Preparation of nanosized cobalt hydroxides and oxyhydroxide assisted by sonication

Zhu, Yanqing; Li, Hongliang; Koltypin, Yuri; Gedanken, Aharon

doi:10.1039/b107750c

Cited by 148 publications

(102 citation statements)

References 31 publications

(43 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The net positive charge of the individual layers has been attributed to a hydroxyl deficiency within the cobalt-containing sheets of Co(OH) 2 which in some cases is explained by the presence of mixed valent octahedrally coordinated cobalt ions (2+ and 3+) in those layers. 9,14 The mineral hydrotalcite (Mg 6 Al 2 (CO 3 )(OH) 16 ?4H 2 O) displays a similar layered crystal structure in which sheets with mixed valence metal ions (2+, 3+) are coordinated octahedrally and the positively charged sheets held together by counter anions (CO 3 22 ). Therefore the a-Co(OH) 2 structure is often referred to as a hydrotalcite-like structure.…”

Section: Resultsmentioning

confidence: 99%

“…This pre-edge feature results from a lack of inversion symmetry in crystal sites due to the presence of tetrahedral coordination of some of the cobalt ions present in the material, supporting the above conclusions. Methods used previously to make a-Co(OH) 2 materials involved electrochemical, 15 chemical, 19,26 and sonication assisted synthesis routes, 13,14 but direct electronic measurements previously could not be carried out on the resulting materials because of the low quality powder morphology, low crystallinity and the absence of suitable thin films. Few publications report the growth of Co(OH) 2 thin films on substrates.…”

Section: 27mentioning

confidence: 99%

“…[9][10][11][12][13][14][15][16] Co(OH) 2 is used as an additive in numerous industrial processes and has potential for applications as an oil additive 17 and in alkaline secondary batteries; 18 it also displays interesting magnetic properties. 10,16 It exists in two phases: a-Co(OH) 2 10,16,19 and the much more common b-Co(OH) 2 .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

et al. 2006

View full text Add to dashboard Cite

) and Mn 3 (PO 4 ) 2 ?7H 2 O thin films have been prepared using a kinetically controlled vapor-diffusion method. Vectorial control by diffusion of ammonia as a base catalyst into an aqueous metal salt solution yields large area (2 cm 2 ) metal hydroxide and metal phosphate films with unique structures. No supporting substrate for growth of the films is necessary in this approach. The films were characterized using X-ray powder diffraction and scanning electron microscopy. The cobalt containing films were studied in more detail using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption near edge structure and various chemical analysis techniques. For the first time the electronic properties and crystal structure of these materials could be studied in thin films not influenced by the presence of an underlying substrate. For Co 5 (OH) 8 (NO 3 ) 2 ?2H 2 O films, which crystallize in a layered hydrotalcite-like structure that is homogeneous from the nanoscale to the macroscale, unprecedented photoconductivity properties were observed. Resistivity measurements show that this material is a p-type semiconductor with an unusually long minority carrier lifetime and high carrier density.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: 27mentioning

confidence: 99%

See 1 more Smart Citation

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

et al. 2006

View full text Add to dashboard Cite

show abstract

“…14,20 Chelate(EDTA)-and sonication-assisted syntheses produce even larger Co(O)OH aggregates. 24,25 Spatially constrained or "caged" syntheses have been performed using Ferritin as a template to control particle size.…”

Section: −23mentioning

confidence: 99%

Photochemical versus Thermal Synthesis of Cobalt Oxyhydroxide Nanocrystals

et al. 2012

View full text Add to dashboard Cite

Photochemical methods facilitate the generation, isolation, and study of metastable nanomaterials having unusual size, composition, and morphology. These harder-to-isolate and highly reactive phases, inaccessible using conventional high-temperature pyrolysis, are likely to possess enhanced and unprecedented chemical, electromagnetic, and catalytic properties. We report a fast, low-temperature and scalable photochemical route to synthesize very small (~3 nm) monodisperse cobalt oxyhydroxide (Co(O)OH) nanocrystals. This method uses readily and commercially available pentaamminechlorocobalt(III) chloride, [Co(NH 3 ) 5 Cl]Cl 2 , under acidic or neutral pH and proceeds under either near-UV (350 nm) or Vis (575 nm) illumination. Control experiments showed that the reaction proceeds at competent rates only in the presence of light, does not involve a free radical mechanism, is insensitive to O 2, and proceeds in two steps: (1) Aquation of [Co(NH 3 ) 5 Cl] 2+ to yield [Co(NH 3 ) 5 (H 2 O)] 3+ , followed by (2) slow photoinduced release of NH 3 from the aqua complex. This reaction is slow enough for Co(O)OH to form but fast enough so that nanocrystals are small (ca. 3 nm). The alternative dark thermal reaction proceeds much more slowly and produces much larger (~250 nm) polydisperse Co(O)OH aggregates. UV-Vis absorption measurements and ab initio calculations yield a Co(O)OH band gap of 1.7 eV. Fast thermal annealing of Co(O)OH nanocrystals leads to Co 3 O 4 nanocrystals with overall retention of nanoparticle size and morphology. Thermogravimetric analysis shows that oxyhydroxide to mixed-oxide phase transition occurs at significantly lower temperatures (up to T = 64 degrees C) for small nanocrystals compared with the bulk. KeywordsAb initio calculations, Aqua complexes, Catalytic properties, control experiments, fast thermal annealing, free radical mechanism, high-temperature pyrolysis, low temperatures, monodisperse, nanoparticle sizes, neutral pH, Oxyhydroxides, Pentaamminechlorocobalt, Photochemical method, thermal synthesis, chlorine compounds, cobalt, cracking (chemical) Disciplines Chemistry CommentsReprinted (adapted) with permission from Journal of Physical Chemistry C 116 (2012)

show abstract

“…The reflections at 9.17 and 4.51 A can be assigned to the (003) and (006) diffractions of the hydrotalcitelike structure (unit cell with three slabs). 38 The peak at 33.56 degrees has the typical broad ''saw-tooth'' shape, with a sharp rise at the lowangle side and pronounced asymmetry on the high-angle side, which is due to the two-dimensional reflection of the turbostratically disordered a-cobalt hydroxide.…”

Section: 10mentioning

confidence: 99%

Preparation of self-assembled cobalt hydroxide nanoflowers and the catalytic decomposition of cyclohexyl hydroperoxide

Wang

Chen

et al. 2011

J. Mater. Chem.

View full text Add to dashboard Cite

a-Co(OH) 2 hierarchical nanoflowers were synthesized using a microemulsion as a nanoreactor. These structures were selfassembled from cobalt hydroxide nanoflakes and possessed flowerlike morphology with a diameter of 200-500 nm. These a-Co(OH) 2 nanoflowers exhibited high specific area and porosity and show high activity in the decomposition of cyclohexyl hydroperoxide. 99% conversion and 94% selectivity for K-A oil could be obtained.Cobalt hydroxides have attracted great interest over the last two decades, owing to their unique physical and chemical properties, such as their layered structure with large interlayer spacing and welldefined electrochemical redox activity, which make them show great potential in magnetics, catalysis, electrochemistry, and sensing devices.

show abstract

Preparation of nanosized cobalt hydroxides and oxyhydroxide assisted by sonication

Cited by 148 publications

References 31 publications

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Photochemical versus Thermal Synthesis of Cobalt Oxyhydroxide Nanocrystals

Preparation of self-assembled cobalt hydroxide nanoflowers and the catalytic decomposition of cyclohexyl hydroperoxide

Contact Info

Product

Resources

About