Uncoated Particles Research Articles

Dissolution of copovidone-based amorphous solid dispersions: Influence of atomic layer coating, hydration kinetics, and formulation

Atomic layer coating (ALC) is an emerging, solvent-free technique to coat amorphous solid dispersion (ASD) particles with a nanolayer ceramic coating that has been shown to improve powder characteristics and limit drug crystallization. Herein, we evaluate the impact of aluminum oxide coatings with varying thickness and conformality on the dissolution of ritonavir/copovidone ASDs. Release performance of powders, neat tablets, and formulated tablets was studied. Confocal fluorescence microscopy (CFM) was used to visualize particle hydration and phase separation during immersion of the ASD in aqueous media. CFM revealed particle hydration requires defects for solvent penetration, but coatings, regardless of thickness, had minor impacts on powder dissolution provided defects were present. In tablets where less surface area is exposed to the dissolution media due to gel formation, slowed hydration kinetics resulted in phase separation of the drug from the polymer in coated samples, limiting release. Formulation with two superdisintegrants, crospovidone and croscarmellose sodium, as well as lactose achieved ∼90% release in less than 10 minutes, matching the uncoated ASD particles of the same formulation. This study highlights the importance of hydration rate, as well as the utility of confocal fluorescence microscopy to provide insight into release and phase behavior of ASDs.

Interparticle interaction effect on superparamagnetic properties of ferrimagnetic particles

Uncoated and oleic acid coated ferrimagnetic particles are synthesized. Both samples contain similar magnetite particles. Structural characterization of these particles is performed using x-ray diffraction, Fourier transform infrared spectra, dynamic light scattering, transmission electron microscopy and thermogravimetric analysis. Average crystallite size of magnetite is 7 nm. Thickness of oleic acid layer on each magnetite particle is 1 nm. The oleic acid coated sample contains 23% oleic acid. Temperature dependence of the zero field cooled and field cooled susceptibility of the uncoated magnetite particles peaks at 120 K and both the curves bifurcate at 195 K. The peak temperature and the bifurcation temperature of the system decrease due to the oleic acid coating. The inverse susceptibility does not vary linearly with temperature in high temperature region. Magnetization versus applied magnetic field data at 250 K are analyzed in three different ways to study the interparticle interaction and the particle size distribution effects on magnetization. We find that the both factors affect the magnetization process of ferrimagnetic nanoparticles.

The Effect of the Surrounding Matrix on Spin Transition Nanoparticles: How Shell Characteristics Alter Core Elastic Properties in Core‐Shell Particles

A surrounding matrix is known to alter nanoparticle spin transitions, the solid state structural phase changes associated with transitions between high spin (HS) and low spin(LS) states. To better quantify how the spin transition solid and surrounding matrix interact, several series of core‐shell particles were prepared based on RbxCo[Fe(CN)6]z∙nH2O, RbCoFe‐PBA, as spin transition core with isostructural shells of different compositions and thicknesses. Synchrotron PXRD through the thermal high HS to LS, the LS to photoexcited high spin (PXHS), and thermal PXHS to LS transitions, show the activation energy is lowered as shells become thicker and stiffer. Calorimetry data coupled with transition state theory analysis indicate the core stiffens in the core‐shell particles relative to the uncoated particles. The conclusion is supported by microstrain analysis that shows stiffer shells limit the extent to which the core distorts as individual sites transition, leading to the lower activation energy. Finally, differences in lattice mismatch with different shell materials are shown to alter the mechanism by which the transition progresses.

Effect of polymer coating on magnetocaloric properties of garnet

In this study, Gd3Fe5O12 nanoparticles were synthesized using the sol–gel autocombustion method and subsequently coated with polyvinylpyrrolidone (PVP) polymer. The study focuses on understanding the influence of PVP coating on garnet particles’ magnetic and magnetocaloric properties. The crystallite size upon PVP-coating remained unaltered, but the grain size and surface area of coated particles increased. The magnetization of PVP-coated particles decreased by around 11% as compared to the uncoated particles at 5 K. Mössbauer and photoelectron spectroscopy confirmed the presence of a paramagnetic phase Fe3+ in the PVP-coated nanoparticles responsible for the reduction in magnetization value. The maximum value of magnetic entropy change (−ΔS m ) for uncoated Gd3Fe5O12 was 3.78 Jkg−1 K−1 at 37.5 K with a 5T applied field, accompanied by a relative cooling power (RCP) of 382 Jkg−1. On the other hand, for PVP-coated Gd3Fe5O12, the maximum −ΔS m was 3.38 Jkg−1 K−1 at 57.5 K with a 5T applied field, and the RCP was 308 Jkg−1. The observed maximum magnetic entropy changes at higher temperatures for the PVP-coated Gd3Fe5O12 sample are noteworthy. This characteristic indicates that the PVP-coated garnet may have an advantage in terms of usability over a wider temperature range compared to the uncoated counterpart, which can potentially be a promising material for applications in cryogenic temperature magnetic refrigeration.

Different Chain Length Tannic Acid Preparations as Coating Agents for Zein Nanoparticles

Proteins that are amphiphilic and have low water solubility can self-assemble into nanoparticles useful in food science, pharmaceutical science, or biotechnology. However, protein nanoparticles exhibit drawbacks such as low stability unless the particles are coated. In the current study, tannic acid is the coating agent for nanoparticles synthesized from the protein zein. Tannic acid is a hydrolyzable tannin comprising a polyol esterified with galloyl residues. The nominal molecular formula of tannic acid (C76H52O46) suggests the material is decagalloyl glucose, obscuring its complex composition as a mixture of galloyl esters of glucose. We prepared hollow zein nanoparticles and coated them with tannic acid preparations that had short or long galloyl ester chains. The % α-helix of zein in nanoparticles is lower than in native zein but there is no effect of coating the particles with tannic acid. Interactions between the tannic acid and the zein slightly perturb the IR spectrum of the protein but there is no effect of galloyl chain length. We confirmed that tannic acid-coated particles have a more negative zeta potential, suggesting greater stability compared to uncoated particles. Coating with longer chain length tannic acid reduces particle diameter and tends to decrease polydispersity but does not change particle digestibility. Coating with shorter galloyl chain length tannic acid tends not to change particle diameter, reduces polydispersity of the particles, and stabilizes particles to enzymatic digestion. Tannic acid is a naturally occurring tunable coating for nanoparticles that can be used to adjust properties such as particle size, polydispersity, and digestibility for specific purposes.

Hard/stiff surface coatings for particle weakening, part I: Methodology

Size-reduction processes are essential for liberating valuable minerals yet energy-inefficient, which needs to be remedied by developing energy-efficient methods. This work is the first part of a wide study that (i) describes a surface coating method, namely, spray coating, and (ii) presents some preliminary results that hard or stiff surface coatings can be used to weaken softer ore particles. The hard surface coatings were achieved with a ceramic spray and two inorganic precipitates (CaCO3 and silica). The fracture energy and/or strength of spray-coated and uncoated particles was measured using the Short Impact Load Cell (SILC). Spray coating can only yield low surface coverage (up to 1–2% of the mass of particles), which is only apparent if particle surfaces are washed before coating. Nevertheless, the preliminary results suggest significant reductions in the fracture force and energy of soft ore particles after they are coated.

Carboxymethyl Chitosan-Coated Cyanidin-3-O-Glucoside-Beared Nanonutriosomes Suppress Palmitic Acid-Induced Hepatocytes Injury.

Cyanidin-3-O-glucoside (C3G) is classified as an anthocyanin (ACN) and is recognized for its remarkable antioxidant properties. Yet, the inadequate physicochemical stability of C3G restricts its potential for various biological applications. Thus, in this study, carboxymethyl chitosan (CMC)-coated nanonutriosomes (NS) were synthesized as a novel carrier for encapsulating C3G (CMC-C3G-NS) to improve C3G stability. CMC-C3G-NS exhibited a diameter of less than 200 nm along with an encouraging encapsulation efficiency exceeding 90%. Notably, the formulated CMC-C3G-NS possessed better stability under various pH, ionic, and oxygen conditions, improved controlled release properties, and higher hepatocellular uptake than uncoated particles (C3G-NS), indicating a longer retention time of C3G in a physiological environment. Of utmost significance, CMC-C3G-NS demonstrated superior alleviating effects against palmitic acid (PA)-induced oxidative hepatic damage compared to C3G-NS. Our study provided promising nanocarriers with the potential to deliver hydrophilic ACNs and controlled release properties for PA-induced hepatotoxicity alleviation.

Diffusiophoretic Behavior of Polyelectrolyte-Coated Particles.

Diffusiophoresis, the movement of particles under a solute concentration gradient, has practical implications in a number of applications, such as particle sorting, focusing, and sensing. For diffusiophoresis in an electrolyte solution, the particle velocity is described by the electrolyte relative concentration gradient and the diffusiophoretic mobility of the particle. The electrolyte concentration, which typically varies throughout the system in space and time, can also influence the zeta potential of particles in space and time. This variation affects the diffusiophoretic behavior, especially when the zeta potential is highly dependent on the electrolyte concentration. In this work, we show that adsorbing a single bilayer (or 4 bilayers) of a polyelectrolyte pair (PDADMAC/PSS) on the surface of microparticles resulted in effectively constant zeta potential values with respect to salt concentration throughout the experimental range of salt concentrations. This allowed a constant potential model for diffusiophoretic transport to describe the experimental observations, which was not the case for uncoated particles in the same electrolyte system. This work highlights the use of simple polyelectrolyte pairs to tune the zeta potential and maintain constant values for precise control of diffusiophoretic transport.

Thermochemical heat storage performance and structural stability of SiO2-coated CaO particles under fluidization in CaO/Ca(OH)2 cycles

The decline in CaO/Ca(OH)2 heat storage performance of CaO-based material with the number of cycles due to its fast expansion and fragmentation is an problem in the fluidized bed reactor. In this paper, a novel SiO2-coated CaO particle was manufactured from limestone and silica sol via wet-mixing method. Exothermic performance (such as exothermic temperature, effective hydration conversion and volumetric energy density) and structural stability of SiO2-coated CaO particles in a fluidized bed reactor were studied. The effects of SiO2 addition and calcination temperature on the exothermic performance and structural stability were analyzed, respectively. The results show that the mass ratio of limestone to silica sol of 1:1 and calcination temperature of 850 °C are recommended for the preparation of SiO2-coated CaO. The SiO2 layer is observed on the surface of the CaO. SiO2-coated CaO particles exhibit superior structural stability than uncoated CaO particles. The SiO2 coating reduces the increase of average particle size during 10 cycles from 33 % to 11 %. After 10 heat storage cycles, SiO2-coated CaO particles achieve a reduction of 45.4 % in expansion rate and 48.5 % in attrition rate compared with uncoated CaO particles, respectively. The volumetric energy density of SiO2-coated CaO particles after 10 cycles is 33.2 % higher than that of uncoated CaO particles. The highest exothermic temperature of SiO2-coated CaO particles after 10 cycles reaches 455.4 °C (steam partial pressure @ 60 kPa). The SiO2-coated CaO seems a promising candidate for the CaO/Ca(OH)2 thermochemical heat storage in the fluidized bed rector.

Detection of a Cobalt-Containing Interphase at the Li6PS5Cl-NMC111 Interface by In Situ μXANES and EIS

Sulfide electrolyte all-solid-state lithium batteries (ASLBs) with uncoated Li-NixMnyCo1−x−yO2 (NMC) cathodes suffer from a large capacity loss during initial cycling and an increase in cell impedance. Decomposition reactions are known to occur at the Li6PS5Cl-NMC111 interface due to incompatibility between the two materials. If a stabilizing coating is applied to the NMC, it delivers full capacity during initial charge. However, the loss in capacity during discharge still occurs. The interface was studied by μXANES and through EIS analysis. A chemically-formed interphase was detected by μXANES, evident from reduction of Co at an uncoated NMC particle surface. This interphase was produced by decomposition at rest. To study the effect of the interphase on electrochemically active surface area, piecewise in situ EIS was performed and the data was modeled using a transmission line model (TLM). The charge transfer resistance RCT was used to estimate the volume specific active surface area (aact). The median value for aact was 296 cm−1, a factor of 7.5 lower than the theoretical value of 2216 cm−1. This provided evidence of a lower electrochemically active surface area in the ASLB.

Lipooligosaccharide Ligands from Respiratory Bacterial Pathogens Enhance Cellular Uptake of Nanoparticles

Several bacterial pathogens contain membrane ligands that facilitate their binding and internalization into human tissues. In this study, lipooligosaccharides (LOS) from the respiratory pathogen non-typeable Haemophilus influenzae (NTHi) were isolated from the bacterial surface and evaluated as a nanoparticle coating material to facilitate uptake into respiratory epithelium. NTHi clinical isolates were screened to select a strain with high binding potential due to their elevated phosphorylcholine content. The association of particles with human bronchial epithelial cells was investigated as a function of particle surface chemistry and incubation time, and the uptake mechanism evaluated via chemical inhibitor and receptor activation studies. A more than two-fold enhancement in particle uptake was achieved by coating the particles with LOS compared to uncoated or gelatin-coated particles, which was further increased by activating the platelet activating factor receptor (PAFR). These findings demonstrate that bacterial-derived LOS ligands can enhance the targeting and binding of nanoparticles to lung epithelial cells.

Magneto-photothermal synergy applied to gold-coated magnetic nanoparticles

In this work, we describe the synthesis of magnetic nanoparticles with a suitable size for easy cellular internalization, avoiding their rapid renal excretion (less than 5 nm) and accumulation in the liver (more than 100 nm). The nanoparticles are functionalized with a biocompatible polymer (low molecular weight, branched polyethylenimine, PEI), and this treatment allows their functionalization with a shell of gold particles in order to improve their ability to absorb electromagnetic radiation in the visible and near infrared wavelength regions. As a result, the magnetic nanostructures are potential agents of local heating (hyperthermia) by exposing them to alternating magnetic fields (magnetic hyperthermia) or to light of the suitable wavelength (photothermia). Magnetic hyperthermia experiments demonstrate that both types of particles can reach the desired temperature range for cell apoptosis, with the difference of a shorter time needed when gold is absent. The released thermal energy is measured by the SAR (specific absorption rate, in W/g), and the values found are promising, up to 600 W/g in the case of uncoated particles. Regarding the photothermia response under the IR radiation, it is comparable for gold-coated and uncoated magnetic particles, but it is enhanced by a factor of almost 10 when the incident light is visible (blue-green) and the particles are provided with their gold shell. Improvements related to the selection of gold particles with resonant absorbance in the infrared are under investigation.

A Pathway for Collisional Planetesimal Growth in the Ice-dominant Regions of Protoplanetary Disks

We present a semi-analytic model for the growth, drift, desorption, and fragmentation of millimeter- to meter-sized particles in protoplanetary disks. Fragmentation occurs where particle collision velocities exceed critical fragmentation velocities. Using this criterion, we produce fragmentation regions in disk orbital radius–particle size phase space for particles with a range of material properties, structures, and compositions (including SiO2, Mg2SiO4, H2O, CO2, and CO). For reasonable disk conditions, compact aggregate H2O, CO2, and CO ice particles do not reach destructive relative velocities and are thus not likely to undergo collisional fragmentation. Uncoated silicate particles are more susceptible to collisional destruction and are expected to fragment in the inner disk, consistent with previous work. We then calculate the growth, drift, and sublimation of small particles, initially located in the outer disk. We find that ice-coated particles can avoid fragmentation as they grow and drift inward under a substantial range of disk conditions, as long as the particles are aggregates composed of 0.1 μm-sized monomers. Such particles may undergo runaway growth in disk regions abundant in H2O or CO2 ice, depending on the assumed disk temperature structure. These results indicate that icy collisional growth to planetesimally relevant sizes may happen efficiently throughout a disk’s lifetime, and is particularly robust at early times when the disk’s dust-to-gas ratio is comparable to that of the interstellar medium.

Preparation of Fe–B/Epoxy Composite Films by the LbL-Assisted Composite Plating Method Using Epoxy-Coated Fe–B Ultrafine Particles

Metal-insulator composite films, including Fe-B ultrafine particles and insulating epoxy films, were synthesized by the layer-by-layer (LbL)-assisted composite plating method. In this method, charged magnetic ultrafine particles were attracted to the cathode by electrostatic force simultaneously with the deposition of insulating epoxy thin film. To suppress the oxidation of Fe-B ultrafine particles in the reaction aqueous solution for Fe-B/epoxy composite film deposition, Fe-B ultrafine particles were coated with epoxy by using the electroless plating method. It was clear that epoxy coating on Fe-B ultrafine particles effectively prevents oxidation. The film deposited using epoxy-coated Fe-B ultrafine particles exhibited a smoother film surface than those obtained using uncoated Fe-B ultrafine particles. However, the highest amount of Fe-B content obtained in the deposited film was approximately 36 vol.% using Fe-B ultrafine particles with a concentration of 1.0 g/L.

Properties of SiO2-B2O3-Li2O-ZnO-Al2O3 glass-ceramic-coated diamond particles prepared by sol-gel method

During the process of sintering diamond/ceramic composites, the wettability between diamond and the ceramic matrix is poor, and there are many irregular pores in the composites, which leads a low bending strength of the composites and easy shedding of diamond. In order to solve these problems, SiO2-B2O3-Li2O-ZnO-Al2O3 glass-ceramic coated diamond was prepared by a sol-gel method, and the properties of the coated diamond abrasive particles were studied. The SBLZA glass-ceramic-coated diamond exhibited high thermal stability and excellent oxidation resistance, making it a good protective material for diamond. The oxidation resistance of the SBLZA glass-ceramic-coated diamond was determined by thermogravimetric analysis (TGA). The uncoated diamond abrasive particles began to oxidize at 723 °C, while the coated abrasive particles were resistant to oxidation at temperatures up to 1000 °C. The glass-ceramic coating significantly improved the bonding between diamond and the ceramic matrix. The use of SBLZA glass-ceramic-coated diamond instead of uncoated diamond in the composites sintered at 750 °C resulted in a decrease in the volume expansion rate of the diamond/ceramic composites from 37.2 % to 28.5 %, and an increase in the bending strength from 38.4 MPa to 61.5 MPa.

The influence of size and surface chemistry on the bioavailability, tissue distribution and toxicity of gold nanoparticles in zebrafish (Danio rerio)

Gold nanoparticles (AuNPs) are widely used in biomedicine and their specific properties including, size, geometrics, and surface coating, will affect their fate and behaviour in biological systems. These properties are well studied for their intended biological targets, but there is a lack of understanding on the mechanisms by which AuNPs interact in non-target organisms when they enter the environment. We investigated the effects of size and surface chemistry of AuNPs on their bioavailability, tissue distribution and potential toxicity using zebrafish (Danio rerio) as an experimental model. Larval zebrafish were exposed to fluorescently tagged AuNPs of different sizes (10–100 nm) and surface modifications (TNFα, NHS/PAMAM and PEG), and uptake, tissue distribution and depuration rates were measured using selective-plane illumination microscopy (SPIM). The gut and pronephric tubules were found to contain detectable levels of AuNPs, and the concentration-dependent accumulation was related to the particle size. Surface addition of PEG and TNFα appeared to enhance particle accumulation in the pronephric tubules compared to uncoated particles. Depuration studies showed a gradual removal of particles from the gut and pronephric tubules, although fluorescence indicating the presence of the AuNPs remained in the pronephros 96 h after exposure. Toxicity assessment using two transgenic zebrafish reporter lines, however, revealed no AuNP-related renal injury or cellular oxidative stress. Collectively, our data show that AuNPs used in medical applications across the size range 40–80 nm, are bioavailable to larval zebrafish and some may persist in renal tissue, although their presence did not result in measurable toxicity with respect to pronephric organ function or cellular oxidative stress for short term exposures.

Study of ultrasonic vibration-assisted particle atomic layer deposition process via the CFD-DDPM simulation

Atomic layer deposition (ALD) is a unique surface modification technology by providing conformal ultrathin films on particulate materials. Fluidized bed ALD (FB-ALD) shows excellent scale-up potential for the mass production of particle coating, where different external fields have been developed to enhance the fluidization quality of cohesive micro-nanoparticles. Ultrasonic vibration is a promising assisting method for it can promote effective agglomeration breakage as well as enhance the heat and mass transfer rates in the reactor. In this paper, a multiscale computational fluid dynamics (CFD) simulation based on the dense discrete phase method (DDPM) is developed to study the ultrasonic vibration-assisted FB-ALD process. Dynamic mesh method and discrete element method are adopted to introduce the ultrasonic field and compute the particle movement with an accurate description of particle-particle and particle-vibrating wall interactions. Results show that ultrasonic vibration effectively promotes the contact efficiency between uncoated particles and precursor molecules in the precursor pulsing process, leading to higher deposition rates and coating uniformity. During the purge process, ultrasonic vibration also increases the removal rate of ALD byproducts, thus shortening the purge time by 25%. Through the CFD-DDPM model, the maximum precursor utilization rate for uniform coating can be predicted quantitatively under a given precursor mass fraction and a ratio of the pulse time to the theoretical saturation time. The multiscale numerical model developed in this work can be adapted to optimize the process conditions for the scale-up of FB-ALD reactors.

The PACE-MAPP algorithm: Simultaneous aerosol and ocean polarimeter products using coupled atmosphere-ocean vector radiative transfer

We describe the PACE-MAPP algorithm that simultaneously retrieves aerosol and ocean optical parameters using multiangle and multispectral polarimeter measurements from the SPEXone, Hyper-Angular Rainbow Polarimeter 2 (HARP2), and Ocean Color Instrument (OCI) instruments onboard the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) observing system. PACE-MAPP is adapted from the Research Scanning Polarimeter (RSP) Microphysical Aerosol Properties from Polarimetry (RSP-MAPP) algorithm. The PACE-MAPP algorithm uses a coupled vector radiative transfer model such that the atmosphere and ocean are always considered together as one system. Consequently, this physically consistent treatment of the system across the ultraviolet, (UV: 300–400 nm), visible (VIS: 400–700 nm), near-infrared (NIR: 700–1100 nm), and shortwave infrared (SWIR: 1100–2400 nm) spectral bands ensures that negative water-leaving radiances do not occur. PACE-MAPP uses optimal estimation to simultaneously characterize the optical and microphysical properties of the atmosphere’s aerosol and ocean constituents, find the optimal solution, and evaluate the uncertainties of each parameter. This coupled approach, together with multiangle, multispectral polarimeter measurements, enables retrievals of aerosol and water properties across the Earth’s oceans. The PACE-MAPP algorithm provides aerosol and ocean products for both the open ocean and coastal areas and is designed to be accurate, modular, and efficient by using fast neural networks that replace the time-consuming vector radiative transfer calculations in the forward model. We provide an overview of the PACE-MAPP framework and quantify its expected retrieval performance on simulated PACE-like data using a bimodal aerosol model for observations of fine-mode absorbing aerosols and coarse-mode sea salt particles. We also quantify its performance for observations over the ocean of dust-laden scenes using a trimodal aerosol model that incorporates non-spherical coarse-mode dust particles. Lastly, PACE-MAPP’s modular capabilities are described, and we discuss plans to implement a new ocean bio-optical model that uses a mixture of coated and uncoated particles, as well as a thin cirrus model for detecting and correcting for sub-visual ice clouds.

High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State‐of‐the‐Art and Future Trends

AbstractThe lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.

Silica-coating of Ca14Al10Zn6O35:Mn4+ particles and their luminescence properties

A simple method for improving water-resistance of Ca14Al10Zn6O35:Mn4+ (CZA) phosphor particles by silica-coating was developed in this work. Coating of the CZA particles having a particle size of ca. 3 µm with silica shells having a thickness of 158.3–194.4 nm was performed by adding tetraethyl orthosilicate/ethanol solution and ammonia solution or sodium hydroxide solution as base catalyst to ethanol dispersing the CZA particle powder (CZA/SiO2). The surfaces of the CZA/SiO2 particles were similar to the surface that appears to be derived from the surfaces of the silica particles prepared by the sol–gel method, i.e., were smoother than those of uncoated CZA particles, the element Si was present on the CZA/SiO2 particle surfaces, and the element Ca was present inside the CZA/SiO2 particles, which indicated that each CZA/SiO2 particle was composed of a CZA particle as its core and silica as its shell. Luminescence intensity of the CZA particles in water was not dominantly decreased with the silica-coating, which indicated that the silica-coating had a water-resistance capability.