Hydroxypropyl-β-cyclodextrin as a versatile additive for the formation of metastable tetragonal zirconia exhibiting high thermal stability

Abstract

Single-phase tetragonal zirconium oxides with enhanced phase stability were successfully synthesized by a precipitation procedure, using hydroxypropyl-b-cyclodextrin (HP-b-CD) as a new macromolecular additive.The samples were prepared in the presence of controlled amounts of HP-b-CD by precipitation of a zirconium oxychloride solution in an aqueous ammonia solution and then annealed at 600 uC to produce the pure tetragonal phase. The as-prepared ZrO 2 particles are composed of nanocrystallites with coherent scattering region sizes of the order of 40 nm at temperatures as high as 600 uC. The formation of the t-phase was investigated at different stages of the process by XRD, TGA-TDA, FTIR and conductivity measurements. The process of crystallization of the hydrous zirconia precursor was found to be retarded by the binding of HP-b-CD to the zirconium metal centres, further leading to structure-controlled t-ZrO 2 nanocrystals with increasing temperature up to 800 uC. The beneficial effect of HP-b-CD was related to its ability to be partially deprotonated in the aqueous ammonia solution and interact with the Zr(IV) species in the early stage of the synthesis. This hypothesis was supported by additional controlled syntheses of materials using other cyclodextrin derivatives.

Controlled Synthesis of ZrO2 Nanoparticles with Tailored Size, Morphology and Crystal Phases via Organic/Inorganic Hybrid Films

“…The diffraction pattern recorded for calcination product at 450 °C is similar to that of the CS-ZrOx calcination product at 800 °C (Fig. 2a ) in assigning the formation of t-ZrO 2 45 . Whereas that obtained for the calcination product of PVA-ZrOx at 800 °C (Fig.…”

“…In fact, Ra peaks diagnosing t-ZrO 2 are discerned from those of c-ZrO 2 not only by their detectably different frequencies (like 265, 316, 459, 600 and 643 cm −1 , Fig. 3b ) 45 , but also by their better definition. Ra spectrum of zirconia NPs recovered from CS-ZrOx at the higher temperature of 1100 cm −1 reveals that t-ZrO 2 remains the major phase together with a co-existing minor phase of m-ZrO 2 (Fig.…”

ZrO2-β-cyclodextrin catalyzed synthesis of 2,4,5-trisubstituted imidazoles and 1,2-disubstituted benzimidazoles under solvent free conditions and evaluation of their antibacterial study

“…The ZrO 2 nanoparticles-supported b-cyclodextrin nanoparticles (ZrO 2 -b-CD) was prepared by a simple one-pot co-precipitation method by using ZrOCl 2 $8H 2 O, and NH 4 OH (Scheme 2). 56 The morphology of the prepared ZrO 2 -b-CD nanoparticles were characterized by ATR-IR, PXRD, SEM, TEM and EDAX analysis, which conrmed the successful preparation of the ZrO 2 -supported b-cyclodextrin nanoparticles. where d is the average grain size of the crystallites, l the incident wavelength, q, the Bragg angle and b the diffracted fullwidth at half-maximum (FWHM) in radians caused by the crystallites.…”

ZrO2-supported Cu(ii)–β-cyclodextrin complex: construction of 2,4,5-trisubstituted-1,2,3-triazoles via azide–chalcone oxidative cycloaddition and post-triazole alkylation

“…The ZrO 2 nanoparticle supported Cu(II)-b-cyclodextrin complex (ZrO 2 -Cu 2 -b-CD) was prepared by a simple one-pot coprecipitation method using ZrOCl 2 $8H 2 O, NH 4 OH and the Cu(II)-b-cyclodextrin complex (Scheme 2). 24,25 XRD analysis of ZrO nanoparticles in DMF at 100 C produced the triazole anion, and subsequent addition of 2-NO 2 -1,4-diuoro benzene afforded the N-2 arylated product in trace amounts. Furthermore, we carried out the reaction for N-2 substitution using different aryl halides like 1,4-dibromo and 1,4-dichloro benzenes, in both cases ending up with trace amounts of the N-2 arylated product.…”