Synthesis Of High Concentrations Research Articles

Continuous Nanomanufacturing of Inorganic Lead Halide Perovskite Nanocrystals with High-Concentration Precursors.

The microscale flow preparation scheme has been widely used in the preparation of inorganic perovskite nanocrystals (NCs). It is considered to be the most promising method for large-scale production. Recently, it has been suggested that increasing the precursor concentration can further improve efficiency, but there is still a lack of understanding of high-concentration synthesis. Here, we develop a microscale flow synthesis scheme using high-concentration precursors, and the typical concentration value in the reaction phase reaches 0.035 mol/L using cesium acetate. The CsPbBr3 NCs with sharp photoluminescence (PL) at 515.7 nm can be obtained, and their PL quantum yield after post-treatment exceeds 90%. The effect of the molar ratio of Pb/Cs (Rm), reaction time, reaction temperature, and excess ligands on this flow reaction is studied. Several new phenomena are observed in our experiment. At 120 °C, some Cs4PbBr6 NCs exist in addition to the usual CsPbBr3 nanoplatelets. Excess ligands lead to the formation of numerous Cs4PbBr6 NCs with a bright green PL, and these NCs will spontaneously transform into a nonemission form in the film. Moreover, mixed-halide CsPbBrxI3-x NCs and CsPbI3 NCs are also prepared in this scheme, and then they are used to obtain LEDs in a range of colors.

Kinetic Trapping of Photoluminescent Frameworks During High-Concentration Synthesis of Non-Emissive Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are porous, crystalline materials constructed from organic linkers and inorganic nodes with potential utility in gas separations, drug delivery, sensing, and catalysis. Small variations in MOF synthesis conditions can lead to a range of accessible frameworks with divergent chemical or photophysical properties. New methods to controllably access phases with tailored properties would broaden the scope of MOFs that can be reliably prepared for specific applications. Herein, we demonstrate that simply increasing the reaction concentration during the solvothermal synthesis of M2(dobdc) (M = Mg, Mn, Ni; dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) MOFs unexpectedly leads to trapping of a new framework termed CORN-MOF-1 (CORN = Cornell University) instead. In-depth spectroscopic, crystallographic, and computational studies support that CORN-MOF-1 has a similar structure to M2(dobdc) but with partially protonated linkers and charge-balancing or coordinated formate groups in the pores. The resultant variation in linker spacings causes CORN-MOF-1 (Mg) to be strongly photoluminescent in the solid state, whereas H4dobdc and Mg2(dobdc) are weakly emissive due to excimer formation. In-depth photophysical studies suggest that CORN-MOF-1 (Mg) is the first MOF based on the H2dobdc2- linker that likely does not emit via an excited state intramolecular proton transfer (ESIPT) pathway. In addition, CORN-MOF-1 variants can be converted into high-quality samples of the thermodynamic M2(dobdc) phases by heating in N,N-dimethylformamide (DMF). Overall, our findings support that high-concentration synthesis provides a straightforward method to identify new MOFs with properties distinct from known materials and to produce highly porous samples of MOFs, paving the way for the discovery and gram-scale synthesis of framework materials.

Simplifying the Synthesis of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are porous, crystalline materials constructed from organic linkers and inorganic nodes that have attracted widespread interest due to their permanent porosity and highly modular structures. However, the large volumes of organic solvents and additives, long reaction times, and specialized equipment typically required to synthesize MOFs hinder their widespread adoption in both academia and industry. Recently, our lab has developed several user-friendly methods for the gram-scale (1-100 g) preparation of MOFs. Herein, we summarize our progress in the development of high-concentration solvothermal, mechanochemical, and ionothermal syntheses of MOFs, as well as in minimizing the amount of modulators required to prepare highly crystalline Zr-MOFs. To begin, we detail our work elucidating key features of acid modulation in Zr-MOFs to improve upon current dilute solvothermal syntheses. Choosing an optimal modulator maximizes the crystallinity and porosity of Zr-MOFs while minimizing the quantity of modulator needed, reducing the waste associated with MOF synthesis. By evaluating a range of modulators, we identify the pKa, size, and structural similarity of the modulator to the linker as controlling factors in modulating ability. In the following section, we describe two high-concentration solvothermal methods for the synthesis of Zr-MOFs and demonstrate their generality among a range of frameworks. We also target the M2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd; dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) family of MOFs for high-concentration synthesis and introduce a two-step preparation of several variants that proceeds through a novel kinetic phase. The high-concentration methods we discuss produce MOFs on multi-gram scale with comparable properties to those prepared under traditional dilute solvothermal conditions. Next, to further curtail solvent waste and accelerate reaction times, we discuss the mechanochemical preparation of M2(dobdc) MOFs utilizing liquid amine additives in a planetary ball mill, which we also apply to the synthesis of two related salicylate frameworks. These samples exhibit comparable porosities to traditional dilute solvothermal samples but can be synthesized in just minutes, as opposed to days, and require under 1 mL of liquid additive to prepare ~0.5 g of material. In the following section, we discuss our efforts to avoid specialized equipment and eliminate solvent use entirely by employing ionothermal conditions to prepare a variety of azolate- and salicylate-based MOFs. Simply combining metal chloride (hydrate) salts with organic linkers at temperatures above the melting points of the salts affords high-quality framework materials. Further, ionothermal conditions enable the syntheses of two new Fe(III) M2(dobdc) derivatives that cannot be synthesized under normal solvothermal conditions. Last, as a demonstrative example, we discuss our efforts to synthesize 100 g of high-quality Mg2(dobdc) in a single batch using a high-concentration (1.0 M) hydrothermal synthesis. Our Account will be of significant interest to researchers aiming to prepare gram-scale quantities of MOFs for further study.

Assessing the reproducibility and up-scaling of the synthesis of Er,Yb-doped NaYF4-based upconverting nanoparticles and control of size, morphology, and optical properties

Lanthanide-based, spectrally shifting, and multi-color luminescent upconverting nanoparticles (UCNPs) have received much attention in the last decades because of their applicability as reporter for bioimaging, super-resolution microscopy, and sensing as well as barcoding and anti-counterfeiting tags. A prerequisite for the broad application of UCNPs in areas such as sensing and encoding are simple, robust, and easily upscalable synthesis protocols that yield large quantities of UCNPs with sizes of 20 nm or more with precisely controlled and tunable physicochemical properties from low-cost reagents with a high reproducibility. In this context, we studied the reproducibility, robustness, and upscalability of the synthesis of β-NaYF4:Yb, Er UCNPs via thermal decomposition. Reaction parameters included solvent, precursor chemical compositions, ratio, and concentration. The resulting UCNPs were then examined regarding their application-relevant physicochemical properties such as size, size distribution, morphology, crystal phase, chemical composition, and photoluminescence. Based on these screening studies, we propose a small volume and high-concentration synthesis approach that can provide UCNPs with different, yet controlled size, an excellent phase purity and tunable morphology in batch sizes of up to at least 5 g which are well suited for the fabrication of sensors, printable barcodes or authentication and recycling tags.

In Situ Biosynthesis of a Metal Nanoparticle Encapsulated in Alginate Gel for Imageable Drug-Delivery System.

Development of drug-delivery systems that allow simultaneous in vivo imaging has gained much interest. We report a novel strategy to encapsulate metal nanoparticles (NPs) within alginate gel for in vivo imaging. The cell lysate of recombinant Escherichia coli strain, expressing Arabidopsis thaliana phytochelatin synthase and Pseudomonas putida metallothionein genes, was encapsulated within the alginate gel. Incubation of alginate gel with metal ion precursors followed by UV irradiation resulted in the synthesis of high concentrations of metal NPs, such as Au, Ag, CdSe, and EuSe NPs, within the gel. The alginate gel with metal NPs was used as a drug-delivery system by further co-encapsulating doxorubicin and rifampicin, the release of which was made to be pH-dependent. This system can be conveniently and safely used for in vitro and in vivo bioimaging, enabled by the metal NPs formed within the gel matrix without using toxic reducing reagents or surfactants.

Ship-in-a-Bottle Synthesis of High Concentration of N2 Molecules in a Cage-Structured Electride.

We report the formation of neutral nitrogen molecules in the cages of [Ca12Al14O32]2+ (C12A7) framework compensated by extra-framework anions. NH3 treatment of C12A7 electride (C12A7:e-) at 800 °C leads to the formation of N2 and NH2- species in the C12A7 cages. N2 and NHx species in the cages are identified using the Raman spectroscopy of 14NH3 and 15NH3-treated C12A7:e-. The concentration of H and N in the C12A7 cages after NH3 treatment is ∼1021 cm-3. We propose a two-step mechanism, supported by density functional theory (DFT) modeling, of N2 incorporation into the C12A7 cages, i.e., incorporation of NH2- formed from decomposition of NH3 at C12A7:e- surface followed by the NH2- species reacting to form N2 molecules. Encapsulation of neutral molecules, as opposed to negatively charged species reported in C12A7 previously, offers new opportunities for trapping and storing gaseous substances in nanoporous materials.

Structure-guided evolution of carbonyl reductase for efficient biosynthesis of ethyl (R)-2-hydroxy-4-phenylbutyrate

This study reported an attractive engineered carbonyl reductase fromGluconobacter oxydansthrough a structure-guided rational design to catalyze the synthesis of high concentration (R)-HPBE.

An aligned octahedral core in a nanocage: synthesis, plasmonic, and catalytic properties.

Plasmonic metal nanostructures with complex morphologies provide an important route to tunable optical responses and local electric field enhancement at the nanoscale for a variety of applications including sensing, imaging, and catalysis. Here we report a high-concentration synthesis of gold core-cage nanoparticles with a tethered and structurally aligned octahedral core and examine their plasmonic and catalytic properties. The obtained nanostructures exhibit a double band extinction in the visible-near infrared range and a large area electric field enhancement due to the unique structural features, as demonstrated using finite difference time domain (FDTD) simulations and confirmed experimentally using surface enhanced Raman scattering (SERS) tests. In addition, the obtained structures had a photoelectrochemical response useful for catalyzing the CO2 electroreduction reaction. Our work demonstrates the next generation of complex plasmonic nanostructures attainable via bottom-up synthesis and offers a variety of potential applications ranging from sensing to catalysis.

Low-cost and high-throughput synthesis of copper nanopowder for nanofluid applications

Copper (Cu) is a low cost and efficient filler for nanofluids. However, commercially available copper nanopowders are as costly as silver. A few methods are available for synthesis of copper nanopowder in the lab, but the amount of powder produced per batch is very small, and it is impractical to produce a large volume of nanofluid using these methods. Solution based high concentration synthesis for production of copper nanopowder using batch reactor has been reported in this work. Cost of production is minimal in this method and nanoparticles are separated from the suspension by a controlled flocculation process. The proposed method relies on the higher solubility of cuprammonium complex in an aqueous medium and its chemical reduction using hydrazine hydrate. The colloid has been stabilised using sodium citrate and obtained as sub 50 nm powder re-dispersible in water and ethylene glycol (EG). Continuous synthesis of this product using a Continuous Stirred Tank Reactor (CSTR) has also been demonstrated. The quality of particles from the CSTR is similar to that of the batch method. Stable nanofluids have been prepared by re-dispersing the nanopowder in water and EG. Moderate enhancement (∼5%) in thermal conductivity for Cu-EG nanofluids and small enhancement (∼2%) for Cu-water nanofluid have been observed with 0.6 vol% of copper loading.

Mesophase Formation Stabilizes High-Purity Magic-Sized Clusters.

Magic-sized clusters (MSCs) are renowned for their identical size and closed-shell stability that inhibit conventional nanoparticle (NP) growth processes. Though MSCs have been of increasing interest, understanding the reaction pathways toward their nucleation and stabilization is an outstanding issue. In this work, we demonstrate that high concentration synthesis (1000 mM) promotes a well-defined reaction pathway to form high-purity MSCs (>99.9%). The MSCs are resistant to typical growth and dissolution processes. On the basis of insights from in situ X-ray scattering analysis, we attribute this stability to the accompanying production of a large (>100 nm grain size), hexagonal organic-inorganic mesophase that arrests growth of the MSCs and prevents NP growth. At intermediate concentrations (500 mM), the MSC mesophase forms, but is unstable, resulting in NP growth at the expense of the assemblies. These results provide an alternate explanation for the high stability of MSCs. Whereas the conventional mantra has been that the stability of MSCs derives from the precise arrangement of the inorganic structures (i.e., closed-shell atomic packing), we demonstrate that anisotropic clusters can also be stabilized by self-forming fibrous mesophase assemblies. At lower concentration (<200 mM or >16 acid-to-metal), MSCs are further destabilized and NPs formation dominates that of MSCs. Overall, the high concentration approach intensifies and showcases inherent concentration-dependent surfactant phase behavior that is not accessible in conventional (i.e., dilute) conditions. This work provides not only a robust method to synthesize, stabilize, and study identical MSC products but also uncovers an underappreciated stabilizing interaction between surfactants and clusters.

Influence of Ag nanoparticles microstructure on their optical and plasmonic properties for photovoltaic applications

This paper shows an experimental attempt to approach plasmonic structure of silver nanoparticles (NPs) for photovoltaic application optimized previously for front side of thin film silicon solar cells. For that purpose the synthesis of high concentration of 100 and 140 nm Ag nanoparticles suspensions and layer-by-layer deposition method was applied. The results of electrical and optical studies of silicon solar cells with Ag nanoparticles as well as the microstructure of nanoparticles assemblies examined by SEM are presented. The results of these measurements are compared with theoretically predicted ones for optimized case and are the basis for further simulation analysis of the influence of the microstructure of actual nanoparticles assemblies. The simulations cover particles size distribution, the presence of agglomerates and arrangement. The results of these simulations show that the microstructure parameters decide on the plasmonic properties leading to the limited cell performance enhancement. Here we present more than 12% increase of short circuit current density and perspectives for further improvement. The outcomes of these studies have a general character and should be considered for optimization of other plasmonic structures used in photovoltaic and optoelectronic devices.

Cytotoxicity and antibacterial assessment of gallic acid capped gold nanoparticles

Cytotoxicity of nanoparticles needs to be examined for their biocompatibility and suitability in biomedical applications. Gallic acid method was used for the high concentration synthesis (1mM) of gold nanoparticles (AuNPs) having narrow size-distribution at ambient temperature (25°C). Gallic acid capped AuNPs were characterized by different techniques such as, UV–vis spectroscopy, TEM, EDAX, SAED, and XPS. In-vitro stability of AuNPs with biomolecules, such as glucose and bovine serum albumin (BSA) was explored at different concertation ranges. The result reveals that AuNPs are biocompatible with normal cell line mouse embryonic fibroblast (MEF) cells up to 100ppm and cell viability can be retained more than 50% even after increasing the dose from 200 to 400ppm. Antibacterial application of AuNPs revealed that both particles and surface chemistry seems to be safer for both gram positive and gram negative bacterial cultures.

Synthesis of high-concentration B and N co-doped porous carbon polyhedra and their supercapacitive properties

High-concentration B and N co-doped porous carbon polyhedra were prepared and showed excellent supercapacitive properties.

Rapid controllable high-concentration synthesis and mutual attachment of silver nanowires

A new well-designed two-step injection solution-based method has been proposed to rapidly prepare uniform silver nanowires on a gram-scale. Uniform silver nanowires with different and controllable aspect ratios can be synthesized in high yields. Due to a high chemical reaction rate arising from high AgNO3 concentration, the whole synthetic process of the silver nanowires is rapid and can be controlled within 20 min. The influences of different experimental parameters on the morphologies of silver nanoproducts in such a high-concentration synthesis were investigated. It was found that the addition of an appropriate amount of Cl− ions had significant impact on the formation and the aspect ratios of the silver nanowires. Solution volume effect was also studied. It was shown that our synthetic method strongly favours the synthesis of silver nanowires in large solution volumes. A reasonable formation mechanism of the silver nanowires was put forward based on novel experimental phenomena. The mutual attachment of silver nanowires was observed and was found to play an important role in such high-concentration synthesis of silver nanowires. This facile scalable preparation method of silver nanowires can decrease the synthetic cost greatly and broaden the research and application areas of silver nanowires.

Facile Synthesis of High-Concentration, Stable Aqueous Dispersions of Uniform Silver Nanoparticles Using Aniline as a Reductant

A facile method was developed for preparing uniform silver nanoparticles with small particle sizes of less than 10 nm at high concentrations, in which aniline was used to reduce silver nitrate (AgNO(3)) to silver nanoparticles in the presence of dodecylbenzenesulfonic acid (DBSA) as a stabilizer. Upon the addition of excess NaOH to the DBSA-aniline-AgNO(3) (DAA) system, the formation of silver nanoparticles was almost complete in just 2 min at 90 °C (in 94% yield). The average size of those resultant silver nanoparticles was 8.9 ± 1.1 nm, and the colloids were stable for more than 1 year at ambient temperature. A possible mechanism for the formation of silver nanoparticles was proposed to be related to two factors: one was the mesoscopic structures of the DAA system in which silver ions were restricted in the dispersed phases composed of DBSA and aniline; the other was Ag(2)O nanocrystallites generated in situ that could be readily reduced by aniline to small silver nanoparticles at high concentrations.

Surfactant‐Free Platinum‐on‐Gold Nanodendrites with Enhanced Catalytic Performance for Oxygen Reduction

Inner value: A new high-concentration synthesis of Pt nanodendrite employs Au-seed-mediated growth inside a hollow silica nanosphere (see picture). The resulting material is substantially more active than commercial Pt black in the oxygen reduction reaction. Pt nanodendrite colloid with tunable dispersity as well as hybrid nanocrystals of various metals were also fabricated by the procedure.

Standardization of an ELISA test using a recombinant nucleoprotein from the Junin virus as the antigen and serological screening for arenavirus among the population of Nova Xavantina, State of Mato Grosso

Arenavirus hemorrhagic fever is a severe emerging disease. Considering that the levels of antibodies against arenavirus in the Brazilian population are completely unknown, we have standardized an ELISA test for detecting IgG antibodies using a recombinant nucleoprotein from the Junin virus as the antigen. This protein was obtained by inserting the gene of the Junin virus nucleoprotein into the genome of Autographa californica nucleopolyhedrovirus, using the Bac-to-Bac baculovirus expression system. This recombinant baculovirus was used to infect S. frugiperda cells (SF9). The infection resulted in synthesis of high concentrations of recombinant protein. This protein was detected on 12.5% polyacrylamide gel and by means of Western blot. Using the standardized ELISA test, 343 samples from the population of Nova Xavantina were analyzed. We observed that 1.4% of the serum samples (five samples) presented antibody titers against arenavirus. These results show the population studied may present exposure to arenavirus infection.

Ultrasonochemical-assisted fabrication and evaporation- induced self-assembly (EISA) of POSS-SiO2 @Ag core/ABA triblock copolymer nanocomposite film

Poly(ethylene glycol)-octafunctionalized polyhedral oligomeric silsesquioxane (POSS) (Mn = 5576.6 g/mol) alloying agent stabilized amphiphilic [email protected] metalloid nanocomposite blended with a triblock copolymer poly(p-dioxanone-co-caprolactone)-block-poly(ethylene oxide)-block-poly(p-dioxanone-co-caprolactone) (POSS-SiO2@Ag/PPDO-co-PCL-b-PEG-b-PPDO-co-PCL) has been synthesized in both water and in organic medium utilizing ultrasonochemical reaction. The POSS stabilized pre-made metalloid was successfully dispersed in amphiphilic PPDO-co-PCL-b-PEG-b-PPDO-co-PCL (ABA) triblock copolymer matrix of molecular weight 45.9 × 104 g/mol. The mechanism of synthesis of high concentration of SiO2@Ag nanocomposite from TEOS/AgNO3 (in the presence of NH4OH as catalyst/NaBH4 as reductant) nonmetal/metal precursors and the successful EISA of POSS-SiO2@Ag/ABA nanocomposite into films has been discussed. The successful synthesis of metalloid nanocomposite was morphologically accessed by field emission-scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Surface plasmon resonance was ensured from UV–visible spectral analysis. Identity and the crystallinity of as prepared nanocomposite were studied by X-ray diffractometer. Structural and luminescence properties of the nanocomposite were examined by Fourier transform infrared spectroscopy and photoluminescence. Thermogravimetric analysis was carried out to study the thermal stability of the resulting hybrid nanocomposite. The resultant inorganic–organic nanocomposite can be easily suspended in water and would be useful in variety of applications. POLYM. COMPOS., 31:1620–1627, 2010. © 2009 Society of Plastics Engineers

Synthesis of block copolymer-stabilized Au–Ag alloy nanoparticles and fabrication of poly(methyl methacrylate)/Au–Ag nanocomposite film

[Poly(2-( N, N-dimethylamino)ethyl methacrylate)]– b–poly(methyl methacrylate)– b–[poly(2-( N, N-dimethylamino)ethyl methacrylate)] ( M n = 45 , 000 ; 20K–5K–20K; PDI = 1.2) block copolymer surfactant stabilized amphiphilic gold–silver alloy nanoparticles (Au–Ag(PDMA– b–PMMA– b–PDMA)) has been synthesized in both water and in organic medium. The block copolymer stabilized pre-made alloy nanoparticles were successfully dispersed in hydrophobic poly(methyl methacrylate) homopolymer matrix (PMMA) of molecular weight 30,000. The successful synthesis of alloy nanoparticles was accessed by Transmission Electron Microscope (TEM), Energy Dispersed X-ray (EDX), and UV–visible spectrophotometric analysis. The surface functionality of the nanoparticles was confirmed by quantitative determining the grafting density of polymer chain around the nanoparticle surface using combination of thermo gravimetric (TGA) and TEM analysis. The hydrodynamic diameter of the alloy particles including the polymer chains was obtained from dynamic light scattering measurement (DLS). The mechanism of synthesis of high concentration of Au–Ag alloy particles from HAuCl 4 and AgNO 3 (in presence of Cl − from reduction of gold salt) metal particles precursors and the successful preparation of poly(methyl methacrylate)/gold–silver nanocomposite films have been discussed.

Insect freeze tolerance: Roles of protein phosphatases and protein kinase A

Freeze-tolerant larvae of the goldenrod gall fly, Eurosta solidaginis Fitch, show multiple metabolic adaptations for subzero survival including the autumn synthesis of high concentrations of polyols. The induction and regulation of cold hardiness adaptations requires the intermediary action of signal transduction enzymes. The present study evaluates changes in the activities of cAMP-dependent protein kinase (PKA), protein phosphatases 1 (PP1), 2A, 2C, and protein tyrosine phosphatases (PTPs) over the course of the winter season and also in insects exposed to −4, −20 °C, or anoxic conditions in the laboratory. The increased PKA and decreased PP1 over the winter season and/or at subzero temperature support a regulatory role for these enzymes in cryoprotectant polyol synthesis. PTP activities were also strongly increased under these conditions and may act to antagonize tyrosine kinase mediated cell growth and proliferation responses and, thereby, contribute to hypometabolism and diapause over the winter.