Use of polyols as particle size and shape controllers: application to boehmite synthesis from sol–gel routes

Abstract

Polyols were successfully used as size and shape controllers of oxide nanoparticles synthesized by soft chemistry in aqueous solution. The efficiency of acyclic polyols as a complexing agent depends obviously on the number of OH groups bonded to the carbon chain (and thus on the carbon chain length), but also on their stereochemistry. This innovating way to control morphology has been experienced for the synthesis of boehmite nanoparticles, whose morphology variations related to xylitol adsorption (C5 alditol) have been previously reported. The use of polyols during synthesis causes a modification of the usual morphologies observed, specifically resulting in an increase of (101) faces area. It is evidenced here that the variations of the nanoparticle aspect ratio are related to polyol complexing ability, and more specifically to molecule topology and configuration. Indeed, the morphology variations increase as a function of polyol carbon chain length and number of hydroxyl groups, and is much pronounced for stereoisomers exhibiting hydroxyl groups all oriented on the same side of the molecule (threo-threo sequences). Thanks to these various polyols used, we showed how the progressive levels of complexing ability allow us to tune boehmite particle size and shape. Material characterizations were performed using relevant methods such as X-ray diffraction powder pattern simulation and zetametry in addition to transmission electron microscopy. Since γ-alumina is obtained from boehmite by a topotactic transformation, we expect that this method will provide a promising way to control surface properties of γ-alumina, an important industrial catalyst support.

Crystalline microstructure of boehmites studied by multi-peak analysis of powder X-ray diffraction patterns

“…Figure 1 shows the TEM images of the samples aged for the longest time: B0168, BM168, and BT168. Differences in the sizes of the particles can be easily noticed, evidencing restriction in growth induced by the additives, previously reported in a number of studies (Mathieu et al ., 2007; Chiche et al , 2009, 2011; Dash et al , 2010). In sample B0168 prepared with no additives prismatic particles with edges of lengths over 50 nm (some of them with rounded corners) were observed [Figure 1(a)].…”

“…It is worth mentioning that boehmite particle shapes commonly found, described as diamond-shaped platelets (Chiche et al , 2009), were not observed in samples BM168 and BT168; only in sample B0168 similar particles with round corners were visible. That particular morphology is mostly found at early stages of boehmite crystallisation, observed mainly when boehmite is prepared in basic aqueous media with relatively low temperatures or for short hydrothermal treatment times (Chen et al ., 2008; Jolivet et al , 2008; He et al , 2009; Chiche et al ., 2011). Within the samples of this study, this set of conditions were fulfilled by B024; Figure 2 shows TEM images of the samples prepared without additive in the different aging stages tested.…”

“…In the topotactic transformation, γ-Al 2 O 3 keeps the microstructure of boehmite that affects critical catalytic features of the former, following from the sizes and distributions of pores, crystallites, and grains (Guzman-Castillo et al, 2001). The microstructure of boehmite can be tuned in the nanoscale through the control of preparation parameters in bottom-up procedures, like the presence of additives (Cai et al, 2010;Chiche et al, 2011;Xia et al, 2013) pH (Mathieu et al, 2007;Chen et al, 2008), temperature (Kaya et al, 2002) or aging time (Pardo et al, 2015). It allows the preparation of nanostructured alumina (Digne et al, 2010;Shen et al, 2012), recently applied in optics, biosensors and biomedicine (Chen et al, 2015a(Chen et al, , 2015b(Chen et al, , 2015c.…”

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

“…5a-c) and Rietveld analysis of the XRD patterns (Supplementary Table 2 and Supplementary Note 4). The latter shows that the average crystallite size along the [010] direction (so the stacking direction of the AlOOH layers) is considerably shorter than the in plane direction [001], which is the most typical signature of boehmite nanoplatelets as discussed in several articles [46][47][48][49] . Carbon, hydrogen and nitrogen (CHN) elemental analysis shows that the carbon content, and therefore the quantity of benzoate species attached to the particle surface generally increases with the reaction temperature (Supplementary Table 1 and Supplementary Note 1).…”

Synthesis and Characterization of Boehmites Obtained from Gibbsite in Presence of Different Environments

“…Boehmite can also be synthesized from liquid phase by hydrothermal/solvothermal routes 9,11,27,[40][41][42][43][44][45][46][47][48][49][50][51][52] or by sol-gel and precipitation techniques 8,[53][54][55][56][57][58][59] . Experimental conditions such as aluminum source, nature of the precipitating agent, pH, presence and nature of organic additives, temperature and time of thermal treatment (hydrothermal/solvothermal or thermal aging) may have a main influence in the resultant boehmite crystallite size and morphology…”