Calcium Fluoride Nanoparticles Research Articles

Defect induced luminescence from surface modified calcium fluoride nanoparticles for in-situ temperature monitoring of lubricating oil

The utilization of functional nano-additives provides us a novel research idea to deal with the in situ temperature sensing/monitoring of lubricating oil. In this work, monodispersed and luminescent calcium fluoride (CaF2) nanoparticles with surface modification were synthesized by a hydrothermal approach, which were employed as nano-additives for polyalphaolefin (PAO6) lubricating oil. Because of the surface modification of hydrophobic oleic acid molecule, the as-prepared CaF2 nanoparticles exhibited excellent oil solubility. The tribological results further suggested that after dispersing in PAO6 lubricating oil, the CaF2 nanoparticles could maintain its original friction and wear properties. In addition to the above basic characteristics for lubricating nano-additives, it was attractive to find that the as-synthesized CaF2 nanoparticles exhibited a doublet luminescence characteristic. The intensity ratio of the two emission peaks presented a nearly linear relationship to the surrounding temperature, which was also effective for CaF2 nanoparticles dispersed in PAO6 base oil. By comprehensive consideration of the oil dispersibility, tribological properties and temperature responsiveness, the as-synthesized CaF2 nanoparticles should be promising nano-additives for temperature monitoring of lubricating oil.

Development and Characterization of Bioadhesive Film Embedded with Lignocaine and Calcium Fluoride Nanoparticles.

The formation of biofilm by Streptococcus mutans on the tooth surface is the primary cause of dental caries and periodontal diseases, and fluoride (F) has shown tremendous potential as a therapeutic moiety against these problems. Herein, we report an efficient multi-ingredient bioadhesive film-based delivery system for oral cavity to combat dental problems with an ease of administration. Thiolated chitosan-based bioadhesive film loaded with calcium fluoride nanoparticles (CaF2 NPs) and lignocaine as a continuous reservoir for prolonged delivery was successfully prepared and characterized. The polygonal CaF2 NPs with an average particle size less than 100nm, PDI 0.253, and + 6.10mV zeta potential were synthesized and loaded in film. The energy dispersive x-ray (EDX) spectroscopy confirmed the presence 33.13% F content in CaF2 NPs. The characterization of the three film trials for their mechanical strength, bioadhesion, drug release, and permeation enhancement suggested film B as better among the three trials and showed significant outcomes, indicating the potential application of the medicated bioadhesive film. In vitro dissolution studies revealed sustained release pattern of lignocaine and CaF2 NP following Krosmeyer-Peppas model over 8h. Franz diffusion studies showed the prolonged contact time of film with mucosa that facilitated the transport of CaF2 NPs and lignocaine across the mucosa. Hence, the prepared bioadhesive film-based system showed good potential for better management of dental problems. Graphical Abstract.

The Effect of Different Remineralizing Agents on Laser Bleached Enamel

One of the most required esthetic measures for patients with teeth discoloration or those who strive to have a beautiful smile and appearance is bleaching. The objective of this study is to analyze enamel morphological changes, chemical composition and microhardness following the application of 35% hydrogen peroxide, utilizing two various protocols for laser activation and the application of 4 different remineralizing agents. Materials and methods: In this study, 40 extracted human lateral and central incisors were chosen where the researcher categorized teeth into 2 groups consisting of 20 incisors, using two different laser-activated bleaching protocols. The researcher then subdivided each group into 4 subsets consisting each of 5 incisors where 4 remineralizing agents were applied to each bleached subset. Enamel surface morphology was studied by ESEM. Calcium and Phosphorus content were measured by EDAX and microhardness Vicker’s test was performed to study the alteration in enamel hardness. Pre- and post-demineralization (bleaching) investigations were conducted and then they were repeated following remineralization. Results: ESEM revealed the improvement of enamel surface morphology in the remineralized groups except in (HD) and (LD) groups. After remineralization, all groups had a higher weight percent of calcium (Ca) and phosphorus (P) levels than its levels after demineralization except in groups (HD) and Vicker’s hardness number in all groups showed significant increase except (HD) and (LD). Conclusion: The use of remineralizing agents containing casein phosphopeptide-amorphous calcium phosphate, fluoride or hydroxyapatite nanoparticles could improve the enamel morphology, microhardness and chemical composition of laser bleached enamel.

Synthesis of CaF2 Nanoparticles Coated by SiO2 for Improved Al2O3/TiC Self-Lubricating Ceramic Composites.

In order to reduce the influence of CaF2 addition on the mechanical properties of self-lubricating ceramic tools, we applied a silicon dioxide (SiO2) coating on calcium fluoride (CaF2) nanoparticles through hydrolysis and condensation reactions using the tetraethoxysilane (TEOS) method. The powder was dried by the azeotropic method, so that it acquired a better dispersibility. The resulting composite powders were characterized using XRD (X-ray diffraction) and TEM (transmission electron microscopy), showing that the surface of CaF2 was coated with a layer of uniform and compact SiO2. SiO2 shells with different thicknesses could be obtained by changing the amount of TEOS added, and the thickness of the SiO2 shells could be controlled between 1.5 and 15 nm. At the same time, a ceramic material containing CaF2 nanoparticles and CaF2@SiO2-coated nanoparticles was prepared. It had the best mechanical properties when CaF2@SiO2-coated nanoparticles were added; its flexural strength, fracture toughness, and hardness were 562 ± 28 MPa, 5.51 ± 0.26 MPa·m1/2, and 15.26 ± 0.16 GPa, respectively. Compared with the ceramic tool containing CaF2 nanoparticles, these mechanical properties were increased by 17.57%, 12.67%, and 4.88%, respectively. The addition of CaF2@SiO2-coated nanoparticles greatly improved the antifriction and wear resistance of the ceramic material, and the antifriction and wear resistance were balanced.

Single compound in-situ synthesis of core-shell CaF2 nanoparticles based broad band antireflective coatings for solar energy conversion

A unique in-situ synthesis approach of formation-deformation-reformation routes lead to high crystalline core-shell Calcium Fluoride (CaF2) nanoparticles. They were tuned by the solvothermal process to achieve superior antireflection property (>95%) in the broadband region (400–1500 nm) after fabricating films by a dip coating method. These nanoparticles capped by cetyltrimethylammonium bromide (CTAB), to increase the porosity in single layer antireflective (AR) film to reduce the refractive index. This efficient antireflection layer with glass implemented on the c-Si solar cell to measure the efficiency and found out to be an improved performance (>5.7% net enhancement) compared to uncoated glass. In addition, the AR coatings exhibited a good mechanical strength which gives us the direction of future development for practical applications like highly transparent window coatings, optical and solar energy conversion applications.

The Remineralizing Effect of Incorporating Ca-Phosphate and Ca-Fluoride Nanoparticles into the Self-Etch Adhesives Used in Restoring Class I Cavities

This study was carried out to investigate the remineralizing effect of amorphous calcium phosphate (ACP) and calcium fluoride (CaF2) nanoparticles incorporated in two-step self etch- adhesives (in vivo). Materials and Methods: The nanoparticles were incorporated into the bond of ClearfilTM SE Bond at a mass fraction of 10%. A total of ten patients in the age range of 17-30 years old, having at least 3 carious lower molars, were enrolled in this study (split mouth design). Class I cavity preparation was performed, leaving the caries affected dentine at the pulpal floor. The 30 molars were divided into 3 groups (n=10) according to the type of adhesive used (A); namely: self-etch adhesive, Clearfil SE Bond (Control)(A1), Clear Fill SE Bond incorporated with ACP NPs (A2) and Clearfil SE Bond incorporated with CaF2 NPs (A3). After restoration placement, each tooth was radiographically evaluated at baseline (I0), after 1 month (I1) and after 3 months (I2) to assess the remineralizing effect of the adhesive systems used. Results: The adhesive containing ACP nanoparticles induced the highest remineralization potential during all the study intervals, followed by the adhesive containing (CaF2) nanoparticles. Conclusion: nanoparticles are capable of remineralizing the caries affected dentin when incorporated into two-step self etch adhesive

The Remineralizing Effect of Incorporating Ca-Phosphate and Ca-Fluoride Nanoparticles into the Self-Etch Adhesives Used in Restoring Class I Cavities

This study was carried out to investigate the remineralizing effect of amorphous calcium phosphate (ACP) and calcium fluoride (CaF2) nanoparticles incorporated in two-step self etch- adhesives (in vivo). Materials and Methods: The nanoparticles were incorporated into the bond of ClearfilTM SE Bond at a mass fraction of 10%. A total of ten patients in the age range of 17-30 years old, having at least 3 carious lower molars, were enrolled in this study (split mouth design). Class I cavity preparation was performed, leaving the caries affected dentine at the pulpal floor. The 30 molars were divided into 3 groups (n=10) according to the type of adhesive used (A); namely: self-etch adhesive, Clearfil SE Bond (Control)(A1), Clear Fill SE Bond incorporated with ACP NPs (A2) and Clearfil SE Bond incorporated with CaF2 NPs (A3). After restoration placement, each tooth was radiographically evaluated at baseline (I0), after 1 month (I1) and after 3 months (I2) to assess the remineralizing effect of the adhesive systems used. Results: The adhesive containing ACP nanoparticles induced the highest remineralization potential during all the study intervals, followed by the adhesive containing (CaF2) nanoparticles. Conclusion: nanoparticles are capable of remineralizing the caries affected dentin when incorporated into two-step self etch adhesive

Antibacterial and Mechanical Properties of Pit and Fissure Sealants Containing Zinc Oxide and Calcium Fluoride Nanoparticles.

Context:Pit and fissure sealants (PFSs) are the most effective preventive materials in dentistry. Secondary caries around the sealed pits and fissures at the material–tooth interface and the wear of the material remains the common problems. To address these problems, efforts have been made by incorporating zinc oxide (ZnO) and calcium fluoride (CaF2) nanoparticles (NPs) into the sealants to develop caries-inhibiting and stress-bearing sealants.Aim:Evaluation of antibacterial and mechanical properties of PFS containing ZnO and CaF2 NPs.Settings and Design:This was an in vitro study.Materials and Methods:A total of 196 fissure sealant samples were divided into six test groups and a control group. The test group samples were prepared by incorporating two concentrations (0.5 wt% and 1 wt%) of ZnO and CaF2 NPs into the sealants. The antibacterial activity was evaluated by direct contact test; compressive and flexural strengths were evaluated by a universal testing machine.Statistical Analysis Used:Statistical analysis was done by one-way ANOVA and post hoc Tukey test.Results:Sealants containing 1 wt% ZnO and CaF2 NPs and their mixture exhibited significantly higher antibacterial activity against Streptococcus mutans and Lactobacillus acidophilus when compared to control group (P < 0.001). Samples with ZnO NPs exhibited similar mechanical properties as conventional sealant (control group); however, the samples with CaF2 NPs showed inferior mechanical properties (P < 0.05).Conclusion:The observations of the study infer that sealants containing 1 wt% ZnO and CaF2 NPs and their mixture exhibited superior antibacterial activity. The mechanical properties of samples containing ZnO and mixture of ZnO and CaF2 particles remained comparable to the conventional sealants.

Theoretical study of small calcium fluoride nanoparticles

CanF2n nanoclusters for n ranging from 2 to 10 were calculated with B3LYP/6-31G ab initio method. For n = 5 and n = 7 no stable configurations were found. The energy parameters, symmetries and stability of the nanoclusters is discussed. The results of ab initio calculations are then compared to pair potentials (PP) classical calculation.

Fine fluorite nanoparticles synthesized from biomass ash

Fine fluorite (CaF2) nanoparticles were synthetised by reaction of ammonium fluoride with calcium carbonate phase obtained by processing of wood chips ash in sodium acetate trihydrate acting as transport medium and liquid environment at 120 °C on air. The synthesized nanoparticles were analysed by SEM-EDS, XRD, XPS and TEM measurements and nanocrystals of calcium fluoride with average size 12 nm were characterised in detail. The properties of the material as an anti-reflexive coating made from the synthesized nanoparticles were successfully tested. The suggested procedure represents a promising route of zero-waste technology of calcium-rich biomass ashes processing and may be utilised for production of large quantities of calcium fluoride nanoparticles.

Monodisperse, colloidal and luminescent calcium fluoride nanoparticles via a citrate-assisted hydrothermal route

Luminescent calcium fluoride (CaF2) nanoparticles, because of their excellent biocompatibility, excellent photostability and strong fluorescence, have received increasing attention as drug carriers and bioprobes in cell imaging. Inspired by the role of citrate in the growth of apatite crystals during natural bio-mineralization, uniform and nearly monodisperse Eu3+-doped CaF2 nanoparticles with excellent colloidal stability and high fluorescence in aqueous media have been successfully synthesized in the presence of sodium citrate using a hydrothermal method. X-ray diffraction and transmission electron microscopy show that CaF2 nanoparticles grown in the presence of sodium citrate are cubes of relatively uniform size (15 nm), and that the Eu3+ doping level has little effect on size and morphology. Zeta potentials and dynamic light scattering demonstrate that in the synthesis with sodium citrate, the colloidal stability of CaF2 nanoparticles is greatly improved upon the increase of Eu3+ doping level. Moreover, aqueous dispersions of these nanoparticles are colloidally stable and can be maintained over a wide range of pH from 5.0 to 11.0 for more than a month. Fluorescence spectra demonstrate that the doped CaF2 nanoparticles display strong red fluorescence. Fourier transform infrared spectra and thermogravimetric analyses demonstrate the adsorption of substantial quantities of sodium citrate on the surfaces of the CaF2 nanoparticles. Taken together, such colloidal behavior should be related to strong crystal inhibition of citrate ions and Eu3+ doping induced promotion thermal-decomplexing between citrate ions and calcium ions. The luminescent CaF2 nanoparticles obtained using this protocol should be promising candidates for use in many bio-related applications.

Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF₂ Nanoparticles.

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F− ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F− ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F− ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

Investigation of anti-bacterial activity and cytotoxicity of calcium fluoride nanoparticles

This paper details about the isolation of Calcium fluoride nanoparticles (CaF2 Nps) through facile co-precipitation method. As-obtained nanoparticles were characterized using XRD, FESEM, AFM, Zeta potential measurements, etc. Further, we evaluated the antibacterial activity of CaF2 Nps against both gram negative (Escherichia coli, Pseudomonas aeruginosa) and gram positive (Bacillus badius, Staphylococcus aureus) bacterial strains. The in-vitro toxicity of CaF2 Nps to mammalian cells, normal African green monkey Chlorocebus kidney epithelial cell line (Vero) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and characterized using phase contrast microscopy. The minimum inhibitory concentration (MIC) values of these nanoparticles towards the prokaryotic micro-organisms were found to be considerably lower than many other nanoparticles and antibiotics. Further the nanoparticles were found to be nontoxic against eukaryotic normal Vero cells. The selective toxicity of CaF2 Nps to prokaryotic bacterial pathogen compared to eukaryotic cell suggests that CaF2 Nps can be used as an excellent antibacterial agent.

A facile synthesis of CaF2:Eu2+ nanoparticles using citrate-stabilized Au catalysts

Europium doped calcium fluoride (CaF2:Eu2+) nanoparticles have been synthesized by hydrothermal method in which NaBH4 is added as reductant and citrate-stabilized gold (Cit-Au) nanoparticles are used as catalyst. The microstructure of CaF2:Eu2+ is investigated by X-ray power diffraction (XRD), energy dispersion spectrum (EDS), and selected area electron diffraction (SAED). Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) have shown that the CaF2:Eu2+ nanoparticles are about 60 nm. Lattice fringes observed in high-resolution TEM further displayed high crystallinity of the CaF2:Eu2+ nanoparticles and Cit-Au NPs. An intensive and broad emission peaked at 425 nm due to 4f7 – 4f65d1 transition of Eu2+ ions is observed. The 4f7(8S7/2) → 4f65d1(t2g)optical transitions exhibit a characteristic “staircase’’ spectrum from 330 nm to 380 nm. The effect of gold concentrations on emission of CaF2:Eu2+ has also been investigated.

Enhancement of polar crystalline phase formation in transparent PVDF-CaF2 composite films

We consider the influence of calcium fluoride (CaF2) nanoparticles on the crystalline phase formation of poly(vinylidene fluoride) (PVDF) for the first time. The transparent PVDF-CaF2 composite films were prepared by casting on PET substrates using N,N-dimethylacetamide (DMAc) as a solvent. It was found that CaF2 promoted the formation of polar crystalline phase of PVDF in composites, whereas nonpolar α-phase was dominant in the neat PVDF film prepared at the same condition. The portion of polar crystalline phase increased in proportional to the weight fraction of CaF2 in the composite films up to 10wt%. Further addition of CaF2 suppressed completely the α-phase formation. Polar crystalline phase observed in as-cast composite films was a mixture of β- and γ-polymorph structures. It was also shown that much ordered γ-phase could be obtained through thermal treatment of as-cast PVDF-CaF2 composite film at the temperatures above the melting temperature of the composite films, but below that of γ-phase.

Refractive index measurement of nanoparticles by immersion refractometry based on a surface plasmon resonance sensor

Accurate determination of the refractive index of nanoparticles has important ramifications for applications, such as pharmaceuticals, cosmetics, paints, textiles, and inks. We describe a new method to determine the refractive index of nanoparticles by immersion refractometry with a surface plasmon resonance sensor. With this method, the refractive index of the nanoparticles is perfectly matched with that of the surrounding liquid. We demonstrate this method for calcium fluoride nanoparticles that have an average diameter of 100nm; the results achieve an accuracy of better than 0.002 refractive index units.

Co-precipitation synthesis and self-reduction of CaF2:Eu2+ nanoparticles using different surfactants

Europium doped Calcium fluoride (CaF2:Eu2+) nanoparticles have been synthesized by co-precipitation method using different surfactants, in which anhydrous ethanol was used as solvent and the nanoparticles was sintered in air. The self-reduction was observed in the as-prepared CaF2:Eu2+ nanoparticles and can be explained by charge compensation model based on the substitution. Scanning electron microscope (SEM) and X-ray power diffraction (XRD) showed that the nanoparticles were about 50nm⿿1μm and in a single phase. A broad emission centered at 425nm due to Eu2+ 4f7⿿4f65d1 transition has been observed with excitation bands between 337 and 385nm by the fluorescence spectrometer. The corresponding excitation spectra showed a wide excitation range in the violet region due to 4f7(8S7/2)⿿4f65d1(t2g) The luminescent properties of the phosphor was thoroughly examined. Furthermore, the effect of using different surfactants on the sizes of CaF2:Eu2+ nanoparticles, related mechanisms was also investigated.

Nanoscale "fluorescent stone": Luminescent Calcium Fluoride Nanoparticles as Theranostic Platforms.

Calcium Fluoride (CaF2) based luminescent nanoparticles exhibit unique, outstanding luminescent properties, and represent promising candidates as nanoplatforms for theranostic applications. There is an urgent need to facilitate their further development and applications in diagnostics and therapeutics as a novel class of nanotools. Here, in this critical review, we outlined the recent significant progresses made in CaF2-related nanoparticles: Firstly, their physical chemical properties, synthesis chemistry, and nanostructure fabrication are summarized. Secondly, their applications in deep tissue bio-detection, drug delivery, imaging, cell labeling, and therapy are reviewed. The exploration of CaF2-based luminescent nanoparticles as multifunctional nanoscale carriers for imaging-guided therapy is also presented. Finally, we discuss the challenges and opportunities in the development of such CaF2-based platform for future development in regard to its theranostic applications.

Calcium fluoride nanoparticles induced suppression of Streptococcus mutans biofilm: an in vitro and in vivo approach.

Biofilm formation on the tooth surface is the root cause of dental caries and periodontal diseases. Streptococcus mutans is known to produce biofilm which is one of the primary causes of dental caries. Acid production and acid tolerance along with exopolysaccharide (EPS) formation are major virulence factors of S. mutans biofilm. In the current study, calcium fluoride nanoparticles (CaF2-NPs) were evaluated for their effect on the biofilm forming ability of S. mutans in vivo and in vitro. The in vitro studies revealed 89 % and 90 % reduction in biofilm formation and EPS production, respectively. Moreover, acid production and acid tolerance abilities of S. mutans were also reduced considerably in the presence of CaF2-NPs. Confocal laser scanning microscopy and transmission electron microscopy images were in accordance with the other results indicating inhibition of biofilm without affecting bacterial viability. The qRT-PCR gene expression analysis showed significant downregulation of various virulence genes (vicR, gtfC, ftf, spaP, comDE) associated with biofilm formation. Furthermore, CaF2-NPs were found to substantially decrease the caries in treated rat groups as compared to the untreated groups in in vivo studies. Scanning electron micrographs of rat's teeth further validated our results. These findings suggest that the CaF2-NPs may be used as a potential antibiofilm applicant against S. mutans and may be applied as a topical agent to reduce dental caries.

Effect of doping of calcium fluoride nanoparticles on the photoluminescence properties of europium complexes with benzoic acid derivatives as secondary ligands and 2-aminopyridine as primary ligand

The present article reports the synthesis of three Eu(III) complexes [Eu(BA)3(2-ap)] (1), [Eu(HBA)3(2-ap)] (2) and [Eu(ABA)3(2-ap)] (3) (BA=benzoic acid, HBA=2-hydroxy benzoic acid, ABA=2-amino benzoic acid and 2-ap=2-aminopyridine) carried out in ethanol solution. The complexes were further doped with CaF2 nanoparticles and a change in the photoluminescence properties was observed. The compositions and structural investigation of the complexes were determined by elemental analysis and Fourier transform infrared spectroscopy (FTIR) which suggest the coordination of ligands with the central Eu(III) ion. The optical properties of the complexes were studied by Ultraviolet Visible absorption spectroscopy (UV–Vis) and photoluminescence studies (PL). The relative PL intensity was enhanced in the Eu(III) complexes doped with CaF2 nanoparticles as compared to the pure Eu(III) complexes, however the increase in intensity varied in the order of ligands ABA>HBA>BA. The photoluminescence lifetime decay curves also revealed the longer lifetime (τ) and higher quantum efficiency (η) for europium complexes with ABA ligands suggesting the efficient energy transfer and better sensitizing ability of the ligand to europium ion. The morphology of the synthesized compounds were studied by Scanning Electron Microscopy (SEM) revealing spherical morphology with agglomeration of the nanoparticles.