Particle Surface Research Articles

Continuous flow synthesis and simulation-supported investigation of tunable plasmonic gold patchy nanoparticles.

Plasmonic nanoparticles have intriguing optical properties which make them suitable candidates for sensing or theranostic applications. Anisotropic patchy particles, where metal is locally deposited on the surface of a core particle, exhibit plasmon resonances that can be specifically adjusted for these applications. However, many existing synthesis routes are complex, yield too little material, or provide particles with limited optical tunability. In this work, we present a simple and scalable continuous flow synthesis of gold-on-polystyrene patchy particles with widely adjustable optical properties. By increasing the chloride concentration in the electroless deposition of gold, we slow down the redox reduction kinetics and obtain a dense patch morphology as well as a reduced nucleation rate. The latter is counteracted by introducing a low-level seeding approach where a small number of gold nanocrystals heterocoagulate with the core particles prior to patch growth. Seeding and patch growth are performed in a continuous flow set-up with two T-shaped milli-mixers. The resulting patchy particle samples exhibit a tunable dipolar plasmon peak between 600 nm and 1100 nm. We also investigate the structure-property relationship for our gold patchy particles using finite element method simulations. After identifying a suitable patch shape model, we elucidate the influence of individual geometric parameters on the optical properties and show that the relationship holds true for a large range of patch coverages. Finally, we apply the relationship to explain the time-dependent change in the optical properties of as-synthesized patches by correlating it with the patch shape transformation revealed by electron microscopy.

Stable and homogeneous intermetallic alloys by atomic gas-migration for propane dehydrogenation

Intermetallic nanoparticles (NPs) possess significant potentials for catalytic applications, yet their production presents challenges as achieving the disorder-to-order transition during the atom ordering process involves overcoming a kinetic energy barrier. Here, we demonstrate a robust approach utilizing atomic gas-migration for the in-situ synthesis of stable and homogeneous intermetallic alloys for propane dehydrogenation (PDH). This approach relies on the physical mixture of two separately supported metal species in one reactor. The synthesized platinum-zinc intermetallic catalysts demonstrate exceptional stability for 1300 h in continuous propane dehydrogenation under industrially relevant industrial conditions, with extending 95% propylene selectivity and propane conversions approaching thermodynamic equilibrium values at 550–600 oC. In situ characterizations and density functional theory/molecular dynamics simulation reveal Zn atoms adsorb on the particle surface and then diffuse inward, aiding in the formation of ultrasmall and highly ordered intermetallic alloys. This in-situ gas-migration strategy is applicable to a wide range of intermetallic systems.

Fluidized Bed Chemical Vapor Deposition of Copper on Micronic Alumina Powders

AbstractUniformly coating micronic particles with metals is of main interest for a broad range of applications. This study demonstrates the feasibility of depositing pure copper on the surface of micronic alumina particles by the fluidized bed chemical vapor deposition process from the cheap and nontoxic copper acetylacetonate precursor. Thanks to the development of a preconditioning protocol, a complete fluidization of the particles organized as porous agglomerates was reached. The coating of the individual particles was favored by using conditions involving low deposition rates. The influence of key operating parameters on the process behavior and on the characteristics of the deposit was studied. The deposited copper was of cubic crystal structure without carbon nor oxide contamination.

Multifunctional gallium doped bioactive glasses: a targeted delivery for antineoplastic agents and tissue repair against osteosarcoma

Osteosarcoma (OS) is the mostly commonly occurring primary bone cancer. Despite comprehensive treatment programs including neoadjuvant chemotherapy and tumour resection, survival rates have not improved significantly since the 1970s. Survival rates are dramatically reduced for patients who suffer a local recurrence. Furthermore, primary bone cancer patients are at increased risk of bone fractures. Consequently, there is an urgent need for alternative treatment options. In this paper we report the development of novel gallium doped bioactive glass that selectively kill bone cancer cells whilst simultaneously stimulating new bone growth. Here we show, using a combination of 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide, LIVE/DEAD assays and image analysis, that bioactive glasses containing gallium oxide are highly toxic and reduce both the proliferation and migration of bone cancer cells (Saos-2) in a dose dependant manner. Glasses containing 5 mol% gallium oxide reduced the viability of OS cells by 99% without being cytotoxic to the non-cancerous normal human osteoblasts (NHOst) control cells. Furthermore, Fourier transform infrared and energy-dispersive x-ray spectroscopy results confirmed the formation of an amorphous calcium phosphate/hydroxyapatite like layer on the surface of the bioactive glass particulates, after 7 d incubating in simulated body fluid, indicating the early stages of bone formation. These materials show significant potential for use in bone cancer applications as part of a multimodal treatment.

Optimization of solvent system for chitosan/polylactic acid/nanocellulose nanofibers using needleless electrospinning

AbstractNeedless electrospinning (NES) is the most advanced and robust method to generate biopolymeric nanofibers. NES overcomes the needle clogging and low throughput issues of conventional needle based electrospinning (ES). However, the issue with all ES techniques is the absence of generalized methods in the literature, and most of the work is being done empirically. The solvent system dictates the feasibility of the ES process, and solvent system based studies can help create more generalized ES methods. The current work provides a systematic approach to fabricating tribiopolymeric nanofibers. NES was used to fabricate chitosan (CS)/polylactic acid (PLA)/nanocellulose (NCC) based nanofibers by optimizing the solvent system using dichloromethane (DCM) and trifluoroacetic acid (TFA). Biopolymeric blend PLA/CS/NCC (10:0.1:0.05 w/v %) in various formulated solvent systems were made and analyzed for their physical properties (sedimentation rate, particle size, viscosity, and surface tension) and subjected to NES. The binary solvent system SS91 (DCM (90):TFA (10) %) showed the lowest sedimentation rate and viscosity while the highest particle size and surface tension, resulting in the beads free nanofibers. The viscosity and surface tension comparison were used to determine a critical point for the feasibility of nanofiber fabrication. Overall, the study showed a systematic approach for fabricating complex tri‐biopolymeric nanofibers in future.

ADVANCES IN NANOMATERIALS AS LUBRICANT ADDITIVES: A SYSTEMIC REVIEW

The paper provides an overview of the significance of nanomaterials as additives, in the tribological performance of lubricants. This review describes the ascendancy of different nanoparticles such as carbon-based nanoparticles, metallic nanoparticles, oxide nanoparticles, sulphide nanoparticles, nanocomposites, hybrid and bimetallic nanoparticles in lubricants. The study also evaluates the underlying principles of lubricant-nanoparticle interactions and their effects on wear prevention and friction reduction. The key parameters including particle morphology, particle size, weight concentration, and functionalization of the particle surface, that determine the friction and wear characteristics are discussed. Also, the science behind surface interaction and various mechanisms involved in friction and wear modification is described. The review highlights the prospect of various nanomaterials in the field of lubrication and facilitates development of advanced nanolubricants with superior tribological properties, that attributes to the reduction in energy consumption and improved performance.

Highly effective ruthenium catalyst support on La2Zr2O7 for ammonia decomposition to COx-free hydrogen

Pyrochlore-type La2Zr2O7 was prepared through a sol–gel route and served as a Ru-based catalyst support for ammonia decomposition to produce H2 without COx emission. The NH3 conversion over Ru/La2Zr2O7 could reach 69.5 % at 450 °C under the pure NH3 gas hourly space velocity (GHSV) of 30 000 mL.gcat-1h−1, which is approximately 3.1 times of that over Ru/ZrO2 and 2.2 times of Ru/La2O3 under the same conditions, respectively. It was found that the presence of oxygen vacancies on La2Zr2O7 surface can strongly interact with Ru particles to form the electronic strong metal-support interaction (EMSI), increasing the dispersion of Ru nanoparticles. Additionally, the mobile electrons are effectively transferred from La2Zr2O7 to the surface of Ru particles through the EMSI effect, consequently boosting the recombination desorption of N and ultimately contributing to the exceptional catalytic activity of Ru/La2Zr2O7.

Sulfidation of Nanoscale Zero-Valent Iron by Sulfide: The Dynamic Process, Mechanism, and Role of Ferrous Iron.

Sulfidation of nanoscale zerovalent iron (nZVI) can enhance particle performance. However, the underlying mechanisms of nZVI sulfidation are poorly known. We studied the effects of Fe2+ on 24-h dynamics of nZVI sulfidation by HS- using a dosed S to Fe molar ratio of 0.2. This shows that in the absence of Fe2+, HS- rapidly adsorbed onto nZVI particles and reacted with surface iron oxide to form mackinawite and greigite (<0.5 h). As nZVI corrosion progressed, amorphous FeSx in solution deposited on nZVI, forming S-nZVI (0.5-24 h). However, in the initial presence of Fe2+, the rapid reaction between HS- and Fe2+ produced amorphous FeSx, which deposited on the nZVI and corroded the surface iron oxide layer (<0.25 h). This was followed by redeposition of colloidal iron (hydr)oxide on the particle surface (0.25-8 h) and deposition of residual FeSx (8-24 h) on S-nZVI. S loading on S-nZVI was 1 order of magnitude higher when Fe2+ was present. Surface characterization of the sulfidated particles by TEM-SAED, XPS, and XAFS verified the solution dynamics and demonstrated that S2- and S22-/Sn2- were the principal reduced S species on S-nZVI. This study provides a methodology to tune sulfur loading and S speciation on S-nZVI to suit remediation needs.

Nanoengineered Injectable Hydrogel: An Advanced Radioprotective Barrier with Magnetic Hyperthermia Synergy.

Despite its effectiveness in eradicating cancer cells, current tumor radiotherapy often causes irreversible damage to the surrounding healthy tissues. To address this issue and enhance therapeutic outcomes, we developed a multifunctional injectable hydrogel that integrates electromagnetic shielding and magnetothermal effects. This innovation aims to improve the efficacy of brachytherapy while protecting adjacent normal tissues. Recognizing the limitations of existing hydrogel materials in terms of stretchability, durability, and single functionality, we engineered a composite hydrogel by self-assembling nickel nanoparticles on the surface of liquid metal particles and embedding them into an injectable hydrogel matrix. The resulting composite material demonstrates superior electromagnetic interference shielding performance (74.89 dB) and a rapid magnetothermal heating rate (10.9 °C/min), significantly enhancing its in vivo applicability. The experimental results confirm that this innovative nanocomposite hydrogel effectively attenuates electromagnetic waves during brachytherapy, thereby protecting normal tissues surrounding the tumor and enhancing radiotherapy efficacy through magnetothermal therapy. This study advances the safety and effectiveness of cancer treatments and provides new insights into the development of multifunctional biomedical materials, promoting the innovative application of nanotechnology in the medical field.

Boron Surface Treatment of Li7La3Zr2O12 Enabling Solid Composite Electrolytes for Li-metal Battery Applications.

Despite being promoted as a superior Li-ion conductor, lithium lanthanum zirconium oxide (LLZO) still suffers from a number of shortcomings when employed as an active ceramic filler in composite polymer-ceramic solid electrolytes for rechargeable all-solid-state lithium metal batteries. One of the main limitations is the detrimental presence of Li2CO3 on the surface of LLZO particles, restricting Li-ion transport at the polymer-ceramic interfaces. In this work, a facile way to improve this interface is presented, by purposely engineering the LLZO particle surfaces for better compatibility with a PEO:LiTFSI solid polymer electrolyte matrix. It is shown that an surface treatment based on immersing LLZO particles in a boric acid solution can improve the LLZO surface chemistry, resulting in an enhancement in the ionic conductivity and cation transference number of the CPE with 20 wt.% of boron-treated LLZO particles compared to the analogous CPE with non-treated LLZO. Ultimately, an improved cycling performance and stability in Li // LiFePO4 cells was also demonstrated for the modified material.

Scale-independent model based on fractal theory for calculating the adhesion force between a particle and rough surfaces

Scale-independent model based on fractal theory for calculating the adhesion force between a particle and rough surfaces

Impact of calcined temperatures on the crystalline parameters, morphological, energy band gap, electrochemical, antimicrobial, antioxidant, and hemolysis behavior of nanocrystalline tin oxide

To construct a battery, the precipitation-synthesized SnO2 products at 450 °C and 650 °C were separately taken and mixed with graphite as the anode and PbO2,V2O5, and graphite materials as cathode materials to make the pellets and examine their open circuit voltage (OCV) values. The microstrain, lattice parameter, and crystallite size values of the above-mentioned tin oxide compounds were obtained through Rietveld refinement-MAUD fit analysis. The microstrain and lattice parameter values of tin oxide were significantly varied at a higher calcined temperature. Surface particle grain growth was increased with the increased calcined temperature from 450 to 650 °C as evidenced by FE-SEM study. Particle size distributions of SnO2 and polycrystalline behavior have been discussed with the aid of TEM analysis. From the UV–visible spectra, optical band gap (Eg) values reduced from 3.73 to 3.69 eV for the SnO2 products with an increase in calcined temperatures from 450 to 650 °C. The antimicrobial responses of the two different calcined SnO2 samples at 450 °C and 650 °C against two different bacterial pathogens (gram-positive-S. aureus and gram-negative-E.coli) were investigated. From the microbicidal assessment, a relatively higher diameter of the zone of inhibition (DZOI) of tin oxide at 650 °C samples was measured to be 19 ± 2 mm and 21 ± 2 mm for S. aureus and E. Coli than the DZOI of SnO2 at 450 °C samples (15 ± 1 mm for S. aureus and 18 ± 1 mm for E. coli. DPPH scavenging activity at 100 μg/ml shows that SnO₂ calcined at 450 °C achieves 68 ± 1 %, while SnO2 calcined at 650 °C exhibits a significantly higher activity of 86 ± 1 %. A slight increase in hemolysis was observed for SnO2 calcined at 650 °C, reaching 1.3 % at higher concentrations, but overall, hemolysis remained below 5 %, indicating high hemocompatibility.

Cerium-Organic Framework UiO-66(Ce) as a Support for Nanoparticulate Gold for Use in Oxidation Catalysis.

An optimised synthesis of the metal-organic framework (MOF) UiO-66(Ce) is reported using a modulator-free route, yielding ~5 g of material with high crystallinity and 22% ligand defect. Two methods developed for loading gold nanoparticles onto the MOF. The first uses a double-solvent method to introduce HAuCl4 onto UiO-66(Ce), followed by reduction under 5% H2 in N2, while the second is a novel one-pot method where HAuCl4 is added to the synthesis mixture, forming Au nanoparticles within the pores of the UiO-66(Ce) during crystallisation. Analysis using powder X-ray diffraction (PXRD), nitrogen adsorption isotherms, transmission electron microscopy and small-angle X-ray scattering (SAXS) reveals that the two-step double-solvent method yields gold crystallites on the external surface of the MOF particles that are visible by PXRD. In contrast, the one-pot method forms smaller gold crystallites, with a distribution of sizes centred on ~4 nm diameter as seen by SAXS, with evidence from PXRD for the smallest particles being present within the MOF structure. The Au-loaded UiO-66(Ce) materials are evaluated for the catalytic oxidation of vanillyl alcohol to vanillin at 60 °C. Our findings indicate that incorporating Au nanoparticles via the one-pot synthesis method, enhances redox activity, achieving 43% conversion and 90% selectivity towards vanillin.

Oscillations of the Local pH Reverses Silver Micromotors in H2O2

Asymmetric chemical reactions on the surfaces of colloidal particles are known to propel them into directional motion. The dynamics of such chemical micromotors are sensitive to their local chemical environments, which also continually evolve with the reactions on motor surfaces. This two‐way coupling between the motor dynamics and the local environment may result in complex nonlinear behaviors. As an example, we report that Janus Ag microspheres, which self‐propel in hydrogen peroxide (H2O2), spontaneously reverse their direction of motion two or more times. We hypothesize that two distinct chemical reactions between Ag and H2O2 drive the micromotor in opposite directions, and which reaction dominates depends on the local pH. Interestingly, the local pH near a Ag micromotor oscillates spontaneously in H2O2, likely due to a complex interplay between the kinetics of the reaction between Ag and H2O2 and the diffusion of chemical species. Consequently, the pH‐sensitive Ag micromotor reverses its direction of motion in response to these pH oscillations. This study introduces a new mechanism for regulating the speed and directionality of micromotors, highlights the potential of Ag micromotors in chemical sensing, and sheds new light on the interplay between chemical kinetics and micromotor dynamics.

Effect of Calcination Temperature on the Surface of Prepared ZnO Nanocatalysts

ZnO nanoparticles (NPs) having nsemiconducting properties are important nanocatalysts for many surface reactions. Because of their extensive use as heterogeneous nanocatalyst for energy production and environmental cleaning, it is essential to understand their surface properties to design better chemical and photochemical nanocatalysts. Here, we used the sol-gel method to develop numerous ZnO NPs at various calcination temperatures (300 - 800 oC) and analyzed by different surface characterization techniques such as FTIR, SEM, XRD and UV-visible absorption spectroscopy. To investigate the catalytic activity a series of photooxidation studies on Remazol Red RR (RRR) were carried out at different conditions. From the surface characteristic analysis, it is found that the crystalline ZnO NPs are formed at above 400 oC temperature. The highest photocatalytic efficiency is found at 500 oC which might be related to the lowest particle size (35.4 ± 5.2 nm) and surface heterogeneity. The experimental results suggest that temperature-controlled growth rate and intra/inter-particle heterogeneity of ZnO nanoparticles have a great impact on the surface properties and photocatalytic activity. In addition to surface area, surface defects and crystal deformation may have a considerable impact on the photocatalytic activity by ZnO NPs. Finally, this study will help to understand what type of surface properties need to optimize to design industrial suit ZnO nanocatalysts. Journal of Engineering Science 15(1), 2024, 75-81

Exopolysaccharides from Weissella cibaria isolated from oats: isolation, characterisation and its application in improving the texture of set‐type yogurt

SummaryIn this study, a lactic acid bacteria strain isolated from oats was used as a producer to obtain exopolysaccharide (EPS) using MRS agar plates. The findings indicated that the bacterial strain identified as Weissella cibaria (accession number: PP515290) was shown to have good probiotic activity, adapt better to alkaline than acidic conditions, and efficiently produce EPS at concentrations of up to 7.93 g L−1. SEM images showed a smooth surface and compact particle whereas FTIR confirmed the basic functional groups of polysaccharides in the sample. Meanwhile, XRD analysis demonstrated a non‐crystalline amorphous structure and thermal analysis indicated two‐phase thermal decomposition with maximum rate at 210 °C. Subsequently, EPS from W. cibaria was applied as stabiliser in set‐type yogurt (ex situ) in comparison with yogurt using mixed culture with W. cibaria (in situ) and traditional starter culture (control). The results showed that the addition of 2% EPS significantly improved syneresis (14.31%) compared to co‐culture (27.50%) and control (29.80%) as well as increased hardness of yogurt during 2‐week refrigeration.

How to Characterize Supported PdOx Catalysts by CO-FTIR Spectroscopy: Importance of Surface Reduction and Particle Size

How to Characterize Supported PdO<i>_x</i> Catalysts by CO-FTIR Spectroscopy: Importance of Surface Reduction and Particle Size

Complex formation and stabilization of Z‐isomer‐enriched astaxanthin esters derived from Haematococcus lacustris with water‐soluble carriers via spray drying

AbstractTo enhance the water solubility and bioavailability of astaxanthin esters, inclusion complexes of Z‐isomer‐enriched astaxanthin esters with water‐soluble carriers were prepared using a spray drying technique. A food‐grade Haematococcus alga extract was used as the source of astaxanthin esters, and the Z‐isomerization was performed via direct heating of the extract. Polyvinylpyrrolidone (PVP) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) were used as water‐soluble carriers. The effects of spray drying conditions on the encapsulation efficiency of astaxanthin esters in the carriers and the total Z‐isomer ratio of encapsulated astaxanthin esters were investigated, and the physical properties and storage stability of the resulting composites were evaluated. Under optimum spray drying conditions, efficient production of highly water‐soluble Z‐isomer‐rich astaxanthin esters was achieved in both carriers: &gt;95% encapsulation efficiency and &gt;55% total Z‐isomer ratio. The physical properties, such as surface morphology and particle size distributions, of the resulting particles differed significantly between PVP and HP‐β‐CD. Storage tests demonstrated that the formulated Z‐isomer‐rich astaxanthin esters were highly stable. Our findings will contribute to the practical applications of Z‐isomer‐rich astaxanthin materials.Practical Applications: The formulation technology developed in this study has the potential to address the industrial challenges of using astaxanthin, that is, low water solubility and low bioavailability. Furthermore, the low storage stability of astaxanthin Z‐isomers, which hinders their industrial use, can be solved simultaneously. The resulting Z‐isomer‐rich astaxanthin powders are expected to be used in a wide range of applications, including nutraceuticals, cosmetics, and animal feeds.

Insights of mechanism and kinetics of acrylonitrile aqueous precipitation polymerization

Aqueous precipitation polymerization is commonly used in the industry due to its efficient heat dissipation, reaction stability and production flexibility. However, its mechanisms and kinetics are still partially unclear. The ammonium persulfate-ammonium sulfite monohydrate (APS-AS) initiated aqueous phase precipitation polymerization of acrylonitrile (AN) at low concentration was deeply investigated, with the APS initiation system as a control. The apparent kinetic equations for the APS and APS-AS initiation systems were determined to be Rp= K[AN]1.706[(NH4)2S2O8]0.704 and Rp= K[AN]3[(NH4)2S2O8]0.704[(NH4)2S2O3]−1.055, respectively. Monitoring AN distribution in the aqueous and polyacrylonitrile (PAN) phases revealed a rapid transition of the reaction site from the aqueous phase to the PAN phase following polymer precipitation. Zeta potential and primary particle number exposed that the nucleation site disparities between initiation systems led to different predominant factors affecting the polymerization rate. The change in molecular weight during polymerization had a maximum due to its dependence on the monomer concentration. The crystallinity of the product initially increased during polymerization, then decreased and eventually stabilized. Scanning electron microscopy (SEM) revealed that the diameter of the internal particles was larger, while the surface particles were smaller after coagulation. These findings offer crucial insights for optimizing aqueous precipitation polymerization and PAN particle property control.

The presence of nanoparticles in aqueous droplets containing plant-derived biopolymers plays a role in heterogeneous ice nucleation.

Organic matter can initiate heterogeneous ice nucleation in supercooled water droplets, thereby influencing atmospheric cloud glaciation. Predicting the ice nucleation ability of organic matter-containing cloud droplets is challenging due to the unknown mechanism for templating ice. Here, we observed the presence of nanoparticles in aqueous samples of known ice-nucleating biopolymers cellulose and lignin, as well as in newly identified ice-nucleating biopolymers xylan and laminarin. Using our drop Freezing Ice Nuclei Counter (FINC), we measured the median ice nucleation temperature (T50) of xylan and of laminarin droplets of 2 μl to be -14.2 and -20.0 °C, respectively. Next, we characterized these samples using nanoparticle tracking analysis, and we detected and quantified nanoparticles with mean diameters between 132 and 267nm. Xylan contained the largest nanoparticles and froze at higher temperatures. Xylan also dictated the freezing in a 1:1:1:1 mixture with cellulose, lignin, laminarin, and xylan. Filtration experiments down to 300 kDa with the xylan sample indicated that the presence of nanoparticles triggered freezing. Overall, only samples with mean diameters above 150nm froze above -20 °C. Furthermore, we determined the ice-active site densities normalized to particle concentrations, surface area, and mass of the nanoparticles to show that the samples' nucleation site densities are similar to sea spray aerosols and nanometer-sized dust. The identification and characterization of xylan and laminarin as nanometer-sized ice-nucleating substances expands the growing list of organic matter capable of impacting cloud formation and thus climate.