Tunable Particle Size Research Articles

Controllable Synthesis of Polymeric Micelles by Microfluidic Platforms for Biomedical Applications: A Systematic Review.

Polymeric micelles (PMs) are one of Nanoscale delivery systems with high stability, loading capacity, and biocompatibility. PMs are nano-sized and spherical particles with a hydrophilic shell and hydrophobic core or reverse depending on their applications. Polymeric micelles could be synthesized by different methods, such as direct dissolution, dialysis method, and lyophilization. Microfluidics is also a relatively modern approach for this purpose, in which chemical reactions are carried out in the microchannels. Compared with conventional preparation methods, the microfluidic technique produces homogeneous polymeric micelles with desirable features, tunable particle size, and relatively high drug loading. These advantages are originated from the ability of microfluidics in precise control over the streamlines of reactants without chaotic turbulence. Although the synthesis of polymeric micelles by the microfluidic platform is advantageous, little or no review has been conducted to provide a clear image of the different PMs preparation by the microfluidic approach. Thus, in this review, the production of the PMs, utilizing microfluidic procedures to enhance their favorable characteristics is investigated. For this purpose, an electronic search is conducted on PubMed, Web of Science, Scopus, and Embase databases for retrieval of relevant papers. Seven papers are included in this systematic review. Preparation of PMs by the microfluidic approach and the effect of different parameters, such as the flow rate ratio, channel dimensions, drug concentration, and organic solvent type on PMs characteristics is obtained from the included papers.

Cucurbituril-assisted formation of tunable carbon dots from single organic precursors in water

A facile method by utilizing the host–guest interaction of Q[n]s for the catalytic fabrication of CDs with high emitting qualities and a tunable particle size from a single organic precursor in water with high output has been demonstrated.

Rapid ultrasound-assisted synthesis of controllable Zn/Co-based zeolitic imidazolate framework nanoparticles for heterogeneous catalysis

While metal-organic frameworks (MOFs) exhibit excellent potential in extensive catalytic reactions, predictably synthesizing MOF nanoparticles (NPs) with desired and uniform sizes remains a great challenge. Here, a mild and efficient ultrasound-assisted synthetic method has been developed to prepare ZIF-8, ZIF-67, and Co/ZIF-8 with well-designed particle size and morphology. By adjusting the cobalt content doped into a heterometallic ZIF-8 structure, tunable particle sizes ranging from 35 nm to over 300 nm have been achieved, resulting from the differences in nucleation and growth rates of zinc and cobalt ZIFs. Impressively, this as-obtained bimetallic Zn/Co-ZIF shows hierarchical porous structure with modified physicochemical properties, leading to a change of nitrogen adsorption-desorption characteristics. In addition, when used as a heterogenous catalyst, the bimetallic Co-doped ZIF-8 is demonstrated to have both enhanced catalytic performance for the activation of peroxymonosulfate (PMS) in organic dye degradation compared to pure ZIF-8, as well as superior structural stability, when compared to monometallic ZIF-67. This work provides a novel strategy for the predictable design and controlled fabrication of bimetallic MOF nanostructures with desired structures and compositions.

The Power of Ionic Liquids: Crystal Facet Engineering of SrTiO3Nanoparticles for Tailored Photocatalytic Applications

AbstractSonochemical synthesis of nano‐sized SrTiO3carried out at close to room temperature, in ionic liquids (ILs) allows the tuning of particle size and particle morphology, that is, tracht and habitus, as well as particle aggregation via the choice of the ionic liquids (ILs) as the reaction medium. The nanoparticles demonstrate high performance for photocatalytic water splitting and photodecomposition of organic material. To this end bis(trifluoromethanesulfonyl)amide ([Tf2N]−)‐based ILs with cations of different properties with respect to specific interactions with the target material are investigated. Isolated, 15±1 nm sized nano‐spheres of SrTiO3are observed to form in [C3mimOH][Tf2N] ([C3mimOH]+ =1‐(3‐hydroxypropyl)‐3‐methylimidazolium). Aggregation of small sized nanoparticles are observed to around 250±100 nm large cube‐like formations in [C4mim][Tf2N] ([C4mim]+ =1‐butyl‐3‐methylimidazolium), raspberry‐like in [C4Py][Tf2N] ([C4Py]+butylpyridinium), and ball‐like in [P66614][Tf2N] ([P66614]+tetradecyltrihexyl phosphonium). Importantly, the different materials show different performance as photocatalysts. SrTiO3prepared in [C4mim][Tf2N] shows the highest photocatalytic activity for H2evolution (1115.4µmol h−1) when using 0.025 wt% Rh as the co‐catalyst, whereas the material prepared in [C3mimOH][Tf2N] shows the highest activity for the photocatalytic degradation of methylene blue (88%) under UV irradiation. The different photocatalytic activities can be correlated with the different crystal surface facets expressed in the respective nanosized SrTiO3material, {110} for material obtained from [C4mim][Tf2N], and {100} for material from [C3mimOH][Tf2N]. First‐principles density functional theory (DFT) calculations are used to support the experimental findings.

The use of hollow sphere pigments as strength additives in paper and paperboard coatings—Part 1: The predictive nature of packing models on coating properties

Hollow sphere pigments (HSPs) are widely used at low levels in coated paper to increase coating bulk and to provide gloss to the final sheet. However, HSPs also provide an ideal system through which one can examine the effect of pigment size and particle packing within a coating due to their unimodal and tunable particle sizes. The work presented in Part 1 and Part 2 of this study will discuss the use of blends of traditional inorganic pigments and HSPs in coating formulations across a variety of applications for improved coating strength. Part 1 of this study focuses on the theory of bimodal spherical packing and demonstrates the predictive nature of packing models on the properties of coating systems containing HSPs of two different sizes. This study also examines conditions where the model fails by examining the effect of particle size on coating strength in sytems like thermal paper basecoats where the non-HSP component has a broad particle size distribution, and how these surprising trends can be used to generate better-than-expected thermal printing performance in systems with low HSP/clay ratios. Part 2 of this study focuses on the incorporation of HSPs of different particle sizes into paperboard formulations to affect coating strength and opacity.

Parametric Modeling Study of PEM Fuel Cell with Platinum Group Metal -Free Cathode Catalyst Layer

Polymer electrolyte fuel cells offer zero-emissions energy conversion but are commercially limited by cost and durability. Stack cost can be reduced by using platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR). PGM-free catalysts have lower volumetric activity relative to PGM catalysts and consequently require thicker catalyst layers. Thicker catalyst layers result in increased oxygen transport resistance and flooding in the cathode, which must be considered to accurately model PGM-free fuel cells and quantify the distinct transport resistance. For this purpose, we have developed a well validated model to elucidate relative contributions to oxygen transport resistance. This two-phase, transient, non-isothermal, channel-to-channel model contains cathode catalyst layer morphology informed by plasma-focused ion beam (P-FIB) SEM. Furthermore, the model includes agglomerate treatment of volumetrically active catalyst primary particles coated by ionomer. The structure of the agglomerate model is well suited for describing the catalyst layers containing metal organic framework (MOF) derived metal-nitrogen-carbon catalysts that are roughly spherical and volumetrically active for ORR. The MOF-derived Fe-N-C catalyst used in this study’s experiments contains atomically dispersed active sites and uniform, tunable primary particle size. In this presentation, we will report on our investigation of the performance sensitivity to a wide variety of operating conditions and MEA design specificiation, including cell temperature, gas pressures, cathode thickness, hydrophobic pore fractions and wettability, catalyst primary particle size, ionomer content, and ionomer equivalent weight. Non-dimensional characteristic parameter analysis on the model results is used to distinguish the transition between proton conductivity limited and oxygen transport limited performance, and indicate critical values that affect the the through plane ultilization of the catalyst. This information and studies on the impact of active site density help us set catalyst-specific targets for meeting fuel cell performance goals. With highly active PGM-free catalysts, we can model the impact of parameter changes on transport with experimental validation.DOE ACKNOWLEDGEMENTThis material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office (FCTO) under award number DE-EE0008076. The authors gratefully acknowledge research support from the Electrocatalysis Consortium (ElectroCat), established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, under contract number DEEE0008076.

Fe(III)-Exchanged Zeolite As Efficient Electrocatalysts for Electrodegradation of Congo Red Dye

The role of the nanostructured iron catalysts hosted by different type of zeolite structures (NaY and ZSM5) on the electrochemical degradation of Congo Red dye (C32H22N6Na2O6S2) was investigated. Here, the nano-iron zeolite catalysts with high surface areas (up to 853 m2 g-1) were prepared by ion-exchange method1 serving tunable particle size and acidity that is highly sensitive to the local reaction environment at the electrode surface. The structural and morphological analysis was carried out using scanning electron microscopy (SEM), X-ray diffraction and N2-sorption techniques. In order to clarify the electrocatalytic trend observed by constant potential electrolysis, we further considered the acidity properties of the zeolites determined by microcalorimetric measurements. Moreover, it was noted that the presence of NH4 +, H+ and Na+ ions in the case of ZSM5 zeolite allows the rearrangement of the iron-zeolite architecture, resulting in a more favorable stabilization of the degradation process as a function of the production rate. Compared with the FeNaY catalysts, the FeZSM5 catalysts (Fe(Na)ZSM5, Fe(H)ZSM5 and Fe(NH4)ZSM5) exhibited excellent activity and stability, with a maximum dye degradation around 64% on the Fe(H)ZSM5 catalyst. This work, revealing the synergetic interactions between the acid sites of the zeolite and the catalytic active sites, provides a new route for the development of electrochemical sensing low-metal content zeolite structures.Acknowledgements:This work was conducted in the framework of the BioTecNorte projects: NORTE-01-0145-FEDER-000004, PTDC/AAGTEC/5269/2014, UID/QUI/00686/2013, and UID/QUI/0686/2016. Z. B. is grateful for ERASMUS research grant.Reference:1. M. Ferreira, F. Pinto, O. S. G. P. Soares, M. F. R. Pereira, J. J. M. Órfão, J. L. Figueiredo, I. C. Neves, A. M. Fonseca, P. Parpot, Chemical Engineering Journal, 228 (2013) 374.

Spray flash evaporation SFE process: Identification of the driving parameters on evaporation to tune particle size and morphology

The spray flash evaporation process enables to recrystallize organic materials on submicron and nano scale and is basically based on the sudden depressurization of the solution from the superheated state to the primary vacuum through a nozzle. The immediate evaporation of the dissolved micro droplets results in the release of submicron or nanoparticles. As a first step, experimental data of recrystallization were collected for different energetic materials by varying the superheating conditions (injection temperature and pressure, solvent) and analyzing their effects on the materials properties (particle size, morphology and polymorphism). Then, the solvent spray is independently studied by measuring the velocity and the size of the generated droplets. Key parameters to master particle size and morphology are identified. This study aims to identify the flash boiling and the spray characteristics. These results pave the way to some understanding of the process to be able to tune particles size and morphology.

Maximizing Amplified Energy Transfer: Tuning Particle Size and Dye Loading in Conjugated Polymer Nanoparticles

We investigate amplified energy transfer in conjugated polymer nanoparticles (CPNs or Pdots) by studying both fluorescence quenching of CPN donors and the sensitization of reactive dye acceptors. B...

Design and One-Pot Synthesis of Capsid-like Gold Colloids with Tunable Surface Roughness and Their Enhanced Sensing and Catalytic Performances.

Viral capsid-like particles tiled with mosaic patches have attracted great attention as they imitate nature's design to achieve advanced material properties and functions. Here, we develop a facile one-pot soft-template method to synthesize biomimetic gold capsid-like colloids with tunable particle size and surface roughness. Uniform submicron-to-micron-sized hollow gold colloidal particles are successfully achieved by using tannic acids as soft templates and reducing agents, which first self-assemble into spherical complex templates before the reduction of Au3+ ions via their surface hydroxyl groups. The surface roughness, the size, and the total number of the patches of the prepared gold particles are further tuned, utilizing a mechanism that offers morphology control by varying the number of surface hydroxyl groups participating in the reduction reactions. Among different capsid-like gold colloids, those possessing a rough surface display superior catalytic properties and show promising results as surface-enhanced Raman spectroscopy (SERS) solid substrates for detecting small organic molecules and biomimetic enzymes in a liquid phase for sensing biomolecules in real samples. These capsid-like gold colloids are also expected to find practical applications in delivery systems, electronics, and optics. We believe that our strategy of imitating nature's design of capsid-like structures should also be used in the design and fabrication of other functional colloidal particles.

Urchin-like Porous Silica Nanoparticles for Simultaneous Intracellular Delivery of Doxorubicin and RNase A

Urchin-like porous silica nanoparticles (UPSNs) with hierarchical dual-pore structure and tunable particle size have been synthesized by utilizing sodium salicylate (NaSal) and cetyltrimethylammoni...

Polydispersity‐Driven Printing of Conformal Solid Metal Traces on Non‐Adhering Biological Surfaces

AbstractMetals and organics possess two very dissimilar surface energies, hence, do not naturally adhere to each other. This incompatibility is exacerbated by surface roughness yet advances in wearables and bioelectronics call for their integration. Mesoscale mechanical bonds, however, transcend the necessities of surface energy matching while taking advantage of surface texture. Herein, transient carrier fluids, particle size polydispersity, and capillary‐driven autonomous size‐sorting are exploited to conformally jam undercooled liquid metal particles on textured soft substrate. The well packed undercooled metal particles are then chemically activated to induce phase change, leading to a solid electrically conductive metal trace. Static and dynamic deposition of the particles is amenable to this surface‐templated printing of conductive traces. This process allows for printing across surfaces with varying surface features like on the brain, on paper (asymmetric porosity), or across smooth and rough brain sections. By tuning particle size and slurry concentration, good particle packing is demonstrated on a multi‐scale rough surface like a rose flower. This printing method is therefore compatible with delicate (low modulus), heat sensitive, and textured substrates hence compatible with biological tissues and organic substrates.

Single-Iron Site Catalysts with Self-Assembled Dual-size Architecture and Hierarchical Porosity for Proton-Exchange Membrane Fuel Cells

Atomically dispersed and nitrogen coordinated single iron site (i.e., FeN4) catalysts (Fe-N-C) are the most promising platinum group metal (PGM)-free cathode for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). However, current Fe-N-C catalysts are limited by the inferior exposure of active FeN4 sites due to the inevitable agglomeration of particles in cathodes. Herein, we report a self-assembled strategy to synthesize the atomically dispersed FeN4 site catalysts with a hierarchically porous matrix derived from dual-size Fe-doped ZIF-8 crystal precursors by using large particles to support small particles. The tailored structure is effective in mitigating the particle migration, agglomeration, and spatial overlap, thereby exposing increased accessible active sites and facilitating mass transport. The best performing catalyst composed of 100 nm “nucleated seed” assembled by 30 nm “satellite” demonstrates exceptional ORR activity in acidic electrolyte and membrane electrode assembly. This work provides new concepts for designing hierarchically porous catalysts with single metal atom dispersion via self-assembly of ZIF-8 crystal precursors with tunable particle sizes and nanostructures.

Synthesis and Characterization of the Properties of Ceria Nanoparticles with Tunable Particle Size for the Decomposition of Chlorinated Pesticides

Ceria nanoparticles are well known for their catalytic properties, which are commonly used in the automotive industry and other chemical branches. In this contribution, ceria nanoparticles were prepared by a simple precipitation reaction of cerium (IV) sulfate and ammonia. Such nanoparticles were very fine, with an approximate crystallite size of 2 nm. Crystallite sizes of these nanoparticles were adjusted by controlled heating, showing different catalytic properties. After thermal treatment, the surface area and crystallite size of nanoparticles were also compared by means of XRD and a sorption analyzer utilizing Brunauer–Emmet–Teller (BET). Morphology was studied by SEM, high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED). Thin layers of ceria nanoparticles on silica glass and alumina ceramic underlays were also prepared and studied by SEM and EDS to demonstrate the possibility of ceria immobilization using thermal treatment of raw nanoparticles. The catalytic activity of the nanoparticles was tested on a 2,4,6-trichlorophenol aqueous solution and compared by UV–VIS spectroscopy.

In vitro and ex vivo relaxometric properties of ethylene glycol coated gadolinium oxide nanoparticles for potential use as contrast agents in magnetic resonance imaging

Magnetic nanoparticles (MNPs) have widely demonstrated their applicability in many biomedical applications including magnetic resonance imaging (MRI), hyperthermia, and drug delivery. However, the effectiveness of MNPs can be limited for in vivo applications due to their hydrophobic surfaces leading to nanoparticle agglomeration and thus requires appropriate surface modification to enhance colloidal stability. Glycols are widely used coating material for surface modifications of MNPs to improve their physicochemical properties and biocompatibility. The present work reports the preparation of two different sized ethylene glycol coated gadolinium oxide nanoparticles (EG@Gd2O3 NPs) using two different synthesis approaches and their applicability as contrast agents in MRI. Thermo-gravimetric analysis and Fourier transform infrared spectroscopy confirmed the successful coating of ethylene glycol on the surface of NPs. We found that independent of the size of NPs, the globular shaped EG@Gd2O3 NPs exhibited similar crystal structures, magnetic properties, and cellular cytotoxicity behavior. However, a significant impact of size on MRI contrast enhancement properties was seen. It was revealed that the relaxivity of EG@Gd2O3 NPs increases with a decrease in particle size. Small sized EG@Gd2O3 NPs (∼12 nm) exhibited a high specific in vitro and ex vivo longitudinal relaxivity of 3.7 and 1.5 mM−1 s−1, respectively, thus clearly elucidating the potential of these NPs for use as local contrast enhancement agents. The present study gives insights into the intrinsic dependence of magnetic resonance contrast effects of NPs on particle size and surface coating layer mass ratio and thus demonstrates the development of efficient magnetic nanoparticles based contrast agents by fine tuning of particle size and surface properties.

Flash nanoprecipitation with Gd(III)-based metallosurfactants to fabricate polylactic acid nanoparticles as highly efficient contrast agents for magnetic resonance imaging.

Polylactic acid (PLA) nanoparticles coated with Gd(III)-based metallosurfactants (MS) are prepared using a simple and rapid one-step method, flash nanoprecipitation (FNP), for magnetic resonance imaging (MRI) applications. By co-assembling the Gd(III)-based MS and an amphiphilic polymer, methoxy poly(ethylene glycol)-b-poly(ϵ-caprolactone) (mPEG-b-PCL), PLA cores were rapidly encapsulated to form biocompatible T1 contrast agents with tunable particle size and narrow size distribution. The hydrophobic property of Gd(III)-based MS were finely tuned to achieve their high loading efficiency. The size of the nanoparticles was easily controlled by tuning the stream velocity, Reynolds number and the amount of the amphiphilic block copolymer during the FNP process. Under the optimized condition, the relaxivity of the nanoparticles was achieved up to 35.39 mM-1 s-1 (at 1.5 T), which is over 8 times of clinically used MRI contrast agents, demonstrating the potential application for MR imaging.

Multifunctional nanoparticles as photosensitizer delivery carriers for enhanced photodynamic cancer therapy.

Photodynamic therapy (PDT) is an emerging cancer treatment combining light, oxygen, and a photosensitizer (PS) to produce highly cytotoxic reactive oxygen species that cause cancer cell death. However, most PSs are hydrophobic molecules that have poor water solubility and cannot target tumor tissues, causing damage to normal tissues and cells during PDT. Thus, there is a substantial demand for the development of nanocarrier systems to achieve targeted delivery of PSs into tumor tissues and cells. This review summarizes the research progress in PS delivery systems for PDT treatment of tumors and focuses on the recent design and development of multifunctional nanoparticles as PS delivery carriers for enhanced PDT. These multifunctional nanoparticles possess unique properties, including tunable particle size, changeable shape, stimuli-responsive PS activation, controlled PS release, and hierarchical targeting capability. These properties can increase tumor accumulation, penetration, and cellular internalization of nanoparticles to achieve PS activation and/or release in cancer cells for enhanced PDT. Finally, recent developments in multifunctional nanoparticles for tumor-targeted PS delivery and their future prospects in PDT are discussed.

Fabrication of large scale uniform copper-island thin film for ultrasensitive surface enhanced Raman scattering

Nanostructured metals with designable and controllable structures have received increasing attention in surface enhanced Raman scattering (SERS) due to the single molecular detection limit. Great challenges still remain in creating large scale substrates with high-density ‘hotspots’ to provide a uniform and stable enhancement of Raman signals. Here, we fabricated a copper island thin film over an 80 cm2 scale substrate with tunable particle sizes by combining sputtering with dealloying processes. The island size can be tailored from 150 nm to 370 nm by controlling parameters and etching conditions and possesses an optimized surface morphology structure. The detection limit of crystal violet (CV) molecules reached 0.1 pM. Meanwhile, the copper island thin film presents good homogeneity and stability. Our method is promising to repeatedly fabricate novel metal SERS substrates on a large scale with standard properties for sensing applications.

Molecular binding scaffolds increase local substrate concentration enhancing the enzymatic hydrolysis of VX nerve agent.

Kinetic enhancement of organophosphate hydrolysis is a long-standing challenge in catalysis. For prophylactic treatment against organophosphate exposure, enzymatic hydrolysis needs to occur at high rates in the presence of low substrate concentrations and enzymatic activity should persist over days and weeks. Here, the conjugation of small DNA scaffolds was used to introduce substrate binding sites with micromolar affinity to VX, paraoxon, and methyl-parathion in close proximity to the enzyme phosphotriesterase (PTE). The result was a decrease in KM and increase in the rate at low substrate concentrations. An optimized system for paraoxon hydrolysis decreased KM by 11-fold, with a corresponding increase in second-order rate constant. The initial rates of VX and methyl-parathion hydrolysis were also increased by 3.1- and 6.7-fold, respectively. The designed scaffolds not only increased the local substrate concentration, but they also resulted in increased stability and PTE-DNA particle size tuning between 25 and ~150 nm. The scaffold engineering approach taken here is focused on altering the local chemical and physical microenvironment around the enzyme and is therefore compatible with active site engineering via combinatorial and computational approaches.

Investigation of precipitation selectivity and particle size concentration dependences in supercritical antisolvent method via online supercritical fluid chromatography

Supercritical antisolvent (SAS) precipitation technique, although being versatile and ecologically friendly, suffers from the lack of convenient methods for necessary thermodynamic parameters measurement. Recently we have proposed a method for solubility measurement in binary fluids based on an online hyphenation of supercritical antisolvent method and supercritical fluid chromatography (SAS-SFC). In this paper, we demonstrate the applicability of this method to the investigation of both selective precipitation from solution and particle size tuning in SAS using lower dicarboxylic acids as model objects. Measured solubility values adequately reflect selective crystallization from solution. SAS precipitation was observed only for those components, which concentration was above solubility in CO2-solvent mixture as predicted by SAS-SFC method. Also, concentration dependences of particle size plotted in supersaturation coordinates instead of direct concentration in initial solution give additional insight into crystallization behaviour in SAS.