Nonaqueous Sol−Gel Syntheses of Microporous Manganese Oxides

Ching, Stanton; Welch, Eric J.; Hughes, Steven M.; Bahadoor, Adilah; Suib, Steven L.

doi:10.1021/cm010780q

Cited by 67 publications

(47 citation statements)

References 47 publications

(118 reference statements)

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“…For example, sol-gel reactions with Li + dopant ordinarily generate spinel manganese oxide in both aqueous [3] or methanol [31] solvent. Similarly, cryptomelane has been obtained in bulk from K-doped gels having a 0.25:1 K:Mn ratio [13], while this same ratio favors Kbirnessite when the gel is cast as a thin film. K-birnessite is only favored in bulk sol-gel synthesis when the K:Mn ratio is raised to 0.5:1 [13].…”

Section: Thin Film Preparationmentioning

confidence: 94%

“…Similarly, cryptomelane has been obtained in bulk from K-doped gels having a 0.25:1 K:Mn ratio [13], while this same ratio favors Kbirnessite when the gel is cast as a thin film. K-birnessite is only favored in bulk sol-gel synthesis when the K:Mn ratio is raised to 0.5:1 [13]. These results implicate some sort of mechanism in which the smooth substrate surface promotes the formation of lamellar manganese oxide structure upon crystallization.…”

Section: Thin Film Preparationmentioning

confidence: 94%

“…In particular, Li-birnessite has shown a propensity for the spinel form at temperatures ranging from 110 o C to 600 o C [5,31,32]. K-birnessite is known to transform into cryptomelane at temperatures in the range of 500-600 o C [12], although this conversion was not observed in nonaqueous bulk sol-gel syntheses [13].…”

Section: Characterizationmentioning

confidence: 99%

“…With potassiumcontaining gels, there was an additional discovery that partial extraction of K + from the gel matrix led to formation of cryptomelane rather than birnessite [9,11,12]. More recently, Ching and Suib reported nonaqueous sol-gel routes to microporous manganese oxides using reactions of alkylammonium permanganates with methanol in the presence of alkali metal cations as dopants [13]. The nonaqueous gels served as precursors to manganese oxides with birnessite, cryptomelane, and spinel structures.…”

Section: Introductionmentioning

confidence: 99%

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Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite

Ching

Hughes

Gray

et al. 2004

Microporous and Mesoporous Materials

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High quality manganese oxide thin films with smooth surfaces and even thicknesses have been prepared with a nonaqueous sol-gel process involving reduction of tetraethylammonium permanganate in methanol. Spin-coated films have been cast onto soft glass, quartz, and Ni foil substrates, with two coats being applied for optimum crystallization. The addition of alkali metal cations as dopants results in exclusive formation of the layered birnessite phase. By contrast, analogous reactions in bulk solgel reactions yield birnessite, tunneled, and spinel phases depending on the dopant cation.XRD patterns confirm the formation of well-crystallized birnessite. SEM images of Li-, Na-, and K-birnessite reveal extremely smooth films having uniform thickness of less than 0.5 µm. Thin films of Rb-and Cs-birnessite have more fractured and uneven surfaces as a result of some precipitation during the sol-gel transformation. All films consist of densely packed particles of about 0.1 µm. When tetrabutylammonium permanganate is used instead of tetraethylammonium permanganate, the sol-gel reaction yields amorphous manganese oxide as the result of diluted Mn sites in the xerogel film.Bilayer films have been prepared by casting an overcoat of K-birnessite onto a Na-2 birnessite film. However, Auger depth profiling indicates considerable mixing between the adjacent layers.

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Section: Thin Film Preparationmentioning

confidence: 94%

Section: Thin Film Preparationmentioning

confidence: 94%

Section: Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite

Ching

Hughes

Gray

et al. 2004

Microporous and Mesoporous Materials

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“…Several novel and effective routes have been devoted to prepare manganese oxides nanomaterials with various shapes and excellent properties, such as hydrothermal method, [17] solgel synthesis, [18] wet chemical route, [19] pulsed laser deposition method, [20] precursor technique, [21] thermal process, [22] precipitation method, [23] sonochemical method, [24] and microemulsion. [25] However, there are very few reports only available about MONPs preparation in the green synthesis.…”

Section: Introductionmentioning

confidence: 99%

Untitled

Haneefa

2017

AJP

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Aim: In this study, we have demonstrated the synthesis of manganese metal oxide nanoparticles (NPs) by a green synthesis manner using lemon extract as a reducing agent and turmeric curcumin extract as capping agent. The as-synthesized nanomaterials were biofunctionalized with salicylalchitosan which was obtained from the source of chitosan to enhance the antimicrobial activity of those materials. Materials and Methods: The synthesized materials were characterized using ultraviolet-visible and Fourier transform infrared spectroscopic techniques. Scanning electron microscopy and transmission electron microscopy analysis were employed to evaluate the morphological and structural properties of the both synthesized nanoforms. Furthermore, the effect of antibacterial and antifungal activity of those materials was analyzed using some standard Gram-positive and Gram-negative bacteria and funguses. Results: The morphological studies represented that both non-functionalized and biofunctionalized manganese oxide NPs (MONPs) formed are of spherical morphology but exhibited with difference in size about 50 nm and 40-60 nm, respectively. The performance of antimicrobial activity of biofunctionalized MONPs was exhibited better than the non-functionalized NPs. Conclusion: The results are revealed that the biofunctionalized MONPs showed higher antibacterial and antifungal activities, and our findings from this work have been provided the new way in the potential application of MONPs through a biofunctionalization process in the clinical and drug invention field.

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Manganese Oxide Octahedral Molecular Sieves (OMS-2) Multiple Framework Substitutions: A New Route to OMS-2 Particle Size and Morphology Control

et al. 2010

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Self-assembled multidoped cryptomelane hollow microspheres with ultrafi ne particles in the size range of 4-6 nm, and with a very high surface area of 380 m 2 g − 1 have been synthesized. The particle size, morphology, and the surface area of these materials are readily controlled via multiple framework substitutions. The X-ray diffraction and transmission electron microscopy (TEM) results indicate that the as-synthesized multidoped OMS-2 materials are pristine and crystalline, with no segregated metal oxide impurities. These results are corroborated by infrared (IR) and Raman spectroscopy data, which show no segregated amorphous and/or crystalline metal impurities. The fi eld-emission scanning electron microscopy (FESEM) studies confi rm the homogeneous morphology consisting of microspheres that are hollow and constructed by the self-assembly of pseudo-fl akes, whereas energy-dispersive X-ray (EDX) analyses imply that all four metal cations are incorporated into the OMS-2 structure. On the other hand, thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) demonstrate that the as-synthesized multidoped OMS-2 hollow microspheres are more thermally unstable than their single-doped and undoped counterparts. However, the in-situ XRD studies show that the cryptomelane phase of the multidoped OMS-2 hollow microspheres is stable up to about 450 ° C in air. The catalytic activity of these microspheres towards the oxidation of diphenylmethanol is excellent compared to that of undoped OMS-2 materials.

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Nonaqueous Sol−Gel Syntheses of Microporous Manganese Oxides

Cited by 67 publications

References 47 publications

Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite

Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite

Untitled

Manganese Oxide Octahedral Molecular Sieves (OMS-2) Multiple Framework Substitutions: A New Route to OMS-2 Particle Size and Morphology Control

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