Tetraethoxyorthosilicate Research Articles

The performance of hybrid titania/silica-derived xerogels as active antifouling/fouling-release surfaces against the marine alga Ulva linza: in situ generation of hypohalous acids

Mixed titania/silica xerogels were prepared using titanium tetraisopropoxide (TTIP) and tetraethoxy orthosilicate (TEOS). Xerogel properties were modified by incorporating n-octyltriethoxysilane (C8). The xerogels catalyze the oxidation of bromide and chloride with hydrogen peroxide (H2O2) to produce hypohalous acids at pH 7 and pH 8. The antifouling/ fouling-release performance of a TTIP/C8/TEOS xerogel in the presence and absence of H2O2 was evaluated for the settlement of zoospores of the marine alga Ulva linza and for the removal of sporelings (young plants). In the absence of H2O2, differences in the settlement of zoospores and removal of sporelings were not significant relative to a titanium-free C8/TEOS xerogel. Addition of H2O2 gave a significant reduction in zoospore settlement and sporeling removal relative to the C8/TEOS xerogel and relative to peroxide-free conditions. The impact of TTIP on xerogel characteristics was evaluated by comprehensive contact angle analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy.

Cation‐assisted adsorption of chlorophenols by nano‐xerogels

With water quality deteriorating globally, identification of novel adsorbents for removal of chloroaromatic compounds for wastewater treatment is of growing interest. Classic xerogels produced by drying sol‐gels of tetraalkoxy silanes, such as tetramethoxy orthosilane (TMOS) or tetraethoxy orthosilane (TEOS), carry a negative surface charge in water when the pH is higher than the Point of Zero Charge (PZC). This feature was employed in this study to load divalent metal cations on the surfaces of these materials to facilitate chlorophenol (CP) adsorption. Although classic xerogels do not show a high affinity for the adsorption of chlorophenols such as 2‐chlorophenol (2CP) in aqueous media, TEOS xerogels loaded with the cations Ni2+, Cd2+, and Zn2+ showed 225, 249, and 306 % increases, respectively, in the adsorption of 2CP compared to the unloaded TEOS xerogel. Adsorption of the divalent cations on the xerogels exhibited the order of Zn2+ > Cd2+ > Ni2+, with maximum adsorption capacities (Q°) of 15.9 and 13 mg/g for Zn2+ on TEOS and TMOS xerogels, respectively. Using TEOS xerogels loaded with Zn2+ (TEOS‐Zn), adsorption of 2CP, 2,4‐dichlorophenol (DCP), and 2,4,6‐trichlorophenol (TCP) in aqueous media was studied. The adsorption was found to be spontaneous and obeyed pseudo‐second order kinetics, suggesting a chemisorption mechanism between CP and TEOS‐Zn. The equilibrium isothermal adsorption data were most closely fitted with a Langmuir equation resulting in Q° values of 13.9, 9.17, and 8.5 mg/g for 2CP, DCP, and TCP, respectively.

Ru nanoparticles in ionic liquids confined by silica gel: A high active iongel catalyst for low temperature water-gas shift reaction

In this study, two different kinds of iongel catalysts were prepared by the dispersion of Ru nanoparticles in 1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) with a particle size of 2.4 nm in tetraethoxy orthosilicate (TEOS), followed by the hydrolysis of TEOS under acidic or basic conditions. The iongel catalyst prepared under acidic conditions had larger surface area, pore volume and higher stability to confine the active component in the silica matrix than that prepared under basic conditions. Thus, the iongel catalyst prepared under acidic conditions showed much higher catalytic activity. The highest CO conversion of 37.8% was achieved at 140 °C over the iongel catalyst prepared under acidic conditions, significantly higher than the 10% achieved on the iongel catalyst prepared under basic conditions. More importantly, it also showed high stability. Besides the superior texture properties of the iongel catalyst prepared under acidic conditions, the stability of Ru nanoparticles also contributed to its high catalytic activity and stability over the iongel catalyst prepared under acidic conditions.

Resistance of modified wood to marine borers

The resistance of differently modified wood to the common shipworm, Teredo navalis, and the wood boring crustacean, Limnoria quadripunctata, was assessed in a field trial and by means of a short term laboratory assay, respectively. Scots pine (Pinus sylvestris) sapwood was treated with TEOS (tetra-ethoxy-ortho-silane) and different thermosetting resins, namely phenol formaldehyde (PF) and methylated melamine formaldehyde (MMF). Additionally, acetylated and untreated Radiata pine (Pinus radiata) was included. In the field trial according to EN 275 in the Baltic Sea over a period of six years the specimens were exclusively attacked by T. navalis. For the laboratory assay, matchstick-sized samples cut from spare panels prepared for the field trial were subjected to individuals of L. quadripunctata; faecal pellet production served as a measure of feeding rate. Treatments that prevented shipworm attack in the field also reduced feeding of L. quadripunctata in the laboratory assay: efficacy of resin treatments was enhanced by parameters that increase the amount of resin in the cell wall (i.e. high WPG and dry curing conditions); acetylation resulted in high resistance; and TEOS treatment was not effective. The results suggest that modification on cell wall level is required to impart marine borer resistance.

Ammonia-free preparation of Ag@SiO2 core/shell nanoparticles

An ammonia-free approach for the preparation of silver@silica core/shell nanocomposites is reported in order to avoid the silver core etching during the preparation in a typical Stöber approach. Silver nanoparticles were used as the core and tetraethoxy orthosilicate (TEOS) was used the silica source. The silica layer formation process was investigated under alkaline conditions. Several bases were selected as the alkaline source and it was found that careful control of the solution pH below 10 during the silica layer formation is critical to ensure stable and aggregation free core–shell nanocomposites preparation as confirmed by UV–Vis spectroscopy and transmission electron microscopy.

Effect of the addition of 3-glycidoxypropyltrimethoxysilane to tetraethoxyorthosilicate-based stone protective coating using n-octylamine as a catalyst

A tetraethoxyorthosilicate (TEOS)-based stone protective coating containing functional 3-glycidoxypropyltrimethoxysilane (GPTMS) has been prepared in order to reduce gel crack formation during the drying phase using n-octylamine as a catalyst. The effect of gel time and viscosity on GPTMS concentration were studied. We have demonstrated that the addition of GPTMS accelerated the gel process and improve viscosity of sol. It was found that GPTMS was chemically incorporated into the gel matrix via Si–O bonds by Fourier transform infrared spectroscopy (FTIR) analysis. Nitrogen adsorption–desorption isotherms of xerogels were measured, they showed that the pore size of xerogels decreased with the addition of GPTMS. Atomic force microscopy (AFM) showed the surface roughness increased as content of GPTMS was higher. The Scotch Tape test and the hardness values showed improvement of cohesion and consolidation ability of hybrid sol. The protective performance evaluation of the treated stones with hybrid sol indicated its acid rain resistance.

Produksi Biodisel dari Minyak Jelantah Menggunakan Katalis Asam padat (Nafion/SiO2)

Production of biodisel from waste cooking oil (WCO) was performed using a double catalyst Nafion/SiO 2 as esterification catalyst and NaOH is used as transesterification catalyst . Study was conducted through three stages:as well as synthesis of Nafion/SiO 2 solid acid catalyst, the synthesis of biodisel using a single catalyst (NaOH) and the synthesis of biodisel using a catalyst (Nafion/SiO 2 and NaOH). Solid acid catalyst is made of Nafion 5 wt.% solution and the (Tetra Ethoxy Ortho silicate, TEOS) using solution phase sol-gel method to produce Nafion/SiO 2 . Furthermore Nafion/SiO 2 was applied as esterification catalyst. Esterification reaction conditions at temperatures of 75 o C and fixed reaction time of 45 minutes. The reaction is run at three-neck flask equipped with a stirrer, thermometer and cooling water. Products are separated and the upper layer is used as a reactant of transesterification reaction using NaOH catalyst and results biodisel (FAME). Result analysis of physical properties, ie viscosity, density and flash point FAME meets the standard requirements of biodisel. Chemical characterization in the FAME show there are more than six kinds of methyl esters indicate that FAME was formed. The percentage of biodisel that is produced by using dual catalyst is higher compared to using a single catalyst proved that the solid acid catalyst plays an important role in converting the free fatty acid in to ester in the WCO.

Effects of silane precursors on curing behavior of UV-curable hybrid coatings

This study demonstrates the effect of some commonly used silane precursors on curing behavior and photopolymerization kinetics of UV-curable hybrid coatings. Tetraethoxyorthosilane (TEOS), vinyltrimethoxysilane (VTMS), and 3-methacryloxypropyltrimethoxysilane (MPS) were polymerized under acidic conditions by the sol–gel method. The resulting structure of the tested siloxane oligomers was characterized using 29Si-NMR and 1H-NMR spectroscopy. Photo-DSC was used to evaluate photocuring enthalpy. A fully integrated model was applied to investigate propagation rate coefficients and to identify the most effective termination mechanism (monomolecular, bimolecular, or mixed). Results showed that oligomers containing MPS effectively promoted total heat of the polymerization process and consequently affected the maximum rate of polymerization and final double bond conversion. Enthalpy rating for samples containing MPS was higher than that of those containing VTMS, showing that MPS was more compatible with the acrylate systems. In addition, evaluations for photopolymerization kinetic constants proved that non-functional oligomers containing TEOS caused radical trapping and increased activity of the monomolecular termination mechanism.

In situ synthesis of ZrC/SiC nanocomposite via carbothermic reduction of binary xerogel

Nano-sized powder composite of zirconium carbide/silicon carbide (ZrC/SiC) was successfully synthesized via a combined sol gel/carbothermic reduction techniques. A sol containing zirconium from zirconium n-propoxide (ZTP) as well as a sol containing silicon from tetraethoxy orthosilicate (TEOS) was separately prepared. The two sols were mixed together for preparing a binary gel containing both. The produced binary xerogel was subjected to a carbothermic reduction reaction at temperature of 1500°C for 3h. The synthesized powder was characterized from compositional as well as morphological point of views using XRD, FT-IR, XPS, SEM and TEM analysis. The XRD data revealed that the powder composite consisted of pure ZrC/SiC was produced. This data was confirmed by presence of main planes (010) and (011) for ZrC and (111) plane for SiC, respectively. Moreover, XPS with help of FT-IR data show obviously that the ZrC/SiC composite was formed with traces of zirconium oxycarbide. Furthermore, SEM and TEM images confirmed that cubic nano-sized ZrC particles of size ∼40nm and hexagonal β-SiC nano-rods of size ∼50nm were obtained. In addition, the thermogravimetric analysis of the produced nanocomposite revealed the high homogeneity in the particle size distribution. Based on the obtained data, a mechanism of nanocomposite formation was postulated.

Metal assisted approach to develop molecularly imprinted mesoporous material exhibiting pockets for the fast uptake of diethyl phthalate as copper complex.

A new molecularly imprinted mesoporous material (MIM) containing specific pockets for the extraction of diethyl phthalate (DEP) as copper complex has been prepared for the first time. The mesoporous material was developed by utilizing copper-phthalate complex (Cu-DEP) as the template molecule, 3-aminopropyltriethoxysilane (APS) as a functional monomer and tetraethoxyorthosilicate (TEOS) as the silica source for polymer network formation. The mesoporous material showed fast uptake kinetics, and equilibrium was obtained within 30 min due to the introduction of copper, which provides an additional site for interaction with the functional monomer. Synthesized polymer was well characterized using UV-Vis spectrophotometry, IR spectroscopy, TGA studies, and TEM. To achieve efficient extraction of the template molecule, various factors including sorption kinetics, quantity of MIM, time required for equilibrium set-up, sorption isotherm and reuse of MIM were optimized. The extracted DEP samples were analyzed quantitatively at 310 nm using an HPLC-DA system. The prepared material is robust and can be reused. In addition, it was found to be selective for DEP as compared to other phthalates.

Physico-chemical of organo-functionalized magnesium phyllosilicate prepared by microwave heating

In this work, organo-functionalized magnesium phyllosilicates were prepared via hydrothermal synthesis with four sources of silicon: 3-aminopropyltriethoxysilane (AMPTS), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TMSPEDA), N-[3-(trimethoxysilyl)propyl]-diethylenetriamine (TMSPETA) and tetraethoxyorthosilane (TEOS). Microwave radiation (MW) was employed as heating source and the results were compared with the analogous materials synthesized by conventional heating in an oven (CE). The materials obtained were characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), solid state 29Si and 13C nuclear magnetic resonance (NMR), thermogravimetry (TG) and elemental analysis of carbon, nitrogen and hydrogen (CHN). The 2:1 type of trioctahedral phyllosilicate was confirmed by the presence of the 060/330 reflection, at 59.5° 2θ. The presence of the organic modifier was proven by the bands at 2930, 2850, and 1490cm−1 and the typical features of the phyllosilicate were found at 3700cm−1 (Mg–OH) and 1014cm−1 (Si–O–Si). 13C-NMR showed that the organic chains were intact in the interlayer space (5–64ppm). Thermogravimetry indicated that these pending groups were stable in this support until 200°C when they begin to decompose. Silicon-29 NMR confirmed that the pending groups were bound directly to the silicon atoms by the resonance of Si–C bond at 48 and 55ppm. The results showed the success of the procedure for all the proportions of the silicon sources used, with a reduction of reaction time in the range from 91% to 96% using microwave radiation in relation to the conventional heating oven.

The cause of absorption and luminescence band shift of disperse Red-13 in silica spheres

Optical absorption and luminescence band shifts have been observed for a disperse red-13 (DR-13) attached on silica spheres. A covalent bond is formed between an isocyanatopropyl triethoxysilane (ICPTES) and a DR-13 prior to DR-13 being incorporated inside the spheres. The Stober synthesis process was performed with the synthesized ICPTES-DR-13 (ICPDR), tetraethoxy orthosilane (TEOS), 2-propanol and NH4OH solution. The final silica spheres with ICPDR (ICPDRSS) were analyzed with Fourier transform infrared, UV-visible and fluorescence spectrometers. Characteristic absorption peaks at 1700 and 1704 cm−1 representing −C=O stretching vibrations for ICPDR and ICPDRSS indicate the formation of urethane linkages. Although the absorption band at 502 nm did not shift with increasing concentration of DR-13 in methanol, the absorption band for the ICPDRSS shifted 28 nm toward shorter wavelength due to the antiparallel geometry of the azochromophores. A broad luminescence was observed for ICPDRSS and shifted toward the blue with increasing excitation wavelength, which was due to a transformation of the DR-13 in silica spheres from a trans-form to a cis-form.

Fabrication and characterization of in situ synthesized iron oxide‐modified polyimide nanoweb by needleless electrospinning

ABSTRACTA series of poly(amic acid) (PAA) solutions were prepared by sol–gel condensation of 4,4′‐oxydianiline (ODA) and 4,4′‐oxydiphthalic anhydride (ODPA), containing various wt % (5, 10, 15) of an iron oxide precursor, that is, tris(acetylacetonato)iron(III) complex. The resulting PAA solutions were electrospun at 78 kV and collected as webs of nonwoven nanofibers of diameter ∼60–70 nm and subsequently converted to iron oxide‐modified polyimide (PI) nanofibers by slow thermal imidization. Aminopropyl triethoxysilane (APTES) and tetraethoxyorthosilicate (TEOS) were used as coupling agent and silica precursor, respectively, to enhance the compatibility between organic polymer matrix and inorganic moieties. SEM images reveal smooth and defect‐free surface morphologies of the nanofibers. Superparamagnetic properties of the nanofibers were revealed by vibrating sample magnetometer (VSM). FT‐infrared spectroscopy (IR), powder XRD, thermogravimetric analysis, and differential scanning calorimetry were employed to systematically characterize material structural properties, thermal stabilities, etc. Nanowebs showed excellent thermal stability around 446°C, with a glass transition temperature around 270°C. The above study demonstrates a good example for fabrication of highly thermally stable bead‐free nanofiber webs by needleless electrospinning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40432.

Comparative Adsorption of CO2 by Mono-, Di-, and Triamino-Organofunctionalized Magnesium Phyllosilicates

Carbon dioxide adsorbents, constituted by organofunctionalized magnesium phyllosilicates, were produced using 3-aminopropyltriethoxysilane (AMPTS), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TMSPEDA), N-[3-(trimethoxysilyl)propyl]-diethylenetriamine (TMSPETA), and tetraethoxyorthosilane (TEOS) as silicon sources with N/Si ratios of 1, 0.75, 0.5, and 0.25, by conventional and microwave heating. Adsorption studies were performed using TGA and temperature programmed desorption (TPD) methods. The results showed that the best temperatures for adsorption were 41, 45, and 90 °C, when magnesium phyllosilicate functionalized with TMSPETA, TMSPEDA, and AMPTS, respectively, were used as adsorbents. Using TPD technique, the maximum efficiency was found to be between 0.285 and 0.899 for 100% AMPTS and 33.33% TMSPETA, obtained by conventional heating. Adsorption efficiency of the materials prepared by conventional method is higher than those obtained using microwave as heating source, except for 100% AMPTS. Desorption kinetics of CO2, described using Avrami's model, show that the CO2 desorption rate constant is in the range from 0.130 to 0.178 min(-1), similar to the values for CO2 desorption from monoetamolamine-functionalized TiO2 and Li4SiO4 but in a narrower range of values.

Thermo‐Stimulable Wax@Water@SiO2 Multicore‐Shell Capsules

Complex wax@water@SiO2 multicore capsules are synthesized by combining sol‐gel process and formulation of wax‐in‐water‐in‐oil double emulsions. The inner direct wax‐in‐water emulsion is stabilized with modified silica nanoparticles using limited coalescence occurring in Pickering emulsions. In a second step, this obtained liquid dispersion is emulsified in poly‐dimethylsiloxane (PDMS) using a non ionic surfactant to stabilize the second water/oil interface. Finally, a sol‐gel process is employed to mineralize the as‐generated double emulsions giving rise to wax@water@SiO2 multicore capsules. Due to the wax volume expansion through melting, the as‐synthesized multicore capsules offer thermally stimulated release that is enhanced when surfactant is added in the surrounding continuous oil phase. In addition, the melted wax release can be tuned from a one‐step process to a more sequential dropping mode by varying the mineral precursor tetraethoxy‐orthosilane (TEOS) concentration in the oily phase during mineralization.

Synthesis and Optical Properties of Organic-Inorganic Hybrid Mesoporous Materials with Naphthalene Bridging Groups

Ordered naphthalene-bridged hybrid periodic mesoporous organosilicas (PMOs) were synthesized by co-condensation of 2,7-bis(3-triethoxysilylpropylaminocarbonyloxy) naphthalene (NIS) and tetraethoxy orthosilane (TEOS) using cationic trimeric surfactant [C10H21N+ (CH 3)2 (CH2)2N +(CH3) (C10H21)(CH2)2N+ (CH3)2C10H21 ] · 3Br as a structure-directing agent.The resulting samples were characterized by powder X-ray diffraction,high resolution transmission electron microscopy,nitrogen adsorption-desorption,and differential scanning calorimetry/thermogravimetric analysis.Ordered mesoporous hybrid materials with a crystal-like pore wall formed when the molar ratio of NIS to the sum of NIS and TEOS was 40%.When this value is below or above 40%,ordered mesoporous hybrid materials with amorphous phase in the pore walls,and nonporous hybrid materials are obtained,respectively.As the number of naphthyl groups in the pore walls increases,the thermal stability of the hybrid materials is enhanced through the strong π-π interactions between organic groups.Because of the fluorescent naphthyl groups in the silica framework,the PMOs exhibit optical behavior consistent with excimer formation.Absorption spectra of the PMOs show blue shifts compared with that of the precursor (NIS),suggesting the formation of aggregates in the pore walls of the hybrid materials.As the molar ratio of NIS to the sum of NIS and TEOS increases,the fluorescence quantum yield of the PMOs decreases through fluorescence quenching caused by aggregation of naphthyl groups.

Directed formation of silica by a non-peptide block copolymer enzyme mimic.

A non-polypeptide block copolymer inspired by the enzyme silicatein α is shown to template the formation of silica from tetraethoxy orthosilicate (TEOS) in neutral pH and ambient temperature. The block copolymer was synthesized to mimic the chemical functionality shown to be necessary for the function of the natural enzyme. In this report we demonstrate the templating function of the enzyme mimic, the formation of hierarchical structures, the presence of dual mechanisms of condensation at low pH, investigate the mechanism of templation as hydrolyzed species diffuse from the site of hydrolysis, and explore the formation of silica at the polymer surface. Numerous analytical methods are employed in this study, including AFM, TEM, FESEM, DLS, NMR, GPC, and TGA. This bio-inspired polymer combines the features of neutral pH, low temperature, and structure control in silica formation.

A microbead-incorporated centrifugal sample pretreatment microdevice

In this study, we present a novel bead-incorporated centrifugal sample pretreatment microdevice to purify influenza A H3N2 viral RNA. Simple revolution per minute (RPM) control can lead to RNA capture on a bead-bed, and the sequential loading of a washing solution and an elution solution. Tetraethoxy orthosilicate (TEOS)-treated glass microbeads were utilized as a capture matrix. The sample pretreatment microdevice consists of four reservoirs for storing an RNA sample, a washing solution, an elution solution, and a collected sample, and they were merged at the microbead-bed microchannel. The washing solution reservoir and the elution solution reservoir were connected to the bead-bed microchannel through a capillary valve and a siphon channel, respectively. An RNA sample (a lysed influenza A H3N2 virus), a washing solution (70% ethanol) and an elution solution (water or a reverse transcription-polymerase chain reaction (RT-PCR) cocktail) were loaded into the designated reservoirs, and they were successively transported to the bead-bed by RPM control owing to the optimized channel design. Purified RNAs could be obtained in 440 s. Then, a target H3 gene was amplified by an off-chip based real-time RT-PCR to evaluate the capture efficiency of RNA on our proposed microdevice. 81% of RNAs were successfully captured and purified. Interestingly, the use of the RT-PCR cocktail itself as an elution solution resulted in a 76% capture yield. Furthermore, we successfully performed RNA purification from the clinical nasopharyngeal swabs to identify the subtype of the influenza A virus. This platform provides high potential for the direct integration of the sample pretreatment microdevice into the downstream micro-PCR unit to create a total genetic analysis microsystem.

The effect of adding PDMS-OH and silica nanoparticles on sol–gel properties and effectiveness in stone protection

Inorganic–organic hybrid crack-free xerogels were obtained using di-n-butyltin dilaurate (DBTL) as a catalyst containing tetraethoxyorthosilicate (TEOS) and hydroxyl-terminated polydimethylsiloxane (PDMS-OH) as an additive. We studied the effect of gelling time and sol pH on DBTL concentration. The xerogels’ structure was studied by FTIR, TGA–DTA and SEM techniques. The results showed that the catalyst (DBTL) would substantially shorten the gelling time of the sol. With the addition of PDMS-OH, the viscosity of the sol increased while the gel time decreased. In addition, we noticed an improvement in the cracking of the xerogel with the addition of PDMS-OH. However, the xerogels were opaque when mole ratio of PDMS/TEOS is higher than 0.153. Addition of silica nanoparticles at 0.1% (w/v) in sol could increase xerogels’ surface roughness and hydrophobicity and did not change color of the xerogels. The protective performance evaluated by its ability to resist acid rain revealed that the protective effects were satisfying.

Effect of the addition of hydroxyl-terminated polydimethylsiloxane to TEOS-based stone protective materials

Inorganic–organic hybrid crack-free xerogels were obtained by using a surfactant n-octylamine as a catalyst containing tetraethoxyorthosilicate (TEOS) and hydroxyl-terminated polydimethylsiloxane as an additive. We studied the effect of gelling time and viscosity on PDMS–OH concentration. We have demonstrated that the addition of poly(dimethylsiloxane) (PDMS) to a silica oligomer associated with a neutral catalyst, in the presence of a surfactant, accelerated the gelling process; this reduction of the time needed for the product to gel in carbonate stones helped to achieve effective stone protection. It was found that PDMS–OH was chemically incorporated into the gel matrix via Si–O–Si bonds by FTIR analysis and an appreciable reduction of gel fracture for hybrids prepared from 3 % w/w of PDMS. Nitrogen adsorption–desorption isotherms of xerogels were measured, it showed the pore size of xerogels decrease with the addition of PDMS when concentration of PDMS was below 6 %, while xerogels showed pores in the macroporous range when adding 12 % w/w of PDMS. The protective performance evaluated by its ability to resist acid rain reveals that the protective effects were satisfying.