Characterization of as-synthesized mesoporous silica using NMR and solid-state fluorescence spectroscopy

Chiba, R.; Kuroiwa, Yosuke; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

doi:10.1016/s1773-2247(14)50135-9

Cited by 4 publications

(4 citation statements)

References 22 publications

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“…The xerogel was prepared using an adaptation of previously described methodologies. − Tetraethylorthosilicate (TEOS; 9.38 mL, 0.042 mol) and ethanol (15 mL, 0.26 mol) were stirred for 15 min in an amber bottle at room temperature. In the next step, NH 4 OH (5.30 mL, 0.133 mol) was added, the mixture was left under stirring for 3 h at room temperature and (3-chloropropyl)trimethoxysilane (CPTS; 3.28 mL, 0.018 mol) was then added and allowed to react for 2 h under stirring.…”

Section: Methodsmentioning

confidence: 99%

Design of Hybrid Electrospun Nanofibers Comprising a Xerogel Functionalized with a Fluorescent Dye for Application as Optical Detection Device

et al. 2019

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The electrospinning technique allows the production of micro- and nanofibers, which can be used to obtain membranes with high surface area and high porosity. These properties are of importance with regard to the use of nanomaterials in the design of optical detection devices. In this Article, electrospun blends comprising poly(ethylene oxide) [PEO] and sodium alginate [SA], with and without the adsorption of a fluorescent dye (4-[4-(dimethylamino)styryl]-1-methypyridinium iodide, [DSMI]), were prepared and characterized. PEO/SA/DSMI nanofibers presented higher fluorescence emission intensity and higher absolute quantum yield compared to DSMI in solution. However, DSMI was leached into the solution during the nanofiber cross-linking process. Thus, in order to avoid this leaching, a xerogel [XSB30] was modified with 4-[4-(dimethylamino)styryl]pyridine [DMASP] to generate covalently anchored dye units [XSB30-DMASP]. The resulting novel material was then electrospun with PEO/SA. Cross-linking of the electrospun hybrid PEO/SA/XSB30-DMASP nanofibers produced a material exhibiting an increase in both fluorescence emission and absolute quantum yield. Cellulose acetate [CA] was used for comparison because of its solubility in acetone, a less polar solvent that leads to a better distribution of the xerogel. These electrospun systems associated with fluorescent dyes have the potential to be applied in the design of logical gates and chemical sensors.

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Section: Methodsmentioning

confidence: 99%

Design of Hybrid Electrospun Nanofibers Comprising a Xerogel Functionalized with a Fluorescent Dye for Application as Optical Detection Device

et al. 2019

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“…The PST sequence was designed to enhance the sensitivity of the directly excited 13 C signals by the nuclear Overhauser effect derived from the presaturated 1 H nuclei, which is commonly used in solution-state 13 C NMR measurements. The 13 C spin–lattice relaxation times of P407 in D 2 O were estimated to be approximately 0.26–0.69 s; therefore, a relatively short relaxation delay of 2 s may allow sufficient relaxation for the dissolved P407 in the solution and simultaneously suppress most of the signals generated from the solid components (which usually have long 13 C spin–lattice relaxation times). Moreover, the application of MAS can increase the resolution of the interfacial components.…”

Section: Resultsmentioning

confidence: 99%

Transition from Amorphous Cyclosporin A Nanoparticles to Size-Reduced Stable Nanocrystals in a Poloxamer 407 Solution

et al. 2021

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Amorphous drug nanoparticles usually exhibit low storage stability. A comprehensive understanding of the molecular states and physicochemical properties of the product is indispensable for designing stable formulations. In the present study, an amorphous cyclosporin A (CyA) nanosuspension with a mean particle size of approximately 370 nm was prepared by wet bead milling with poloxamer 407 (P407). Interestingly, the prepared amorphous CyA nanoparticles were transformed into uniform CyA nanocrystals with a reduced mean particle size of approximately 200 nm during storage at 25 °C. The CyA nanocrystals were stably maintained for at least 1 month. The particle morphologies and molecular structures of the CyA nanosuspensions before and after storage were thoroughly characterized by cryogenic transmission electron microscopy and magic-angle spinning nuclear magnetic resonance spectroscopy, respectively. They revealed that the freshly prepared amorphous CyA nanoparticles (∼370 nm) were secondary particles composed of aggregated primary particles with an estimated size of 50 nm. A portion of P407 was found to be entrapped at the gaps between the primary particles due to aggregation, while most of P407 was dissolved in the solution either adsorbing at the solid/liquid interface or forming polymeric micelles. The entrapped P407 is considered to play an important role in the destabilization of the amorphous CyA nanoparticles. The resultant CyA nanocrystals (∼200 nm) were uniform single crystals of Form 2 hydrate and showed corner-truncated bipyramidal features. Owing to the narrow particle size distribution of the CyA nanocrystals, the rate of Ostwald ripening was slow, giving long-term stability to the CyA nanocrystals. This study provides new insights into the destabilization mechanism of amorphous drug nanoparticles.

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“…The xerogel was prepared and modified previously according to an adaptation of methodologies previously described. , …”

Section: Methodsmentioning

confidence: 99%

“…The xerogel was prepared and modified previously 37 according to an adaptation of methodologies previously described. 54,55 Preparation of the Solutions. An amount of mass of PCL and PLA equivalent of 15% (w/w) was dissolved in an amount of mass of CHCl 3 equivalent of 75% (w/w) of solvent for 12 h. Subsequently, an amount of mass of MeOH equivalent of 25% (w/w) of solvent was added, and the mixture was stirred for 2 h. The final electrospinning solution, PLA/PCL in a 1:1 mixture (w/w), was vortexed for 5 min, and the mixture was stirred for 6 h.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Electrospun Nanofibers of Immiscible Blends Containing a Fluorescence Dye: Direct Investigation of Polymer Domains

Dreyer

Gross

Bellettini

et al. 2020

ACS Appl. Polym. Mater.

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Poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) are two immiscible polymers which are biodegradable and bioabsorbable, being therefore widely applied for medical materials. The formation of homogeneous fibers of PCL by electrospinning represents a difficult task due to the low viscosity of the solutions of this polymer in comparison to the PLA solutions. In addition, the development of simple techniques for the characterization of these systems represents a field of interest. In this paper, nanofibers of PLA/PCL (1:1 w/w) in a CHCl 3 :MeOH (3:1 w/w) solvent system with and without 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (DSMI), a perichromic dye, were electrospun. The electrospun nanofibers obtained present a homogeneous diameter distribution, with average of 874 ± 205 nm in optimization condition for PLA/PCL and 627 ± 199 nm for PLA/PCL/DSMI. The analysis of the differences in the fluorescence emission of DSMI distributed in each polymer of the nanofibers allowed the direct investigation of the polymeric domains. It is proposed that these emission differences result from the preferential stabilization of resonant forms of the dye with each polymeric chain. For the PLA−DSMI system, green emission was observed, while for PCL−DSMI, red emission occurred. The fluorescence results corroborated thermal analyses, where the absence of solvents was possible to confirm. The nanofibers were compared with the dye anchored in an xerogel, which did not exhibit different emission regions due to its homogeneous distribution in the matrix.

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Characterization of as-synthesized mesoporous silica using NMR and solid-state fluorescence spectroscopy

Cited by 4 publications

References 22 publications

Design of Hybrid Electrospun Nanofibers Comprising a Xerogel Functionalized with a Fluorescent Dye for Application as Optical Detection Device

Design of Hybrid Electrospun Nanofibers Comprising a Xerogel Functionalized with a Fluorescent Dye for Application as Optical Detection Device

Transition from Amorphous Cyclosporin A Nanoparticles to Size-Reduced Stable Nanocrystals in a Poloxamer 407 Solution

Electrospun Nanofibers of Immiscible Blends Containing a Fluorescence Dye: Direct Investigation of Polymer Domains

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