Preparation Of Nanocrystals Research Articles

Preparation of cellulose nanocrystals from commercial dissolving pulp using an engineered cellulase system

There is increasing attention to the production of cellulose nanocrystals (CNCs) from lignocellulosic biomass by enzymatic hydrolysis with cellulase. In this study, the feasibility of the application of a cellulase system from engineered strain Penicillium oxalicum cEES in the production of CNCs was assessed. Using commercial eucalyptus dissolving pulp (EDP) as substrate, the CNCs were successfully obtained by enzymatic hydrolysis with the cellulase cEES, and the total yields of CNCs reached 15.7% through three-step enzymatic hydrolysis of total 72 h (24 h for each step). The prepared CNCs were characterized and found that their crystallinity and thermal stability were higher than that of EDP. In the later stage of enzymatic hydrolysis, the process efficiency of enzymatic preparation of CNCs greatly decreased because of the high crystallinity of cellulosic substrate, and a simple homogenization treatment can promote the enzymatic hydrolysis, as well as produce fusiform CNCs with more uniform size and more fermentable sugar that could be further converted into fuels and bulk chemicals through fermentation. This study provides a feasible enzymatic preparation process for CNCs with engineered cellulase and commercial cellulosic materials.Graphical

Analysis of dominant and intense XRD peak of (111) plane of ZnS nanocrystals for microstructural study through single line Voigt method: Calculated low dislocation density value emphasizes larger stacking of (111) plane

In this work, a wet chemical synthesis method has been used for the preparation of ZnS nanocrystals using the precursor Zn(NO3)2 (Zinc Nitrate) and Na2S (Sodium sulfide), where 3-Mercaptopropionic acid has been used as a capping agent. Morphological characterization of the prepared ZnS nanocrystals has been performed through HR-TEM and FE-SEM analysis and the average particle size has been obtained as approximately 26 nm. The HR-TEM image also suggests the formation of smooth crystalline ZnS nanoparticles with dominance of the (111) plane. The XRD pattern firmly indicates dominance of (111) crystalline planes over the other planes. For this, different microstructural properties of prepared ZnS nanoparticles have been studied considering only the dominant (111) diffraction peak using single line Voigt method. Finally, the average particle size calculated from morphological analysis has been compared with the crystallite size calculated by XRD analysis through the Single line Voigt method. Calculated dislocation density value indicates presence of less defects states in the sample and confirms the growth of ZnS nanoparticles in a particular direction of (111) plane with pure crystalline nature.

Nanocrystal Array Engineering and Optoelectronic Applications of Organic Small-Molecule Semiconductors.

Organic small-molecule semiconductor materials have attracted extensive attention because of their excellent properties. Due to the randomness of crystal orientation and growth location, however, the preparation of continuous and highly ordered organic small-molecule semiconductor nanocrystal arrays still face more challenges. Compared to organic macromolecules, organic small molecules exhibit better crystallinity, and therefore, they exhibit better semiconductor performance. The formation of organic small-molecule crystals relies heavily on weak interactions such as hydrogen bonds, van der Waals forces, and π-π interactions, which are very sensitive to external stimuli such as mechanical forces, high temperatures, and organic solvents. Therefore, nanocrystal array engineering is more flexible than that of the inorganic materials. In addition, nanocrystal array engineering is a key step towards practical application. To resolve this problem, many conventional nanocrystal array preparation methods have been developed, such as spin coating, etc. In this review, the typical and recent progress of nanocrystal array engineering are summarized. It is the typical and recent innovations that the array of nanocrystal array engineering can be patterned on the substrate through top-down, bottom-up, self-assembly, and crystallization methods, and it can also be patterned by constructing a series of microscopic structures. Finally, various multifunctional and emerging applications based on organic small-molecule semiconductor nanocrystal arrays are introduced.

Colloidal Polymer-Templated Formation of Inorganic Nanocrystals and their Emerging Applications.

Inorganic nanocrystals possess unique physicochemical properties compared to their bulk counterparts. Stabilizing agents are commonly used for the preparation of inorganic nanocrystals with controllable properties. Particularly, colloidal polymers have emerged as general and robust templates for in situ formation and confinement of inorganic nanocrystals. In addition to templating and stabilizing inorganic nanocrystals, colloidal polymers can tailor their physicochemical properties such as size, shape, structure, composition, surface chemistry, and so on. By incorporating functional groups into colloidal polymers, desired functions can be integrated with inorganic nanocrystals, advancing their potential applications. Here, recent advances in the colloidal polymer-templated formation of inorganic nanocrystals are reviewed. Seven types of colloidal polymers, including dendrimer, polymer micelle, stare-like block polymer, bottlebrush polymer, spherical polyelectrolyte brush, microgel, and single-chain nanoparticle, have been extensively applied for the synthesis of inorganic nanocrystals. Different strategies for the development of these colloidal polymer-templated inorganic nanocrystals are summarized. Then, their emerging applications in the fields of catalysis, biomedicine, solar cells, sensing, light-emitting diodes, and lithium-ion batteries are highlighted. Last, the remaining issues and future directions are discussed. This review will stimulate the development and application of colloidal polymer-templated inorganic nanocrystals.

Production and Characterization of Cellulose Nanocrystals from Eucalyptus Dissolving Pulp Using Endoglucanases from Myceliophthora thermophila

Endoglucanase (EG) is a key enzyme during enzymatic preparation of cellulose nanocrystals (CNCs). Myceliophthora thermophila is a thermophilic fungus that has thermal properties and a high secretion of endoglucanases (EGs), and could serve as potential sources of EGs for the preparation of CNCs. In this work, four different GH families (GH5, GH7, GH12, and GH45) of EGs from M. thermophila were expressed and purified, and their enzymatic characteristics and feasibility of application in CNC preparation were investigated. It was shown that the MtEG5A from M. thermophila has good potential in the enzymatic preparation of CNCs using eucalyptus dissolving pulp as feedstock. It was also observed that there was a synergistic effect between the MtEG5A and other MtEGs in the preparation of CNCs, which improved the yield and properties of CNCs obtained by enzymatic hydrolysis. This study provides a reference for understanding the enzymatic characteristics of different families of EGs from M. thermophile and their potential application in nanocellulose production.

One-Pot Biosynthesis of Carbon-Coated Silver Nanoparticles Using Palm Leaves as a Reductant and a Carbon Source.

In this study, carbon-coated silver nanoparticles (Ag@C NPs) were synthesized with a one-pot hydrothermal method using palm leaves as a reductant and a carbon source. SEM, TEM, XRD, Raman, and UV-vis analyses were employed to characterize the as-prepared Ag@C NPs. Results showed that the diameter of silver nanoparticles (Ag NPs) and the coating thickness could be controlled by changing the amount of biomass and the reaction temperature. The diameter ranged from 68.33 to 143.15 nm, while the coating thickness ranged from 1.74 to 4.70 nm. As the biomass amount and the reaction temperature increased, the diameter of Ag NPs and the coating thickness became larger. Thus, this work provided a green, simple, and feasible method for the preparation of metal nanocrystals.

Preparation and characterization of cellulose nanocrystals from spent culture substrate of Auricularia auricula

Preparation and characterization of cellulose nanocrystals from spent culture substrate of Auricularia auricula

Bio synthesis and characterization of tin oxide for photocatalytic, anti-microbial and anti-oxidant applications

The advancement of new synthetic ways for the preparation of monodispersed nanocrystals by the use of cheap, non-toxic and environmentally benign materials become a challenge to the research community in science. The present study deals with the biosynthesis of SnO2 nanoparticles making use of the extract of Garcinia Cambogia as reducing and stabilizing agent. This method is simple, efficient, economic, harmless and eco-friendly. The morphological, surface, and structural studies have been conducted by employing X-ray diffraction analysis (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM), Brunauer-Emmet-Teller (BET), Fourier -Transform Infrared spectroscopy (FT-IR) and Raman Spectroscopy. The thermal and optical studies have been performed using TG-DTA analysis, UV–Visible diffuse reflectance spectroscopy and Photoluminescence spectroscopy. The photocatalytic activity of NPs is investigated against methylene blue. Agar well diffusion method is used to study the antibacterial action of the SnO2 nanoparticles with Gram-positive S.aureus along with Gram-negative E. coli. The anti-oxidant activity of SnO2 nanoparticles is confirmed using the DPPH assay.

Preparation and Characterization of Cellulose Nanocrystals from Bamboos and Their Application in Cassava Starch-Based Film.

Cellulose from different species of bamboo (Thyrsostachys siamesi Gamble, Dendrocalamus sericeus Munro (DSM), Bambusa logispatha, and Bambusa sp.) was converted to cellulose nanocrystals (CNCs) by a chemical-mechanical method. First, bamboo fibers were pre-treated (removal of lignin and hemicellulose) to obtain cellulose. Next, the cellulose was hydrolyzed with sulfuric acid using ultrasonication to obtain CNCs. The diameters of CNCs are in the range of 11-375 nm. The CNCs from DSM showed the highest yield and crystallinity, which was chosen in the film fabrication. The plasticized cassava starch-based films with various amounts (0-0.6 g) of CNCs (from DSM) were prepared and characterized. As the number of CNCs in cassava starch-based films increased, water solubility and the water vapor permeability of CNCs decreased. In addition, the atomic force microscope of the nanocomposite films showed that CNC particles were dispersed uniformly on the surface of cassava starch-based film at 0.2 and 0.4 g content. However, the number of CNCs at 0.6 g resulted in more CNC agglomeration in cassava starch-based films. The 0.4 g CNC in cassava starch-based film was found to have the highest tensile strength (4.2 MPa). Cassava starch-incorporated CNCs from bamboo film can be applied as a biodegradable packaging material.

Research progress on the preparation and application of flavonoid nanocrystals.

Flavonoids have been reported to possess significant pharmacological activities,such as antioxidant, anti-inflammatory and anticancer effects. However, the low solubility and low bioavailability limits their clinical application. Nanocrystal technology can solve the delivery problems of flavonoids by reducing particle size, increasing the solubility of insoluble drugs and improving their bioavailability. This article summaries nanosuspension preparation methods and the stabilizers for flavonoid nanocrystals, and reviews the drug delivery routes including oral, Injection and transdermal of flavonoid nanocrystals, to provide information for further research on nanocrystal delivery system of flavonoids.

Preparation and Properties of Cellulose Nanocrystals Based Self-healing Polyurethane

Preparation and Properties of Cellulose Nanocrystals Based Self-healing Polyurethane

Prediction and analysis of preparation of cellulose nanocrystals with machine learning

Prediction and analysis of preparation of cellulose nanocrystals with machine learning

Synthesis of nanosized MFI zeolites using Cu-containing complexes

Nanosized MFI type zeolites were synthesized in the presence of Cu-containing complexes. The use of ethylene diamine tetraacetic acid (EDTA) as a ligand promoted the solubility and guaranteed the exclusive configuration of the copper-bearing chelate in the precursor solutions. The EDTA-assisted MFI zeolite nanocrystals (Cu-MFI-EDTA) was found to contain low amount of silanols due to formation of flexible Si–O–Cu bonds. On the contrary, when ammonia (NH3) was used as a ligand, the copper species in the corresponding sample (Cu-MFI-NH3) only present in the form of extra framework [Cuδ+···Oδ−···Cuδ+]n clusters. The introduction of transition metals assisted by ligands permitted the preparation of nanocrystals with variable amount of silanols and modified water affinity.

Preparation and characterization of cellulose nanocrystals from paper mulberry fibers

The applicability of paper mulberry fiber (PM-FB), which is bast fiber, for manufacturing cellulose nanocrystals (CNCs) with high-yield was investigated. The PM-FB and hardwood bleached kraft pulp (Hw-BKP) were hydrolyzed under different sulfuric acid concentrations, reaction times, and reaction temperatures. The dependence of the CNC yield on the hydrolysis conditions and crystallinity of the raw materials was analyzed. The functional groups of the CNCs and their zeta potentials were determined. The fiber length and width of the individual CNCs were determined by transmission electron microscopy image analysis. The PM-FB showed a higher crystallinity of 86.8% compared to that of Hw-BKP and exhibited a high CNC yield of 55% under strong hydrolysis conditions. The sulfate group was introduced into the CNCs, which increased their negative charge. The fiber width of PM-FB-based CNCs (PM-CNCs) was larger than that of Hw-BKP-based CNCs (Hw-CNCs), and the aspect ratio ranged from 29.0 to 12.2 depending on the hydrolysis conditions. The yield of PM-CNCs was higher than that of Hw-CNCs under the same hydrolysis conditions. In addition, both CNCs exhibited similar quality. Therefore, PM-FB is a promising raw material for efficient CNC manufacturing.

Controllable preparation of mesoporous spike gold nanocrystals for surface-enhanced Raman spectroscopy detection of micro/nanoplastics in water

Microplastics and nanoplastics are emerging classes of environmental contaminants that pose significant threats to human health. In particular, small nanoplastics (<1 μm) have drawn considerable attention owing to their adverse effects on human health; for example, nanoplastics have been found in the placenta and blood. However, reliable detection techniques are lacking. In this study, we developed a fast detection method that combines membrane filtration technology and surface-enhanced Raman spectroscopy (SERS), which can simultaneously enrich and detect nanoplastics with sizes as small as 20 nm. First, we synthesized spiked gold nanocrystals (Au NCs), achieving a controlled preparation of thorns ranging from 25 nm to 200 nm and regulating the number of thorns. Subsequently, mesoporous spiked Au NCs were homogeneously deposited on a glass fiber filter membrane to form an Au film as a SERS sensor. The Au-film SERS sensor achieved in-situ enrichment and sensitive SERS detection of micro/nanoplastics in water. Additionally, it eliminated sample transfer and prevented the loss of small nanoplastics. Using the Au-film SERS sensor, we detected 20 nm to 10 μm standard polystyrene (PS) microspheres with a detection limit of 0.1 mg/L. We also realized the detection of 100 nm PS nanoplastics at the 0.1 mg/L level in tap water and rainwater. This sensor provides a potential tool for rapid and susceptible on-site detection of micro/nanoplastics, especially small-sized nanoplastics.

Microemulsion-Based Fabrication of Organic Nanocrystals for Persistent Phosphorescence Bioimaging

Persistent phosphorescence eliminates the need for light excitation and thus avoids the issue of autofluorescence, holding great promise in various fields. To achieve bright phosphorescence emission, many methods were developed to confine most organic persistent phosphorescent materials in a rigid environment aiming to quench nonradiative relaxation pathways; among them, the nanocrystal method is a good candidate which can rigidify the molecules as well as offer the desirable water dispersity and size for further bioapplications. However, the current efficient preparation of phosphorescent nanocrystals still remains challenging. This study reports an efficient microemulsion-based method for the fabrication of phosphorescent nanocrystals with a desired diameter in the nanosize range (below 200 nm), a high phosphorescence quantum yield of about 6.5%, and ultralong persistent phosphorescence to the timescale after the removal of the external light source, making it easy for the commercial imaging system to detect, which is suitable for practical bioimaging. Furthermore, the synthesized nanocrystals with biocompatibility were utilized directly for in vitro imaging, showing effective cellular uptake and bright phosphorescence emission, which provides a reasonable strategy to develop a phosphorescent nanocrystal for application.

Life cycle assessment and mechanical properties of nanocomposites based on cellulose nanocrystals

AbstractThe present work focuses on the preparation of cellulose nanocrystals (CNCs) reinforced composites based on polyhydroxybutyrate (PHB) and polypropylene (PP). The effects of the CNCs content as reinforcement and the addition of maleic anhydride (MA) as a coupling agent on the mechanical and morphological properties of the composites were studied. In addition, the biodegradability of the composites was investigated. Samples were prepared using PP and PHB as matrixes and CNCs as reinforcement. Test samples were prepared using the injection molding machine. The studied parameters were microscopic analysis and tensile strength measurement. Tensile strength increased with increasing CNC, but it decreased slightly when 5 wt% of CNC was added. Tensile strength decreased with the addition of MA. Environmental impacts from the production of 100 g of PP and PHB were evaluated using the life cycle assessment (LCA) approach. The results showed that the environmental impacts of composites containing PHB biopolymer are higher than PP ones.

Preparation and performance of CsPbBr3 nanocrystals in a fluorophosphate glass matrix

Preparation and performance of CsPbBr3 nanocrystals in a fluorophosphate glass matrix

Preparation of Cellulose Nanocrystals by Synergistic Action of Ionic Liquid and Recyclable Solid Acid under Mild Conditions

Cellulose nanocrystals (CNCs) are nanoscale particles made from cellulose. They have many unique properties such as being lightweight, stiff, and renewable, making them promising for a variety of applications in a wide range of industries, including materials science, energy storage, and biomedicine. In this paper, a two-stage (swelling-SA-catalyzed) method including IL pretreatment and solid acid hydrolysis process was developed to extract CNCs with high purity and good thermal stability from microcrystalline cellulose (MCC). In the first stage, the swelling of MCC in ionic liquid was studied with the assistance of ultrasonication, and it was found that the amorphous regions became more disordered while the crystalline areas were selectively retained under the conditions of 30 min of reaction time, 45 °C of temperature, 2% of ionic liquid water content and 1:4 mass ratio of cellulose to ionic liquid. CNCs were extracted using solid acid hydrolysis, with a 45 wt% solid acid to cellulose ratio and a 5.0 h hydrolysis process at 45 °C. The morphology, crystallinity, surface characteristics and thermo stability of the sample were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Results demonstrated the highly thermostable CNCs were successful extracted with rodlike shape of 300 ± 100 nm in length and 20 ± 10 nm in width. Solid acid recovery and reuse were also studied, revealing a promising candidate that can reduce the environmental impact associated with chemical products.

Controlled preparation of spinel CoCr2O4 nanocrystals with variable proportions of mixed redox couplings for enhanced sensing to hydrogen peroxide

Chromium-based spinels with multiple mixed valence states have been considered as promising electrocatalysts. However, they are rarely reported as electrochemical sensors. Herein, spinel CoCr2O4 nanocrystals with mixed redox couplings were controllably synthesized through a simple sol-gel method followed by air calcination at 500 °C and 600 °C. The X-ray photoelectron spectrum analyses reveal that CoCr2O4-500 and CoCr2O4-600 products possess different surface ratios of Co3+/Co2+ and Cr3+/Cr2+. Meanwhile, non-enzymatic H2O2 electrochemical sensors were successfully fabricated by drop-coating the aforementioned nanomaterials onto the surface of bare glassy carbon electrode (GCE). Amongst, CoCr2O4-500/GCE shows high sensitivity (1016 μA mM-1 cm-2), low detection limit (150 nM) and wide detection range to H2O2 in 0.1 M NaOH solution. These important indicators are better than those of CoCr2O4-600/GCE. It is also the first time to achieve highly sensitive detection of H2O2 by pure chromite spinels so far. Such excellent electrochemical sensing performance stems from the synergistic effect of its large apparent electrode area, high electrical conductivity and proper surface ratio of mixed redox couplings for Co3+/2+/Cr3+/2+. Moreover, it also exhibits good selectivity, stability and recovery rate to trace H2O2 in milk whey, mouthwash and contact lens cleaning solution.