Morphological Control of Hydrothermal Ni(OH)₂ in the Presence of Polymers and Surfactants: Nanocrystals, Mesocrystals, and Superstructures

Abstract

Polymers with different hydrophilic groups [polyvinylpyrrolidone (PVP), ammonium polyacrylate (APA), and hydroxypropylmethyl cellulose (HPMC)] and surfactants [cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzensulfonate (SDBS)] were used as additives to modify the crystallization of β-Ni(OH) 2 in hydrothermal conditions. Marked morphological changes in the β-Ni(OH) 2 particles were observed depending on the additive concentration and on the duration of the hydrothermal treatment. The final morphology is the result of a complex, time-dependent self-assembly and growth process. Well-defined particles with sizes from submicrometer range to a few micrometers corresponding to hexagonal lamellae, hexagonal tabular mesocrystals, rosette-and flowerlike aggregates of lamellae, hexagonal prismatic mesocrystals, and acicular nanocrystals were easily obtained after a short time (2-24 h) aging at 150-200 °C. With PVP and CTAB, there is evidence of a growth process dominated by self-assembly of nanocrystals to produce mesocrystals. The formation of spherical superstructures (with SDBS, up to 70 µm in diameter) and hollow spheres (with PVP) is observed at long times (>24 h) as a result of solvent-mediated recrystallization processes, like Ostwald ripening. The overall results show that hydrothermal synthesis of β-Ni(OH) 2 in the presence of polymers with hydrophilic groups and surfactants is a versatile tool for crystal morphogenesis.

Reversed Crystal Growth: Implications for Crystal Engineering

“…Therefore, it is possible to produce microspheres of AlPO 4 ‐11 with a similar structure to the polycrystalline spheres of zeolite analcime shown in Figure 1c. Polycrystalline microspheres of β‐Ni(OH) 2 were also synthesized 12. On the other hand, hollow cubes of perovskite CaTiO 3 13 showing a similar structure to hollow cubes of zeolite A,8 were synthesized by a solvothermal method using a mixture of calcium nitrate and tetrabutyl titanate in poly(ethylene glycol) as precursors.…”

Control of uniform nanostructured α-Ni(OH)2 with self-assembly sodium dodecyl sulfate templates

“…Therefore, studies on morphology effect to the performance of Ni(OH) 2 are predominated in literature. For bNi(OH) 2 , morphological control can be achieved by synthetic conditions as well as incorporation of polymers or surfactants [21,22]. In particular, special care has to be taken for synthesis of a-Ni(OH) 2 since their morphology is relatively difficult to control in an uniform manner.…”

Surfactant Effects on the Morphology and Pseudocapacitive Behavior of V2O5⋅H2O

“…After the addition of acid, the pH of the eventually stable red-yellow solution reached2 .0, and layered V 2 O 5 made of square pyramidal [VO 5 ] units with intercalated water was formed by polycondensation of the neutralp recursor [VO(OH) 3 (OH 2 ) 2 ] 0 . [34,35] In summary,w e believe that PEG-6000 servesa sasoft template that allows the linear nanowires of V 2 O 5 ·H 2 Ot of orm an ordered and smooth structure because of its adsorption to V 5 + and because of selfassembly along ac ertain orientation.N evertheless, despite similar electrostatic interactions, the negatively charged SO 3 À ions from the SDBS molecules might absorbo nto smooth flakes that are preferentially grown from the vanadium particles and then stack into flower-like shapes owing to the role of SDBS as an adsorbing agent. [17,33] Therefore, it is reasonable to believe that there should be some oriented chemical adsorption between V 5 + and the anionic SDBS surfactant from which SO 3 À1 is dissociated, and consequently,t his results in the formation of as tacked flower structure through the directed growth of thin flakes.I n detail, there could be morphological evolution from smooth square flakes to stacked flakes to flower shapes;t his is driven by ordered agglomeration with the centered self-assembly surfactanta nd results in the formation of as table structure.…”

“…Furthermore, SDBS can bind to the surfaces of the nanocrystals, which consequently leads to the particular crystal growth of oriented agglomeration and self-assembly. [34,35] In summary,w e believe that PEG-6000 servesa sasoft template that allows the linear nanowires of V 2 O 5 ·H 2 Ot of orm an ordered and smooth structure because of its adsorption to V 5 + and because of selfassembly along ac ertain orientation.N evertheless, despite similar electrostatic interactions, the negatively charged SO 3 À ions from the SDBS molecules might absorbo nto smooth flakes that are preferentially grown from the vanadium particles and then stack into flower-like shapes owing to the role of SDBS as an adsorbing agent.…”