Addition Of NH4F Research Articles

Co(II)-TiO2/Ti Thin Film as Antibacterial Photocatalysts Escherichia Coli Under Visible Light Ilumination

A thin layer of TiO2 doped with Cobalt (II) immobilized on the surface of a titanium foil (Co(II)-TiO2/Ti) has been synthesized from a titanium foil (Ti) as a TiO2 precursor as well as a thin layer matrix and CoCl2.6H2O as a source of Co(II) on variations of 0.5%, 1% and 2%. Synthesis was carried out by anodizing method using ethylene glycol electrolyte solution with the addition of NH4F and followed by calcination treatment at 450ºC for 3 hours. The obtained Co(II)-TiO2 /Ti thin films were characterized using Fourier-transform infrared (FT-IR) spectroscopy, Diffuse Reflectance UV-Vis (DRSUV-Vis) and X-ray diffraction (XRD) methods. Doping Co(II) variations of 0.5%, 1.0% dan 2.0% in the TiO2 structure causes a shift in the vibrational absorption peak of Ti-O (460.99 cm-1) towards a smaller wave number of 459.06 cm-1 respectively ; 453.27 cm-1 and 451.34 cm-1. This is supported by the results of the DRUV-Vis analysis using the tauc plot method, which shows a decrease in the band gap energy of TiO2 (3.24 eV) to 2.57 eV, 2.47 eV and 2.28 eV. Based on XRD analysis, it is known that the Co(II)-TiO2/Ti photocatalyst has anatase phase with a crystal size of 15-17 nm. The photocatalytic activity of Co(II)-TiO2/Ti under visible light illumination was evaluated for inhibition of Escherichia coli bacterial growth. Co(II)-TiO2/Ti photocatalyst at 2.0% Co(II) concentration had the best inhibition (43.2%) compared to 0.5% and 1.0% Co(II) concentrations, respectively 18% inhibition and 27%.

Crystal growth of fluorine-doped tin oxide structures with extraordinary morphology by the hydrothermal method and their electrical conductivity

In this work, fluorine-doped tin oxide (FTO) crystal structures with different morphology and the phase composition were synthesized by the hydrothermal method. It was shown that the controlled addition of NH4F to the initial solution leads to a change in the pH of the reaction mixture. Varying the pH of the initial mixture results in a change in the shape of growing crystals from a flower-like to a prismatic and phase transformation of the resulting crystal structures. Flower-like FTO structures obtained at a mass ratio of F/SnO2 = 0.05 show the highest conductivity in the synthesized series. A detailed microstructural analysis indicates that these structured particles consist of primary nanocrystals that are misoriented and have different preferential growth directions. It is assumed that an enhancement in the conductivity can be due to the synergistic effect of defects formed during the spontaneous growth of FTO nanocrystals under hydrothermal conditions and their local interaction.

Synthesis and thermoluminescence of Ce-doped CaF2 phosphor: Study of defect centers responsible for the TL emission by EPR analysis

We present here the thermoluminescence (TL) properties of Ce-doped CaF2 (CaF2:Ce) phosphor synthesized by combustion of the precipitate formed from the addition of NH4F to (Ca(NO3)2)⋅4H2O. The structure analysis of the synthesized sample was carried out by X-ray diffraction (XRD) technique. The CaF2:Ce phosphor shows an intense peak at about 120 °C and a low-intensity peak at 280 °C. Both peaks' thermoluminescence (TL) intensity was observed to increase with γ-dose. The kinetic parameters of TL peaks were calculated for CaF2:Ce phosphor using the Tm-Tstop and deconvolution methods. Electron paramagnetic resonance (EPR) is utilized to identify the defect centers formed in γ-irradiated CaF2:Ce phosphor and also to infer the defect centers involved in the TL process. The presence of two defect centers is inferred and center I has a g-value equal to 2.018 and is identified as an O− ion. The O− ion correlates with the TL peak at 120 °C. Center II with a g-value of 2.0057 is ascribed to a radiation-induced Fe3+ ion and is observed to relate to the high-temperature TL peak at 280 °C. The UV–Vis optical absorption of pure CaF2 and Ce-doped phosphors was investigated.

Seed-assisted synthesis of Ga-MFI slabs and nanocrystal agglomerates and comparative study of acidic properties

A series of Ga-MFI zeolites were one-step synthesized following the seed-assisted strategy without using additional organic template. The effects of synthesis parameters on the framework fabrication, morphology evolution, and gallium incorporation were systematically investigated by XRD, N2-adsorption, UV-Raman, STEM, TEM, solid state NMR, NH3-TPD, and Py-IR analyses. The Si/Ga seed exhibited a highly efficient structure-directing capability in the assembly of MFI framework and the amount of the costly tetrapropylammonium hydroxide (TPA+) was thus decreased to less than one-tenth in comparison with the traditional synthesis. Crystallization temperature and pre-aging conditions played the key roles in the Ga-MFI zeolite synthesis. Both of the morphology and the intraframework gallium concentration can be facilely controlled by adding the mineralizer and surfactant. The addition of NH4F and CTAB was favorable for the formation of the slabs-form product but against to the gallium substitution. Only with the help of Si/Ga seed, the synthesized Ga-MFI nanocrystal agglomerates possess a highly accessible hierarchical mesopore structure that consisted solely of interparticle-type mesopores. Simultaneously, it also exhibited a remarkable gallium incorporation, which ensured the great acidic properties, including strong acidic strength and high acid amount. As a consequence, the Ga-MFI nanocrystal agglomerates performed the excellent catalytic activity in the LDPE degradation.

Synthesis and structural features of black TiO2 nanotubes after annealing in hydrogen

TiO2 nanotubes (TiO2 NTs) with a diameter of 60 nm, a wall thickness of 12 nm, and a length of 13 μm were synthesized by anodic oxidation of Ti plates in ethylene glycol with the addition of NH4F and H2O. The intense black color of TiO2 NTs is acquired after heating in hydrogen at 500 °C. The carbon content on the surface of the black TiO2 TNs is 20.1 ± 1 at.%, of which 13.8 at.% is graphite carbon. It was found that only 2.4 at.% of the titanium ions exist as Ti3+ ions. It has been concluded that carbon contributes to the black color of TiO2 NTs. The ordering in the arrangement of carbon networks of amorphous carbon in the black TiO2 NTs is revealed. There is an oriented arrangement of carbon rings along the walls of the black TiO2 NTs, which is similar to the formation of carbon nanotubes inside the pores of TiO2 NTs. The formation of graphitized carbon in a regular TiO2 nanoporous structure makes it possible to obtain intensely colored films.

Simultaneous trace determination of three natural estrogens and their sulfate and glucuronide conjugates in municipal waste and river water samples with UPLC-MS/MS.

Analytical method for three natural estrogens (NEs) and their sulfate and glucuronide conjugates in waste and river waters using solid-phase extraction (SPE) coupled with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) has been available, but problems including poor recovery exist. In order to solve these, some optimizations have been performed in this work. For sample preparation, both rinse and elution solutions were optimized, in which 6mL of MeOH/water (1:9, v/v), MeOH/Ace/water (10:2:88, v/v/v), and MeOH/NH4OH/water (10:2:88, v/v/v) were determined as the rinse solution, while 6mL of 2.0% NH4OH/MeOH was determined as the elution solution for conjugated NEs (C-NEs). For mobile phase, addition of NH4F could obviously enhance the signal response of the nine target compounds, and the optimized addition concentration was 0.5mmol/L. The developed efficient method was validated and showed excellent linearity for each target compound (R2 > 0.998), low limit of quantifications (LOQs, 0.07-1.29ng/L) in four different water matrices, and excellent recovery efficiencies of 81.0-116.1% in influent, effluent, ultra-pure, and river water samples with low relative standard deviations (RSDs, 0.6-13.6%). The optimized method was successfully applied to influent, effluent, and Pearl River water, among which three NEs were all detected, while five C-NEs were found in the influent, three C-NEs were detected in the effluent, and two C-NEs were found in the Pearl River water, indicating the wide distribution of NEs and C-NEs in different water environments. This work provided a reliable and efficient analytical method for simultaneous trace determination of NEs and C-NEs, which had satisfactory absolute recoveries with low RSDs, low LOQs, and time-saving for both analysis and nitrogen drying.

Discovery of Two Polymorphs of TiP4 N8 Synthesized from Binary Nitrides.

TiP4N8 was obtained from the binary nitrides TiN and P3N5 upon addition of NH4F as a mineralizer at 8 GPa and 1400 °C. An intricate interplay of disorder and polymorphism was elucidated by in situ temperature‐dependent single‐crystal X‐ray diffraction, STEM‐HAADF, and the investigation of annealed samples. This revealed two polymorphs, which consist of dense networks of PN4 tetrahedra (degree of condensation κ=0.5) and either augmented triangular TiN7 prisms or triangular TiN6 prisms for α‐ and β‐TiP4N8, respectively. The structures of TiP4N8 exhibit body‐centered tetragonal (bct) framework topology. DFT calculations confirm the measured band gaps of α‐ and β‐TiP4N8 (1.6–1.8 eV) and predict the thermochemistry of the polymorphs in agreement with the experiments.

Discovery of Two Polymorphs of TiP4N8Synthesized from Binary Nitrides

AbstractTiP4N8was obtained from the binary nitrides TiN and P3N5upon addition of NH4F as a mineralizer at 8 GPa and 1400 °C. An intricate interplay of disorder and polymorphism was elucidated by in situ temperature‐dependent single‐crystal X‐ray diffraction, STEM‐HAADF, and the investigation of annealed samples. This revealed two polymorphs, which consist of dense networks of PN4tetrahedra (degree of condensationκ=0.5) and either augmented triangular TiN7prisms or triangular TiN6prisms for α‐ and β‐TiP4N8, respectively. The structures of TiP4N8exhibit body‐centered tetragonal (bct) framework topology. DFT calculations confirm the measured band gaps of α‐ and β‐TiP4N8(1.6–1.8 eV) and predict the thermochemistry of the polymorphs in agreement with the experiments.

Construction of superior performance LiVPO4F/C cathode assisting by a regulating additive NH4F and the “Combination-Protection-Release” mechanism for lithium ion batteries

The commercialization of LiVPO4F/C cathode for lithium ion batteries is hindered by its low electrical conductivity and the presence of Li3V2(PO4)3 impurity. In this work, pure LiVPO4F/C with superior electrochemical performance is successfully prepared by adding regulating additive NH4F in one-step rapid reduction method. N-doped LiVPO4F/C without Li3V2(PO4)3 is synthesized by adding 0.025 mol NH4F, which possesses high electrical conductivity (0.896 S cm−1) and large Li-ion diffusion coefficient (3.65 × 10−10 cm2 s−1). It presents superior capacity of 144.8, 127.5 and 112.7 mAh g−1 at 1, 5 and 15 C and high capacity retention of 85.13% after 300 cycles at 1 C and excellent long term performance after 1000 cycles at 8 C. The in-situ X-ray diffraction analysis reveals the transformation process of the crystal structure of LiVPO4F. The added NH4F can effectively improve the electrochemical performance by adjusting the negative logarithm of the effective hydrogen-ion concentration to refine the grain and serve as nitrogen-doping source, leading to increased Li-ion diffusion coefficient and electrical conductivity. The precipitate LiHF2 is formed after the addition of NH4F, which can suppress the volatilization of fluorine and supplement its loss in the precursor. The “Combination-Protection-Release” mechanism has been proposed to explain the preparation of LiVPO4F/C without impurity Li3V2(PO4)3.

Understanding the effect of HF-based wet shallow etching on optical performance of reactive-ion-etched fused silica optics.

The optical performance of fused silica optics used in high-power lasers is known to depend not only on their surface damage resistance, but also on their surface quality. Previous studies have shown that good fused silica damage performance and surface quality can be achieved by the use of reactive ion etching (RIE), followed by HF-based wet shallow etching (3 μm). In this study, two kinds of HF-based etchants (aqueous HF and HF/NH4F solutions) were employed to investigate the effect of HF-based etching on the optical performance of reactive-ion-etched fused silica surfaces at various HF-based shallow etching depths. The results showed that the addition of NH4F to HF solution makes it possible to produce a high-quality optical surface with a high laser-induced damage threshold, which is strongly associated with the surface roughness and fluorescence defect density. Additionally, changing the HF-based etching depth over the range from 1 μm to 3 μm can affect the surface damage resistance and absorption performance of RIE-treated fused silica. The light-scattering results indicate that the point defect density plays an important role in the determination of the HF-based etching depth. Understanding these trends can enable the advantages of the combined technique of RIE and HF-based etching during the fabrication of high-quality fused silica optics.

Accelerating F-doping in transparent conducting F-doped SnO2 films for electrochromic energy storage devices

In this study, we designed a unique method for increasing F-doping concentration in F-doped SnO2 (FTO) films, without the extra addition of NH4F as a doping source, using NaOH acting as a functional additive during ultrasonic spray pyrolysis. The NaOH triggers a chemical reaction with HF, resulting in the presence of dissociated F− acting as a doping source. To optimize the NaOH effect on the transparent conducting performance in the FTO films, we adjusted the volume percentages of the NaOH to 0, 1, 5, and 10 vol% during FTO deposition. Compared with other FTO films, the FTO film prepared with 5 vol% NaOH revealed enhanced carrier concentration (7.81 × 1020 cm−3) generated by the increased F-doping concentration (3.57 at%) and high Hall mobility (27.18 cm2/(V S)) through smooth surface morphology. Such behaviors through the NaOH effect resulted in FTO films with decreased sheet resistance (5.3 ± 0.16 Ω/□), leading to improved electrochromic (EC) energy storage performances of fast switching speed (6.6 s for coloration speed and 8.4 s for bleaching speed) due to faster electrochemical kinetics at the active electrodes, high coloration efficiency (58.1 cm2/C) and high specific capacitance (65.2 F/g at 2 A/g) via enhanced electrochemical activity in the active electrodes that widens the transmittance modulation. Therefore, our study suggests a novel method to improve the transparent conducting performances of FTO films for application in EC energy storage devices.

Nanomagnetism variation with fluorine content in Co(OH)F

Magnetic behaviors of cobalt hydroxide fluoride, Co(OH)F2-x Fx (x = 1.09 and 1.26), which are consisted with nanorods of ∼5 μm length and diameter ∼100 nm, obtained by a facile hydrothermal method, have been researched with the variation of fluorine content as a result of the different amount of reactant NH4F addition. Magnetic coupling performance are characterized based on the observation and analysis of magnetic susceptibility, X-ray Absorption Fine Structure (XAFS) and specific heat. Co(OH)F2-x is found to undergo an antiferromagnetic transition at 40 K. The peak temperature (T) on the transition curves shifts to lower temperature according with the increased magnetic field (H) following the rule of H2/3∞ (-T) because of the surface spin-glass behavior. The paramagnetic susceptibility can be fitted with the modified Curie–Weiss law between 100 K and 320 K. The negative Curie-Weiss temperature indicates that the antiferromagnetic coupling becomes stronger with the fluorine content. In addition, at temperatures below 5 K, the magnetic reordering was observed as spin-glass. Exchange bias behavior in Co(OH)F2-x was found after field cooling process demonstrating an exotic surface magnetic behavior generated with high fluorine contents due to the deformation of CoO6 octahedral induced large spin-glass behavior.

Revisiting the phenanthroline and ferrozine colorimetric methods for quantification of Fe(II) in Fenton reactions

Abstract Colorimetric methods for Fe(II) determination based on complexation of heterocyclic amines, such as phenanthroline (Phen) and ferrozine (FZ), have been widely used for analysis of iron species in solution, which is critical to discuss the mechanism of Fenton and related reaction systems. However, the reliability of both methods in the background of hydrogen peroxide has never been addressed. In this study, we demonstrate that serious Fe(II) overestimation possibly occurs for both methods in Fenton systems, particularly for the Phen method. A systematic variation of incubation conditions reveals that the available Fe(II) concentration depends greatly on the incubation time after mixing the colorimetric reagents with the sample. Also, it is highly sensitive to pH and temperature as well as the initial concentrations of Fe(III), H2O2, and acetate buffer. The experimental results combined with simulations indicate that Fe(II) overestimation mainly results from the reduction of Fe(III)-Phen or Fe(III)-FZ complexes by residual H2O2 during analysis, a reaction that is facilitated by the ligand field effect of the heterocyclic amine. An effective remedy for the instability and inaccuracy of the methods in the presence of H2O2 is the addition of NH4F to the incubation mixture (55 mM for Phen and 35 mM for FZ), which converts residual Fe(III) to a colorless and reduction-insensitive fluoride complex.

Influence of Plasma Treatment on Physical Properties of Thin SnO2 Films Obtained from SnCl4 Solutions with Additions of NH4F and NH4OH

This paper considers the effect of oxygen and hydrogen plasma on SnO2 films synthesized from solutions of tin tetrachloride containing NH4F and NH4OH additives. It was found that the treatment of samples with oxygen plasma for 5 min led to a decrease in transparency by 1.11 and 1.17 times. On the transmission spectra, a decrease in the transmittance at a wavelength of 450 nm to 38.1% (1.24 times) in samples obtained from solutions with the addition of NH4F and up to 29.9% (1.53 times) in samples obtained from solutions with the addition of NH4OH is observed. The formation of tin oxide (II) under the influence of the reducing properties of hydrogen plasma is assumed. At the same time, the formation of metal tin from tin dioxide is not observed here. Due to the decreasing of transmission coefficient in the long-wave region of the spectrum. There is an increase in surface resistance after treatment with oxygen plasma, due to filling oxygen vacancies. Treatment of hydrogen plasma films leads to a decrease in surface resistance. Perhaps due to the increase in oxygen vacancies under the influence of hydrogen plasma. Within five minutes, the oxygen and hydrogen plasma had a more active effect on the films obtained from the solution with the addition of ammonium hydroxide, which is associated with a higher porosity of the sample. Consequently, irrespective of the time of plasma exposure with increasing the surface of contact between ionized gases and the film material, the interaction efficiency will increase.

Morphology engineering of CoSe2 as efficient electrocatalyst for water splitting

Transition-metal cobalt-based chalcogenides have wide application in the fields of energy conversion and storage. Suitable morphologies can effectively improve the surface area and performance of the materials. Herein, we reported a simple and controlled strategy to fabricate the CoSe2 with various shapes and applied these in water splitting. We successfully synthesized the spheres, wires and rods of CoSe2 via facile hydrothermal process through regulating the addition of NH4F to alter the morphologies of samples. Among these samples, the as-prepared CoSe2 spheres have urchin-like morphology with highly hollow structure, leading to large specific surface area and a great number of channels for promoting mass transfer efficiency. Therefore, the CoSe2 spheres as electrocatalyst exhibits excellent oxygen evolution reaction and hydrogen evolution reaction performance in alkaline and acidic conditions, respectively. Electrochemical measurement illustrated that the CoSe2 spheres as electrocatalyst shown small overpotential and superior stability, which could be a promising candidate of effective electrocatalyst.

Bismuth Oxychloride Nanoplatelets by Breakdown Anodization.

Herein, the synthesis of BiOCl nanoplatelets of various dimensions is demonstrated. These materials were prepared by anodic oxidation of Bi ingots in diluted HCl under dielectric breakdown conditions, triggered by a sufficiently high anodic field. Additionally, it is shown that the use of several other common diluted acids (HNO3, H2SO4, lactic acid) resulted in the formation of various different nanostructures. The addition of NH4F to the acidic electrolytes accelerated the growth rate resulting in bismuth‐based nanostructures with comparably smaller dimensions and an enormous volume expansion observed during the growth. On the other hand, the addition of lactic acid to the acidic electrolytes decelerated the oxide growth rate. The resulting nanostructures were characterized using SEM, XRD and TEM. BiOCl nanoplatelets received by anodization in 1 M HCl were successfully employed for the photocatalytic decomposition of methylene blue dye and showed a superior performance compared to commercially available BiOCl powder with a similar crystalline structure, confirming its potential as a visible light photocatalyst.

NH4F-assisted one-pot solution synthesis of hexagonal ZnO microdiscs for efficient ultraviolet photodetection.

One-pot solution method to grow large hexagonal ZnO microdiscs with the aid of ammonium fluoride (NH4F) mineralizer has been realized. The size, morphology, crystallinity and optical properties of the synthesized ZnO microdiscs can be efficiently modulated by the concentration of NH4F. X-ray diffraction and scanning electron microscopy analyses illustrate that hexagonal ZnO microdiscs achieved at 0.03 M NH4F concentration have larger disc size and narrower full-width value at half maximum of (002) peak. It implies better crystal quality compared with those from other additive concentrations. Photoluminescence results also demonstrate the same trend. These results indicate that with proper addition of NH4F, the crystal quality of ZnO microdiscs has been improved and defects have been suppressed. Furthermore, a UV photodetector has been fabricated by simply transferring the ZnO microdiscs grown with 0.03 M NH4F onto a p-type silicon substrate. The device exhibits photosensitive behaviour at 365 nm UV light illuminating when −0.6 V is applied. The response time as well as recovery time is less than 0.1 s. The relatively large photoresponsivity of 1.19 A W−1 with power consumption less than 10 nW makes it possible in application field of highly efficient low power consumption UV detection.

A Facile Method Using a Flux to Improve Quantum Efficiency of Submicron Particle Sized Phosphors for Solid-State Lighting Applications

This work successfully verified that the addition of a flux (NH4F, NH4Cl, and H3BO3) during synthesis has an impact on the crystallite size and quantum efficiency of submicron-sized particles of CaMgSi2O6:Eu2+ phosphors. The addition of NH4F or NH4Cl increased the crystallite size in the submicron-sized particles, yielding an increase in emission intensity and quantum efficiency. On the other hand, the use of the H3BO3 flux crystallized a secondary phase, SiO2, and changed the lattice parameters, which degraded the luminescent properties. In addition, an excessive amount of NH4Cl was examined, resulting in nucleation of a secondary phase, CaSiO3, which changed the lattice parameters with no improvement in luminescent properties. These results demonstrate that the addition of a flux could be a method to improve the quantum efficiency of submicron-sized particles composed of nanocrystallites; however, a judicious choice of the flux composition and amount has to be carefully considered.

Facile fabrication and configuration design of Co3O4 porous acicular nanorod arrays on Ni foam for supercapacitors

The configuration of electrode materials is of great significance to the performance of supercapacitors (SCs) because of its direct effects on specific surface area and electron transfer path. Given this, herein, a series of Co3O4 hierarchical configurations composed of porous acicular nanorods are designedly synthesized on Ni foam with in-site self-organization method depending on the addition of NH4F. In the absence of NH4F, Co3O4 nanorods self-assemble into porous urchin-like structure (PULS), while the introduction of NH4F can induce the vertical growth of Co3O4 acicular nanorods, forming porous acicular nanorod arrays (PANRAs). By simply tuning the concentration of NH4F, the Co3O4 PANRAs with different specific surface area can be obtained. As expected, Co3O4 PANRAs electrode for SCs (using 1 mmol of NH4F) exhibits high specific capacitance (1486 F g−1 at 1 A g−1) and excellent cycling stability (98.8% retention after 5000 continuous charge–discharge cycles), which are better than those of Co3O4 PULS electrode (658.2 F g−1 at 1 A g−1, 90.4%). Corresponding solid-state symmetric SC achieves a high energy density of 48.63 Wh kg−1 at power density of 600 W kg−1. Such superior performance is attributed to fast charge transfer kinetics, facile electron transport and ions diffusion rate resulting from porous array structure, indicating the importance of configuration design of electrode materials for high performance SCs.

Influence of NH4F additive on the combustion synthesis of β-SiAlON in air

The preparation of β-SiAlON, Si6–zAlzOzN8–z (z = 1–4), was investigated using the combustion synthesis (CS) technique with Si, Al, and CO(NH2)2 as the main raw materials in air. Different amounts of NH4F were used as a low-melt additive to the raw materials to decrease the reaction temperature and promote β-SiAlON formation. Phase and microstructural analyses of the reaction products were performed by X-Ray diffraction (XRD) and FE-SEM/energy dispersive X-ray spectrometer techniques. FT-IR spectroscopy was also used to demonstrate the formation of β-SiAlON in the final product. The phase and microstructural analysis results showed that NH4F addition improved the exothermic reaction of β-SiAlON phase formation and increased its content in the final synthesized powders. Additional heat treatment of the sample at the optimum z-value (z = 4) and different percentages of NH4F revealed the positive effect of the low-melt additive on β-SiAlON phase formation under very low N2 pressure.