Nm-sized Nanoparticles Research Articles

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Ceramic Catalysts: Materials, Synthesis, and Applications

We report a facile synthesis of nanostructured Cu-incorporated SnO2. Aggregates composed of uniform ∼ 5 nm-sized nanoparticles were obtained through a simple room-temperature reaction between CuO and SnC2O4 in aqueous solution. The material is single-phase with copper incorporated mainly as Cu+. The synthesis approach also allows mixing with CuO to prepare SnO2/CuO nanocomposites. The synthesized materials show an improved cycle performance as anode materials in lithium ion batteries due to an improved morphology and in situ formation of metallic copper upon cycling (in the voltage range 0.05–1.1 V vs. Li/Li+).

Encina slates plastics recycling plant as Brightmark cancels

We report a facile synthesis of nanostructured Cu-incorporated SnO2. Aggregates composed of uniform ∼ 5 nm-sized nanoparticles were obtained through a simple room-temperature reaction between CuO and SnC2O4 in aqueous solution. The material is single-phase with copper incorporated mainly as Cu+. The synthesis approach also allows mixing with CuO to prepare SnO2/CuO nanocomposites. The synthesized materials show an improved cycle performance as anode materials in lithium ion batteries due to an improved morphology and in situ formation of metallic copper upon cycling (in the voltage range 0.05–1.1 V vs. Li/Li+).

A Size-Controlled Graphene Oxide Materials Obtained by One-Step Electrochemical Exfoliation of Carbon Fiber Cloth for Applications to In Situ Gold Nanoparticle Formation and Electrochemical Sensors-A Preliminary Study.

A simple, one-step and facile method has been introduced to prepare fluorescent and electrochemically active carbon nanoparticles with single-size distribution and good long-term stability by electrochemical exfoliation of polyacrylonitrile-based carbon fibers in an alkaline solution-phase condition. The preparation condition was systematically optimized by studying the effect of temperature and electrolytes. It has been found that an electrochemical exfoliation reaction carried out at an applied potential of 2 V vs. Ag/AgCl in a phosphate-ion-containing alkaline solution at a temperature of 40 °C is an ideal condition for the preparation of 14 ± 4 nm-sized carbon nanoparticles. Unlike the literature protocols, there are no filtration and membrane dialysis-based off-line sample pretreatments adopted in this work. The as-prepared carbon nanoparticles were characterized by fluorescence, Raman spectrum, transmission electron microscope, and X-ray photoelectron spectroscopic characterization methods. It was found that the carbon–oxygen functional group rich in graphene–oxide quantum dots (GOQDs) such as carbon nanoparticles were formed in this work. A preliminary study relating to simultaneous electrochemical oxidation and the sensing of uric acid and ascorbic acid with well-resolved peaks was demonstrated as a model system to extend the new carbon material for electroanalytical applications. Furthermore, in situ synthesis of 2 nm-sized gold nanoparticles stabilized by GOQDs was presented. The carbon nanoparticles prepared by the direct method in this work have shown good stability over 6 months when stored at room temperature. The electrochemical exfoliation reaction has been found to be highly reproducible and suitable for bulk synthesis of luminescence-effective carbon nanoparticles to facilitate fundamental studies and practical applications.

Development of methods for fabricating nanoparticles composed of magnetite, gold, and silica toward diagnostic imaging

Nontoxic nanoparticle contrast agents with multiple imaging functions are required for medical diagnostic imaging, and coating the nanoparticle contrast agents with less toxic materials meets this requirement. This work proposes a method for fabricating magnetite, gold (Au), and silica nanoparticles toward diagnostic imaging. The proposed method involved four steps: the synthesis of magnetite (Fe3O4) nanoparticles, synthesis of Au nanoparticles, formation of a composite of Fe3O4 and Au (Fe3O4/Au), and silica coating of Fe3O4/Au nanoparticles. The synthesis of 6.3 ± 1.2 nm-sized Fe3O4 nanoparticles was performed via a salt-based reaction in an aqueous solution containing FeCl3, FeCl2, citric acid, HCl, and NaOH. The synthesis of 2.2 ± 0.4 nm-sized Au nanoparticles was performed with a reduction of HAuCl4 in an aqueous solution containing tetrakis (hydroxymethyl) phosphonium chloride, and NaOH. The silica coating of Fe3O4/Au nanoparticles was performed with a sol–gel reaction in ethanol containing Fe3O4 nanoparticles, Au nanoparticles, poly-diallyldimetheylammonium chloride, tetraethylorthosilicate, NaOH, and water under sonication. The Fe3O4/Au/SiO2 nanoparticles were degraded in a fetal bovine serum/phosphate-buffered saline solution, PEGylated Fe3O4/Au/SiO2 (Fe3O4/Au/SiO2–PEG) nanoparticles adsorbed protein after PEGylation, and Fe3O4/Au/SiO2–PEG nanoparticles had a magnetic property and an X-ray imaging ability, revealing that the composite nanoparticles were expected to function as a safe and excretable contrast agent of MRI and X-ray.

Structural and Magnetic Properties of Nanosized Half-Doped Rare-Earth Ho0.5Ca0.5MnO3 Manganite

We investigated the structural and magnetic properties of 20 nm-sized nanoparticles of the half-doped manganite Ho0.5Ca0.5MnO3 prepared by sol-gel approach. Neutron powder diffraction patterns show Pbnm orthorhombic symmetry for 10 K < T < 290 K, with lattice parameters a, b, and c in the relationship c/√2 < a < b, indicating a cooperative Jahn–Teller effect, i.e., orbital ordering OO, from below room temperature. In contrast with the bulk samples, in the interval 250 < T < 300 K, the fingerprint of charge ordering (CO) does not manifest itself in the temperature dependence of lattice parameters. However, there are signs of CO in the temperature dependence of magnetization. Accordingly, below 100 K superlattice magnetic Bragg reflections arise, which are consistent with an antiferromagnetic phase strictly related to the bulk Mn ordering of a charge exchange-type (CE-type), but characterized by an increased fraction of ferromagnetic couplings between manganese species themselves. Our results show that in this narrow band half-doped manganite, size reduction only modifies the balance between the Anderson superexchange and Zener double exchange interactions, without destabilizing an overall very robust antiferromagnetic state.

Simple nanoprecipitation method for size-restricted synthesis of aloevera nanoparticles: Characteristic analysis and its application as an adsorbent

The Nanoprecipitation method has been proved favorable to synthesize size-restricted Aloevera nanoparticles from the aloevera polysaccharide in a very simple and single step. Dropwise addition of 1% homogeneous aloevera solution (1 ​mL) to absolute alcohol (20 ​mL) resulted in the formation of 50–100 ​nm-sized Aloevera nanoparticles. The results showed that the amount of ethanol played a significant role in deciding the shape and size of nanoparticles. The synthesis of aloevera nanoparticles has been confirmed by SEM, FTIR, XRD, and BET studies. The effect of other precipitating mediums and surfactants has also been studied to analyze their effect on the size of nanoparticles. The nanoparticles are also found to be potential adsorbents of Reactive Blue H5G dye which showed an affinity for AVNP and the adsorption study indicated 95% adsorption of the dye in 4 ​h. This indicates its efficacy as an adsorbent for wastewater treatment.

Influence of glucose, sucrose, and dextran coatings on the stability and toxicity of silver nanoparticles

Aqueous colloids, consisting of 15–30 nm-sized silver nanoparticles (Ag NPs), were prepared using the reducing and stabilizing abilities of glucose, sucrose, and dextran. The long-term stability of coated Ag NPs increases from glucose over sucrose to dextran, i.e., with the increase of the molecular weight of carbohydrate molecules. The density functional theory (DFT) calculations of the partial atomic (Mulliken) charges and adsorption energies are applied to explain the enhanced stability of coated Ag NPs. All coated Ag NPs have a significantly broader concentration range of nontoxic behavior toward pre-osteoblast cells than bare Ag NPs prepared using sodium borohydride. The carbohydrate-coated Ag NPs display the same level of toxic ability against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria as bare Ag NPs. The differences in toxicity mechanism of the coated and bare Ag NPs are a consequence of the absence and presence of co-occurring Ag+ ions in examined dispersion, respectively.

Single-pot solvothermal strategy toward support-free nanostructured LiBH4 featuring 12 wt% reversible hydrogen storage at 400 °C

Lithium borohydride (LiBH4) exhibits poor hydrogen storage reversibility because of phase separation between LiH and B due to foaming during thermal dehydrogenation. Herein, we report that by synthesizing nanostructured LiBH4 without any supports, the foaming and phase separation can be effectively suppressed, and consequently, the hydrogen storage reversibility of LiBH4 can be considerably improved. Using a facile single-pot solvothermal approach, a hierarchical porous nanostructured LiBH4 composed of 50–60 nm-sized primary nanoparticles is synthesized. The resulting neat nano-LiBH4 reversibly desorbs and absorbs approximately 12 wt% of H at 400 °C and under 100 bar H2. The superior hydrogen storage performance is attributed to the effective inhibition of foaming upon heating. The formation of LiH and B prior to melting, which can be associated with the largely reduced particle sizes and porous agglomeration structure, plays a crucial role in suppressing foaming. Our findings offer a new strategy for the preparation of nanoscaled freestanding borohydrides, and also important insights into the development of highly reversible metal borohydrides for hydrogen storage applications.

Seed-Mediated Synthesis and Catalytic ORR Reactivity of Facet-Stable, Monodisperse Platinum Nano-Octahedra

Shape-selective, sub-10 nm-sized metal nanoparticles are of high fundamental and practical interest in catalysis and electrocatalysis, where the surface structure dictates the kinetic properties of the nanomaterials. Unlike their bimetallic analogues, the synthesis of size-controlled, pure Pt octahedral nanocatalysts has remained a formidable chemical challenge. In bimetallic shaped systems, however, the benefit of shape is often convoluted with surface composition in complex ways. In the present work, a seed-templated approach is presented for the preparation of ultrasmall octahedral platinum nanoparticles (Pt NPs), harnessing the effect of monocrystalline anisotropic seeds and strict control of the reduction rate and other physicochemical parameters while avoiding polymers, surfactants, and organic solvents. The procedure yields previously elusive 6.7 nm, strictly single-crystal, Pt NPs with partially truncated octahedral shape and prevalent extended {111} surface facets. Electrochemical measurements using rotating disk electrodes in an acid electrolyte revealed a much higher electrochemical active surface area (ECSA) over the state-of-the-art octahedral Pt NPs, which is ascribed to small-sized, poison-free, and preferentially {111} orientated facets. The dramatic kinetic benefit for the oxygen reduction reaction (ORR) of the octahedral shape over spherical particle shapes of same size is convincingly demonstrated. More important for practical applications is the fact that the intrinsic specific ORR activity is about 2.4-fold higher than commercial optimized spherical Pt NPs deployed in fuel cell cathodes at comparable ORR stability. In doing this analysis, we validate the voltammetric correspondence between Pt single crystals and Pt nanoparticulate materials and highlight the kinetic benefits of limiting the proportion of {100} facets. Prolonged suppression of {100} facet growth in octahedral Pt catalysts is the reason for the unusually high specific activity and fair stability and calls for their integration and testing as cathode catalysts in fuel cell membrane electrode assemblies.

Molecular dynamics simulations of sodium nanoparticle deposition on magnesium oxide

The interaction of mass-selected atomic clusters and nanoparticles with surfaces attracts strong interest in view of fundamental research and technological applications. Understanding the dynamics of the deposition process is important for controlling structure and functioning of deposited nanoparticles on a substrate, but experimental techniques can usually observe only the final outcome of the deposition process. In this paper, the deposition of 4 nm-sized sodium nanoparticles on an experimentally relevant magnesium oxide substrate is studied by means of classical molecular dynamics simulations. An empirical force field is derived which accounts for the interaction of highly polarizable Na atoms with the surface, reproducing the results of previously reported quantum mechanics/molecular mechanics simulations. Molecular dynamics simulations permit exploring the dynamics of deposited nanoparticles on long timescales on the order of hundreds of picoseconds, thus enabling the analysis of energy relaxation mechanisms and the evolution of nanoparticle structure up to its thermalization with the substrate. Several nanoparticle characteristics, such as internal structure, contact angle, and aspect ratio, are studied in a broad deposition energy range from the soft landing to multi-fragmentation regimes.

Effects of particle size of cerium oxide nanoparticles on the combustion behavior and exhaust emissions of a diesel engine powered by biodiesel/diesel blend

Meeting the emission norms specified by governing bodies is one of the major challenges faced by engine manufacturers, especially without sacrificing engine performance and fuel economy. Several methods and techniques are being used globally to reduce engine emissions. Even though emissions can be reduced, doing so usually entails a deterioration in performance. To address this problem, nanoadditives such as cerium oxide (CeO2) nanoparticles are used to reduce engine emissions while improving engine performance. However, some aspects of the application of these nanoadditives are still unknown. In light of that, three sizes of CeO2 nanoparticles (i.e., 10, 30, and 80 nm) and at a constant volume fraction of 80 ppm were added to a 20% blend of waste cooking oil biodiesel and diesel (B20). A single-cylinder diesel engine operating at a 1500 rpm speed and 180 bar fuel injection pressure was used to compare the performance and emission characteristics of the investigated fuel formulations. The results showed that the addition of CeO2 nanoparticles led to performance improvements by reducing brake specific fuel consumption. Moreover, the catalytic action of CeO2 nanoparticles on the hydrocarbons helped achieve effective combustion and reduce the emission of carbon monoxide, unburnt hydrocarbon, oxides of nitrogen, and soot. Interestingly, the size of the nanoadditive played an instrumental role in the improvements achieved, and the use of 30 nm-sized nanoparticles led to the most favorable performance and the lowest engine emissions. More specifically, the fuel formulation harboring 30 nm nanoceria reduced brake specific fuel consumption by 2.5%, NOx emission by 15.7%, and smoke opacity by 34.7%, compared to the additive-free B20. These findings could shed light on the action mechanism of fuel nanoadditives and are expected to pave the way for future research to develop more promising fuel nanoadditives for commercial applications.

Molten salt synthesis of LiMn 1 . 2 Ni 0 . 3 Cr 0 . 1 Co 0 . 15 Al 0 . 23 La 0 . 02 O 4 as a positive electrode for lithium‐ion batteries

The molten salt synthesis method became an excellent synthesis technique to elaborate nanomaterials because of its meritorious advantages including low cost, easy to scale up, simple to operate, and environmental friendliness. For this reason, the compound LiMn1.2Ni0.3Cr0.1Co0.15Al0.23La0.02O4 was synthesized for the first time by molten salt method using NaCl as the salt and a nonstandard manganese source with metallurgical grade. The obtained cathode material was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transformer infra-red (FT-IR), and electrochemical characterization. XRD and FT-IR results confirm the stability and formation of pure spinel phase without any impurities. TEM images showed that the spinel synthesized phase consists of 77 to 135 nm-sized polyhedral nanoparticles. The cyclic voltammogram results showed that the synthesized spinel cathode material exhibits two-main redox peaks at 4.06/3.9 V and 3.1/2.8 V vs Li+/Li, which indicate the possibility of insertion of extra lithium in the spinel structure. Galvanostatic charge-discharge studies were also carried out showed that the prepared spinel material has two discharge plateaus in the potential window of 1.5 to 5 V and a discharge capacity of 179 mAh g−1 at 0.1 C, which is higher than the theoretical value which confirms the insertion of extra lithium in the spinel structure and enhance the capacity of the cathode material. The electrochemical impedance spectroscopy was performed, and the Li-ion diffusion coefficient was also calculated.

Nuclearity and Host Effects of Carbon-Supported Platinum Catalysts for Dibromomethane Hydrodebromination.

The identification of the active sites and the derivation of structure-performance relationships are central for the development of high-performance heterogeneous catalysts. Here, a platform of platinum nanostructures, ranging from single atoms to nanoparticles of ≈4nm supported on activated- and N-doped carbon (AC and NC), is employed to systematically assess nuclearity and host effects on the activity, selectivity, and stability in dibromomethane hydrodebromination, a key step in bromine-mediated methane functionalization processes. For this purpose, catalytic evaluation is coupled to in-depth characterization, kinetic analysis, and mechanistic studies based on density functional theory. Remarkably, the single atom catalysts achieve exceptional selectivity toward CH3 Br (up to 98%) when compared to nanoparticles and any previously reported system. Furthermore, the results reveal unparalleled specific activity over 1.3-2.3nm-sized platinum nanoparticles, which also exhibit the highest stability. Additionally, host effects are found to markedly affect the catalytic performance. Specifically, on NC, the activity and CH3 Br selectivity are enhanced, but significant fouling occurs. On the other hand, AC-supported platinum nanostructures deactivate due to sintering and bromination. Simulations and kinetic fingerprints demonstrate that the observed reactivity patterns are governed by the H2 dissociation abilities of the catalysts and the availability of surface H-atoms.

Single-step Zno nanorod bunches formation on p-type Si-conductive substrates by electrophoretic deposition

To date, EPD obtained ZnO one-dimensional nanostructures have been achieved by depositing ZnO nanoparticles through a sacrificial anodic alumina membrane or promoted by the presence of pre-deposited Au nanoclusters on the substrate. In the present work, we explored using boron (p-type)-doped crystalline Si (100) substrates with different conductivities. We found the conditions for the direct self-assembly of one-dimensional ZnO nanorod bunches, in a novel and easy way, at room temperature. A colloidal dispersion of ≈5 nm-sized ZnO nanoparticles in 2-propanol was used. The results showed differences in the morphology of ZnO nanostructures depending on the Si substrate conductivity used. XRD patterns indicated that ZnO nanorods were preferentially formed in (002) direction corresponding to c-axis orientation in the wurtzite structure. Photoluminescence measurements revealed the presence of quantum confined excitons and high emission intensity in the visible range. Photoluminescence spectra showed that emission was dominated by the ZnO nanoparticles that form the nanostructures and not by the morphology or size of the nanostructures themselves. The results presented in this work expand the EPD technique applications to form nanorod nanostructures in a single step.

Enhanced photovoltaic performance of perovskite solar cells based on sufficient pore-filling in the mesoporous TiO2 electron transport layer

Mesoporous TiO2 (m-TiO2) layer has been widely used as a photoelectrode of solar cells. Compared with conventional planar TiO2 layer, appropriate pore size dramatically improves infiltration of perovskite (PVK) into the mesoporous layer because of the larger voids formed within the TiO2 mesoporous layer and further enhances the light absorption efficiency of PVK for the better light-scattering ability of 20 nm TiO2 nanoparticles. In our study, 75–95 nm pore size of TiO2 scaffold layer was successfully prepared by adding different contents of ethyl cellulose (EC) as a template and terpineol as a leveling agent into conventional TiO2 paste composed of 20 nm-sized TiO2 nanoparticles and then applied to PVK solar cells (PSCs).The novel mesoporous layer was conducive to increase light-harvesting capacity and photovoltaic performance of PSCs. The influence of different contents of EC was discussed systematically for TiO2 scaffold layer, the charge carrier dynamic, and the hysteresis behavior for our devices. Finally, by optimizing the parameters of the electron transport layer, the power conversion efficiency of the champion device with a 16.5% mass fraction of EC reached as high as 18%.

Efficient reduction of dyes to leuco form over silver nanoparticles on functionalised SBA-15 and aminoclay

ABSTRACT In this work, a simple chemical method for synthesis of Ag nanoparticles (NPs) incorporated on amine-functionalised mesoporous silica SBA-15 support (Ag/NH2-SBA-15) is reported for various dye degradation as the first time. The synthesised sample was characterised by powder XRD, BET surface area and pore size analyser, ICP-OES, XPS HRTEM, and HRSEM techniques. About 5 nm-sized Ag nanoparticles are dispersed over the support. The Ag/NH2-SBA-15 catalytic efficiency was investigated on various dyes degradation such as Malachite green (MG), Phenol red (PR), Bromophenol blue (BPB), Rose Bengal (RB), Methylene Blue (MB), Rhodamine derivatives (Rh 6 G, Rh B), Congo red (CR) and 4-Nitrophenol (4-NP) in the presence of NaBH4. About 90% degradation efficiency resulted in 6 min of reaction time in the presence of a catalyst. Besides, the Ag/NH2-SBA-15 catalyst activity has been compared with homogeneous Ag/aminoclay and shown higher catalytic activity. All the reactions were monitored by UV-Visible spectrometer. The reaction kinetics of Ag nanoparticle catalysed reduction illustrates pseudo-first-order kinetics with the rate constant for the reduction is in the order Ag/NH2-SBA-15 (3.34 × 10−1 s−1) and Ag/aminoclay (1.80 × 10−2 s−1).

Heterostructured g-CN/TiO2 Photocatalysts Prepared by Thermolysis of g-CN/MIL-125(Ti) Composites for Efficient Pollutant Degradation and Hydrogen Production.

Photocatalysts composed of graphitic carbon nitride (g-CN) and TiO2 were efficiently prepared by thermolysis of the MIL-125(Ti) metal organic framework deposited on g-CN. The heterojunction between the 12 nm-sized TiO2 nanoparticles and g-CN was well established and the highest photocatalytic activity was observed for the g-CN/TiO2 (3:1) material. The g-CN/TiO2 (3:1) composite exhibits high visible light performances both for the degradation of pollutants like the Orange II dye or tetracycline but also for the production of hydrogen (hydrogen evolution rate (HER) up to 1330 μmolh−1g−1 and apparent quantum yield of 0.22% using NiS as a cocatalyst). The improved visible light performances originate from the high specific surface area of the photocatalyst (86 m2g−1) and from the efficient charge carriers separation as demonstrated by photoluminescence, photocurrent measurements, and electrochemical impedance spectroscopy. The synthetic process developed in this work is based on the thermal decomposition of metal organic framework deposited on a graphitic material and holds huge promise for the preparation of porous heterostructured photocatalysts.

N‐Heterocyclic Carbene (NHC)‐Stabilized Ru0 Nanoparticles: In Situ Generation of an Efficient Transfer Hydrogenation Catalyst

Tethered and untethered ruthenium half-sandwich complexes were synthesized and characterized spectroscopically. X-ray crystallographic analysis of three untethered and two tethered Ru N-heterocyclic carbene (NHC) complexes were also carried out. These RuNHC complexes catalyze transfer hydrogenation of aromatic ketones in 2-propanol under reflux, optimally in the presence of (25 mol %) KOH. Under these conditions, the formation of 2-3 nm-sized Ru0 nanoparticles was detected by TEM measurements. A solid-state NMR investigation of the nanoparticles suggested that the NHC ligands were bound to the surface of the Ru nanoparticles (NPs). This base-promoted route to NHC-stabilized ruthenium nanoparticles directly from arene-tethered ruthenium-NHC complexes and from untethered ruthenium-NHC complexes is more convenient than previously known routes to NHC-stabilized Ru nanocatalysts. Similar catalytically active RuNPs were also generated from the reaction of a mixture of [RuCl2 (p-cymene)]2 and the NHC precursor with KOH in isopropanol under reflux. The transfer hydrogenation catalyzed by these NHC-stabilized RuNPs possess a high turnover number. The catalytic efficiency was significantly reduced if nanoparticles were exposed to air or allowed to aggregate and precipitate by cooling the reaction mixtures during the reaction.

Optimization of a Solid-Phase Extraction Procedure for the Analysis of Drug-Loaded Lipid Nanoparticles and its Application to the Determination of Leakage and Release Profiles

To understand and predict the efficacy and toxicity of nanoparticle-based drugs in vivo, the free and entrapped forms of the drug have to be determined using suitable characterization methods. Herein, a solid-phase extraction (SPE) method combined with high-performance liquid chromatography (HPLC) measurements were used to separately quantify free and entrapped cyclosporine A (CsA) in 50 and 120 nm-sized lipid nanoparticles (NPs). Combined with colloidal stability measurements, HPLC quantification of the free and entrapped drug, separated using SPE, was used to monitor the stability of the nanotherapeutics under storage or physiological conditions. The SPE method was proven not to alter the core-shell template of the lipid nanocarriers. Method validation demonstrated suitable linearity, repeatability, accuracy, and specificity to quantify the free, entrapped, and total drug. Under storage conditions, the %free and %entrapped CsA remained constant over 9 weeks for both NPs. Under physiological conditions, the release profile was similar for both buffers/mediums used, indicating a biphasic mode of release. The validated SPE method was proven to be suitable for the determination of a wide range of free versus entrapped compounds.