X-ray Diffraction Curves Research Articles

Harnessing hyperaccumulator (Brassica oleracea var. alboglabra) extract for green synthesis of nickel oxide nanoparticles: A prospective route for post-phytoremediation

Even though phytoremediation is considered a green technology for remediating heavy metals, there are some problems with the application of this technology, particularly when it comes to managing the biomass that is used. So, processing biomass needs to be given a lot of attention. This study outlined the utilization of extracts obtained from the hyperaccumulator plant Brassica oleracea var. alboglabra to synthesize nickel oxide nanoparticles. Subsequently, the nanoparticle underwent testing to determine its suitability as an absorbent for heavy metals, specifically lead, as well as its efficacy as an antifungal agent against Fusarium sp. strain. The characterization of nickel oxide nanoparticles involved several measurements, such as scanning electron microscopy analysis, high- and low-resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and hysteresis curve acquisition. The research findings indicate that the extract from hyperaccumulators can be utilized for the synthesis of NiO, which exhibits an absorption capacity exceeding 98% and serves as an efficient antifungal agent against Fusarium sp. pathogens. The approach utilized in this study not only prioritizes "green" and sustainability factors but also takes into account the economic aspects associated with the items being manufactured. The research has important implications in two areas. Firstly, it demonstrates the utilization of natural resources (B. oleracea var. alboglabra) in the production of nickel oxide, which serves as a safer and more eco-friendly substitute for dangerous chemicals. Furthermore, it aids in the advancement of novel techniques for effectively managing biomass hyperaccumulators.

Edible antibacterial gelatin/zein fiber films loaded with cinnamaldehyde for extending the shelf life of strawberries by electrospinning approach

Strawberries are a kind of nutritious fruit but they are easily spoilt by mold. Therefore, it is significant to prolong the shelf life of strawberries for the avoidance of their numerous wastes. To achieve the aforementioned objective, in this paper, the edible and biodegradable natural polymers of gelatin/zein were used to prepare the antibacterial fiber films loaded with cinnamaldehyde by electrospinning method. The fibers prepared in this study were smooth and bead-free, with the average diameters ranging from 1.46 to 2.02 μm. The successful encapsulation of cinnamaldehyde in obtained fiber films was confirmed by Fourier transform infrared spectra. The prepared fiber films decomposing at about 230 °C were shown by thermogravimetric analysis curves, indicating their high thermal stability. The amorphous structure of the polymers in the produced fiber films was displayed by X-ray diffraction curves. Compared with the untreated strawberries, strawberries treated with fiber films encapsulated with 15 wt% and 20 wt% cinnamaldehyde showed the smallest changes in appearance, weight loss rate, hardness, pH, and total soluble solids at 6 d. The shelf life of strawberries was increased to 6 days by the fiber films containing 15 wt% and 20 wt% cinnamaldehyde. The fiber films prepared in this study were potentially expected to be used as edible antibacterial packaging films, nutrient and drug carriers.

Numerical Simulation of Time-Varying Characteristics in a High-Permeability Sandstone Reservoir: A Case of Gaoqian Southern Area

In the process of long-term water flooding in the Gaoqian Southern Area with an average porosity of 30% and an average permeability of 1333.5×10−3 μm2, the fluid-solid interaction among oil, water, and rock has a great influence on the pore structure. It has resulted in changes in reservoir parameters with the extension of time. This paper used electron microscopy scanning, mercury injection, X-ray diffraction, physical properties, and oil-water relative permeability curves to study the variation of clay mineral content, pore throat structure, porosity, permeability, and relative permeability curves of high-permeability sandstone after high-pressure water flooding. The results showed that clay minerals such as montmorillonite and kaolinite were dissolved, hydrated, and migrated after long-term water flooding, which resulted in the decrease of clay mineral content in fine sandstone and medium sandstone, the increase of pore throat radius, and the decrease of displacement pressure, median pressure, and separation coefficient. The saturation of the isotonic point of the oil-water relative permeability curve was obviously shifted to the right, the hydrophilicity was significantly enhanced, and the porosity and permeability were effectively improved, but there was a blockage of the throat less than 2 μm in the fine sandstone. In addition, this paper established the equations of water injection, permeability, irreducible water saturation, residual oil saturation, and oil-water relative permeability curve coefficient and establishes the initial permeability model with the well data before water flooding. The logging interpretation results of development wells in the process of water flooding as verification data were used, and the relative error of permeability far lower than the general requirement of permeability error within an order of magnitude was less than 30%, which verified the rationality of the method.

Improved anti-cancer effects of luteolin@ZIF-8 in cervical and prostate cancer cell lines

Luteolin, a naturally occurring pharmaceutical compound with significant antitumor properties, faces challenges in clinical applications due to its low solubility in water and limited bioavailability. To address these issues, a one-step synthesis method was employed to encapsulate luteolin within ZIF-8. The successful preparation of luteolin@ ZIF-8 nanoparticles was confirmed through various analytical techniques, including fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), laser size distribution analysis, X-ray diffraction (XRD), and release curve assessment. Results indicate that the formulated luteolin@ ZIF-8 nanoparticles exhibited high drug loading (1360 mg/g) and demonstrated selective drug release in acidic microenvironments. Furthermore, the encapsulation of luteolin increased the size of ZIF-8 from 168.4 ± 0.2 nm to 384.7 ± 1.4 nm, but did not change its crystalline structure significantly. Notably, the results of in vitro anti-cervical and prostate cancers experiments revealed that luteolin@ ZIF-8 had better efficacy in inhibiting the proliferation and migration of HeLa and PC3 cells than free luteolin. The antitumor activity of luteolin@ ZIF-8 was sustained for 72 h, with a particularly pronounced inhibitory effect on HeLa cells as compared to PC3 cells. This study underscores the effective enhancement of luteolin's antitumor activity through encapsulation in ZIF-8, offering substantial implications for improving its clinical applications.

Effect of Neutron Irradiation on the Electronic and Optical Properties of AlGaAs/InGaAs-Based Quantum Well Structures.

The effect of neutron irradiation on the structural, optical, and electronic properties of doped strained heterostructures with AlGaAs/InGaAs/GaAs and AlGaAs/InGaAs/AlGaAs quantum wells was experimentally studied. Heterostructures with a two-dimensional electron gas of different layer constructions were subjected to neutron irradiation in the reactor channel with the fluence range of 2 × 1014 cm-2 ÷ 1.2 × 1016 cm-2. The low-temperature photoluminescence spectra, electron concentration and mobility, and high-resolution X-ray diffraction curves were measured after the deactivation. The paper discusses the effect of neutron dose on the conductivity and optical spectra of structures based on InGaAs quantum wells depending on the doping level. The limiting dose of neutron irradiation was also estimated for the successful utilization of AlGaAs/InGaAs/GaAs and AlGaAs/InGaAs/AlGaAs heterostructures in electronic applications.

Fabrication of the cross-linked PVA/TiO2/C nanocomposite membrane for alkaline direct methanol fuel cells

A crosslinked Poly(vinyl alcohol) based composite membrane was developed through a phase inversion process for use in alkaline direct methanol fuel cells (ADMFCs). The titanium dioxide (TiO2) and carbon nanoparticles (NPs) have been incorporated into the PVA polymer matrix to improve the mechanical and thermal properties. The membrane samples were further modified with maleic acid, a carboxylic acid acting as the cross-linker, under controlled temperature and time conditions to enhance electrochemical properties. The mechanical strength and thermal stability of membranes were determined using a Universal testing machine (UTM) and thermogravimetric analysis (TGA), while the crystallographic and morphological features were examined through X-ray diffraction (XRD) and Scanning electron microscopy (SEM), respectively. The proton conductivity (σ), methanol permeability, and water uptake (%) were also assessed. The XRD curves, SEM images, and TGA trends confirmed the successful cross-linking of maleic acid, uniform dispersion of nanoparticles (NPs), and excellent thermal stability in the crosslinked PVA-TiO2-C membrane. This sample also exhibited the highest tensile strength (163 MPa), and lower permeability (45000 Ss/cm3). Moreover, the ionic conductivity was obtained in the order of 10−2 S/cm. These combined characteristics position the cross-linked PVA-TiO2-C membrane as a promising candidate for application in alkaline direct methanol fuel cells (ADMFCs).

Study of correlations between glass-transition temperature and local structure of Ge-As-Se, Ge-As-Se-S chalcogenide glasses

ABSTRACT The local structure and glass transition of Ge-As-Se, Ge-As-Se-Schalcogenide glasses have been studied by X-ray diffraction and differential scanning calorimetry. By applying the theory of topological constraints and considering chemically ordered network models, it has been determined that Ge10As20S10Se60 (average coordination number = 2.4), Ge25As10S25Se40 ( = 2.6) are the compositions associated with the more stable glasses. This result is related to the larger differences between the glass transition (Tg ) and crystallization-transition (Tcr ) temperatures (ΔTg-cr ∼ 38 and 43 K) at these compositions. Relatively high values of short-range (d∼5.7–6.34 Å) and medium-range (L∼26.59–33.74 Å) order parameters of the local structure in the glass compositions satisfying the mentioned conditions affect the glass-transition temperature (Tg ) and cause its value to increase (Tg ∼589–689 K). As a result of comparative analyses of X-ray diffraction and differential scanning calorimetry curves it has been determined that there is a correlation between the glass-transition temperature (Tg ) with the short range (d) and medium range order (L) parameters of the local structure.

Investigating the crystallization behavior of TiO2 during annealing: Molecular dynamics simulations

TiO2 is a dielectric material with excellent photocatalytic and photochemical properties. The conversion of TiO2 from an amorphous to crystalline phase significantly improves the photocatalytic activity of TiO2. However, the crystallization behavior of TiO2 during annealing has been little studied in the field of molecular dynamics. In this paper, the crystallization behavior of TiO2 during annealing under different conditions was analyzed using molecular dynamics simulation. To investigate the phase transition process of TiO2, the melting point temperature of the system was calculated by mean square displacement at about 2400 K. The effect of size on structural stability was explored. The radial distribution function and x-ray diffraction curves revealed that the anatase phase appeared over 800 K. Moreover, with the increase in annealing temperature, the anatase content in TiO2 first increased and then decreased, and the rutile phase gradually increased. At a specific temperature, a structure is formed where rutile and anatase coexist. Anatase atoms compete with rutile atoms, and by increasing the temperature, anatase is converted to rutile. The amorphous structure is reduced at high temperatures, improving the crystalline quality. The crystallization behavior of the amorphous structure can improve the photocatalytic efficiency of TiO2. TiO2 nanometers have good prospect for application. Therefore, studying the crystallization behavior of TiO2 is essential.

Hydrothermal crystal growth of tetralithium octafluoridozirconate (Li4ZrF8) and its physicochemical properties

A single crystal of tetralithium octafluridozirconate (Li4ZrF8) has been obtained by using a hydrothermal process. The crystal phase was analyzed using a powder X-ray diffraction pattern and matched with standard reference data. The high-resolution X-ray diffraction curve indicates that the crystal has good crystalline perfection. The thermal behavior of the crystal sample was investigated by TGA/DSC analysis. The optical bandgap of the crystal sample was calculated from the Tauc plot and found to be 5.8 eV. The crystal sample exhibits intrinsic X-ray excited luminescence with a peak maximum of 265 nm. The thermoluminescence measurement shows two peaks, one is at the high-temperature region of 545 K and another one is at the low-temperature region at 383 K. TL kinetic parameters such as activation energy (E) and frequency factor (s) for the peak at 545 K was estimated as 1.20 eV and 2.06 × 10−10 respectively. The sample has good TL sensitivity to the neutron dose in the order of µsv. The low-temperature thermoluminescence measurements were carried out to study the trap levels and found two major glow peaks at 108 and 130 K. Scintillation properties were analyzed under α-rays from a 241Am source. The decay time profile was well fitted with three components and the fitted values show the fast component of 500 ns (9 %), the medium component of 2.4 μs (24 %), and a slow component of 12.8 μs (67 %).

Enhanced Fluorescence Characteristics of SrAl2O4: Eu2+, Dy3+ Phosphor by Co-Doping Gd3+ and Anti-Counterfeiting Application.

A series of long-afterglow luminescent materials (SrAl2O4: Eu2+ (SAOE), SrAl2O4: Eu2+, Dy3+ (SAOED) and SrAl2O4: Eu2+, Dy3+, Gd3+ (SAOEDG)) was synthesized via the combustion method. Temperature and concentration control experiments were conducted on these materials to determine the optimal reaction temperature and ion doping concentration for each sample. The crystal structure and luminescent properties were analyzed via X-ray diffraction (XRD), photoluminescence (PL), and afterglow attenuation curves. The outcomes demonstrate that the kind of crystal structure and the location of the emission peak were unaffected by the addition of ions. The addition of Eu2+ to the matrix's lattice caused a broad green emission with a central wavelength of 508 nm, which was attributed to the characteristic 4f65d1 to 4f7 electronic dipole, which allowed the transition of Eu2+ ions. While acting as sensitizers, Dy3+ and Gd3+ could produce holes to create a trap energy level, which served as an electron trap center to catch some of the electrons produced by the excitation of Eu2+ but did not itself emit light. After excitation ceased, this allowed them to gently transition to the ground state to produce long-afterglow luminescence. It was observed that with the addition of sensitizer ions, the luminous intensity of the sample increased, and the afterglow duration lengthened. The elemental structure and valence states of the doped ions were determined with an X-ray photoelectron spectrometer (XPS). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the samples. The results show that the sample was synthesized successfully, and the type and content of ions in the fluorescent powder could be determined. The fluorescence lifetime, quantum yield, bandgap value, afterglow decay time, and coordinate position in the coherent infrared energy (CIE) diagram of the three best sample groups were then analyzed and compared. Combining the prepared phosphor with ink provides a new idea and method for the field of anti-counterfeiting through screen printing.

Diagnosis of durability-related problems in concrete structures through comprehensive analysis and non-destructive testing: a case study

ABSTRACT The present study investigated concrete durability problems at the National University of Sciences and Technology,Pakistan, through comprehensive analysis and non-destructive testing. During the visual inspection of concrete structures, different deterioration mechanisms such as alkali-silica aggregate reaction (ASR), carbonation, abrasion and drying shrinkage were found. After visual inspection, the data on ingredients used in the construction of various structures were collected, revealingthat different brands of cement used in construction contained high alkali-equivalent content. Fine aggregates were used from two different quarries during construction. The available literature and X-ray Diffraction (XRD) results showed that both the quarries’ aggregates have the potential for alkali-silica reactivity. Furthermore, the XRD results of gel-type material collected from mapped cracking indicated the presence of delhayelite, similar to alkali-silica gel, suggesting ASR. The XRD curves of the whitest powder collected from various sites showed the presence of sodium sulfate and calcium carbonate peaks, indicating salt hydration attacks. The carbonation rate in concrete ranges from 4.33 to 5.77 mm/year. The results of the rebound hammer and pulse velocity test indicated that concrete used in parking has low strength which is the main cause of abrasion. Based on these findings a few recommendations have been presented to avoid durability-related problems in future structures.

Effect of curing temperatures on geopolymerization and heavy metal solidification in alkali-activated zeolite/MSWI fly ash specimens

Admixtures of pozzolanic materials or solid wastes with municipal solid waste incineration fly ash (MSWIFA) can improve heavy metal stabilization/solidification (S/S) properties in alkali-activated MSWIFA specimens. In this work, the compressive strength of MSWIFA admixes with zeolite activated by Na2O·1.7SiO2·nH2O (FZNS) specimens with different curing times (3, 7, 14, and 28 d) and temperatures (20, 50, and 80 ℃) is investigated. The results reveal that a 40 wt% zeolite replacement of MSWIFA in FZNS specimens (FZNS40) not only increases the early compressive strength by 129% but also reduces strength loss during continuous high-temperature (50 or 80 ℃) curing. Moreover, zeolite addition promotes the creation of geopolymers at 28.5°–30.5°in X-ray diffraction (XRD) curves. During 50 or 80 ℃ curing, the NaCl peak disappears and a marginal Friedel's salt peak can be detected at 11.4°. The gel contents are more concentrated on C-S-H in FZNS0 and C-(A)-S-H/N-A-S-H in FZNS40, as demonstrated by differential thermogravimetry (DTG) and magic angle spinning nuclear magnetic resonance (MAS NMR) analysis. With zeolite addition, long-time and high-temperature curing can improve the heavy metal solidification ratio in FZNS specimens. After high-temperature curing, the honeycomb or cluster morphologies of the gel products, visible by scanning electron microscopy (SEM) in the FZNS specimens, reveal high heavy metal stabilization properties. It is easier to form the fibrous C-(A)-S-H/N-A-S-H gel near zeolite owing to the high content of SiO2 and Al2O3. Zeolite modifies the compressive strength, high-temperature stability, and heavy-metal S/S efficiency in FZNS specimens, which promotes the utilization of MSWIFA as an ecologicalresource in the future.

Challenges in correlating oxygen stable isotope ratios of hydrates on uranium ore concentrates to process waters

Abstract Exchange of oxygen stable isotopes (δ18O values) between precipitation waters and uranium oxides is governed by thermodynamics or kinetics. It has been assumed that meteoric waters can be related to precipitation waters in uranium ore concentrates and their calcined and reduced uranium oxide products. With this assumption, the δ18O values of uranium materials could provide forensic signatures that identify the production history and geolocation of nuclear materials. To further exploit the potential of δ18O values in nuclear material analysis, this study examines the oxygen stable isotope exchange in two UOCs, magnesium diuranate (MDU) and sodium diuranate (SDU). MDU and SDU were synthesized from solutions of uranyl nitrate hexahydrate using precipitation waters with unique oxygen isotope compositions. The structures of the MDU and SDU were analyzed using powder X-ray diffraction (p-XRD) and thermal mass loss curves, while the δ18O values of waters generated during thermal decomposition were analyzed using a thermogravimetric analyzer coupled to an isotope ratio infrared spectrometer (TGA-IRIS). By p-XRD, the MDU was uniform and amorphous across all syntheses with residual crystalline material incorporated as a minor component. Combined with the TGA results, all of the MDU is likely amorphous MgU2O7·3H2O with MgO impurities present throughout. In contrast, the SDU synthesis resulted in multiple phases with many samples exhibiting crystalline phases including a combination of Na(UO2)4O2(OH)5·5H2O and Na2(UO2)6O4(OH)6·8H2O with a Na2U2O7 minor phase. A small fraction of the SDU samples were amorphous with no crystalline XRD peaks observed. Mass loss curves of the SDU samples revealed that the amorphous samples contained inclusions of similar crystalline phases compared to the crystalline materials. The uniformity of the MDU samples enabled highly reproducible measurements of δ18O values of the water vapor yielded from two dehydration events at 170 °C and 500 °C. In contrast, the multiphase composition of the SDU samples resulted in poor reproducibility in δ18O values. Neither system revealed any correlation between the δ18O values of precipitation water and the waters released during dehydration of the UOCs.

A computational study of cellulose regeneration: Coarse-grained molecular dynamics simulations

Understanding the microscopic mechanisms of regeneration of cellulose is prerequisite for engineering and controlling its material properties. In this paper, we performed coarse-grained Martini 3 molecular dynamics simulations of cellulose regeneration at a scale comparable to the experiments. The X-ray diffraction (XRD) curves were monitored to follow the structural changes of regenerated cellulose and trace formation of cellulose sheets and crystallites. The calculated coarse-grained morphologies of regenerated cellulose were backmapped to atomistic ones. After the backmapping we find that the regenerated coarse-grained cellulose structures calculated for both topology parameters of cellulose Iβ and cellulose II/III, are transformed to cellulose II, where the calculated XRD curves exhibit the main peak at approximately 20–21 degrees, corresponding to the (110)/(020) planes of cellulose II. This result is in good quantitative agreement with the available experimental observations.

Identification of the clay minerals of some chosen soils in Aljabal Alakhdar district, Libya by Ethylene Glycol and Heat: X-ray Diffraction studies

Due to the widespread use of clay minerals and their importance in various industries and agricultural projects, sufficient knowledge of clay minerals as well as how to identify them is so important. Therefore, understanding these minerals can optimize the use and application of them. Al-Jabal Al-Akhdar, as it represents the only green spot in northeastern of Libya, the identification of clay minerals in this region is very important for its relationship to the management of the chemical and physical properties of its soil. Four samples were selected from the Al-Haniya area, and due to the shallow depths of its soil, these samples were taken from the last depth (35-60 cm). X-ray diffraction device used to obtain clear X-ray diffraction (XRD) curves for identification of clay minerals in selected samples from the study area. The results of the qualitative analysis of the minerals showed that there was a similarity in the types of pyrophyllite silicates and the illite is the most crystalline mineral indicated by the relative strength in these soils. The results also showed the presence of kaolinite minerals and the chlorite-vermiculite complex. The results did not show the presence of expansion minerals such as montomorollonite.

Photoluminescence Properties of InGaN/InGaN MQWs with Different Electron Injection Layers

The structural and optical properties of InxGa1-xN/InyGa1-yN multi quantum well (MQW) light emitting devices with/without electron injection layers were studied. The samples with electron injection layer consist of step-graded (GIE) and two step staircase (SEI) electron injection layer between n-type GaN and MQWs active region. Edge and screw type of dislocation densities were deduced from High Resolution X-Ray Diffraction (HR-XRD) curves and no significant difference were realized. The zeroth and higher order satellite peaks were more clearly observed in the sample without electron injection layer. Optical characterization was carried out by temperature dependent photoluminescence (PL) technique. It was found that the PL densities of samples with step-graded and two step-staircase electron injection layers had almost two times lower temperature dependence compared to the reference sample without electron injection layer. On the other hand, the line width of the photoluminescence peak associated with MQWs is much narrower at low temperature for sample without electron injection layer than the other two samples.

Influence of silicon-dioxide nanoparticles in cementitious mortars: verification using x-ray diffraction, thermal analysis, physical, and mechanical tests

In recent years, nanotechnology has been applied to building materials, such as cementitious composites (e.g., mortar and concrete), to improve their properties. The aim of this study was to analyze the thermal, physical, and mechanical properties of mortars with and without silicon-dioxide (SiO2) nanoparticles. Experiments such as thermogravimetry and differential thermal analysis (TG-DTA), x-ray diffraction (XRD), fresh density, incorporated-air content, bulk density, capillary absorption, capillarity coefficient, flexural tensile strength, and compressive strength on prismatic specimens were performed on mortars and analyzed for different levels of nanosilica (nS). These levels were 1% and 3%, in addition to the reference mortar (0% nS). The TG-DTA curves showed an elevated content of chemically combined water and a lower content of calcium hydroxide (Ca(OH)2) in the 3% nS compositions, while the XRD curves presented a lower content of calcite and portlandite in the same mortar. These results indicate the fixation capacity of lime for the formation of calcium silicate hydrate (C-S-H), which is the primary cause of resistance in cementitious mortars. In addition, it was found that the use of nanosilica contributed to a fresh density increase of approximately 15%, which caused a minimum air-incorporated content decrease of 37% and a minimum bulk density increase of 10%. Higher densities resulted in a minimum water absorption reduction of 36%, owing to fewer pores in the mortars. Therefore, the capillarity coefficient decreased by a minimum of 41%. These nanoparticles also improved the minimum flexural tensile and compressive strengths by 88% and 158%, respectively, when using a 3% nS composition. These results can enable the use of lightweight aggregates in cementitious composites, improving their physical and mechanical characteristics and allowing greater reuse of these materials, including construction waste.

Identification of the clay minerals of some chosen soils in Aljabal Alakhdar district, Libya by Ethylene Glycol and Heat: X-ray Diffraction studies

Due to the widespread use of clay minerals and their importance in various industries and agricultural projects, sufficient knowledge of clay minerals as well as how to identify them is so important. Therefore, understanding these minerals can optimize the use and application of them. Al-Jabal Al-Akhdar, as it represents the only green spot in northeastern of Libya, the identification of clay minerals in this region is very important for its relationship to the management of the chemical and physical properties of its soil. Four samples were selected from the Al-Haniya area, and due to the shallow depths of its soil, these samples were taken from the last depth (35-60 cm). X-ray diffraction device used to obtain clear X-ray diffraction (XRD) curves for identification of clay minerals in selected samples from the study area. The results of the qualitative analysis of the minerals showed that there was a similarity in the types of pyrophyllite silicates and the illite is the most crystalline mineral indicated by the relative strength in these soils. The results also showed the presence of kaolinite minerals and the chlorite-vermiculite complex. The results did not show the presence of expansion minerals such as montomorollonite.

Facile one-step hydrothermal synthesis of monolayer and turbostratic bilayer n-doped graphene quantum dots using sucrose as a carbon source.

Graphene quantum dots (GQDs) have attracted attention from researchers owing to their outstanding properties, such as chemical inertness, stable photoluminescence (PL), biocompatibility, and low toxicity, which make them suitable for bioimaging, optoelectronic device, sensor, and others. At present, there are several studies that report the effect of the size of GQDs on their properties; however, but there is only a few studies that report the effect of the thickness of GQDs on their properties. It may be attributed to the difficulty to obtain the accurate information on the thickness of GQDs. In this study, we demonstrate the facile and one-step hydrothermal synthesis of monolayer and bilayer n-doped graphene quantum dots (NGQDs) using sucrose as a carbon source. UV-visible and PL spectra show the quantum yield of the NGQDs is 4.9 times higher than that of the GQDs. Besides, the NGQDs exhibit sensitive PL for Ag+ ions. In addition, the thickness distribution and interlayer spacing of NGQDs are revealed by X-ray diffraction (XRD) curve fitting, which is calculated using a simple and accurate equation. The information on the structure of the NGQDs from the XRD curve fitting is in a good agreement with the Raman results. This accurate estimation of the structure of GQDs by XRD curve fitting using the simple equation may extend the limits of GDQ study.

Study on the Automatic Identification of ABX3 Perovskite Crystal Structure Based on the Bond-Valence Vector Sum

Perovskite materials have a variety of crystal structures, and the properties of crystalline materials are greatly influenced by geometric information such as the space group, crystal system, and lattice constant. It used to be mostly obtained using calculations based on density functional theory (DFT) and experimental data from X-ray diffraction (XRD) curve fitting. These two techniques cannot be utilized to identify materials on a wide scale in businesses since they require expensive equipment and take a lot of time. Machine learning (ML), which is based on big data statistics and nonlinear modeling, has advanced significantly in recent years and is now capable of swiftly and reliably predicting the structures of materials with known chemical ratios based on a few key material-specific factors. A dataset encompassing 1647 perovskite compounds in seven crystal systems was obtained from the Materials Project database for this study, which used the ABX3 perovskite system as its research object. A descriptor called the bond-valence vector sum (BVVS) is presented to describe the intricate geometry of perovskites in addition to information on the usual chemical composition of the elements. Additionally, a model for the automatic identification of perovskite structures was built through a comparison of various ML techniques. It is possible to identify the space group and crystal system using just a small dataset of 10 feature descriptors. The highest accuracy is 0.955 and 0.974, and the highest correlation coefficient (R2) value of the lattice constant can reach 0.887, making this a quick and efficient method for determining the crystal structure.