Conventional Synthesis Approaches Research Articles

Self-Assembly of Heterogeneous Ferritin Nanocages for Tumor Uptake and Penetration.

Well-defined nanostructures are crucial for precisely understanding nano-bio interactions. However, nanoparticles (NPs) fabricated through conventional synthesis approaches often lack poor controllability and reproducibility. Herein, a synthetic biology-based strategy is introduced to fabricate uniformly reproducible protein-based NPs, achieving precise control over heterogeneous components of the NPs. Specifically, a ferritin assembly toolbox system is developed that enables intracellular assembly of ferritin subunits/variants in Escherichia coli. Using this strategy, a proof-of-concept study is provided to explore the interplay between ligand density of NPs and their tumor targets/penetration. Various ferritin hybrid nanocages (FHn) containing human ferritin heavy chains (FH) and light chains are accurately assembled, leveraging their intrinsic binding with tumor cells and prolonged circulation time in blood, respectively. Further studies reveal that tumor cell uptake is FH density-dependent through active binding with transferrin receptor 1, whereas in vivo tumor accumulation and tissue penetration are found to be correlated to heterogeneous assembly of FHn and vascular permeability of tumors. Densities of 3.7FH/100nm2 on the nanoparticle surface exhibit the highest degree of tumor accumulation and penetration, particularly in tumors with high permeability compared to those with low permeability. This study underscores the significance of nanoparticle heterogeneity in determining particle fate in biological systems.

In Situ Reactive Formation of Mixed Oxides in Additively Manufactured Cobalt Alloy.

Oxide-dispersion-strengthened (ODS) alloys have long been considered for high temperature turbine, spacecraft, and nuclear reactor components due to their high temperature strength and radiation resistance. Conventional synthesis approaches of ODS alloys involve ball milling of powders and consolidation. In this work, a process-synergistic approach is used to introduce oxide particles during laser powder bed fusion (LPBF). Chromium (III) oxide (Cr2O3) powders are blended with a cobalt-based alloy, Mar-M 509, and exposed to laser irradiation, resulting in reduction-oxidation reactions involving metal (Ta, Ti, Zr) ions from the metal matrix to form mixed oxides of increased thermodynamic stability. A microstructure analysis indicates the formation of nanoscale spherical mixed oxide particles as well as large agglomerates with internal cracks. Chemical analyses confirm the presence of Ta, Ti, and Zr in agglomerated oxides, but primarily Zr in the nanoscale oxides. Mechanical testing reveals that agglomerate particle cracking is detrimental to tensile ductility compared to the base alloy, suggesting the need for improved processing methods to break up oxide particle clusters and promote their uniform dispersion during laser exposure.

Hydrothermal Synthesis of Ni3TeO6 and Cu3TeO6 Nanostructures for Magnetic and Photoconductivity Applications.

Despite great attention toward transition metal tellurates especially M3TeO6 (M = transition metal) in magnetoelectric applications, control on single phasic morphology-oriented growth of these tellurates at the nanoscale is still missing. Herein, a hydrothermal synthesis is performed to synthesize single-phased nanocrystals of two metal tellurates, i.e., Ni3TeO6 (NTO with average particle size ∼37 nm) and Cu3TeO6 (CTO ∼ 140 nm), using NaOH as an additive. This method favors the synthesis of pure NTO and CTO nanoparticles without the incorporation of Na at pH = 7 in MTO crystal structures such as Na2M2TeO6, as it happens in conventional synthesis approaches such as solid-state reaction and/or coprecipitation. Systematic characterization techniques utilizing in-house and synchrotron-based characterization methods for the morphological, structural, electronic, magnetic, and photoconductivity properties of nanomaterials showed the absence of Na in individual particulate single-phase MTO nanocrystals. Prepared MTO nanocrystals also exhibit slightly higher antiferromagnetic interactions (e.g., T N-NTO = 57 K and T N-CTO = 68 K) compared to previously reported MTO single crystals. Interestingly, NTO and CTO show not only a semiconducting nature but also photoconductivity. The proposed design scheme opens the door to any metal tellurates for controllable synthesis toward different applications. Moreover, the photoconductivity results of MTO nanomaterials prepared serve as a preliminary proof of concept for potential application as photodetectors.

One-step green synthesis of meso-microporous carbons by self-activation of lemon wastes for high-performance supercapacitors

A green self-activating system is introduced for the synthesis of porous carbons. This system is introduced to overcome the environmental concerns regarding the harmful by-products of the conventional synthesis approaches. The introduced system is based on the circulating active gases, released during the carbonization treatments at T ≤ 500 °C. These active gases are stored in the system and participate in the activation process at T ≥ 700 °C. During the activation process, there is no exhaust gas and any need for a protective atmosphere. Lemon wastes were pyrolyzed in this system at several temperatures (400 to 900 °C). It is demonstrated that the introduced system is applicable for the synthesis of turbostratic carbons with relatively high graphitization levels. Pyrolyzation at T ≥ 800 °C can appropriately activate the lemon biomass. The prepared meso-microporous carbon has a large specific surface area of up to 2111 m2.g−1 and a pore volume of 1.28 cm3.g−1 can be obtained after pyrolyzation at 900 °C. Meso-microporous carbon are applied as an electrode for supercapacitors. The prepared supercapacitor performs an electric double layer with minor pseudo-capacitance behavior. The supercapacitor illustrates the capacitance of 254 F.g−1 at 10 A.g−1 and excellent stability of 92 % retention after 30,000 cycles.

Synthesis of 5(S)-Methyl-L-Proline Containing Peptidomimetic Compounds and their In Vitro Evaluation for Dipeptidyl Peptidase-4 Inhibition

Background: Type 2 diabetes mellitus (T2DM), which is the epidemic of the 21st century, has affected millions of people worldwide. Traditional methods available for the treatment are associated with various side effects. Among the newer therapies, DPP-4 (Dipeptidyl peptidase-4) inhibition has been a promising therapy for the past decade with the scope of further development, especially in peptidomimetics. Objective: 5(S)-methyl-L-proline containing peptidomimetic compounds were designed in the previous work. The designed compounds were synthesized and characterized by spectral methods, such as mass spectrometry, 1H NMR, and 13C NMR (Nuclear magnetic resonance) spectroscopy. The purity of the final compounds was determined by high-performance liquid chromatography (HPLC). The synthesized compounds were in vitro evaluated for their DPP-4 inhibitory activity. Method: Compounds were peptide in nature and were synthesized using the conventional synthesis approach, where peptide synthesis was done using an acid-amine coupling reagent. They were evaluated through fluorimetric enzyme-based assay using a DPP-4 inhibitor screening kit. Moreover, the CLARIOstar microplate reader instrument was used to measure fluorescence. Results: 5(S)-methyl-L-proline containing 13 compounds were synthesized. All of them were characterized for structural integrity using spectral methods. They had HPLC purity of more than 95% and were evaluated for DPP-4 inhibition. Compounds 1, 7, 10, 11, 14 and 17 were found to have good inhibition than others. These compounds were further evaluated at different concentrations to develop a linear correlation coefficient (R2). Conclusion: Six compounds were found to have good DPP-4 inhibition, hence it further opens the possibility of developing DPP-4 inhibitor-containing 5(S)-methyl-L-proline.

Green synthesis of SrO bridged LaFeO3/g-C3N4 nanocomposites for CO2 conversion and bisphenol A degradation with new insights into mechanism

Very recently the green synthesis routes of nanomaterials have attracted massive attention as it overcome the sustainability concerns of conventional synthesis approaches. With this heed, in this novel research work we have synthesized the g-C3N4 nanosheets based nanocomposites by utilizing Eriobotrya japonica as mediator and stabilizer agent. Our designed bio-caped and green g-C3N4 nanosheets based nanocomposites have abundant organic functional groups, activated surface and strong adsorption capability which are very favorable for conversion CO2 into useful products and bisphenol A degradation. Beneficial to further upgrade the performances of g-C3N4 nanosheets, the resulting pristine g-C3N4 nanosheets are coupled with LaFeO3 nanosheets via SrO bridge. Based on our experimental results such as TEM, XRD, DRS, TPD, TGA, PL, PEC and FS spectra linked with OH amount it is confirmed that the biologically mediated green g-C3N4 nanosheets are eco-friendly, highly efficient and stable. Furthermore, the coupling of LaFeO3 nanosheets enlarged the surface area, enhanced the charge separation, while the insertion of SrO bridge worked as facilitator for electron transportation and photo-electron modulation. In contrast to pristine green g-C3N4 nanosheets (GCN), the activities of final resulting sample 6LFOS-(4SrO)-GCN are improved by 8.0 times for CO2 conversion (CH4 = 4.2, CO = 9.2 μmol g−1 h−1) and 2.5-fold for bisphenol A degradation (88%) respectively. More specifically, our current research work will open a new gateway to design cost effective, eco-friendly and biological inspired green nanomaterials for CO2 conversion and organic pollutants degradation which will further support the net zero carbon emission manifesto and the optimization of carbon neutrality level.

Hemicryptophane Cages with a C1-Symmetric Cyclotriveratrylene Unit

Two new hemicryptophanes combining a cyclotriveratrylene unit with either an aminotrisamide or a tris(2-aminoethyl)amine (tren) moiety have been synthesized. Although a conventional synthesis approach was used, the molecular cages obtained are devoid of the expected C3 symmetry. NMR analyses and X-ray crystal structure determination showed that these hemicryptophanes exhibited C1 symmetry due to the unusual arrangement of the substituents of the cyclotriveratrylene unit. This unprecedented arrangement is related to a change in the regioselectivity of the Friedel-Crafts reactions that led to the CTV cap. This constitutes an original approach to access enantiopure chiral molecular cages with low symmetry.

One-step synthesis and its mechanism of potassium hexatitanate whiskers from potassium dititanate and metatitanic acid

The high price of potassium hexatitanate (K2Ti6O13) whiskers restricts its broad applications. The current production method is composed of complex processes and generates a large amount of wastewater. In this work, we propose a new one-step synthesis approach for producing potassium hexatitanate whiskers. Potassium dititanate and metatitanic acid are mixed at the ratio of TiO2/K2O = 4 and then calcined at 1000 °C to synthesize potassium hexatitanate whiskers. We used XRD, SEM, TG-DSC, and other characterization techniques combined with thermodynamic calculations to study the synthesis mechanism of such one-step process. The thermodynamic calculations show that the reaction free energy of K2Ti6O13 whiskers synthesized by this process is negative even at room temperature, confirming that this process has a higher reactivity than the conventional synthesis approach by K2CO3 and TiO2. Moreover, the melting of K2Ti2O5 at 916 °C provides a necessary environment for the crystal growth of K2Ti6O13 nanoparticles, which is the key to the preparation of K2Ti6O13 whiskers. This new synthesis approach will significantly reduce the producing cost of K2Ti6O13 whiskers, thereby expanding its applications.

A review on phytosynthesis, affecting factors and characterization techniques of silver nanoparticles designed by green approach

Nature has a massive range of diverse species of flora. The phytochemical content of each plant may vary due to the diverse climate and different geographical areas. Several plants have been outlined for their reducing properties and highly exploited for the green synthesis of metal nanoparticles. Moreover, phytochemicals present in plant parts (leaf, root, flower, fruit, etc.) act as both reducing and capping agents for the production of nanoparticles. Plant-mediated nanoparticles have gained so much attention in the present era for its green and rational approach and developed as a green substitute to conventional synthesis approaches. This critical review encloses literature, phytosynthesis methods, and factors affecting the synthesis of silver nanoparticles. Also, the main characterization techniques especially, spectroscopic techniques are epigrammatically summarized and discussed here.

A review on bio-synthesized Co3O4 nanoparticles using plant extracts and their diverse applications

Developing a rapid, reliable and eco-accommodating methodology for the synthesis of metal/metal oxide nanoparticles (NPs) is an important step in the area of nanotechnology. Cobalt oxide nanoparticles (Co3O4 NPs) have been widely studied due to their potential applications including, antibacterial, antifungal, electrochromic sensors, heterogeneous catalysis, and energy storage devices. Due to the large rate of perilous chemicals employed in the physical and chemical production of these NPs, green methods employing the use of plants, fungus, algae, and bacteria have been adopted. However, plant-mediated synthesis of metal NPs has been developed as a substitute to defeat the restrictions of conventional synthesis approaches such as physical and chemical methods. Biomolecules, such as tannins, saponins, proteins, amino acids, steroids, enzymes, flavonoids, and vitamins from several plant extracts have been used as a stabilizing and reducing agents for the synthesis of Co3O4 NPs. Recently, several attempts were made to develop plant-mediated synthesis methods to produce stable, cost-effective, and eco-accommodating Co3O4 NPs. In this review, a comprehensive study was conducted on synthesis, characterization, and various applications of Co3O4 NPs produced using various plant sources.

Photoelectrochemical Driving and Simultaneous Synthesis of 3-pyridinecarboxylic Acid and Hydrogen in WO3 Photoanode-Based Cell

In conventional photoelectrochemical (PEC) cell for solar water splitting, its solar-to-hydrogen efficiency is limited by the sluggish oxygen evolution on its photoanode. 3-pyridinecarboxylic acid (3-PA) is an important organic in industry, but there are several disadvantages in its conventional synthesis approaches. Here, we reported that the oxidation of 3-methylpyridine (3-MP) into 3-PA as an alternative to the oxygen evolution on WO3 photoanode for improving the hydrogen-evolution efficiency and the product added-value of PEC cell. In a WO3 film photoanode-based dual-chamber PEC cell, 3-PA and hydrogen were simultaneously synthetized. Since the oxidation of 3-MP into 3-PA is more thermodynamically and kinetically favorable than water oxidation, higher efficiency of hydrogen evolution was achieved in the PEC cell with function of 3-PA synthesis relative to the conventional PEC cell for water splitting. Our investigations indicated that the oxidation of 3-MP into 3-PA on WO3 photoanode is co-initiated by the photogenerated holes and the H2O2 intermediate that originated from two-holes pathway of solar water oxidation on WO3. Additionally, the Cr2O72−/Cr3+ redox pair could mediate and promote the oxidation of 3-MP into 3-PA on WO3 photoanode, and thus the PEC efficiency of 3-PA synthesis can be improved by adding Cr3+ into the H2SO4-3-MP electrolyte.

Steam-Assisted Synthesis of an Extra-Stable Polyoxometalate-Encapsulating Metal Azolate Framework: Applications in Reagent Purification and Proton Conduction.

Different from the conventional synthesis approaches, such as hydrothermal or solvothermal synthesis, a porous metal azolate framework encapsulating Keggin-type [SiW12 O40 ](4-) anions was prepared by an environmentally friendly, low-cost, and highly efficient steam-assisted conversion method for the first time. The nanosized polyoxometalates as a template were encapsulated by a zeotype 6(4) 4(8) cage constructed by 28 nuclear zinc atoms connected through 32 Trz ligands. The obtained composite exhibits excellent thermal and chemical stability; meanwhile, its special ability to selectively absorb water from alcohols makes it efficiently separate water from analytically pure ethanol, with the result that water content decreases from 0.23 to 0.05 wt %, which is superior to the standard of chromatographic grade ethanol (<0.1 wt %). Besides, alternating current (ac) impedance experiments also reveal that the hybrid is a kind of proton conductive material.

Synthesis of wormhole mesoporous silica by compressed carbon dioxide and application in catalytic hydrogenation

Mesoporous silica materials were prepared by infusion and selective condensation of silicon alkoxides within self-assembly formed from protonated hexadecylamine by CO2 in aqueous media. Compared to the conventional synthesis approach, the introduction of CO2 facilitates the hydrolysis of silicon alkoxide precursor and does not need adding any co-solvent in the course of the synthesis of mesoporous material. Moreover, CO2 can be used as a swelling agent increasing the average pore size form 3.2–5.4 nm with expansion rate of approximately 69 %. The influence of CO2 pressure and temperature were carefully investigated. During the preparation, nonionic surfactant hexadecylamine can turn into cationic surfactant in situ as mesostructure-directing template under pressurized CO2 condition, which is the key factor for the formation of ordered mesoporous silica. In addition, the supported Pd catalysts were prepared and characterized thoroughly by X-ray diffraction, 1H NMR, 13C NMR, ICP-AES analysis, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption measurements. On the basis of the characterization and hydrogenation performance of the catalysts, the roles of different supports were discussed.

Microfluidic Method for Synthesizing Cu2O Nanofluids

NANOFLUIDS, fluid suspensions of nanometer-sized particles, have recently been demonstrated to have thermal conductivities far superior to that of the liquid alone [1–4]. This and their other distinctive features offer unprecedented potential for many applications in various fields, including energy, biological, pharmaceutical, chemical, electronic, environmental, material, medical, and thermal engineering industries [1–8]. Yet the functional outcomes of existing nanofluids have not been satisfactory because of the inadequacies of conventional synthesis approaches in engineering microstructures and properties of nanofluids [1–9]. For creating nanofluids by design, we have recently developed a one-step chemical solution method (CSM) that is capable of synthesizing nanofluids of various microstructures [9–11]. The method has been successfully applied to produce the nine kinds of nanofluids [9–11]. The nanofluids synthesized by theCSMhave both higher conductivity enhancement and better stability than those produced by other methods. The CSM is also distinguished from the others by its controllability. The nanofluid microstructure can be easily varied and manipulated by adjusting synthesis parameters such as temperature, acidity (pH), ultrasonic and microwave irradiation, types and concentrations of reactants and additives, and the order in which the additives are added to the solution [9–11]. Problems with the CSM come from that reactions take place in macroscale batch reactors such as beakers and flasks. The CSM uses a bottom-up approach to generate nanoparticles through chemical reactions in the liquid phase, and thereby it has the potential to manipulate atoms and molecules for synthesis of tailor-made nanofluids. However, the difficulty of controlling the microscale while operating at the macroscale is insuperable. Mixing in a macroscale batch reactor is usually achieved by stirring. In this case, the fluid entity is broken into fragments by circular motion. The last part of mixing takes place based on molecular diffusion. In the diffusion process, the mixing time t depends on the diffusion path d in the form of t / d=D, where D is the diffusion coefficient. Therefore, if the diffusion path becomes smaller, the mixing time becomes shorter. However, it is very difficult to make small-sized fragments by conventional stirring in solution phase. At the macroscale, therefore, mixing time is usually much larger than reaction time. The reaction rate is normally determined by the mixing time and is usually very low. Moreover, the longer mixing time and lack of effective ways to accurately control mixing also lead to poor product selectivity of competitive parallel reactions and competitive consecutive reactions, thereby yielding poor quality of synthesized nanofluids containing some undesired side products. Because of the work-up demand, a batch-model operation is not commercially economical. The repeatability of nanofluids’ structures is also poor with the batch-model operation. To resolve these critical issues, we propose to replace batch-based macroreactors in the CSM by continuous-flow microfluidic microreactors, allowing a continuous and scalable (simply by numberingup) synthesis of nanofluidswith amore accurate and effective control over particlemicrostructures such as the size, distribution, and shape. Here, we report such a microfluidic system for synthesizing Cu2O nanofluids: suspensions of Cu2O nanoparticles in water.

Band gap engineering of a carbon nanotube by hydrogen functionalization

Realization of carbon nanotube (CNT)-based transistors requires preexisting semiconducting CNTs, which are not selectively grown by the conventional synthesis approaches. While CNT heterojunction and cross-junction formed with different chiralities have demonstrated the required performance for CNT transistors, these relied on an junction formation accidentally obtained during sample preparation. We propose that hydrogen functionalization of CNTs can transform the electronic structure systematically from metallic (narrow-gap semiconducting) to semiconducting (large-gap semiconducting). We visualize this phenomenon by fabricating a heterojunction between the pristine and the functionalized CNTs that clearly shows both rectifying and gating effects even at room temperature.

Rational Synthesis of The Metastable Compounds BixCo4-xFexSb12

AbstractThe synthesis of many targeted ternary compounds using conventional synthesis approaches has been unsuccessful because the ternary compounds are thermodynamically unstable with respect to disproportionation to a mixture of binary compounds. Typically these compounds have been synthetic targets based on predictions of enhanced properties. The ternary skutterudites with formula M'xM4Sbl2 (where M' = La, Lu, Y) are prime examples. Compounds with this structure have been found to be very promising thermoelectric materials having both good electrical properties and low thermal conductivities. Inserting heavy M' atoms into this crystal structure has been predicted to further decrease the thermal conductivity by increased phonon scattering. Attempts to make the title compound using conventional synthesis approaches failed due the formation of binary compounds as reaction products. Using modulated elemental reactants we were able to prepare the title compound at 160°C. Annealing at temperatures above 500°C resulted in exothermic decomposition into binary compounds. The Bi containing compounds are therefore thermodynamically unstable with respect to disproportionation at all temperatures. The amount of Bi can be varied by varying the composition of the starting modulated elemental reactant. Preliminary measurements to determine the variation of electrical conductivity and Seebeck coefficient as a function of bismuth content are presented.