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Peng R, Khan MA, Wu J, Chen Z. In Situ Dielectric Spectroscopy Monitoring of Silica Nanoparticle Synthesis in Cationic Water-in-Oil Microemulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4121-4128. [PMID: 35333536 DOI: 10.1021/acs.langmuir.2c00218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In situ monitoring of microemulsion-based nanoparticle synthesis is significant for understanding the particle formation mechanism and for advancing controlled nanoparticle synthesis by this means. In this study, the processes of silica nanoparticle synthesis in a CTAB/n-hexanol/cyclohexane/ammonia microemulsion were monitored via dielectric spectroscopy in situ and in real time, with the influences of the water content and precursor concentration being considered. Two dielectric relaxations in addition to a water-induced one were observed in the frequency range of 1 MHz to 3 GHz, which persist throughout the synthesis processes. It is suggested that the lower-frequency relaxation is ascribed to interfacial polarization and the higher-frequency one is caused by the orientational polarization of the ion pair consisting of a counterion and a surfactant polar group. The latter and water-induced relaxations were found to be barely changed during the synthesis processes, while the former changes obviously with synthesis time. The evolution of the lower-frequency relaxation and direct current conductivity with synthesis time are presented and discussed, on the basis of which the particle formation process is inspected from a dielectric spectroscopic point of view.
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Affiliation(s)
- Rui Peng
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Muhammad Asadullah Khan
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Jiao Wu
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Zhen Chen
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, China
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2
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Study on the three-stage growth of silica nanoparticles prepared by the drop-by-drop precipitation method. POWDER TECHNOL 2022. [DOI: 10.1016/j.powtec.2022.117115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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3
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Das A, Yadav N, Manchala S, Bungla M, Ganguli AK. Mechanistic Investigations of Growth of Anisotropic Nanostructures in Reverse Micelles. ACS OMEGA 2021; 6:1007-1029. [PMID: 33490761 PMCID: PMC7818115 DOI: 10.1021/acsomega.0c04033] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 12/21/2020] [Indexed: 06/12/2023]
Abstract
Tailoring the characteristics of anisotropic nanostructures like size, morphology, aspect ratio, and size dispersity is of extreme importance due to the unique and tunable properties including catalytic, optical, photocatalytic, magnetic, photochemical, electrochemical, photoelectrochemical, and several other physical properties. The reverse microemulsion (RM) method offers a useful soft-template and low-temperature procedure that, by variation of experimental conditions and nature of reagents, has proved to be extremely versatile in synthesis of nanostructures with tailored properties. Although many reports of synthesis of nanostructures by the RM method exist in the literature, most of the research studies carried out still follow the "hit and trial" method where the synthesis conditions, reagents, and other factors are varied and the resulting characteristics of the obtained nanostructures are justified on the basis of existing physical chemistry principles. Mechanistic investigations are scarce to generate a set of empirical rules that would aid in preplanning the RM-based synthesis of nanostructures with desired characteristics as well as make the process viable on an industrial scale. A consolidation of such research data available in the literature is essential for providing future directions in the field. In this perspective, we analyze the literature reports that have investigated the mechanistic aspects of growth of anisotropic nanostructures using the RM method and distil the essence of the present understanding at the nanoscale timescale using techniques like FCS and ultrafast spectroscopy in addition to routine techniques like DLS, fluorescence, TEM, etc.
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Affiliation(s)
- Anirban Das
- Department
of Chemistry, Biochemistry and Forensic Sciences, Amity School of
Applied Sciences, Amity University Haryana, Gurugram, Haryana 122413, India
| | - Nitin Yadav
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi, Delhi 110016, India
| | - Saikumar Manchala
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi, Delhi 110016, India
| | - Manisha Bungla
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi, Delhi 110016, India
| | - Ashok K. Ganguli
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi, Delhi 110016, India
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Yu Y, Khan MA, Chen Z. In Situ and Real-Time Monitoring of Nanoparticle Formation in Microemulsion by Means of Dielectric Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:11110-11116. [PMID: 32878445 DOI: 10.1021/acs.langmuir.0c02128] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Dielectric spectroscopy was employed, for the first time, to monitor the formation process of silica nanoparticles in a nonionic surfactant-based microemulsion in situ and in real time. Two dominant relaxations were observed in the frequency range of 1 MHz-3 GHz during this process. The relaxation at the lower frequency range was confirmed to be mainly ascribed to interfacial polarization, whose relaxation parameters, together with the electrical property of the synthesis system, were used to characterize the evolution of this dynamic formation process. Four evolution stages are distinctively revealed, including an induction stage, a nucleation dominant stage, an early particle growth stage, and a late growth stage. The dynamic features at each evolution stages were discussed in terms of the dielectric characteristics of the system. It is strongly suggested that dielectric spectroscopy is an effective tool for the in situ mechanistic study of nanoparticle formation in microemulsion.
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Affiliation(s)
- Yanqiang Yu
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, P. R. China
| | - Muhammad A Khan
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, P. R. China
| | - Zhen Chen
- Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, P. R. China
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Ngoi KH, Xiang L, Wong JC, Chia CH, Jin KS, Ree M. Morphology details and size distribution characteristics of single-pot-synthesized silica nanoparticles. J IND ENG CHEM 2020. [DOI: 10.1016/j.jiec.2020.05.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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6
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Back M, Trave E, Zaccariello G, Cristofori D, Canton P, Benedetti A, Riello P. Bi 2SiO 5@g-SiO 2 upconverting nanoparticles: a bismuth-driven core-shell self-assembly mechanism. NANOSCALE 2019; 11:675-687. [PMID: 30565630 DOI: 10.1039/c8nr08649d] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Core-shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core-shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.
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Affiliation(s)
- Michele Back
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, via Torino 155, 30172 Mestre, Italy.
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Richard B, Lemyre JL, Ritcey AM. Nanoparticle Size Control in Microemulsion Synthesis. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4748-4757. [PMID: 28437114 DOI: 10.1021/acs.langmuir.7b00773] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Quasi-monodisperse populations of (H3O)Y3F10·xH2O nanocrystals of varying size are prepared in Igepal-stabilized microemulsions. Correlations between microemulsion composition, micelle hydrodynamic radius, and final nanoparticle size are established and shed light on the mechanism of particle size control. Under the conditions considered here, size control appears to be primarily governed by the number of micelles and the quantities of precursor ions. More specifically, the number of NPs formed can be successfully correlated with the number of micelles present and final NP size is, in turn, determined by the number of nuclei and the total amount of material available for nanocrystal formation. This insight into nanoparticle formation facilitates the selection of appropriate synthetic conditions for the preparation of populations of a targeted size.
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Affiliation(s)
- Benoit Richard
- Département de Chimie and CERMA, Université Laval , Québec, Canada
- Pavillon Alexandre-Vachon, 1045, Avenue de la Médecine, Québec, Canada G1V 0A6
| | - Jean-Luc Lemyre
- Département de Chimie and CERMA, Université Laval , Québec, Canada
- Pavillon Alexandre-Vachon, 1045, Avenue de la Médecine, Québec, Canada G1V 0A6
| | - Anna M Ritcey
- Département de Chimie and CERMA, Université Laval , Québec, Canada
- Pavillon Alexandre-Vachon, 1045, Avenue de la Médecine, Québec, Canada G1V 0A6
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Sacco P, Paoletti S, Cok M, Asaro F, Abrami M, Grassi M, Donati I. Insight into the ionotropic gelation of chitosan using tripolyphosphate and pyrophosphate as cross-linkers. Int J Biol Macromol 2016; 92:476-483. [DOI: 10.1016/j.ijbiomac.2016.07.056] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/14/2016] [Indexed: 10/21/2022]
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9
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Lu D, Gai F, Qiao ZA, Wang X, Wang T, Liu Y, Huo Q. Ru(bpy)2(phen-5-NH2)2+ doped ultrabright and photostable fluorescent silica nanoparticles. RSC Adv 2016. [DOI: 10.1039/c6ra02917e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Ru(bpy)2(phen-5-NH2)2+ doped silica nanoparticles with high fluorescence brightness and controllable size are synthesized via reverse microemulsion method by introducing ethanol to reaction system.
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Affiliation(s)
- Dongdong Lu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Fangyuan Gai
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Zhen-An Qiao
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Xue Wang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Tao Wang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Yunling Liu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Qisheng Huo
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
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10
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Lin CH, Chang JH, Yeh YQ, Wu SH, Liu YH, Mou CY. Formation of hollow silica nanospheres by reverse microemulsion. NANOSCALE 2015; 7:9614-26. [PMID: 25952307 DOI: 10.1039/c5nr01395j] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.
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Affiliation(s)
- Cheng-Han Lin
- Center for Condensed Matter Sciences and Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China.
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11
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Olliges-Stadler I, Rossell MD, Süess MJ, Ludi B, Bunk O, Pedersen JS, Birkedal H, Niederberger M. A comprehensive study of the crystallization mechanism involved in the nonaqueous formation of tungstite. NANOSCALE 2013; 5:8517-8525. [PMID: 23863978 DOI: 10.1039/c3nr02020g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present a detailed study on the nonaqueous synthesis of tungstite nanostructures with the focus on crystallization processes and the evolution of particle morphology. Time-dependent transmission electron microscopy (TEM) revealed a complex, particle-based crystallization mechanism involving first the formation of spherical and single-crystalline primary particles of 2-8 nm, which are cross-linked to large and unordered agglomerates, followed by their organization into rod-like structures of 40 × 200-400 nm. These rods undergo an internal ordering process, during which crystallographically oriented stacks of platelets develop. In situ small angle X-ray scattering (SAXS) experiments confirm this pathway of particle formation. The scattering intensity is dominated by the fast formation of rod-like particles, which cause an inter-platelet peak in the SAXS pattern with ongoing internal ordering. With continuous reaction time, the platelet stacks start to fall apart forming shorter assemblies of just a few platelets or even single platelets.
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Affiliation(s)
- Inga Olliges-Stadler
- Laboratory for Multifunctional Materials, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
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12
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Shtykova EV, Malyutin A, Dyke J, Stein B, Konarev PV, Dragnea B, Svergun DI, Bronstein LM. Hydrophilization of Magnetic Nanoparticles with Modified Alternating Copolymers. Part 2: Behavior in solution. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2010; 114:21908-21913. [PMID: 21243096 PMCID: PMC3018835 DOI: 10.1021/jp1072846] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Aqueous solutions of iron oxide nanoparticles (NPs) stabilized by poly(maleic acid-alt-1-octadecene) (PMAcOD) modified with the 5,000 Da poly(ethylene glycol) (PEG) or the short ethylene glycol (EG) tails were analyzed by small-angle X-ray scattering (SAXS). Advanced SAXS data analysis methods were employed to systematically characterize the structure and interactions between the NPs. Depending on the type of the grafted tail and the grafting density all NPs can be separated into three groups. All the samples contain mixtures of individual nanoparticles, their dynamic clusters and aggregates, and the fractions of these species are different in the different groups. The first group consists of NPs coated with PMAcOD modified with the long PEG tails with the maximal grafting density, and the content of dynamic clusters and aggregates in the samples of this group does not exceed 4%. The samples from the second group with less dense coatings demonstrate a larger amount (5-7%) of the aggregates and dynamic clusters. The samples from the third group consisting of the NPs protected by EG modified PMAcOD contain mostly individual NPs and some amount of dumbbell dimers without noticeable aggregation. Importantly, the solution behavior of the NPs is independent on the iron oxide core size. Our results therefore provide means of predicting stabilization and avoiding aggregation of NPs based on the type of a protective shell.
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Affiliation(s)
- Eleonora V. Shtykova
- Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 117333 Moscow, Russia
| | - Andrey Malyutin
- Indiana University, Department of Chemistry, 800 East Kirkwood Av., Bloomington, IN 47405, USA
| | - Jason Dyke
- Indiana University, Department of Chemistry, 800 East Kirkwood Av., Bloomington, IN 47405, USA
| | - Barry Stein
- Indiana University, Department of Biology, 1001 East Third Street, Bloomington, IN 47405, USA
| | - Peter V. Konarev
- EMBL, Hamburg Outstation, Notkestraße 85, D-22603 Hamburg, Germany
| | - Bogdan Dragnea
- Indiana University, Department of Chemistry, 800 East Kirkwood Av., Bloomington, IN 47405, USA
| | | | - Lyudmila M. Bronstein
- Indiana University, Department of Chemistry, 800 East Kirkwood Av., Bloomington, IN 47405, USA
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Asaro F, Benedetti A, Freris I, Riello P, Savko N. Evolution of the nonionic inverse microemulsion-acid-TEOS system during the synthesis of nanosized silica via the sol-gel process. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:12917-12925. [PMID: 20604556 DOI: 10.1021/la101737x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The cyclohexane-igepal inverse microemulsion, comprehensively established for the synthesis of silica nanoparticles in an ammonia-catalyzed sol-gel process, was alternatively studied with an acid-catalyzed sol-gel process. Tetraethyl orthosilicate (TEOS) was used as the silica precursor, while two different aqueous phases containing either HNO(3) or HCl at two different concentrations, 0.1 and 0.05 M, were examined in the presence and in the absence of NaF, a catalyst of the condensation step. The evolution of the overall reacting system, specifically hydrolysis and polycondensation of reaction intermediates, was monitored in situ by time-resolved small-angle X-ray scattering. No size variation of the inverse micelles was detected throughout the sol-gel process. Conversely, the density of the micellar core increased after a certain time interval, indicating the presence of the polycondensation product. The IR spectra of the reacting mixture were in agreement with such a hypothesis. (1)H and (13)C NMR measurements provided information on the soluble species, the surfactant, and TEOS. The TEOS consumption was well fitted by means of an exponential decay, suggesting that a first-order kinetics for TEOS transpires in the various systems examined, with rate constants dependent not only on the acid concentration but also on its nature (anion specific effect), on the presence of NaF, and on the amount of water in the core of the inverse micelle. The self-diffusion coefficients, determined by means of PGSTE NMR, proved that a sizable amount of the byproduct ethanol was partitioned inside the inverse micelles. Characterization of the final product was carried out by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM), which concurrently confirmed that the silica isolated from the inverse nonionic microemulsion is not significantly different from the product of a bulk acid-catalyzed sol-gel synthesis. TEM micrographs illustrated particles with diameters smaller than the diameter of the inverse micelles as determined by SAXS, due to a shrinkage effect, in addition to nanostructured aggregates in the range 20-100 nm.
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Affiliation(s)
- F Asaro
- Department of Chemical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
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Fouilloux S, Désert A, Taché O, Spalla O, Daillant J, Thill A. SAXS exploration of the synthesis of ultra monodisperse silica nanoparticles and quantitative nucleation growth modeling. J Colloid Interface Sci 2010; 346:79-86. [DOI: 10.1016/j.jcis.2010.02.052] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 02/04/2010] [Accepted: 02/23/2010] [Indexed: 10/19/2022]
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15
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Harada M, Saijo K, Sakamoto N, Ito K. Characterization of water/AOT/benzene microemulsions during photoreduction to produce silver particles. J Colloid Interface Sci 2010; 343:423-32. [DOI: 10.1016/j.jcis.2009.12.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Revised: 11/30/2009] [Accepted: 12/02/2009] [Indexed: 10/20/2022]
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Asaro F, Benedetti A, Savko N, Pellizer G. Inverse nonionic microemulsion studied by means of 1H, 13C, and PGSTE NMR during silica nanoparticle synthesis. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:3224-3231. [PMID: 19437786 DOI: 10.1021/la803826c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The soluble species present in the reaction mixture that leads to silica nanoparticle production through the base catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) and the successive condensation were investigated in situ, under the actual synthesis conditions, by means of 1H, 13C, and 29Si NMR spectroscopy. The two former nuclei, owing to higher sensitivity and their presence both in the reacting species and in the constituents of the W/O microemulsion (cyclohexane-igepal-CA-520-concentrated ammonia solution) afforded insight into the inverse microemulsion and allowed us to assess the kinetic rate of the hydrolysis step. It was verified that the microemulsion microstructure is maintained during the reaction. The characterization of the final nanoparticles was carried out by means of transmission electron microscopy (TEM). Special attention was paid to the reaction medium, and an extended assignment of the 1H and 13C resonances of the surfactant headgroup is reported together with the discussion of the changes they undergo due to the environmental modifications induced by transition from cyclohexane solution to W/O microemulsion and further to NH3 containing W/O microemulsion. The self-diffusion coefficient measurements revealed that NH3 exchanges among the inverse micelles diffusing through cyclohexane and confirmed that the preferred localization for ethanol, a byproduct of the reaction, is the bulk oil.
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Affiliation(s)
- Fioretta Asaro
- Department of Chemical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
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