Surfactant Cetyltrimethylammonium Bromide Research Articles

Facile synthesis of silver-rhenium nanoparticles with plasmonic and mesoporous properties

Cetyltrimethylammonium bromide (CTAB) capped rhenium (Re0@CTA(aq)) NPs were prepared by using chemical reduction method at room temperature in aqueous solution. The resulting Re0@CTA(aq) sol was utilized as sacrificial template and silver ions (Ag+) for the synthesis of silver-rhenium bimetallic NPs (Ag0-Re0@CTA(aq)) under metal displacement galvanic cell reaction in aqueous solution with CTAB. Surface Plasmon resonance (SPR) band intensity and wavelength maxima of Plasmon band of Ag0-Re0@CTA(aq) depends on the concentration of CTAB. The Plasmon band was blue shifted from 434, 439, 519, 535, 465, and 445 nm, respectively, for 0.0, 0.75, 1.0, 1.25, 1.5, and 2.0 mM of CTAB. Oxidation states, crystalline nature, elemental composition, surface morphology, shape, size, and textural properties of as-prepared silver-rhenium were determined with X-ray photoelectron spectrometry (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and nitrogen adsorption-desorption isotherm (BET). Fourier transform infrared spectrometry (FTIR), 1H NMR, 13C NMR, and gas chromatography-mass spectrometry (GC-EIMS) analysis were used to establish the capping properties of CTAB. Application of FTIR, 1H NMR, 13C NMR and GC-EIMS analysis shows that the CTAB consistently remains adsorbed on Ag0-Os0 NPs. Optical properties of plasmonic nanomaterials can be tuned by using a suitable concentration of CTAB surfactant.

Stability, Rheological Behavior, and pH Responsiveness of CTAB/HCl Acidic Emulsion: Experimental Investigation.

Cetyltrimethylammonium bromide (CTAB) surfactant was proven to be a reliable emulsifier for creating stable emulsions used for drilling, well stimulation, and EOR. The presence of acids like HCl during such operations may lead to the formation of acidic emulsions. No previous comprehensive investigations have been done to study the performance of CTAB-based acidic emulsions. This paper, therefore, presents experimental investigations of the stability, rheological behavior, and pH responsiveness of a CTAB/HCl-based acidic emulsion. The effects of temperature, pH, and CTAB concentration on the emulsion stability and rheology have been investigated using a bottle test and a TA Instrument DHR1 rheometer. Viscosity and flow sweep were analyzed for the steady state at a shear range of 2.5-250 s-1. For the dynamic tests, the storage modulus (G') and loss modulus (G″) were observed by applying the oscillation test at the range of shear frequency from 0.1 to 100 rad/s. The results revealed that the emulsion exhibits steady rheological behaviors ranging from Newtonian to shear-dependent (psedosteady), depending on the temperature and CTAB concentration. The tendency of the emulsion to exhibit a solid-like behavior is also dependent on CTAB concentration, temperature, and pH. However, the pH responsiveness of the emulsion is more significantly observed within the acidic range of the pH.

Effect of different pre-treatments on the redispersion capacity of spray-dried microfibrillated cellulose: Elaboration and characterization of biofilms

This study aimed to evaluate the influence of the addition of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in microfibrillated cellulose (MFC/CNFs) suspensions submitted to different pretreatments to produce redispersible spray-dried (SD) MFC/CNFs. Suspensions pretreated with 5 % and 10 % sodium silicate and oxidized with 2,2,6,6,-tetramethylpiperidinyl-1-oxyl (TEMPO) were modified with CTAB surfactant and subsequently dried by SD. The SD-MFC/CNFs aggregates were redispersed by ultrasound to produce cellulosic films by the casting method. In summary, the results demonstrated that the addition of CTAB surfactant to the TEMPO-oxidized suspension was critical to achieving the most effective redispersion. The experimental results obtained using micrographs, optical (UV–Vis), mechanical, water vapor barrier properties, and the quality index confirmed that the addition of CTAB to the TEMPO-oxidized suspension favored the redispersion of spray-dried aggregates, development of cellulosic films with attractive properties, offering possibilities for the elaboration of new products, for example, in the production of bionanocomposites with higher mechanical performance. This research brings interesting insights into the redispersion and application of SD-MFC/CNFs aggregates, strengthening the commercialization of MFC/CNFs for industrial use.

Sensing characterization of an amorphous PDMS/Ecoflex blend composites with an improved interfacial bonding and rubbing performance

In this paper, a polymer blend labeled PDMS/Ecoflex (PE) was fabricated using Polydimethylsiloxane (PDMS) and Ecoflex 00-30 in various proportions. An innovative carbon nanotube/carbon black (CNT/CB) hybrid filler reinforced cetyltrimethylammonium bromide (CTAB) surfactant was prepared and sprayed to obtain CNT/CB/PE composite material. The resulting PE blend matrix showed excellent mechanical properties, including high stretchability of nearly 500% strain, minimal hysteresis, and reduced friction by up to 75% with decreasing wear. These properties were attributed to the combined effect of Young’s modulus, stiffness, and hardness of PDMS and Ecoflex. Additionally, three types of contacts CNT-CB, CB-CB, and CNT-CNT were produced by the favorable interaction of CNT and CB particles, stabilizing the sensor signal. The CNT/CB/PE sensor had an improved wear resistance, conductivity stabilization, stretchability, gauge factor during the tensile test, and strain-dependent sensitivity across a broad range of fixed strains (up to 100% strain). Furthermore, the sensor was attached to various human body joints to track the related human motions, proving the fascinating perspective in detecting varioushuman movements and making it appropriate for application in multifunctional wearable devices in hostile environments.

Synthesis of Graphene Oxide-Coated Mesoporous Silica with Cetyltrimethylammonium Bromide (CTAB) Template for Methylene Blue Adsorption

The synthesis of graphene oxide-coated mesoporous silica (MS_GO) with the template surfactant (Cetyltrimethylammonium Bromide) CTAB has been carried out. The effect of combining mesoporous silica and graphene oxide was studied by knowing the bonds, functional groups and crystalline structures. Functional groups C=O and C=C were formed at wave numbers 1,722, 1,617 and 1,647 cm−1, respectively, as a characteristic of GO compounds. XRD data showed that MS_GO has a more amorphous structure than graphite and GO due to the incorporation of silica onto the graphene oxide surface. The MS_GO synthesis was also applied as an adsorbent for methylene blue dye in water. The adsorption results showed that MS_GO was more effective than pure GO. The percent adorption efficiency (R %) of MS_GO against 10 ppm methylene blue was 93.1 % while that of pure GO was 91.5 %. The addition of mesoporous silica to graphene oxide makes MS_GO adsorbent more effective in adsorption dyes than pure GO, this is supported by the larger total surface area of BET MS_GO was 161.066 m2·g−1, while that of pure GO was 103.818 m2·g−1. HIGHLIGHTS Preparation of graphene oxide from graphite by the modified hummer method Mesoporous silica is synthesized with Graphene Oxide (GO) and occupies between GO layers in the GO interlayer space CTAB is used as a template and forms pores in the synthesis of layered Mesoporous Silica-Graphene Oxide (MS_GO) Graphene Oxide-Coated Mesoporous Silica will be applied for adsorption of methylene blue dye in water. The adsorption efficiency (% R) of GO against methylene blue is lower than % R of MS_GO against methylene blue GRAPHICAL ABSTRACT

Nanoparticles of (calcium/aluminum/CTAB) layered double hydroxide immobilization onto iron slag for removing of cadmium ions from aqueous environment

The novel point of this study represents by manufacturing new material for treating of aqueous solution laden with cadmium ions. This can achieve through utilizing of alum as cheapest and available substance, plaster kiln dust wastes from gypsum industry, and cetyl trimethyl ammonium bromide surfactant in the preparation of nano-sized layered double hydroxide of aluminum and calcium in the existence of mentioned surfactant. The gel-solution of nanoparticles can be co-precipitated on the iron slag to obtain new sorbent identified “iron-slag coated with (calcium/aluminum- cetyl trimethyl ammonium bromide) layered double hydroxide” and composition of all materials was characterized by analysis of X-ray diffraction. The outcomes proved that the area of slag surfaces was increased significantly from 0.49 to 10.21 m2/g due to the surfactant intercalation and precipitation of nanoparticles. The synthesis parameters require surfactant 0.035 g/50 mL, pH 10, molar ratio of (calcium/aluminum) 2, and mass of slag 1 g/50 mL. Batch tests proved that more than 99.3% cadmium can remove at time 60 min, initial pH 7, coated slag mass 0.5 g/50 mL, and speed 250 rpm for 50 mg/L initial concentration to obtain highest capacity of sorption of 14.50 mg/g. The measurements of kinetic tests were well followed the model of Pseudo second-order and; accordingly, the chemisorption mechanism will predominate the removal process. Model of intra-particle diffusion demonstrate that the electrostatic attraction, hydrogen bonding and diffusion are major mechanisms required in the cadmium removal onto the prepared sorbent. Also, Langmuir model is an ideal formula for representing the sorption data with determination coefficient = 0.99. Characterization tests certified that the nanoparticles on the slag can play a prime role in the enhancement of cadmium sorption. In addition, the exhausted sorbent can be regenerated and its efficiency was not less than 83% for removal of cadmium after 9 regeneration cycles.

Surface modification of cellulosic nanofibrils by spray drying: Drying yield and microstructural, thermal and chemical characterization

This study investigated the effect of the addition of cationic surfactant cetyltrimethylammonium bromide (CTAB) in cellulose nanofibril suspensions (CNF) on the efficiency of the spray drying process, as well as on the properties of the dried microparticles and on their water redispersibility. The results indicated that CNF pretreated with 10% sodium silicate and modified with surfactant resulted in higher drying yields. The particle sizes formed by drying depended on the characteristics of the precursor CNF, in general, the particles were smaller than 8 µm. The crystalline fraction of all particles produced was higher than that of never dried (ND) CNF, furthermore the powders were thermostable at elevated temperatures (>200 °C), which provides good evidence for applications in composites. Water stability showed that the rehydrated cellulose solutions were influenced by the treatments and the drying process. The addition of surfactant proves attractive to increase the spray drying yield of CNF, bringing prospects regarding cost reduction and expansion of CNF commercialization. Furthermore, the results provide fundamental insights into the relationship between the surface modification of CNF associated with the drying process with the characteristics of the spray-dried material.

CTAB-assisted synthesis of porous cuboid NiCo2O4 powders for high-performance supercapacitor

NiCo2O4 powders with columnar-, rod-, porous cuboid-, and octahedral-like morphologies were prepared by hydrothermally treatment of oxalate precipitates in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) surfactant. The structural, microstructural, and electrochemical properties of NiCo2O4 powders were characterized by X-ray diffractometry, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge/discharge techniques. Because of agglomeration of NiCo2O4 nanoparticles, the specific surface areas decreased from 36.3 to 14 m2 g−1 with CTAB content. The porous cuboid-like NiCo2O4 powders showed the highest specific capacitance of 1353 F g−1 at 1 A g−1, decreasing to 1021 F g−1 at 10 A g−1. The analyzed contribution of various storage mechanisms showed that a mixture of capacitive and diffusion-controlled processes was necessary for obtaining the highest specific capacitance. The porous cuboid-like NiCo2O4 powders//activated carbon hybrid capacitor showed the comparable performance of electrochemical energy storage, including energy density of 23.3 Wh kg−1 at power density of 1398 W kg−1.

Insight of molecular interactions between short‐chain tetraalkylammonium bromides and cetyltrimethylammonium bromide: A spectroscopic and thermodynamic approach

AbstractThe influence of tetraalkylammonium salts, viz., tetraethylammonium, tetrapropylammonium, and tetrabutylammonium bromides (0.005, 0.010, 0.015 mol kg−1) on the micellar behavior of aqueous solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB, 0.2–2 mmol kg−1) over the 298.15–313.15 K temperature range has been studied by conductometric method. From conductivity versus surfactant concentration plots, the critical micelle concentration (CMC) of CTAB has been determined, which shows that the tetraalkylammonium bromides promote the formation of CTAB aggregates. Further, from the temperature dependence of CMC values, the degree of ionization, the counterion binding constant along with some thermodynamic parameters of micellization, such as standard free energy change (), standard enthalpy change (), standard entropy change () have been calculated. From the values of , and , it has been concluded that our ternary system is both enthalpy as well as entropy controlled. Similar CMC values were obtained from UV–Visible spectrometry measurements, using pyrene as a probe at ambient temperature. Also 1H‐NMR and FTIR methods give a greater understanding of the molecular scale interactions between the tetraalkylammonium bromides and the cationic surfactant.

Gold Nanorods with Mesoporous Silica Shell: A Promising Platform for Cisplatin Delivery.

The versatile combination of metal nanoparticles with chemotherapy agents makes designing multifunctional drug delivery systems attractive. In this work, we reported cisplatin's encapsulation and release profile using a mesoporous silica-coated gold nanorods system. Gold nanorods were synthesized by an acidic seed-mediated method in the presence of cetyltrimethylammonium bromide surfactant, and the silica-coated state was obtained by modified Stöber method. The silica shell was modified first with 3-aminopropyltriethoxysilane and then with succinic anhydride to obtain carboxylates groups to improve cisplatin encapsulation. Gold nanorods with an aspect ratio of 3.2 and silica shell thickness of 14.74 nm were obtained, and infrared spectroscopy and ζ potential studies corroborated surface modification with carboxylates groups. On the other hand, cisplatin was encapsulated under optimal conditions with an efficiency of ~58%, and it was released in a controlled manner over 96 h. Furthermore, acidic pH promoted a faster release of 72% cisplatin encapsulated compared to 51% in neutral pH.

Characterization of both anionic and cationic surfactant-modified natural zeolite and its application for removal of metal-ions from aqueous medium

Natural zeolite from Nor Koghb deposit (Armenia) was modified by anionic surfactant sodium dodecyl sulfate and cationic surfactant cetyltrimethylammonium bromide; and the modified samples were used for the removal of metal-ions from aqueous medium. The surface and textural characteristics of both natural and modified zeolites were studied by nitrogen adsorption/desorption isotherms and FTIR methods. The specific surface area, microporous surface area, volume of macro- and microporous both for natural and surfactant-modified zeolites were determined. It was shown that the surfactant-modified zeolites are effective adsorbents for the removal of metal-ions from aqueous medium. It was established that the optimal conditions of Co2+, Ni2+, Fe2+, Cu2+, Zn2+, Mn2+, and Pb2+ metal-ions adsorption are as follows: mMe2+=50 mg/l, Vsolution=500 ml, mSMZ=0.7 g, pH=6.5, T=298 K. Under these conditions, it is possible to remove the 88.27% Co2+, 87.54% Fe2+, 81.37% Ni2+, 76.49% Cu2+, 58.79% Zn2+, 29.32% Mn 2+, 23.49% Pb2+ and 75% Cr(VI) from single-component system. In the multi-component system, the effectiveness of metal-ions removal is lower. From presented study, it is allowed that due to the low cost, industrial quantities availability of the natural Armenian zeolite and the high efficiency of their surfactant-modified samples as metal-ions removal sorbents, as well as easy and non-valuable process of modification, they can find wide application as effective adsorbents for purification of wastewaters.

Simple method for Cr(VI) determination by liquid-liquid microextraction combined with total reflection X-ray fluorescence spectrometry: Application to water samples and industrial extracts

In the present contribution, a simple and inexpensive method for the determination of hexavalent chromium in aqueous solutions was developed. The analytical methodology consists of the combined use of a low cost Cr(VI) isolation procedure followed by the analysis using total reflection X-ray spectrometry (TXRF). The liquid-liquid microextraction procedure (LLME) used is based on the formation of an ion-pair between the cationic part of the surfactant cetyltrimethylammonium bromide (CTAB) and the corresponding anionic Cr(VI) species, which is extracted in few microliters of chloroform. TXRF analysis can be performed directly by deposition of 15 μL of the preconcentrated sample on a sample carrier, without any additional sample treatment.Experimental parameters affecting Cr(VI) extraction and TXRF analysis were studied in detail. Under optimum conditions, a good linearity was obtained in the range of 5–5000 μg/L with a limit of detection for hexavalent chromium of 0.9 μg/L. This fact opens the possibility of Cr determination in aqueous samples characterized by different concentration levels. The methodology was successfully applied for the determination of Cr(VI) species in different type of water matrices (tap, well, river and sea water) as well as industrial aqueous samples including in industrial waste water from a galvanic industry and aqueous clinker extracts. For comparison purposes, the determination of Cr(VI) in industrial samples was also carried out by using the colorimetric method EPA Method 7196.

Impacts of Structure-Directing Agents on the Synthesis of Cu3Mo2O9 for Flexible Lignin-Based Supercapacitor Electrodes

Due to demands for sustainability, the interest in energy storage devices constructed from green materials has increased immensely. These devices currently have yet to be satisfactory. Issues include high production costs and toxicity, limited dependability, and subpar electrochemical performance. In this research, low-cost, plant-based electroactive Cu3Mo2O9 materials were synthesized via co-precipitation followed by an annealing method using two different structure-directing agents, i.e., the commonly used surfactant cetyltrimethylammonium bromide (CTAB) and the biomolecule deoxyribonucleic acid (DNA) as a greener alternative, and these materials were studied for the first time. Further, the Cu3Mo2O9 nanoparticles developed using CTAB and DNA were integrated into the lignin matrix and studied as flexible electrodes for supercapacitor application. Here, the morphological advantages of the nanorods and nanosheets formed by varying the synthesis methods and their effects during supercapacitor studies were studied in detail. After 1200 cycles, the Al/lig-Cu3Mo2O9@DNA supercapacitor exhibited higher capacitive performance when compared to the Al/lig-Cu3Mo2O9@CTAB supercapacitor. The Al/Lig-Cu3Mo2O9@DNA supercapacitor had an initial specific capacitance of 404.64 mF g−1 with a ~70% retention, while the Al/Lig-Cu3Mo2O9@CTAB supercapacitor had an initial specific capacitance of 309.59 mF g−1 with a ~50% retention. This study offers a new approach to creating scalable, low-cost, green composite CuMoO4-based electrodes for flexible supercapacitors.

Study of Physiochemical Properties of Cetyltrimethylammonium Bromide (CTAB) Surfactant: its Micellization, Almond Oil Water Emulsification and Industrial Applications

Study of Physiochemical Properties of Cetyltrimethylammonium Bromide (CTAB) Surfactant: its Micellization, Almond Oil Water Emulsification and Industrial Applications

Reduction-triggered Disassembly of Organic Cationic Nanorods Produces a Cysteine Protease Mimic (Miravet et al.).

The emergence of catalytic activity associated with a disassembly process is reported, reminiscent of complex biological systems. A cystine derivative with pendant imidazole groups self-assembles into cationic nanorods in the presence of the cationic surfactants cetylpyridinium chloride (CPC) or cetyltrimethylammonium bromide (CTAB). Disulfide reduction triggers nanorod disassembly and the generation of a simple cysteine protease mimic, which shows a dramatically improved catalytic efficiency in the hydrolysis of p-nitrophenyl acetate (PNPA).

Dye-surfactant interaction in aqueous premicellar and micellar environments in the alkaline fading of di-positive methyl green carbocation

The alkaline fading of di-positive methyl green carbocation (MeG2+) has been studied in different aqueous premicellar and micellar environments of anionic, cationic as well as non-ionic surfactants. Mono- and di-negative anions like halides and sulphate have been found to show an inhibiting effect on the fading reaction owing to the formation of dye-anion ion-pair adduct before hydrolysis. The binding strength of the dye-anion ion-pair adduct is in the order: SO42- > I- > Br- > Cl- which rationalizes the same order of inhibition of the rate. A substantial change in the electronic spectra of MeG2+ in the presence of anionic surfactants, sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), in the pre-CMC region indicates a change in the equilibrium distribution of the two stereo isomers of the dye owing to the formation of MeG2+-surfactant ion-pair and ion-pair micelle. The premicellar rate inhibition of the fading reaction by SDS and AOT occurs due to the formation of 1:1 MeG2+-surfactant ion-pair (where ≥ 85 % of MeG2+ remain associated) through electrostatic interaction before hydrolysis. The cationic surfactant cetyltrimethylammonium bromide (CTAB) shows a retarding effect in the post-micellar region as the HO- ion experiences both electrostatic repulsion and steric hindrance to approach the carbocation centre of the dye, embedded in the micelle. The polar hydroxyl group and the polyoxyethylene groups present in the moiety of the non-ionic surfactant Brij35 assist to increase the local concentration of HO- and MeG2+ in the palisade layer resulting in a catalyzing effect on the fading reaction in the post CMC region. Both pre- and post-micellar rate effects have been analyzed quantitatively by different established kinetic models. Detailed calculations have been made to find out different enthalpy and entropy of activation as well as of binding in order to establish the nature of interactions between the dye MeG2+ and monomeric surfactant(s) /micelles as well as solvent molecules. Results of spectrophotometric and tensiometric investigations strongly support the existence of different molecular interactions in different stages of the hydrolysis reaction in the presence of surfactants.

Design of Innovative Biocompatible Cellulose Nanostructures for the Delivery and Sustained Release of Curcumin

Poor aqueous solubility, stability and bioavailability of interesting bioactive compounds is a challenge in the development of bioactive formulations. Cellulose nanostructures are promising and sustainable carriers with unique features that may be used in enabling delivery strategies. In this work, cellulose nanocrystals (CNC) and cellulose nanofibers were investigated as carriers for the delivery of curcumin, a model liposoluble compound. Nanocellulose modification with the surfactant cetyltrimethylammonium bromide (CTAB), tannic acid and decylamine (TADA), and by TEMPO-mediated oxidation were also tested and compared. The carrier materials were characterized in terms of structural properties and surface charge, while the delivery systems were evaluated for their encapsulation and release properties. The release profile was assessed in conditions that mimic the gastric and intestinal fluids, and cytotoxicity studies were performed in intestinal cells to confirm safe application. Modification with CTAB and TADA resulted in high curcumin encapsulation efficiencies of 90 and 99%, respectively. While no curcumin was released from TADA-modified nanocellulose in simulated gastrointestinal conditions, CNC-CTAB allowed for a curcumin-sustained release of ca. 50% over 8 h. Furthermore, the CNC-CTAB delivery system showed no cytotoxic effects on Caco-2 intestinal cells up to 0.125 g/L, meaning that up to this concentration the system is safe to use. Overall, the use of the delivery systems allowed for the reduction in the cytotoxicity associated with higher curcumin concentrations, highlighting the potential of nanocellulose encapsulation systems.

Surfactant-assisted synthesis of highly dispersed ZnS(C) /BiOBr/GO ternary composites for effectively improve the degradation ability of organic pollutants under visible light

In this paper, the highly dispersed ZnS(C)/BiOBr/ GO ternary composite was prepared by a two-step hydrothermal method with the help of the surfactant cetyltrimethyl ammonium bromide (CTAB). Its structure and morphology were studied by XRD, SEM, TEM, EDX spectra, UV–VIS absorption spectra, Mott-Schottky curve and Brunau-Emmett-Teller (BET) characterization. The results show that the ZnS(C)/BiOBr/GO ternary photocatalyst with excellent degradation effect and stable specific surface area has been successfully prepared. Orthogonal and photocatalytic experiments showed that the prepared photocatalyst had high photocatalytic performance for the degradation of brilliant blue (BB), Rhodamine B (RhB) and tetracycline hydrochloride (TCH). The degradation rate constants for BB, TCH and RhB were 0.12515, 0.06194 and 0.76750 min−1, respectively. Moreover, the photocatalytic performance of ZnS(C)/BiOBr/GO composite is significantly better than that of the original ZnS(C) and BiOBr. It is worth noting that ZnS(C)/BiOBr/GO ternary composite assisted by CTAB has the best photocatalytic activity, mainly for two reasons. First, the presence of surfactant CTAB significantly reduces the agglomeration of ZnS and enhances the dispersion of ZnS. Second, GO can be used as an electron trapping agent between ZnS and BiOBr to promote carrier separation. Therefore, the synthesis of ternary compounds with appropriate additional surfactants can effectively improve the photocatalytic efficiency of the degradation of organic pollutants. This study is expected to expand the application of surfactants in the preparation of semiconductor photocatalysts.

Selective Styrene Oxidation Catalyzed by Phosphate Modified Mesoporous Titanium Silicate

Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in the silica framework to obtain highly ordered 2D hexagonal mesoporous material STP-1. STP-1 has been synthesized by using tetraethyl orthosilicate, triethyl phosphate, and titanium isopropoxide as Si, P, and Ti precursors, respectively, in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The observed specific surface area and pore volume of STP-1 were 878 m2g−1 and 0.75 ccg−1, respectively. Mesoporous STP-1 has been thoroughly characterized by XRD, FT-IR, Raman spectroscopy, SEM, and TEM analyses. Titanium incorporation (Ti/Si = 0.006) was confirmed from the EDX analysis. This mesoporous STP-1 was used as a heterogeneous catalyst for the selective oxidation of styrene into benzaldehye in the presence of dilute aqueous H2O2 as an oxidizing agent. Various reaction parameters such as the reaction time, the reaction temperature, and the styrene/H2O2 molar ratio were systematically studied in this article. Under optimized reaction conditions, the selectivity of benzaldehyde could reach up to 93.8% from styrene over STP-1. Further, the importance of both titanium and phosphate in the synthesis of STP-1 for selective styrene oxidation was examined by comparing the catalytic result with only a phosphate-modified mesoporous silica material, and it suggests that both titanium and phosphate synergistically play an important role in the high selectivity of benzaldehyde in the liquid phase oxidation of styrene.

Mn-Activated Fluoride Phosphors Modified by Surfactant with Outstanding Water Resistance and Luminescent Thermal Properties.

Although Mn4+-activated fluoride phosphors have high luminescence quality, their poor water resistance and thermal fluorescence properties significantly limit their practical applications. Here, we propose a surfactant modification strategy by adding the surfactant cetyltrimethylammonium bromide (CTAB) to the synthesis and modifying the surface of the phosphor with ethylene diamine tetraacetic acid (EDTA) to obtain a phosphor with excellent luminescence thermal properties and water resistance, K2TiF6:Mn4+-xCTAB-EDTA (KTFM-xC-E) phosphors. The experimental and X-ray diffraction Rietveld refinement results confirm that the phosphor has higher structural rigidity and thus improved thermal stability. The surface modification with EDTA resulted in the formation of a dilute Mn4+ shell layer on the phosphor surface, which prevented the inward hydrolysis of the phosphor and resulted in excellent water resistance. Therefore, we have successfully modified K2TiF6:Mn4+ (KTFM) phosphors using low-cost surfactants, which also provides new ideas for other commercial high-quality phosphors.