Vaterite Phase Research Articles

REUSE OF WASTE CRAB SHELLS FOR SYNTHESIS OF CALCIUM CARBONATE AS A CANDIDATE BIOMATERIAL

The crab shell (Portunus Pelagicus) wastes are constituted of major calcium carbonate (account for 70 wt. %) and have the potential to reuse as a starting biomaterial for precipitated calcium carbonate (PCC) products. The purpose of the present work was to synthesize PCC powder using crab shells based on the gas-solid-liquid carbonation route. In this experiment, crab shell powder was prepared by washing, drying, and subsequent grinding. The resulting powder was then calcined at 900 ℃ for 5 h before being used for the synthesis of the PCC product. Later, the calcined crab shell powder was dissolved with 2M HNO3 solution in a glass beaker with the pH solution of 12 set up by adding NH4OH. The solution was subsequently stirred magnetically for 30 min. The carbonation process ended when the PCC solid was obtained at a pH of 7. The crab shell powder, crab shell powder after calcination, and the obtained PCC solid were then characterized using XRD, SEM-EDX, and FTIR methods, respectively. The resulting PCC product has been shown to have calcium carbonate with the major vaterite phase. This experimental work demonstrated the potential application of crab shells for a low-cost biomaterial of future medical applications.

Lignin-Induced CaCO3 Vaterite Structure for Biocatalytic Artificial Photosynthesis.

The vaterite phase of CaCO3 exhibits unique characteristics, such as high porosity, surface area, dispersivity, and low specific gravity, but it is the most unstable polymorph. Here, we report lignin-induced stable vaterite as a support matrix for integrated artificial photosynthesis through the encapsulation of key active components such as the photosensitizer (eosin y, EY) and redox enzyme (l-glutamate dehydrogenase, GDH). The lignin-vaterite/EY/GDH photobiocatalytic platform enabled the regeneration of the reduced nicotinamide cofactor under visible light and facilitated the rapid conversion of α-ketoglutarate into l-glutamate (initial conversion rate, 0.41 mM h-1; turnover frequency, 1060 h-1; and turnover number, 39,750). The lignin-induced vaterite structure allowed for long-term protection and recycling of the active components while facilitating the photosynthesis reaction due to the redox-active lignin. Succession of stability tests demonstrated a significant improvement of GDH's robustness in the lignin-vaterite structure against harsh environments. This work provides a simple approach for solar-to-chemical conversion using a sustainable, integrated light-harvesting system.

Structure and phase analysis of calcium carbonate powder prepared by a simple solution method

This paper focused on the analysis of the crystal structure and phase transformation of CaCO3 synthesized by simple solution method from 0.5 M Ca(NO3)2 precursor and 0.5 M Na2CO3 precipitant at ambient temperature (300 K). The pH of the sample solution at various reaction times of 5, 10, 15, and 30 min were measured and correlated with the supersaturating condition in the presence of the Na2CO3 which is responsible for vaterite phase formation. The formation of the polymorph structure of obtained CaCO3 powders was characterized using powder X-ray diffraction patterns and their crystal structure and phase transformation were evaluated using the Rietveld refinement method. Moreover, the qualitative analysis of the CaCO3 powders phase was conducted by Fourier Transform Infrared (FTIR) spectroscopy to evaluate the effect of reaction time correlated with their crystal formation. The XRD analysis showed that the vaterite formation was 89 % at a reaction time of 15 min and confirmed also by FTIR that the amount of vaterite increased due to the effect of increasing reaction time. The crystallite size of vaterite was stable at 36 nm at the reaction time of 15 and 30 min. The morphology of the CaCO3 powders obtained from Scanning Electron Microscope (SEM) was spherical with sizes of 2–5 μm. It was highlighted that the supersaturating condition started occurred at a reaction time of 15 min at pH 7.88 which was responsible for vaterite formation took place. It was concluded that the amount of precipitant (Na2CO3) and reaction times play an important role to determine the saturation of carbonate source to allow vaterite phase formation of CaCO3 powders to occur.

Comprehensive Profiling of Microbiologically Induced CaCO3 Precipitation by Ureolytic Bacillus Isolates from Alkaline Soils.

Microbiologically induced CaCO3 precipitation (MICP) is a well-known bio-based solution with application in environmental, geotechnical, and civil engineering. The significance of the MICP has increased explorations of process efficiency and specificity via natural bacterial isolates. In this study, comprehensive profiling of five soil ureolytic Bacillus strains was performed through a newly formed procedure that involved six steps from selection and identification, through kinetic study, to the characterization of the obtained precipitates, for the first time. To shorten the whole selection procedure of 43 bioagents with the MICP potential, Standard Score Analysis was performed and five selected bacteria were identified as Bacillus muralis, B. lentus, B. simplex, B. firmus, and B. licheniformis by the MALDI-TOF mass spectrometry. Despite following the targeted activity, kinetic studies were included important aspects of ureolysis and the MICP such as cell concentration, pH profiling, and reduction in calcium ion concentration. At the final step, characterization of the obtained precipitates was performed using FTIR, XRD, Raman, DTA/TGA, and SEM analysis. Although all tested strains showed significant potential in terms of precipitation of calcite or calcite and vaterite phase, the main differences in the MICP behavior can be observed at the bacterial strain level. B. licheniformis showed favorable behavior compared to the reference Sporosarcina pasteurii DSM 33.

Insights into the influence of cell concentration in design and development of microbially induced calcium carbonate precipitation (MICP) process.

Microbially induced calcium carbonate precipitation (MICP) process utilising the biogeochemical reactions for low energy cementation has recently emerged as a potential technology for numerous engineering applications. The design and development of an efficient MICP process depends upon several physicochemical and biological variables; amongst which the initial bacterial cell concentration is a major factor. The goal of this study is to assess the impact of initial bacterial cell concentration on ureolysis and carbonate precipitation kinetics along with its influence on the calcium carbonate crystal properties; as all these factors determine the efficacy of this process for specific engineering applications. We have also investigated the role of subsequent cell recharge in calcium carbonate precipitation kinetics for the first time. Experimental results showed that the kinetics of ureolysis and calcium carbonate precipitation are well-fitted by an exponential logistic equation for cell concentrations between optical density range of 0.1 OD to 0.4 OD. This equation is highly applicable for designing the optimal processes for microbially cemented soil stabilization applications using native or augmented bacterial cultures. Multiple recharge kinetics study revealed that the addition of fresh bacterial cells is an essential step to keep the fast rate of precipitation, as desirable in certain applications. Our results of calcium carbonate crystal morphology and mineralogy via scanning electron micrography, energy dispersive X-ray spectroscopy and X-ray diffraction analysis exhibited a notable impact of cell number and extracellular urease concentration on the properties of carbonate crystals. Lower cell numbers led to formation of larger crystals compared to high cell numbers and these crystals transform from vaterite phase to the calcite phase over time. This study has demonstrated the significance of kinetic models for designing large-scale MICP applications.

Crack sealing evaluation of self-healing mortar with Sporosarcina pasteurii: Influence of bacterial concentration and air-entraining agent

Microbial induced calcium carbonate precipitation has been recognized as a novel pathway to repair concrete cracks. This study aimed to explore the application of Sporosarcina pasteurii in self-healing mortar preparation, and further investigate the influence of bacterial concentration and air-entraining agent content on crack sealing performance. X-ray diffraction and scanning electron microscope tests were carried out to identify the calcium carbonate in vaterite phase for biomineralization precipitations of S. pasteurii which was utilized for self-healing mortar beam specimens production. Subjected to 3-point-bending test, a V-shape crack was induced from the beam bottom with 0.4 mm width which can be automatically healed due to bacteria metabolic activity. Four different S. pasteurii concentrations, i.e., 0, 2 × 105, 2 × 106 and 2 × 107 cells/ml, were comparatively studied with respect to self-healing mortar property. In general, the higher bacterial concentration corresponded to faster crack healing and 2 × 106 cells/ml was deemed as the proper bacterial concentration. Afterwards, self-healing mortar with various air-entraining agent contents (0%, 0.005%, 0.01%, 0.015% and 0.02% of cementitious material) was also discussed, implying that best flexural strength regain is achieved at 0.01% air-entraining agent. Finally, the crack filling crystals were examined to find bacterial imprints leaving on the surface of calcium carbonate.

Maximizing the red emission of CaCO3:Eu3+ phosphors by using a Taguchi L9 orthogonal design

This work reports the structural, morphological and luminescent properties of CaCO3:Eu3+ phosphors synthesized by a precipitation method. Those phosphors were made under different conditions such as: mole ratio for Ca:CO3 (1:1, 1:2 and 1:3), pH (from 7 to 11), temperature (from 25 to 75 °C) and Eu3+ concentration (from 1 to 5 at.%). We used a Taguchis’ design (orthogonal L9 array) to find the optimum conditions that allow the synthesis of CaCO3:Eu3+ phosphors with the highest red emission intensity. After this, only 9 samples were synthesized. According to the X-ray diffraction patterns, all the samples presented a mixture of vaterite and calcite phases. Different morphologies were also observed by scanning electron microscopy such as porous microspheres, stacked pillars, microbelts or coalesced particles. We also measured the photoluminescence (PL) spectra for these 9 samples and calculated their integrated PL intensity. Those values were used as input in the ANOVA analysis, which was employed to find the critical parameters that affect the emission intensity of the samples. As a result, we found that the temperature and the mole ratio of Ca:CO3 are the most influential factors on the luminescent properties. We also employed the McCamy formula to calculate the correlated color temperature (CCT) and obtained values in the range of 1763–2797 K, which correspond to warm lighting sources. Moreover, the phosphor with the highest orange/red emission intensity presented a color purity of 96.66%, which is close to that used by the National Television Standard Committee (NTSC). Hence, the results presented here demonstrated that the CaCO3:Eu3+ phosphors could be used as a red-emitting component in White LEDs excited with UV chips.

Controllable crystallization of pure vaterite using CO2-storage material and different Ca2+ sources

The controllable synthesis of pure vaterite with the good properties and broad application prospects is considered as an important, yet a challenging task because the product properties are greatly affected by reaction conditions. In the present work, the controllable synthesis of pure vaterite crystals was explored with four different Ca2+ sources including CaCl2, Ca(NO3)2, CaBr2 and Ca(Ac)2 using an CO2-storage material (CO2SM) prepared by an indirect CO2 utilization approach as the CO32− source. The effects of five major reaction conditions including reaction medium, hydrothermal reaction temperature, hydrothermal reaction time, Ca2+ concentration and sources, and pH and conductivity on the crystallization of CaCO3 were systemically investigated. It is found that the amounts of CO2SM required for the formation of pure vaterite phase are in the order of CaBr2 (20 g/L CO2SM) > Ca(NO3)2 (16 g/L CO2SM) > Ca(Ac)2 (8 g/L CO2SM) due to the effects of ethylenediamine (EDA), diethylene glycol (DEG) and their anions. Especially, vaterite was not found in CaCl2 system. The effects of Ca2+ sources on the crystal phase composition of CaCO3 are revealed for the controllable synthesis of CaCO3 crystals. Our work not only provides a controllable synthesis method of pure vaterite, but also an indirect CO2 utilization strategy.

Curcumin and quercetin as templates in the in vitro biomineralization of CaCO3: A comparative study on phase modulation

Biomineralization of calcium-based biominerals is influenced by organic molecules containing oxygen donor atoms. In this work, we were able to synthesize and stabilize the least stable crystalline phase of CaCO3, vaterite, using the biologically useful organic molecule curcumin as the template. The vaterite phase formed was stable in solution at least for 18 h. A comparative study with chemically similar molecule quercetin, a flavonoid, was performed. Though quercetin as a template could not stabilize the vaterite phase, an interesting observation was made in terms of the morphology of the calcite particles obtained. A dumbbell-shaped morphology, different from the usual rhombohedral morphology of the calcite crystals was obtained under ambient conditions. The maturation of the CaCO3 crystals in solution with time was studied to observe the changes in terms of phase and morphology of the particles. Additionally, extended studies were performed to investigate the influence of the change in parameters such as; template concentration, the sequence of addition, temperature and ionic strength on the phase, morphology and size of the particles in the presence of both the templates.

Эволюция спектральных и структурных характеристик ортоборатов La-=SUB=-0.98-x-=/SUB=-Lu-=SUB=-x-=/SUB=-Eu-=SUB=-0.02-=/SUB=-BO-=SUB=-3-=/SUB=-

The structure, IR absorption, luminescence, and luminescence excitation spectra of La0.98xLuxEu0.02 BO3 orthoborates synthesized at 970°C were studied at 0 ≤ x ≤ 0.98. An increase in х leads to a sequential change of the structural state of the orthoborates. At first, the compound has the aragonite structure. Then, it becomes two-phase and contains the aragonite and vaterite phases. With a further increase in х, the compounds have the vaterite structure, then the vaterite and calcite structure, and, finally, the calcite structure. Correspondence between the structure and spectral characteristics of these compounds was established. Luminescence spectra were investigated at different wavelengths of exciting light. This allowed obtaining information on the structure of a near-surface layer and the bulk of microcrystals of the investigated samples. It is shown that the vaterite phase arises in the bulk of microcrystals of samples that have the aragonite structure.

Особенности спектральных характеристик различных структурных модификаций Lu-=SUB=-1-x-=/SUB=-RE-=SUB=-x-=/SUB=-BO-=SUB=-3-=/SUB=-

The structure, IR absorption and luminescence spectra of the microcrystals of Lu1-xEuxBO3, Lu0.99-xTbxEu0.01BO3, and Lu0.99−xYxEu0.01BO3 orthoborates (0 ≤ x ≤ 0.25) synthesized at 970°С were studied. An increase in х leads to a sequential change of the structural state of the orthoborates. At х ≤ 0.07 – 0.09, the compounds form a solid solution with the calcite structure and microcrystal size of 8 – 20 µm. Then, they become two-phase: the vaterite phase arises along with the calcite structure. At х ≥ 0.2 – 0.25, the entire bulk of a sample has the vaterite structure. A correspondence between the structure and spectral characteristics of these compounds was established. Luminescence spectra were investigated at different wavelengths of exciting light. This allowed obtaining information on the structure of a near-surface layer and the bulk of microcrystals of the investigated samples. It is shown that the vaterite phase arises both in the bulk of large microsrystals (8 – 20 µm) and in the form of small microsrystals (1 – 2 µm).

Influence of Cerium on the Spectral and Structural Characteristics of LuBo3(Ce,Tb)

Studies of the structure, IR absorption spectra, luminescence spectra, and excitation of luminescence of Ce3+ and Tb3+ ions in crystals of solid solutions of Lu1 – x – yCexTbyBO3 at 0 ≤ x ≤ 0.01 and 0.07 ≤ y ≤ 0.16 have been performed. It has been shown that the solid solution Lu1 – yTbyBO3 synthesized at T = 970°C has the structure of calcite at 0 ≤ y ≤ 0.07, at y ≥ 0.16—the structure of vaterite, and in the range 0.07 < y < 0.16 is two-phase. It has been found that additional doping of 0.5–1 at % Ce3+ of two-phase Lu1 ‒ yTbyBO3 samples, in which the proportion of the vaterite phase does not exceed ∼20%, leads to a significant reduction of the vaterite phase. It has been shown that Ce3+ ions can be used as structurally sensitive and optically active marks in the analysis of the structural state of rare earth element orthoborates.

Structure and luminescent properties of CaCO3:Eu3+ phosphors prepared in ethylene glycol-water mixed solvent

Abstract A series of CaCO3:Eu3+ phosphors with novel morphology were successfully synthesized in an ethylene glycol–water system by a simple carbonation method without using any surfactant, catalyst, or template. It is indicated that the ratio of mixed solvent and reaction temperature play an important role in the morphology, structure, and the luminescence properties of the CaCO3:Eu3+ phosphors. Various morphologies of CaCO3:Eu3+ phosphors, such as rod-like, polyhedron, dendritic, spindle, and rhombohedral, can be obtained only by just adjusting the ratio of mixed solvent or reaction temperature. In addition, high ratio of ethylene glycol in mixed solvent and low temperature favor the formation of metastable vaterite phase. Furthermore, the photoluminescent intensity, the ratio of red-orange of Eu3+ ions change with the morphological and structural changes of the CaCO3:Eu3+ crystal, which is attributed to the variation of the environment around Eu3+ ions. The symmetry and surrounding environment of Eu3+ ions in the CaCO3 matrix are analyzed by Judd Ofelt theory. Finally, the possible formation mechanism of CaCO3:Eu3+ phosphors has been also discussed.

Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement.

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to form a cement paste and study how mechanical strength is created during the setting reaction. In-situ X-ray diffraction (XRD) was used to monitor the transformation of amorphous calcium carbonate (ACC) and vaterite phases into calcite and a rotational rheometer was used to monitor the strength evolution. There are two characteristic timescales of the strengthening of the cement paste. The short timescale of the order 1 h is controlled by smoothening of the vaterite grains, allowing closer and therefore adhesive contacts between the grains. The long timescale of the order 10–50 h is controlled by the phase transformation of vaterite into calcite. This transformation is, unlike in previous studies using stirred reactors, found to be mainly controlled by diffusion in the liquid phase. The evolution of shear strength with solid volume fraction is best explained by a fractal model of the paste structure.

The Effect of Variation Concentration Sodium Hydroxide (NaOH) on the Structure of Calcium Carbonate (CaCO&lt;sub&gt;3&lt;/sub&gt;) Based on Natural Sand

Utilization of abundant natural resources has been an important issue in recent years. CaCO3 was successfully prepared from natural sand by purification bubbling methods with flowing CO2 gas into an aqueous Ca(OH)2 medium with NaOH as catalyst. In the experimental set-up, natural sand was dissolved with different NaOH concentrations of 5, 6, and 7 M, respectively. In the carbonation process, room temperature is used as reaction temperature, while CO2 gas flow rate was carried out at 5 SCFH (Square Cubic Feet per Hour) and the speed of stirring was kept constant. The reaction was occurred around 5 minutes to produce precipitation of CaCO3. The influences of reaction parameters such as the various concentrations of NaOH were studied by using X-ray fluorescence spectrometer (XRF), X-ray powder diffraction (XRD), Particle size analyzer (PSA), and Scanning Electron Microscopy (SEM) to investigate the element composition, crystal structure, size of particles, and morphology of particles, respectively. The results showed that NaOH concentration effected not only on the phases of CaCO3 but also on the microstructure and morphology of CaCO3. Calcite and vaterite phases are observed which have a rhombic and spherical morphology in micro-scale, respectively.

Preparation and characterization of phosphate-stabilized amorphous calcium carbonate nanoparticles and their application in curcumin delivery

Nano-sized amorphous calcium carbonate (ACC) have a great potential for drug transport and drug delivery because of their high drug loading capacity, excellent biocompatibility and biodegradability. However, ACC is the thermodynamically least stable phase of calcium carbonate, and such thermal metastability often transforms it into more stable vaterite or calcite phases, so the inhibition of the phase transformation of ACC is of great significance for its application in drug delivery systems. Herein, phosphate as a morphology controlling additive was introduced to stabilize the metastable ACC. The results showed that the composite nanoparticles (named here the ACCP) with narrow size distribution located at approximately 128 nm (measured by dynamic light scattering) were obtained, when Ca2+ concentration and C/P were 10 mM and 7/3 respectively, prepared at 30 °C for 10 min. The powdered X-ray diffraction (XRD) results showed that phosphate has an excellent ability to stabilize ACC, and even after storage for 60 days at room temperature, the structure of ACCP remains amorphous. The in vitro drug release tests showed that ACCP nanoparticles had a high curcumin (Cur) loading capacity and a sustained drug release property. Moreover, the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) radical scavenging activity assay showed that ACCP-encapsulating strategy could effectively prevent the decomposition of Cur. In vitro cytotoxicity tests demonstrated that the resultants have excellent biocompatibility. Therefore, the as-prepared ACCP nanoparticles are promising for drug delivery applications.

Development of a bone substitute material based on additive manufactured Ti6Al4V alloys modified with bioceramic calcium carbonate coating: Characterization and antimicrobial properties

This investigation shows that composite structures based on additive manufactured electron beam melted Ti6Al4V scaffolds coated with calcium carbonate particles can be used as a potential biocomposites for bone substitutes. A continuous bioceramic coating of CaCO3 was deposited on additive manufactured titanium alloy under the influence of ultrasound. XRD analysis revealed the formation of a mixture of calcite and vaterite phases. CaCO3 coating led to decreasing roughness of additively manufactured (AM) scaffolds and improved surface hydrophilicity. In vitro assay demonstrated enhanced inorganic bone phase formation on the surface of CaCO3-coated AM scaffolds compared to as-manufactured ones. The short-term adhesion of S. aureus onto sample surface was evaluated by fluorescent microscopy 0, 3, and 72 h after cell seeding. It revealed that the surface modification resulted in the decreased number of bacteria attached to the surface after CaCO3 deposition. The morphology, roughness, solubility and superhydrophilic character of the CaCO3 coated EBM-manufactured Ti6Al4V alloy surface are suggested as factors contributing to preventing S. aureus adhesion. Thus, the developed biocomposites based on additively manufactured Ti6Al4V alloy scaffolds and CaCO3 coating can be successfully used in bone tissue regeneration providing the effective growth of inorganic bone phase and preventing the bacteria adhesion.

Effect of pH and temperatures on the fast precipitation vaterite particle size and polymorph stability without additives by steamed ammonia liquid waste

This paper reports on the effect of pH and temperature on size and polymorph stability of calcium carbonate (vaterite) formed without use of additives by Steamed ammonia liquid waste. The effect of the reaction temperature (20–80 °C), the initial Steamed ammonia liquid waste pH (1.5–12.1) and the stirring speed (800 and 1200 rpm/min) on the preparation of CaCO3 with respect to the particle size and polymorph stability of final product were investigated. The obtained different CaCO3 size and polymorphs were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and a Laser particle size analyzer (LPSA). The phase of vaterite transformed to calcite with increasing temperature 20 to 80 °C. The SEM and LPSA show that the CaCO3 particle size increased from nano to several micron with the increase of temperature. When the initial CaCl2 aqueous solution in low pH (1.5 and 2.6), nano-micro porous spherical vaterite can be obtained. When the initial CaCl2 aqueous solution in high pH (11.7 and 12.1), preparation of CaCO3 is mainly for the vaterite contains a small amount of calcite and the size particle increased. The possible mechanisms for the porous vaterite CaCO3 formation have also been discussed. Since requirements for the physical properties of CaCO3 particles are diverse for industrial and medical applications, it is important to understand CaCO3 crystallization behavior for tailored particle synthesis.

Vaterite submicron particles designed for photodynamic therapy in cells.

Calcium carbonate (CaCO3) is one of the most abundant materials in the world. It has several different crystalline phases as present in the minerals: calcite, aragonite and vaterite, which are anhydrous crystalline polymorphs. Regarding the preparation of these microparticles, the most important aspect is the control of the polymorphism, particle size and material morphology. This study aimed to develop porous microparticles of calcium carbonate in the vaterite phase for the encapsulation of chloro-aluminum phthalocyanine (ClAlPc) as a photosensitizer (PS) for application in Photodynamic Therapy (TFD). In this study, spherical vaterite composed of microparticles are synthesized by precipitation route assisted by polycarboxylate superplasticizer (PSS). The calcium carbonate was prepared by reacting a mixed solution of Na2CO3 with a CaCl2 solution at an ambient temperature, 25 °C, in the presence of polycarboxylate superplasticizer as a stabilizer. The photosensitizer was incorporated by adsorption technique in the CaCO3 microparticles. The CaCO3 microparticles were studied by scanning electron microscopy, steady-state, and their biological activity was evaluated using in vitro cancer cell lines by trypan blue exclusion method. The intracellular localization of ClAlPc was examined by confocal microscopy. The CaCO3 microparticles obtained are uniform and homogeneously sized, non-aggregated, and highly porous microparticles. The calcium carbonate microparticles show an average size of 3 μm average pore size of about 30-40 nm. The phthalocyanine derivative loaded-microparticles maintained their photophysical behavior after encapsulation. The captured carriers have provided dye localization inside cells. The in vitro experiments with ClAlPc-loaded CaCO3 microparticles showed that the system is not cytotoxic in darkness, but exhibits a substantial phototoxicity at 3 μmol.L-1 of photosensitizer concentration and 10 J.cm-2 of light. These conditions are sufficient to kill about 80 % of the cells. All the performed physical-chemical, photophysical, and photobiological measurements indicated that the phthalocyanine-loaded CaCO3 microparticles are a promising drug delivery system for photodynamic therapy and photoprocesses.

Влияние церия на спектральные и структурные характеристики LuBO-=SUB=-3-=/SUB=-(Ce, Tb)

The structure, IR absorption, luminescence and luminescence excitation spectra of Ce3+ and Tb3+ ions have been studied in the crystals of Lu1−x−yCexTbyBO3 solid solutions at 0 ≤ x ≤ 0.01, 0.07 ≤ y ≤ 0.16. It has been shown that Lu1−yTbyBO3 solid solution synthesized at Т = 970°С has the structure of a calcite at 0  y ≤ 0.07, the structure of a vaterite at y ≥ 0.16, and is two-phase in a range of 0.07  y &lt; 0.16. It has been determined that additional alloying of two-phase Lu1-yTbyBO3 samples with the vaterite phase fraction of not more than ~ 20 % with 0.5 – 1 at.% of Ce3+ leads to a significant decrease in the amount of the vaterite phase. It has been demonstrated that Ce3+ ions can be used as structure-sensitive and optically active marks when analyzing the structural state of rare earth orthoborates.