Journal of Crystal Growth最新文献

Amorphous Ca–Mg carbonate (ACMC) is an important precursor phase of carbonate, and it is of great significance for understanding the process of microbial induced carbonate mineralization and the synthesis of new biomimetic mineral materials. Currently, the biomineralization role of ACMC remains controversial. Therefore, this study conducted experiments on ACMC-induced mineralization under the action of bacteria and their extracellular polymeric substances (EPS). The results show that bacteria and their secretion of EPS contributed to the formation and stability of hydrated Mg-rich ACMC, and affected the polymorphism and morphology of minerals. Bacterial cells and EPS could provide nucleation sites for ACMC precipitation, and they could also be easily adsorbed or encapsulated by ACMC and mineral particles. EPS, Mg²⁺, or both were conducive to the formation of aqueous amorphous phase, and could stabilize ACMC through surface adsorption and incorporation. The results of this study help to reveal the biomineralization role of ACMC and promote understanding of the formation and transformation process of Ca-Mg carbonate.

Solid solutions based on (Eu_,Gd)Sc₃(BO₃)₄ (C2/c) and Gd_0.25Sc_0.75BO₃ (R $\overline{3}$) in the EuSc₃(BO₃)₄-GdSc₃(BO₃)₄ system were studied. Synthesis at 1250 °C provides wide homogeneity regions which are stable at room temperature. Melt-solution crystallization of both compounds from LiBO₂-LiF flux was shown. All the obtained samples have luminescence characteristic of Eu³⁺ with a largest peak at 615 nm corresponding to the ⁵D₀ → ⁷F₂ transition. In this series the luminescence intensity monotonically increases with an increase of Eu content. The largest quantum yield of luminescence (53 %) in the EuSc₃(BO₃)₄-GdSc₃(BO₃)₄ system is demonstrated by EuSc₃(BO₃)₄ sample.

Bismuth Selenide has gained a great deal of attention as a thermoelectric material owing to its lower toxicity compared to Bi₂Te₃ based materials. In this work, Sulfur substitution in Bi₂Se₃ is carried out by the vertical Bridgman method and the influence of Sulfur on the structural, electrical and thermal properties of Bi₂Se₃ was studied. The thermoelectric figure of merit (ZT) was calculated from electrical conductivity, Seebeck coefficient and thermal conductivity, which were measured from 303 K to 773 K. Sulfur incorporation did not improve the electrical conductivity of Bi₂Se₃ but proved to be beneficial in improving the Seebeck coefficient and reducing thermal conductivity. Hence, the calculated figure of merit of Bi₂Se_2.7S_0.3 crystal comes out to be 0.72 at 543 K, which is higher than that of pure Bi₂Se₃ crystal, which is 0.31 at 533 K.

The present work will systematically study the effect of different linear antenna microwave plasma enhanced chemical vapor deposition (LACVD) processing parameters on the optimal deposition of the diamond films. The low pressure and low temperatures of LACVD growth conditions is expected to deposit diamond films on otherwise reactive gallium nitride (GaN) surfaces, without any intermediate nitride buffer layer. First, the distances between the quartz tube and the samples put on the stage are varied (3–15 cm), which has a direct impact on the substrate temperature (415°–300 °C). Thereafter, the microwave input power was also altered (1.5–2.8 kW) to attain low substrate temperatures. It was found that 300 °C is the temperature limit, which can be attained by heating only with microwave plasma when the substrates are kept farthest (15 cm) away from the liner antenna quartz tube. An additional heater was used under the stage for rapidly achieving such minimum substrate temperature of 300 °C. Substrate heater was used for efficient growth of the diamond phase while using pulse mode frequency of microwave power input for optimization of the diamond films. The microstructure (plate-like and cauliflower-like) of the deposited nanocrystalline diamond (NCD) films and the cross-sectional images for thickness measurements was observed under the scanning electron microscope and the elemental analysis of the film surfaces was done by electron diffraction spectroscopy. Moreover, the diamond film quality and crystallinity were evaluated by Raman spectroscopy with 488 nm laser light. Diamond-on-GaN film results were compared with conventional Si substrate. Different LACVD reactor parameters like, antenna to stage distances, microwave input power in continuous wave mode, and growth temperatures have significant impacts on the grown films, both in terms of their quality and microstructure. It was found that the optimum deposition of nanocrystalline diamond film on GaN substrates without its surface etching was possible, under pulse mode (20 kHz, 45 % duty cycle) with 2 kW average input microwave power.

This study describes the RF magnetron sputtering growth of nickel (Ni) doped zinc oxide (ZnO) thin films with nanocolumns (NCs) structures. Using a nickel seed layer, homogeneous and vertically aligned ZnO nanocolumns with a diameter of around 30 nm were successfully grown. The X-ray diffraction (XRD) results confirmed the incorporation of Ni atoms into the ZnO lattice, producing single crystalline structures without secondary phases. High-resolution transmission electron microscopy showed clear lattice planes with a d-spacing value of 3.243 Å corresponding to the wurtzite phase of ZnO. Optimal crystalline quality was achieved by growing the films at 300 °C followed by thermal annealing at 300–500 °C in an oxygen ambient.

The escalating occurrence of antibiotic resistance has focused scientific investigation on the creation of alternative treatments. In this work, an environmentally benign and sustainable method of producing silver nanoparticles (AgNPs) utilizing an aqueous extract from Artocarpus heterophyllus leaves is reported. The study aimed to evaluate the antibacterial and antibiofilm properties of AgNPs against a range of pathogens, specifically Methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. The antioxidant activity of these AgNPs was also determined.

Methods

The biosynthesis of silver nanoparticles was confirmed and characterized using a range of analytical methods. These methods included UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Laser Particle Sizer, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), and X-ray diffraction (XRD) analysis. Broth microdilution method was used to assess their antibacterial activity. A free radical scavenging assay was used to determine their antioxidant activity.

Results

At 471 nm in wavelength, the AgNPs’ peak absorbance was measured. The AgNPs had an average size of 97.3 nm. AgNPs were found to have a face-centered cubic structure according to XRD measurements. The EDX analysis represented elemental silver (Ag⁰) at a concentration of 87.6 %. The synthesized AgNPs possessed antioxidant activity with IC₅₀ value of 35.16 μg/mL. The synthesized nanoparticles demonstrated remarkable antibacterial activity against several bacterial strains, as evidenced by their low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values in the ranges of 62.5 to 125 μg/mL. Furthermore, the AgNPs demonstrated potent anti-biofilm properties, significantly decreasing the formation of biofilms. In addition to these promising antimicrobials, antibiofilm and antioxidant properties.

Conclusions

The results of this study indicate that the environmentally friendly AgNPs that were synthesized have considerable potential as antibacterial and antibiofilm agents; they provide a sustainable substitute for addressing the issue of antibiotic resistance. Their possible application in clinical settings calls for further thorough research.

Single crystals of a novel silver borate nitrate, Ag₁₂(B₉O₁₈)(NO₃)₃ (1), were produced as a byproduct upon preparation of Ag₃B₆O₁₀(NO₃). 1 is hexagonal, (P6₃/m, a = 11.2896(3) Å, c = 11.6693(3) Å); its structure exhibits just a second example of unique [B₉O₁₈]^9– nonaborate anions [9B:6Δ3□:3(<2Δ□>–)<3□>] which can be described as three triborate groups linked in a large cycle. As commonly observed among silver borates, the Ag⁺ cations exhibit strongly anharmonic vibrations which were described using Gram–Chariler series up to 4th order. 1 is characterized by single-crystal X-ray diffraction, variable-temperature powder X-ray diffraction, IR, Raman, and UV–vis-NIR spectroscopy, complex thermal analysis, and DFT calculations. The thermal expansion of 1 is slightly anisotropic (α_a = 15.0, α_c = 17.7 × 10⁻⁶ °C⁻¹ at 200 °C). Upon heating, the compound decomposes with formation of metallic silver and another borate, AgBO₂, which could be earlier prepared only at high oxygen pressure.

The cross-point (Cp), which appears in the vacancy (C_V) and interstitial Si atom (C_I) concentration curves, is a simple controlling factor for ingot growth and provides a final goal to obtain a defect-free Si ingot using general Si melt growth. The importance of Cp is demonstrated using the noncontact crucible method (NOC), which has a relatively small temperature gradient due to an ingot grown inside the melt. The control of temperature gradient G at a constant growth rate v is simple for the actual ingot growth; thus, the present simulated results are expressed by G at a constant v. The concentration at the Cp point becomes smaller as G becomes smaller and finally becomes zero (Cp = 0), in which C_V and C_I are practically zero (C_V=C_I=0). The estimated G and temperature T at Cp = 0 for v = 0.000144 cm s⁻¹ are 6.3, 12.5, and 18.5 K cm⁻¹ and 1216 K (943 °C), 1354 K (1081 °C), and 1371 K (1098 °C), corresponding to each combination. At 1216 K, G should be precisely controlled within 6.3 ± 3 % K cm⁻¹ in the region substantially close to Cp = 0 to maintain the remaining concentration of point defects substantially lower than 1.0 × 10¹³ cm⁻³. G should be changed during growth from larger G to smaller G, such as 6.3 K cm⁻¹, to efficiently grow the ingot within the limited time. The changing point, x of G, is an important key parameter for the timing variation, where x denotes the normalized distance from the growing interface. The initial G is large; thus, the changing point of G approaches the growing interface. The growth condition necessary to obtain a defect-free Si ingot can be demonstrated using the Cp = 0 point, which is fully compatible with the perfect critical point where C_V and C_I are practically zero. The present results are mainly considered using the C_V and C_I concentration curves. However, these results largely help understand the approximate trend of G and v for the growth of defect-free ingot and the relation between Cp and the commonly used critical point between C_V and C_I.

This study presents the controlled growth of 3-Mercaptopropionic acid (MPA)-capped ZnS quantum dots (QDs) using a concentration-modulated single injection hydrothermal method. Employing the Concentration optimization by optical spectra (COOS) method, we optimized the MPA:Zn:S ratios to investigate the influence of the capping agent, cation, and anion for exceptional properties suitable for optoelectronic and sensor applications. CMSIH operates as a single-step synthesis process, reducing processing time and complexity. This streamlined approach not only enhances efficiency but also minimizes the risk of contamination and ensures batch-to-batch consistency in QD production. Its moderate operating conditions, compared to other high-energy methods, also contribute to reduced energy consumption and environmental impact, aligning with sustainable manufacturing practices. Further, X-ray diffraction (XRD) confirmed the Zinc blend (cubic) phase of ZnS, and Fourier-transform infrared spectroscopy (FTIR) validated MPA capping. The QDs exhibited strong quantum confinement, causing a blue shift in absorption peaks compared to bulk ZnS. Higher MPA concentrations ranging from 0.02 M to 0.1 M induced a red shift in the absorption edge due to prolonged reaction times and strong cation binding by MPA. Variations in cation Zn and anion S ratios from 0.02 M to 0.1 M caused blue and red shifts in the absorption edge, respectively. For instance, Zn:S = 0.04:0.01 M increased cation concentrations, reducing QD size up to 0.67 nm, while enhanced anion concentrations Zn:S = 0.04:0.04 M enlarged the QDs size up to 2.35 nm. Remarkably, calculated QD sizes using Brus’ equation were smaller than the Bohr radius, even at an elevated temperature of 95 °C, indicating significant quantum confinement. Luminescence studies revealed reduced luminescence with higher MPA concentrations, increased luminescence intensity with higher cation Zn+ concentrations, and a red shift in the luminescence peak with higher anion S concentrations. As the temperature rises, there is an observable decrease in luminescence intensity. Furthermore, the investigation into the relationship between chemical composition and optical properties of MPA-capped ZnS QDs at elevated temperatures expands understanding of quantum confinement effects. The synthesised unique ultra small ZnS QDs can be used in advanced quantum sensors mainly as radiation detectors.

La₃Ga_5.5Nb_0.5O₁₄ (LGN) crystal is a promising material for optical parametric chirped-pulse amplification (OPCPA) with high laser damage threshold and wide transmission range which is able to achieve high peak power laser. LGN with a diameter of 25 mm was successfully grown by the vertical Bridgman method for the first time and a series of characterizations were performed. The 1.7 µm absorption peak in transmittance spectra of LGN crystal which was caused by the Czochralski technique can be effectively eliminated by the vertical Bridgman method. LGN crystal possesses a high transmittance of 81.3 % in the range of 0.294 ∼ 7.500 μm. The experimental optical band gap of LGN is 4.16 eV which is positively correlated with laser damage threshold. The experimental laser damage threshold of LGN was determined to 1.416 GW/cm² by Nd:YAG. The outstanding thermal properties of LGN indicate that it possesses thermal stability in high energy laser field. This work demonstrates that LGN crystal holds great potential for OPCPA applications and the vertical Bridgman method is proved to be a effective and excellent technique to grow high quality LGN crystal.