to the in vitro Franz diffusion test with reservoir patch formulation as well as in vivo pharmacokinetics study with enteric capsules. We tested these formulations regarding their nanocrystal physical properties, size effect, and dissolution rate, respectively. We found that DCS nanocrystals showed good performance in the Franz diffusion test and rodent pharmacokinetic studies due to the nanoparticle size and faster dissolution as compared with the commercial DCS powder. These DCS nanocrystal formulations could offer a new approach for the development of an advanced drug delivery system for the treatment of CNS disorders.

Identification of percolation threshold of spray‐dried cellulose nanocrystals in homopolymer polypropylene composites

AbstractUnderstanding the percolation threshold is essential for determining the performance of particle‐reinforced polymer composites. Spray‐dried cellulose nanocrystals (SDCNC) of micrometer size reinforced homopolymer polypropylene (HPP) composites at 20, 30, 40, and 50 wt.% were prepared to investigate the percolation threshold of SDCNC particles in HPP. The effect of a compatibilizer (maleic anhydride polypropylene (MAPP)) at 3, 5, and 7 wt.%, on the SDCNC percolation networks and composites performance were also studied. The results indicated that SDCNC particle percolation networks in HPP were established between 30 and40 wt.%. For composites without MAPP, the impact strength significantly increased by up to 23% below the percolation threshold and declined beyond it. The peak crystallization temperature of HPP was steadily increased until 30 wt.% SDCNC particles were added due to the SDCNC saturated nucleation function at the threshold. Introducing MAPP significantly improved tensile strength (58%), tensile strain (61%), flexural strength (45%), and impact strength (91%) compared with the corresponding composites without MAPP, attributed to the enhanced interfacial adhesion between the SDCNC particles and HPP. Water absorption results indicated that adding MAPP changed the SDCNC particle distribution networks within the matrix above the percolation threshold but did not change it below the threshold.

Real-time imaging reveal anisotropic dissolution behaviors of silver nanorods

The morphology and size control of anisotropic nanocrystals are critical for tuning shape-dependent physicochemical properties. Although the anisotropic dissolution process is considered to be an effective means to precisely control the size and morphology of nanocrystals, the anisotropic dissolution mechanism remains poorly understood. Here, using in situ liquid cell transmission electron microscopy, we investigate the anisotropic etching dissolution behaviors of polyvinylpyrrolidone (PVP)-stabilized Ag nanorods in NaCl solution. Results show that etching dissolution occurs only in the longitudinal direction of the nanorod at low chloride concentration (0.2 mM), whereas at high chloride concentration (1 M), the lateral and longitudinal directions of the nanorods are dissolved. First-principles calculations demonstrate that PVP is selectively adsorbed on the {100} crystal plane of silver nanorods, making the tips of nanorods the only reaction sites in the anisotropic etching process. When the chemical potential difference of the Cl− concentration is higher than the diffusion barrier (0.196 eV) of Cl− in the PVP molecule, Cl− penetrates the PVP molecular layer of {100} facets on the side of the Ag nanorods. These findings provide an in-depth insight into the anisotropic etching mechanisms and lay foundations for the controlled preparation and rational design of nanostructures.

Interzeolite Transformation from FAU-to-EDI Type of Zeolite.

This study reports for the first time the transformation of the pre-made FAU type of zeolite to the EDI type of zeolite. The concentration of the KOH solution controls this interzeolite transformation, which unusually occurs at both room temperature and under hydrothermal conditions. The transformation involves the amorphization and partial dissolution of the parent FAU phase, followed by the crystallization of EDI zeolite. At room temperature, the transformation (11-35 days) provides access to well-shaped nano-sized crystals and hollow hierarchical particles while the hydrothermal synthesis results in faster crystallization (6-27 h). These findings reveal an example of an interzeolite transformation to a potassium zeolite that lacks common composite building units with the parent zeolite phase. Finally, this work also demonstrates the first room-temperature synthesis of EDI zeolite from a gel precursor.