Size-controlled Synthesis Research Articles

Size-Controlled Synthesis of L10-CoPt Intermetallic Fuel Cell Catalysts on Nitrogen-Doped Mesoporous Graphitized Carbon Support

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). However, after subjecting to a widely used postsynthesis annealing treatment, the particle size of intermetallic catalysts inevitably increases, leading to a poor performance in practical fuel cell application. In this work, ordered L10-CoPt intermetallic catalyst of small particle size was prepared through using nitrogen-doped mesoporous graphitized carbon (NMGC) support. The porous feature and nitrogen doping of NMGC support immobilized CoPt particles and prevented sintering during annealing treatment. These small and ordered L10-CoPt nanoparticles exhibit outstanding ORR activity (~ 1.18 A/mgPt) and superior high current density in fuel cell testing. Moreover, this L10-CoPt/NMGC catalyst performs remarkably enhanced stability in comparison with L10-CoPt/high surface area carbon (HSC) counterpart and commercial Pt/C catalyst, surpassing the DOE 2020 target. The enhancement in catalyst durability can be attributed to strong particles-support interaction via nitrogen heteroatoms and the strengthened p bonding. To better understand the support effect on particle growth, L10-CoPt particles on NMGC with different porosity/graphitization were prepared and their fuel cell performances were systematically studied. This study demonstrates an effective strategy to control the particle size of intermetallic catalysts with using NMGC support, which achieves excellent practical fuel cell performance.

Size-controlled synthesis of gold nanostars and their characterizations and plasmon resonances

Gold nanostar particles were synthesized using seed-mediated method. Au-seed was synthesized with the diameter of approximately 3 nm and a considerably low STDEV of less than 1 nm. Then, different amount of Au seed was introduced into the growth solution of nanostars and the influence of the changes in concentration of Au seed on the growth process was investigated. The size of gold nanostars increased with decreasing the concentration of Au seeds. We further extended this method to enable size-control of gold nanostars from approximately 70 nm to 140 nm in size. Also the longer branch length caused red shifting of resonant plasmonic peaks in the absorption spectra of the sample with the lower amount of Au seed. Thanks to this method, we could control size, and spikes of gold nanostars and the obtained results broaden the concept of the formation and morphology of gold nanostars. The plasmon band shift was attributed to variations in branch numbers, and overall star size.

Formation of Size and Density Controlled Nanostructures by Galvanic Displacement.

Gold (Au) and copper (Cu)-based nanostructures are of great interest due to their applicability in various areas including catalysis, sensing and optoelectronics. Nanostructures synthesized by the galvanic displacement method often lead to non-uniform density and poor size distribution. Here, density and size-controlled synthesis of Au and Cu-based nanostructures was made possible by galvanic displacement with limited exposure to hydrofluoric (HF) acid and the use of surfactants like L-cysteine (L-Cys) and cetyltrimethylammonium bromide (CTAB). An approach involving cyclic exposure to HF acid regulated the nanostructure density. Further, the use of surfactants generated monodisperse nanoparticles in the initial stages of the deposition with increased density. The characterization of Au and Cu-based nanostructures was performed by scanning electron microscopy, atomic force microscopy, UV-Visible spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. The surface enhanced Raman spectroscopic measurements demonstrated an increase in the Raman intensity by two to three orders of magnitude for analyte molecules like Rhodamine 6G dye and paraoxon.

Size controllable synthesis and photocatalytic performance of mesoporous TiO2 hollow spheres

Hollow mesoporous TiO2 spheres (THs) were prepared via template-directed deposition of TiO2 nanoparticles on the surface of carbon spheres. The carbon spheres were used as hard templates. Their diameters were controlled by pH adjustment prior to a hydrothermal process. Physical properties, such as crystallinity, optical characteristics, microstructure and surface morphology of the samples were characterized. The results showed that the diameter of the carbon template could be well controlled in the range of 397–729 nm by adjusting the initial pH value of the dextrose solution from 3 to 10. Hollow TiO2 spheres with average diameters ranging from 171 to 668 nm and shell thicknesses ranging from 28 to 47 nm formed by heat treatment at 450 °C. The photocatalytic performance of hollow TiO2 spheres and TiO2 nanoparticles was examined under UVA irradiation using a methyl orange aqueous solution as an artificial dye. The study revealed that the THs synthesized using a dextrose solution at pH 7 had a higher photocatalytic activity compared to other samples since it had the lowest shell thickness and the proper optical band gap of 3.12 eV with the longest lifetime of electron-hole pair separation.

Insights into mechanism of size-controlled synthesis of CH3NH3PbBr3 perovskite quantum dots and large nanoparticles with tunable optical properties

There is a common phenomenon in the preparation of perovskite quantum dots (QDs) by reprecipitation method that large particles were always produced with desired QDs. Understanding the fabrication mechanism can contribute to improve this phenomenon. Herein, we demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles (LNPs), where the growth of QDs and LNPs involves two possible pathways, the quick intercalation reaction process and the dissolution-recrystallization process. Following two pathways, we have created QDs with high photoluminescence quantum yields (ca. 46–71%), tunable size (ca. 3.2–5.4 nm) and LNPs with tunable size from 25 to 300 nm, where their emission wavelength can be tuned from 500 nm to 534 nm. Importantly, based on the comprehensive insight into the formation mechanism, we have achieved the conversion from LNPs to QDs partly through adding surfactants properly, which is expected to pave the way for the development of pure production of perovskite QDs. • We demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles. • The perovskite QDs with tunable size (ca. 2.3–5.4 nm) manifest high photoluminescence quantum yields. • We have achieved the conversion from perovskite large nanoparticles to QDs partly through adding surfactants properly. • The possible mechanism was reported to make clear the function of surfactants on the formation of perovskite QDs and LNPs.

Lignin-fatty acid hybrid nanocapsules for scalable thermal energy storage in phase-change materials

Abstract Development of affordable thermal energy storage (TES) has been hampered by the lack of environmentally benign and scalable phase-change materials (PCM). Here we show size-controlled colloidal synthesis of fatty acid-lignin hybrid nanocapsules and demonstrate their applicability as PCM in dry and wet states. The one-pot fabrication allowed for facile preparation of hybrid capsules with a predictable concentration of tall oil fatty acid, oleic acid, or lauric acid in core-shell particles stabilized by softwood kraft lignin. Phase-change peaks of capsules containing 40 wt% of lauric acid were observed in aqueous dispersion, indicating a possibility to develop colloidal TES systems. In dry form, the hybrid capsules prevented fragmentation of the phase-change peaks during 290 heating-cooling cycles, while in wet state the capsules appeared stable for 25 cycles. The nanoscaled morphology of the capsules was characterized using thermoporometry-differential scanning calorimetry (tp-DSC), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and small angle X-ray scattering (SAXS). Extraction of lauric acid from the capsules allowed for investigation of the intraparticle space previously occupied by the fatty acid. The fatty acid-deficient nanocapsules were found to contain an internal volume that was 19 times as high as that of lignin nanoparticles. Approximately 20 nm thick lignin shells of the capsules were found to be readily accessible to water, permitting heat transfer across the capsules. The possibility to tailor the hybrid capsules by altering the chain length and saturation degree of the fatty acids opens applications that extend beyond the TES systems.

Surface curvature-confined strategy to ultrasmall nickel-molybdenum sulfide nanoflakes for highly efficient deep hydrodesulfurization

Size-controlled synthesis of two-dimensional (2D) catalysts with low stacking numbers and small nanoflake lengths is crucial for promoting the catalytic performance in diverse heterogeneous catalysis. Herein, we report a facile and general “surface curvature-confined synthesis” strategy to modulate the slab lengths and stacking numbers of 2D transition metal sulfides by controlling the strain induced by different surface curvature of supports. An efficient NiMo sulfide with shorter slab length (average 3.71 nm), less stacking number (1–2 layers) and more edge active sites is synthesized onto ZSM-5 zeolites with the average size of 100 nm, which shows superior kHDS value of dibenzothiophene (14.05 × 10−7 mol/(g·s)), enhanced stability up to 80 h, and high direct desulfurization selectivity (> 95%). This design concept is also proved to be generally applicable to modulate the slab lengths and stacking numbers of other 2D catalysts such as MoS2 and WS2 nanoflakes, which shows great potentials for developing more ultrasmall 2D catalysts with controlled sizes and excellent catalytic activities.

Capturing the Equilibration Pathway of Nanomaterials Metastable in Both Crystal Structure and Morphology

In this issue of Matter, Li et al. used in situ electron microscopy to investigate the equilibration pathway of Au nanoribbons that are metastable in terms of both crystal structure and morphology when they are subjected to thermal stress.

Correction to “Investigating Particle Size Effects in Catalysis by Applying a Size-Controlled and Surfactant-Free Synthesis of Colloidal Nanoparticles in Alkaline Ethylene Glycol: Case Study of the Oxygen Reduction Reaction on Pt”

ADVERTISEMENT RETURN TO ISSUEPREVCorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Investigating Particle Size Effects in Catalysis by Applying a Size-Controlled and Surfactant-Free Synthesis of Colloidal Nanoparticles in Alkaline Ethylene Glycol: Case Study of the Oxygen Reduction Reaction on Pt”Jonathan Quinson*Jonathan QuinsonMore by Jonathan Quinsonhttp://orcid.org/0000-0002-9374-9330, Masanori InabaMasanori InabaMore by Masanori Inaba, Sarah NeumannSarah NeumannMore by Sarah Neumann, Andreas A. SwaneAndreas A. SwaneMore by Andreas A. Swane, J. BucherJ. BucherMore by J. Bucher, Søren B. SimonsenSøren B. SimonsenMore by Søren B. Simonsenhttp://orcid.org/0000-0001-7172-1225, Luise Theil KuhnLuise Theil KuhnMore by Luise Theil Kuhn, Jacob J. K. KirkensgaardJacob J. K. KirkensgaardMore by Jacob J. K. Kirkensgaardhttp://orcid.org/0000-0001-6265-0314, Kirsten M. Ø. JensenKirsten M. Ø. JensenMore by Kirsten M. Ø. Jensenhttp://orcid.org/0000-0003-0291-217X, Mehtap OezaslanMehtap OezaslanMore by Mehtap Oezaslanhttp://orcid.org/0000-0001-8545-7576, Sebastian KunzSebastian KunzMore by Sebastian Kunz, and Matthias Arenz*Matthias ArenzMore by Matthias Arenzhttp://orcid.org/0000-0001-9765-4315Cite this: ACS Catal. 2020, 10, 4, 2692–2693Publication Date (Web):February 10, 2020Publication History Published online10 February 2020Published inissue 21 February 2020https://doi.org/10.1021/acscatal.0c00452Copyright © 2020 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1254Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (720 KB) Get e-AlertsSUBJECTS:Metal nanoparticles,Mixtures,Platinum,Precursors,X-ray scattering Get e-Alerts

Size-controlled synthesis of gold nanoparticles by ultrafine bubbles and pulsed ultrasound

Size-controlled gold nanoparticles (AuNPs) were synthesized by ultrasonic irradiation of HAuCl4 aqueous solutions with the aid of ultrafine bubbles (UFBs) in the absence of any capping and reducing agents. Upon addition of air-UFBs, the mean diameter of the spherical AuNPs decreased. This result was attributed to the sonochemical reduction of gold ions in aqueous solution being accelerated by the UFBs. Moreover, the AuNPs were stable in a solution containing UFBs because AuNPs electrostatically adsorbed onto UFBs, whose lifetime in water was very long. Compared with the mean diameter of AuNPs synthesized with argon-, nitrogen- and oxygen-UFBs, that of AuNPs synthesized with air-UFBs was smaller. Pulsed ultrasound delivered with the same time-averaged power as continuous-wave irradiation further decreased the mean diameter of the AuNPs. Size-controlled synthesis of AuNPs without the use of a capping or reducing agent was successful through optimization of the number air-UFBs and the pulsed ultrasound conditions.

Ferritins as natural and artificial nanozymes for theranostics.

Nanozymes are a class of nanomaterials with intrinsic enzyme-like characteristics which overcome the limitations of natural enzymes such as high cost, low stability and difficulty to large scale preparation. Nanozymes combine the advantages of chemical catalysts and natural enzymes together, and have exhibited great potential in biomedical applications. However, the size controllable synthesis and targeting modifications of nanozymes are still challenging. Here, we introduce ferritin nanozymes to solve these problems. Ferritins are natural nanozymes which exhibit intrinsic enzyme-like activities (e.g. ferroxidase, peroxidase). In addition, by biomimetically synthesizing nanozymes inside the ferritin protein shells, artificial ferritin nanozymes are introduced, which possess the advantages of versatile self-assembly ferritin nanocage and enzymatic activity of nanozymes. Ferritin nanozymes provide a new horizon for the development of nanozyme in disease targeted theranostics research. The emergence of ferritin nanozyme also inspires us to learn from the natural nanostructures to optimize or rationally design nanozymes. In this review, the intrinsic enzyme-like activities of ferritin and bioengineered synthesis of ferritin nanozyme were summarized. After that, the applications of ferritin nanozymes were covered. Finally, the advantages, challenges and future research directions of advanced ferritin nanozymes for biomedical research were discussed.

A size-controlled green synthesis of silver nanoparticles by using the berry extract of Sea Buckthorn and their biological activities

Herein, by using the Sea Buckthorn berry extract, we present a new eco-friendly approach for green synthesis of AgNPs, which reveal superior antioxidation and anticancer but poor antimicrobial activities.

Size-controlled synthesis of metal-organic frameworks and their performance as fluorescence sensors.

Metal-Organic Frameworks (MOFs) are of bright promise as new fluorescence sensors because of their accurate framework structure and unique fluorescence properties. Many MOFs have been reported as fluorescence sensors, including bulk-MOF-crystals and nano-MOF-powder. Obviously, the sensing performance of these MOF sensors should be diverse due to their different sizes. However, bulk-MOF-crystals and nano-MOF-powder have completely different dispersibility in solvents, and the effects of this difference on the analytical performance like precision and sensitivity are significant but have not been discussed systematically. To investigate such effects, rodlike bulk-MOFs and nano-MOFs with the same structure but different sizes are required. In this work, we obtained MOFs with a crystal width ranging from 9.7 μm to 170 nm by controlled synthesis, and then proved that they have the same structure by PXRD, SEM, TGA and FTIR analysis. After that, taking folic acid as the target molecule, fluorescent sensing experiments were carried out to compare the sensing performance between bulk-MOFs and nano-MOFs. From the results, we found that nano-MOFs have obviously better dispersity, a lower precipitation speed, a smaller standard deviation, ten times higher fluorescence intensities and a much lower LOD than bulk-MOFs. Finally, we draw a conclusion that nano-MOFs are more in line with the requirements of analytical performance as fluorescence sensors, and the size of MOFs as fluorescence sensors should be as small as possible.

Salt-assisted size-controlled synthesis and luminescence studies of single phase CaWO4:Dy3+: an insight into its morphological evolution, energy transfer and colour evaluation

The size of the particles of CaWO4:Dy3+ increases with the addition of NH4Cl/KCl electrolyte and enhances its luminescence.

General criteria for evaluating suitable polymer ligands for the synthesis of aluminum nanocrystals.

Herein, we evaluate the suitablity of polystyrenes with thiol, dithioester and trithiocarbonate end-groups for the synthesis of Al nanocrystals. Both the end-groups and molecular weight of the polymer ligands play important roles for controlling the size and shape of the Al nanocrystals. A general criterion for evaluating polymers as the ligand for the synthesis of Al nanocrystals is proposed.

Novel route to size-controlled synthesis of MnFe2O4@MOF core-shell nanoparticles

Nanoscale metal-organic framework (nMOF) is a distinctive type of crystalline compounds that consists of metal ions or clusters coordinated to organic ligands. This hybrid material has attracted fast-growing attention due to its tunable pore sizes, remarkably large surface areas, and high selectivity in uptaking small molecules. In this paper, we successfully developed a novel approach for synthesizing a core-shell structure with MIL-88B–4CH3 as a tunable nMOF shell and MnFe2O4 as a magnetic core. We controlled the growth of the core-shell particles by introducing different acetic acid concentrations and with varied reaction time. Acetic acid works as a modulating agent that allows for nucleation rate control, leading to tailored particle size. Our results show an increase in the particle size with increasing acetic acid concentration or reaction time. This study provides a valuable methodology for synthesis of core-shell nanoparticles with controlled sizes based on nMOF platforms.

Photomagnetic Prussian blue nanocubes: Synthesis, characterization, and biomedical applications

Nanoparticles play an important role in biomedicine. We have developed a method for size-controlled synthesis of photomagnetic Prussian blue nanocubes (PBNCs) using superparamagnetic iron oxide nanoparticles (SPIONs) as precursors. The developed PBNCs have magnetic and optical properties desired in many biomedical diagnostic and therapeutic applications. Specifically, the size-tunable photomagnetic PBNCs exhibit high magnetic saturation, strong optical absorption with a peak at approximately 700 nm, and superior photostability. Our studies demonstrate that PBNCs can be used as MRI and photoacoustic imaging contrast agents in vivo. We also showed the utility of PBNCs for labeling and magnetic manipulation of cells. Dual magnetic and optical properties, together with excellent biocompatibility, render PBNCs an attractive contrast agent for both diagnostic and therapeutic applications. The use SPIONs as precursors for PBNCs provides flexibility and allows researchers to design theranostic agents according to required particle size, optical, and magnetic properties.

Staggered Herringbone Microfluid Device for the Manufacturing of Chitosan/TPP Nanoparticles: Systematic Optimization and Preliminary Biological Evaluation.

Chitosan nanoparticles (CS NPs) showed promising results in drug, vaccine and gene delivery for the treatment of various diseases. The considerable attention towards CS was owning to its outstanding biological properties, however, the main challenge in the application of CS NPs was faced during their size-controlled synthesis. Herein, ionic gelation reaction between CS and sodium tripolyphosphate (TPP), a widely used and safe CS cross-linker for biomedical application, was exploited by a microfluidic approach based on a staggered herringbone micromixer (SHM) for the synthesis of TPP cross-linked CS NPs (CS/TPP NPs). Screening design of experiments was applied to systematically evaluate the main process and formulative factors affecting CS/TPP NPs physical properties (mean size and size distribution). Effectiveness of the SHM-assisted manufacturing process was confirmed by the preliminary evaluation of the biological performance of the optimized CS/TPP NPs that were internalized in the cytosol of human mesenchymal stem cells through clathrin-mediated mechanism. Curcumin, selected as a challenging model drug, was successfully loaded into CS/TPP NPs (EE% > 70%) and slowly released up to 48 h via the diffusion mechanism. Finally, the comparison with the conventional bulk mixing method corroborated the efficacy of the microfluidics-assisted method due to the precise control of mixing at microscales.

New hydrothermal synthesis strategy of nano-sized BiFeO3 for high-efficient photocatalytic applications

A simple hydrothermal synthesis strategy is proposed for optimization of the BiFeO3 size and structure to enhance its photocatalytic activity for removal of organic dyes. The results of the comparison tests show that the photodegradation rate of such nano-sized BiFeO3 can possess at least 5.5 times higher than that of the most used micro-sized form, up to 6.161 h−1 for photodegradation of MO anionic dye. Initial analysis indicates that large specific surface area, higher photocurrent response and fast photogenerated charge transfer should be responsible for the excellent photocatalytic activity of nano-sized BiFeO3. Such size-controlled synthesis strategy would provide a promising way to design and regulate the kind of iron oxide semiconductors photocatalysts for high-efficient photocatalytic applications.

Size-controlled synthesis of Mo powders via hydrogen reduction of MoO2 powders with the assistance of Mo nuclei

The size-controlled preparation of Mo powders is always a challenge and important task in the molybdenum metallurgy. In the current study, Mo powders with controllable sizes are synthesized by hydrogen reduction of MoO2 powders with the assistance of Mo nuclei in the range of 900–1100 °C. The influences of the particle sizes of Mo nuclei, the additive amount as well as reaction temperature on the morphology and particle sizes of the final products are studied. For the hydrogen reduction of MoO2 without any additive, the obtained Mo powders always have large particle sizes. However, the addition of small amounts of nuclei in MoO2 can help Mo nucleate dispersedly, and the growth of Mo could be also controlled by adjusting the sizes of added nuclei, amount of addition and the reaction temperature. With the addition of Mo nuclei, the different sizes of Mo powders with the good dispersity can be prepared. As adding commercial Mo powders with the particle size of about 2.03 μm, the micron-sized Mo powders ranged from 2.11 μm to 3.25 μm could be prepared. While for the case of adding ultrafine Mo nuclei of about 170 nm, Mo powders from 0.28 μm to 0.88 μm can be obtained. Moreover, the more the amounts of nuclei added and the lower the reaction temperature (in the range of 900–1100 °C) is, the smaller the particle size of the prepared Mo powder will be. The current method is a facile and feasible method, and is potential to be used for industrial production of Mo powder with controllable particle sizes.