Granular Nanoparticles Research Articles

Tailoring the luminescent and structural behaviors of pH-driven PPy/gC3N4/ZrO2 nanocomposite as an emissive layer material for OLED application

The polymeric nanocomposites were synthesized via an in-situ polymerization method, optimized through pH adjustment of zirconium oxide rather than concentration variation. X-ray powder diffraction analysis revealed phase transitions and average crystallite sizes ranging from approximately 6.52–9.16 nm, depending on the pH levels. Field Emission Scanning Electron Microscopy tool is used to analyze the granular nanosheets and nanoparticles like the microstructure of polypyrrole, graphitic carbon nitride and zirconium oxide at a high resolution. UV–visible spectroscopy determined an optical bandgap energy of about 2.44 eV, a refractive index of 2.17, and an optical conductivity of 3.15 × 1010 S/cm2. Forster resonance energy transfer between Zirconium dioxide and graphitic carbon nitride significantly enhanced photoluminescence emission. PL emission and color purity (45 %) of the optimized sample were examined using photoluminescence data. Electrical conductivity of ∼15.9 × 10−4 S/cm and dielectric constant of ∼14.77 were obtained from I to V and LCR meter measurements. These properties indicate that the pH-driven nanocomposite exhibits optimized electron-hole recombination rates, electrical conductivity, and suitable bandgap energy, making its potential impact as an emissive layer material for OLED applications.

Electrodeposition of iron from 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and reverse microemulsions of Triton X-100.

Electrodeposition of iron (Fe) was investigated in three different media, namely a hydrophilic ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, conventional reverse microemulsion (RME)/reverse micellar solution, and IL-based RME of a non-ionic surfactant, Triton X-100, with a view to electrodepositing iron with desired morphology. Electrochemical behaviour of Fe2+ was studied using cyclic voltammetric technique with a copper electrode as the working electrode. Electrochemical reduction of Fe2+ in all the studied media was found to be an electrochemically irreversible, diffusion-controlled process. Successful potentiostatic electrodeposition of metallic iron was performed in all the studied media on copper substrate using bulk electrolysis method. The obtained iron electrodeposits were characterized using a scanning electron microscope and an X-ray diffractometer. The controlled diffusion of Fe2+ towards electrode surface in all the media resulted in the formation of nanoparticles of iron, but compact layers of granular nanoparticles could be achieved from both the conventional and IL-based RME systems. The IL-based microemulsions synergistically combined the advantageous features of both the IL and RME and showed promise for tuning the size, shape, and morphology of the electrodeposited iron.

High-temperature planar heating elements using RuO2 nanosheets

Planar heating elements employ carbon nanotubes, graphene, and metals. However, the high-temperature (300–500 °C) applications of heating elements based on metallic and organic materials are limited because they oxidize at high temperatures. Oxide materials such as RuO2 are promising alternatives. The electrical conductivity of heating elements are strongly dependent on the aspect ratios of fillers; thus, RuO2 nanosheets are suitable fillers for high-temperature planar heating elements because RuO2 remains stable at high temperatures, and RuO2 nanosheets have high aspect ratios of over 1000, as the lateral sizes and thicknesses of the RuO2 nanosheets are 2∼5 μm and 1–3 nm, respectively. Consequently, the electrical conductivity of planar heating elements using RuO2 nanosheets as fillers is 940 times higher than that of heating elements using conventional granular RuO2 nanoparticles. Therefore, the RuO2 nanosheet-based heating elements will be suitable in various applications requiring high temperatures and high uniformity.

Probing the interactions of the HIV-1 matrix protein-derived polybasic region with lipid bilayers: insights from AFM imaging and force spectroscopy.

The human immunodeficiency virus type 1 (HIV-1) matrix protein contains a highly basic region, MA-HBR, crucial for various stages of viral replication. To elucidate the interactions between the polybasic peptide MA-HBR and lipid bilayers, we employed liquid-based atomic force microscopy (AFM) imaging and force spectroscopy on lipid bilayers of differing compositions. In 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers, AFM imaging revealed the formation of annulus-shaped protrusions upon exposure to the polybasic peptide, accompanied by distinctive mechanical responses characterized by enhanced bilayer puncture forces. Importantly, our AFM-based force spectroscopy measurements unveiled that MA-HBR induces interleaflet decoupling within the cohesive bilayer organization. This is evidenced by a force discontinuity observed within the bilayer's elastic deformation regime. In POPC/cholesterol bilayers, MA-HBR caused similar yet smaller annular protrusions, demonstrating an intriguing interplay with cholesterol-rich membranes. In contrast, in bilayers containing anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) lipids, MA-HBR induced unique annular protrusions, granular nanoparticles, and nanotubules, showcasing its distinctive effects in anionic lipid-enriched environments. Notably, our force spectroscopy data revealed that anionic POPS lipids weakened interleaflet adhesion within the bilayer, resulting in interleaflet decoupling, which potentially contributes to the specific bilayer perturbations induced by MA-HBR. Collectively, our findings highlight the remarkable variations in how the polybasic peptide, MA-HBR, interacts with lipid bilayers of differing compositions, shedding light on its role in host membrane restructuring during HIV-1 infection.

Fe2O3 Nanoparçacıkların Yeşil Sentezi ve Karakterizasyonu

The aim of this study is to produce iron III oxide (Fe2O3) nanoparticles due to their wide application area. The ethanolic extract of curcuma was used in the synthesis method due to number of advantages. These benefits include being inexpensive, widely accessible, simple to extract, and less prone to contamination. The produced particles were analyzed via scanning electron microscope (SEM), energy dispersive analysis (EDX), and transmission electron microscope (TEM). Furthermore, the zeta potential of Fe2O3 particles was determined, ultraviolet–visible spectroscopy (UV) analysis and fourier transform infrared spectroscopy (FTIR) analysis were done. According to the results obtained, granular nanoparticles with particle sizes ranging from 30 to 80 nm were synthesized and it was determined that they were sufficiently stable.

Densification of transparent hydroxyapatite ceramics via cold sintering process combined with biomineralization

We report for the first time transparent hydroxyapatite (HAp) ceramics densified using a cold sintering process and biomineralization. Under a uniaxial pressure of 800 MPa at 180 °C, granular HAp nanoparticles mixed with simulated body fluid were densified up to 98.5% relative density. During the densification, pseudo-biomineralization occurred among the HAp nanoparticles, leading to the precipitation of a new HAp phase. Additionally, the transformation of granular HAp nanoparticles into nearly circular grains produced fine microstructures with uniform and nanosized grains, reducing light scattering. As a result, the transmittance of 81.6% at λ = 550 nm was achieved. Transparent HAp exhibited Vickers hardness (3.88 ± 0.22 GPa), fracture toughness (0.62 ± 0.03 MPa·m1/2), biaxial flexural strength (41.69 ± 1.23 MPa), and Young's modulus (78.1 ± 2.04 GPa). These findings will pave the way for the fabrication and potential applications of transparent ceramics at low temperatures.

Effect of sunkist orange peel nanoparticle granules on cardiac and aorta histopathology in diabetic rats

Sunkist oranges (Citrus sinensis (L.) Osbeck) is rich in anthocyanins (95% of which are represented by cyanidin-3-glucoside and cyanidin-3-6"-malonyl-glucoside), flavanones (hesperidin and narirutin), hydroxycinnamic acid, carotenoids, sugars, minerals, and fiber, which offer health benefits. This study aimed to evaluate the efficacy of sunkist orange peel nanoparticle granules on the histopathological appearance of the cardiac and aorta in alloxan-induced diabetic rats. This study used a post-test experimental design, with a control group. Twenty-five male Wistar rats were randomly divided into five groups: negative control (alloxan+distilled water), positive control (alloxan+metformin), treatment 1 (alloxan+granular nanoparticles 50 mg/kg BW), treatment 2 (alloxan+granular nanoparticles 70 mg/kg BW), and treatment 3 (alloxan+granular nanoparticles 100 mg/kg BW). The heart and aorta were prepared for observation using 10x ocular magnification and 40x objective lens magnification. Kruskal-Wallis statistical test results revealed a significant difference in the average cardiac histopathological score between the treatment groups (p = 0.011). The amount of aortic endothelial cell damage can be seen from the presence of foam cells in the K(-) treatment group, while the K(+), P1, P2, and P3 groups did not have foam cells in the aortic endothelium. The findings of this study indicate that sunkist orange peel extract nanoparticles in granular form improve cardiac and aortic histopathology, with a dose of 100 mg/kg BB being the best dose for improving cardiac and aortic histopathology.

SYNTHESIS AND CHARACTERIZATION OF Al-DOPED ZnO THIN FILMS AS ANTI-REFLECTION COATINGS FOR SOLAR CELL APPLICATIONS

In this work, we have synthesized ZnO:Al thin films by pulsed laser deposition technique and investigated their microstructural and optical properties. The XRD study confirmed a polycrystalline structure of wurtzite ZnO in all films. Further, Al doping has improved the crystallinity and decreased the crystal size and volume of the unit cell. The surface morphology was homogeneous with nanoscopic crystals clustered to form granular nanoparticles. The optical properties significantly improved by increasing the Al doping concentration. The produced thin films are excellent candidates for use as an anti-reflection layer in solar cells due to their outstanding properties.

Characterization of Pickering emulsions stabilized by delipidated egg yolk granular protein nanoparticles crosslinked with ultraviolet radiation

In this study, delipidated egg yolk proteins were used for the first time to prepare nanoparticles by the self-assembling method at pH 8.0, then treated with UV-C as a crosslinking agent, and their stability tested at pH 7.0, which is a more convenient pH for food applications. According to the results obtained, non-irradiated nanoparticles had a size of 431.8 ± 75.7 nm at pH 7.0, but the 10 min UV-C irradiated nanoparticles had an average size of 139.7 ± 5.9 nm. These nanoparticles also showed a high resistance to destabilization by SDS, urea or DTT and noticeable antioxidant and ferrous chelating activities. Pickering emulsions prepared at the nanoparticle concentration of 1 % (w/w) showed the smallest average droplet size and the lowest Turbiscan stability index value after 80 days of storage. All in all, these results have important implications for the utilisation of these proteins as a conventional Pickering emulsifying agent.

Исследование механического поведения эластомерных нанокомпозитов в условиях двухосного нагружения

Biaxial cyclic tests of elastomeric composites filled with granular nanoparticles (carbon black and detonation nanodiamonds), nanoplates (few-layer nanographene) and nanofibers (multi-walled carbon nanotubes) have been carried out. The experiments were carried out on Zwick/Roell's unique four-vector test stand using special fan-type cruciform specimens. Studies have shown that carbon nanotubes have the greatest influence on the change in the mechanical properties of a material during cyclic deformation in mutually perpendicular directions. It is they, due to their length and flexibility, that most effectively partic-ipate in the restructuring of the microstructure, thereby forming the macroscopic behavior of the material.

ZIF-8 derived porous C, N co-doped ZnO modified B-g-C3N4: A Z-Scheme charge dynamics approach operative towards photocatalytic hydrogen evolution and ciprofloxacin degradation

Herein, the fabrication of a robust CNZ/BCN nanocomposite is achieved by a facile in-situ calcination of ZIF-8 along with BCN precursors. Morphologically the dodecahedral ZIF-8 farmeworks are transformed into granular CNZ nanoparticles that were densely adhered to the BCN nanosheet surface with interfacial interactions. MOF derived strategy plays significant role in reducing the optical band gap via introducing C, N into the ZnO lattice as known from UV–vis-DRS as well as XPS studies. Additionally the composite formation lead to significantly enhanced exciton anti-recombination as suggested from EIS and PL analysis. The optimal CNZ/BCN (1:1) nanohybrid exhibits enhanced photocatalytic H2 evolution rate of 7020 µmol h−1 g−1 which is nearly-two and eight folds greater than that of pristine CNZ and BCN respectively along with maximal ciprofloxacin photo-degradation rate (86.7 %). The radical trapping experiments deduced the formation of both superoxide and hydroxyl radicals that promotes the nanocomposite to follow Z-scheme charge transfer pathway during photocatalysis. Intermediates formed during CIP photo-degradation were identified by using LC-MS technique that showed ten intermediates formed through two different routes. Hence, MOF derived CNZ and BCN nanocomposite acts as a robust Z-scheme mediated photocatlyst that can be employed for varied energy and environmental purposes.

Tuning of dielectric properties in Ti-Doped granular HfO2 nanoparticles for high-k applications

An array of titanium (Ti) doped HfO2 [(Hf1-xTixO2) (x = 0.0–1.0)] nanoparticles (NPs) synthesis and the study of their structural, spectroscopic, and dielectric properties is reported. The Hf1-xTixO2 NPs were synthesized by a sol-gel type wet chemical process. The crystal structure of pure HfO2 and TiO2 NPs revealed by structural analysis is monoclinic (m) and tetragonal (t), respectively. The crystallinity of the doped samples was found to be dopant concentration-dependent. The microstructure of the obtained NPs was investigated along with their spectroscopic and dielectric characteristics. The tunable dielectric properties of Hf1-xTixO2 NPs make them ideal for high frequency, high-k applications.

Two Dimensional Mxene (Ti3C2) Decorated By SnO2 Nanocrystals for Enhanced Chemical Gas Sensors at Room Temperature

IntroductionA low-cost chemical sensor for ammonia (NH3) detection is highly demanded nowadays for several important applications. Two-dimensional (2D) nanomaterials such as graphene/reduced graphene oxide (rGO), transitional metal dicharcogenides, black phosphor and transition metal carbonitride (MXene) have found a promising application in the fields of gas sensing electronics at room temperature due to their unique microstructure, electrical properties and excellent gas adsorptions ability. Decoration of the secondary phase such as noble metals and metal oxide nanocrystals to form heterojunctions with two-dimensional materials can effectively improve the inadequacy of two-dimensional materials based gas sensors. It takes advantages of the difference in the Fermi level of each phase to make the electrons transfer from one material to the other and thus enriching the electron concentration on the surface of one material that is dominant in the electrical transport. In this way, more ionized oxygen is chemisorbed, leading to the improvement of the gas sensing properties [1].In this work, 2D MXene heterojunctions incorporated with SnO2 nanoparticles have been synthesized by using hydrothermal method. The as-fabricated MXene/SnO2 heterojunction based chemiresistive-type sensor showed excellent sensitivity to different concentrations of ammonia from 0.5-100 ppm at room temperature. The response has about 20 times higher than those reported in literature to 100 ppm NH3 and an excellent selectivity.Preparation and characterizations The Ti3AlC2 was purchased directly from Beijing Forsman Corp. The concentrated hydrochloric acid (HCl) was diluted to 9 M. 2 g of lithium fluoride (LiF) was added into 20 ml diluted hydrochloric acid and stirred with magnetic mixer. 2 g Ti3AlC2 was slowly and evenly dispersed in the solution over a period of several minutes and subsequently stirred at 35 ℃ for 48 h to obtain the MXene. 70 mg of MXene powder was dispersed in 30 ml of deionized water after grinding and sonicated for 30 min. 73.5 mg of stannic chloride pentahydrate (SnCl4·5H2O) was added into the suspension and stirred with magnetic stirrer at room temperature. The suspension was then loaded in a 50 ml Teflon-lined autoclave. The autoclave was sealed and heated in an KSL-1200X hydrothermal system at 180 ℃ for 12 h to obtain the MXene-SnO2 hybirds. The samples were then characterized by XRD, SEM, XPS, Raman and TEM-ED. The MXene/SnO2 based chemirestive-type sensor was measured by a static volumetric method. The resistance of the sensor is directly measured by a digital multimeter (Agilent 34410A). The responses of the sensors were defined as the relative change in the resistances of the sensors in the air and those in the tested gas. Results and Conclusions Fig.1a shows the XRD of the prepared samples. Appearance and down-shift of the peak at ~10 oC indicates the successful achievements of MXene and thus the MXene-SnO2 composite heterojunctions [2-3].Fig.1 (b-c) show the micrographs of the surface morphology of the MXene and heterojunctions. The etched MXene material has obvious layered structure with sizes ranging from 2 μm to 4 μm. The thickness of MXene is about 75 nm indicating the sample contains about 100 single layers of MXene. The granular SnO2 nanoparticles are intimately attached to the surface of MXene. Fig.2 (b) shows the Raman spectra of MXene and Mxene/SnO2 heterojunction. The appearance of both D-band and G-band in the MXene/SnO2 heterojunction sample indicated that MXene remained well during the hydrothermal reaction. Fig.2(c) shows the Ti core level (2p) spectra of the MXene and MXene/SnO2. Ti - X corresponds to titanium carbide or titanium oxynitride. Fig.2d indicates that the peaks at 530.1 and 532 eV correspond to oxygen vacancies and O=C-OH, respectively, suggesting that these and surface-adsorbed oxygen tend to form more active sites, thereby enhancing sensing capability.The sensors using MXene/SnO2 heterojuction shows excellent response and selectivity to low-level NH3 from 0.5-9 ppm at RT (Fig.3). Since the work function of MXene (3.4 eV) was slightly lower than that of SnO2 (4.7 eV), Schottky-type junctions were formed across MXene/SnO2 interfaces (Fig.4). Electrons would transfer from SnO2 to MXene, and the depletion layer was deepened on the surface of MXene. MXene could then chemically adsorb more oxygen, and the response of the MXene/SnO2 heterojunction was thus significantly enhanced.

Enhanced photocatalytic activity of biogenically synthesized CuO nanostructures against xylenol orange and rhodamine B dyes

In the present article we report the Tamarindus indica L extract mediated biogenic green synthesis of CuO nanostructures. The synthesis consisted of reacting mixtures of copper salt solution and fruit extract at elevated temperatures. Heating under hydrothermal conditions for a very short duration (1 h) and under normal conditions for several hours were employed. The role of the heat treatment method on the growth of the nanostructures and their photocatalytic properties has been investigated. To the best of our knowledge, no one else has reported such a rapid synthesis of CuO nanostructures biogenically employing plant extracts. Moreover, no one else has reported the synthesis of CuO nanostructures such as nanosheets using fruit extracts of Tamarindus indica L. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results reveal that the CuO nanostructures grow in the monoclinic and cubic phases. Morphological studies indicate the material grown under short duration (hydrothermal conditions) predominantly consists of nanosheets (~27 nm thick) while that grown with prolonged heating consists of granular nanoparticles (diameter ~ 19 nm), both agglomerated as spherical structures. Thermogravimetric results show good thermal stability of the nanostructures even at high temperatures. Optical properties indicate the material is visible light active and possesses an indirect energy band gap ~ 1.7 eV. Photoluminescence (PL) spectra of the nanostructures showed prominent emission at ~700 nm and a small amount of emission around 400 nm. The color coordinates of the nanoparticles determined from the PL data were located in the blue region of the Commission internationale de l'éclairage (CIE) diagram. Surface area analysis revealed mesoporous nature of the nanostructures. The nanosheets exhibit larger surface area (35.4 m2/g) than the granular nanoparticles (22.6 m2/g). The microspheres made of agglomerated nanosheets were used to carry out the photocatalytic degradation of rhodamine B (RhB) and xylenol orange (XO) dyes under UV–Visible light illumination. The nanosheets exhibited strong photocatalytic behavior and photodegraded 96% of RhB and 87% of XO in 150 and 90 min of light illumination, respectively. The photocatalyst showed good stability during the photocatalytic reactions. High activity and better stability of the nanosheets indicate the photocatalysts have potential ability to get commercialized.

Conformational transition and gelation of κ-carrageenan in electrostatic complexation with β-lactoglobulin aggregates

The goal of this study was to evaluate the impact of electrostatic complexation with three different β-lactoglobulin aggregates on the conformational transition and gelation of κ-carrageenan (κ-car). We prepared native granular β-lactoglobulin (NGBLG), nanoparticle β-lactoglobulin (NPBLG), and fibrillary β-lactoglobulin (FBLG), and then assessed their electrostatic complexation with κ-car and the resultant impact on κ-car conformational transition, gelation, and microstructural changes. A quantitative model based on the McGhee-Hippel theory was adopted as a means of describing the impact of electrostatic complexation on the κ-car conformational transition in the presence of these protein aggregates. FBLG resulted in the most significant inhibition of κ-car conformational transition and gelation, whereas NPBLG had the least significant impact on this process. This was attributed to the fact that NPBLG imposed the least steric hindrance of these three aggregates. Together, these data highlight promising approaches to regulating polysaccharide gelation, viscoelasticity, rheological behavior, and conformational transition for use in a range of industrial applications.

Additively manufacturing-enabled hierarchical NiTi-based shape memory alloys with high strength and toughness

ABSTRACT A hierarchical microstructure was obtained, including the unique interlaced dual-phase structure, the solidified molten pool, the coarse columnar B2 grains and fine equiaxed B19’ grains, and a great many nanoparticles, during laser powder bed fusion (LPBF) of NiTi alloys. The effect of laser processing parameter on the growth of nanoparticles was assessed. A combination of low laser power and high scanning speed was conducive to the formation of fine granular nanoparticles with a more uniform distribution. Subsequently, effects of rotation angle between adjacent layers on the compressive deformation behaviour of LPBF-processed NiTi alloys were studied. At a small rotation angle (6–36°), the samples could exhibit an excellent combination of high compressive fracture strength and ductility (e.g. 3094 MPa/39.85%). Meanwhile, samples with small rotation angle tended to get a large strain span for the martensite transformation stage and a large deformation capacity (e.g. 4.64% and 9.25% for θ = 6° and σmax = 800 MPa).

Frequency Dependence of Initial Heat Generation in Granular Magnetite Nanoparticles

The frequency dependence of heat generation in granular magnetite nanoparticles was studied using vibrating sample magnetometry and the nanoTherics Magnetherm™ hyperthermia testing system. First, the particle size and its distribution were obtained by fitting the M-H curve to the classical Langevin function weight-averaged with a modified log-normal size distribution function. Next, the ac power dissipation model for monodispersed nanoparticles was extended to the polydispersed case, and the volumetric heating rate was predicted as a function of the frequency of the applied field under the assumption of the Neel relaxation mechanism. Finally, the temperature increase caused by the application of an ac magnetic field was measured experimentally at frequencies of 50, 112, 261, 335, 474 and 523 kHz, with the root-mean-squared field fixed to 250 Oe, and the results were compared with those from theoretical calculation. The frequency dependence of the initial heating rates was found to be in good agreement with the results predicted by using the polydispersed power dissipation model.

Iron coral: Novel fungal biomineralization of nanoscale zerovalent iron composites for treatment of chlorinated pollutants

In this research, a facile fungal biomineralization method was developed for the synthesis of nanoscale zerovalent iron (nZVI) with a unique N-doped branching structure, which showed excellent stability and mediated high degradation of carbon tetrachloride (CCl4) in aqueous solution. The ureolytic fungus Neurospora crassa was cultured in medium containing Fe2+ and urea which resulted in iron carbonate biomineral precipitation. Following carbonization at 900 °C, the fungal-carbonate composite became highly porous and granular nanoparticles (~50 nm diameter) were distributed evenly around the carbonized hyphae in a coralline manner. This ‘iron coral’ composite was identified as a mixture of zerovalent iron (Fe0), carbon iron (Fe1.91C0.09) and iron oxide (Fe3O4). The porous branching hyphal framework improved the capture efficiency of CCl4, and the N-doped sites may accelerate the electron transfer between CCl4 and nZVI. Geochemical simulation was applied to verify the formation of the biominerals, and chemical analyses confirmed its significant degradation ability for CCl4. These findings have therefore demonstrated that ureolytic fungi can provide a promising environmental-friendly system for the novel preparation of nZVI through biomineralization with the resulting ‘iron coral’ capable of significant removal of a chlorinated compound and therefore indicating new bioremediation applications.

Flower-like calcium phosphoserine complex as biomimetic mineral with high bioactivity

Biomineralization is a set of processes whereby living organisms generate hierarchically structured organic–inorganic materials. Studies on biomineralization not only elucidate the natural process of biomineral formation but also contribute to the development of functional biomaterials. However, the function of small molecules in the process has not been clarified. In this study, phosphoserine (PS) was used as a phosphorus source to prepare biomimetic minerals, and a new flower-like organic–inorganic complex of calcium PS (CaPS) was obtained. The CaPS samples were self-assembled plate-like crystals in the first 10 min. Then, over the next 5 h of the reaction, the plate-like crystals were broken down into fine granular nanoparticles. The chemical and thermal properties of CaPS were characterized, and the results indicated that the CaPS was or had a similar structure to Ca(C3H6NO6P)·H2O. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure spectra (EXAFS) were obtained, which clearly revealed 6-fold-coordinated Ca-O bonds with lengths of 2.319 (±0.0147) Å, 2.358 (±0.0147) Å, and 2.435 (±0.0147) Å. Furthermore, the results of a CCK-8 assay indicated the high biocompatibility of CaPS. When the samples were co-cultured with mouse preosteoblast cells (MC3T3-E1), CaPS exhibited good bioactivity to promote the osteoblast differentiation of cells. Owing to its excellent chemical and biological properties, the as-prepared CaPS complex is promising for various biomedical applications.

Two Dimensional Mxene (Ti3C2) Decorated By SnO2 Nanocrystals for Enhanced Chemical Gas Sensors at Room Temperature

Introduction A low-cost chemical sensor for ammonia (NH3) detection is highly demanded nowadays for several important applications. Two-dimensional (2D) nanomaterials such as graphene/reduced graphene oxide (rGO), transitional metal dicharcogenides, black phosphor and transition metal carbonitride (MXene) have found a promising application in the fields of gas sensing electronics at room temperature due to their unique microstructure, electrical properties and excellent gas adsorptions ability. Decoration of the secondary phase such as noble metals and metal oxide nanocrystals to form heterojunctions with two-dimensional materials can effectively improve the inadequacy of two-dimensional materials based gas sensors. It takes advantages of the difference in the Fermi level of each phase to make the electrons transfer from one material to the other and thus enriching the electron concentration on the surface of one material that is dominant in the electrical transport. In this way, more ionized oxygen is chemisorbed, leading to the improvement of the gas sensing properties [1].In this work, 2D MXene heterojunctions incorporated with SnO2 nanoparticles have been synthesized by using hydrothermal method. The as-fabricated MXene/SnO2 heterojunction based chemiresistive-type sensor showed excellent sensitivity to different concentrations of ammonia from 0.5-100 ppm at room temperature. The response has about 20 times higher than those reported in literature to 100 ppm NH3 and an excellent selectivity. Preparation and characterizations The Ti3AlC2 was purchased directly from Beijing Forsman Corp. The concentrated hydrochloric acid (HCl) was diluted to 9M. 2g of lithium fluoride (LiF) was added into 20ml diluted hydrochloric acid and stirred with magnetic mixer. 2g Ti3AlC2 was slowly and evenly dispersed in the solution over a period of several minutes and subsequently stirred at 35℃ for 48h to obtain the MXene. 70 mg of MXene powder was dispersed in 30ml of deionized water after grinding and sonicated for 30min. 73.5mg of stannic chloride pentahydrate (SnCl4·5H2O) was added into the suspension and stirred with magnetic stirrer at room temperature. The suspension was then loaded in a 50ml Teflon-lined autoclave. The autoclave was sealed and heated in an KSL-1200X hydrothermal system at 180℃ for 12h to obtain the MXene-SnO2 hybirds. The samples were then characterized by XRD, SEM, XPS, Raman and TEM-ED. The MXene/SnO2 based chemirestive-type sensor was measured by a static volumetric method. The resistance of the sensor is directly measured by a digital multimeter (Agilent 34410A). The responses of the sensors were defined as the relative change in the resistances of the sensors in the air and those in the tested gas. Results and Conclusions Fig.1a shows the XRD of the prepared samples. Appearance and down-shift of the peak at ~10 oC indicates the successful achievements of MXene and thus the MXene-SnO2 composite heterojunctions [2-3].Fig.1 (b-c) show the micrographs of the surface morphology of the MXene and heterojunctions. The etched MXene material has obvious layered structure with sizes ranging from 2 μm to 4 μm. The thickness of MXene is about 75 nm indicating the sample contains about 100 single layers of MXene. The granular SnO2 nanoparticles are intimately attached to the surface of MXene. Fig.2 (b) shows the Raman spectra of MXene and Mxene/SnO2 heterojunction. The appearance of both D-band and G-band in the MXene/SnO2 heterojunction sample indicated that MXene remained well during the hydrothermal reaction. Fig.2(c) shows the Ti core level (2p) spectra of the MXene and MXene/SnO2. Ti - X corresponds to titanium carbide or titanium oxynitride. Fig.2d indicates that the peaks at 530.1 and 532 eV correspond to oxygen vacancies and O=C-OH, respectively, suggesting that these and surface-adsorbed oxygen tend to form more active sites, thereby enhancing sensing capability.The sensors using MXene/SnO2 heterojuction shows excellent response and selectivity to low-level NH3 from 0.5-9 ppm at RT (Fig.3). Since the work function of MXene (4.465 eV) was slightly lower than that of SnO2 (4.7 eV), Schottky-type junctions were formed across MXene/SnO2 interfaces (Fig.4). Electrons would transfer from SnO2 to MXene, and the depletion layer was deepened on the surface of MXene. MXene could then chemically adsorb more oxygen, and the response of the MXene/SnO2 heterojunction was thus significantly enhanced.