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Template Route to Chemically Engineering Cavities at Nanoscale: A Case Study of Zn(OH)(2) Template.

Wu D, Jiang Y, Liu J, Yuan Y, Wu J, Jiang K, Xue D - Nanoscale Res Lett (2010)

Bottom Line: The rudimental Zn(OH)(2) core is eliminated with ammonia solution.In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process.Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties.

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ABSTRACT
A size-controlled Zn(OH)(2) template is used as a case study to explain the chemical strategy that can be executed to chemically engineering various nanoscale cavities. Zn(OH)(2) octahedron with 8 vertices and 14 edges is fabricated via a low temperature solution route. The size can be tuned from 1 to 30 μm by changing the reaction conditions. Two methods can be selected for the hollow process without loss of the original shape of Zn(OH)(2) template. Ion-replacement reaction is suitable for fabrication of hollow sulfides based on the solubility difference between Zn(OH)(2) and products. Controlled chemical deposition is utilized to coat an oxide layer on the surface of Zn(OH)(2) template. The abundant hydroxyl groups on Zn(OH)(2) afford strong coordination ability with cations and help to the coating of a shell layer. The rudimental Zn(OH)(2) core is eliminated with ammonia solution. In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process. Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties.

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a Zn(OH)2 coated with a layer of ZnS, b core/shell structure after reacted with ammonia for 10 min, c low-magnification SEM image and d TEM image of hollow ZnS octahedra. e XRD patterns of the products generated during the process, f PL spectrum of ZnS shell obtained under an ultraviolet excitation at 350 nm
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Figure 5: a Zn(OH)2 coated with a layer of ZnS, b core/shell structure after reacted with ammonia for 10 min, c low-magnification SEM image and d TEM image of hollow ZnS octahedra. e XRD patterns of the products generated during the process, f PL spectrum of ZnS shell obtained under an ultraviolet excitation at 350 nm

Mentions: Two strategies were applied to fabricate different octahedral hollow structures by using Zn(OH)2 as templates. Transition metal sulfides were prepared through a facile chemical conversion. Zn(OH)2 templates were directly immersed into 0.20 M Na2S solution, leading to core/shell Zn(OH)2/ZnS structures (Fig. 5a), which were clearly observed after an ammonia treatment for 10 min (Fig. 5b). The diameter of the core/shell structure is almost unchanged. Figure 5c shows the low magnified SEM image, the diameter of hollow structure is 3–4 μm. From the inset of Fig. 5c, a broken part can be seen. The hole can serve as the entrance for sensitive materials such as medicine molecules or proteins. The corresponding TEM image is depicted in Fig. 5d. The interior of the products is completely hollowed and the shell is comprised of numerous nanoparticles. The whole conversion process was recorded by XRD patterns (Fig. 5e). After the core was thoroughly removed, only ZnS diffraction peaks existed with cell constant a = 5.406 Å which is consistent with the standard value (JCPDS Card No. 05-0566). In order to promote the chemical conversion, high solubility Zn5(CO3)2(OH)6 was used as a sacrificing template instead of ZnO. For the same purpose, a thioglycolic acid-assisted route was also used to activate the Zn2+ on the surface of inert ZnO template [28,29]. In our case, except the well solubility of Zn(OH)2 (Ksp = 1.2 × 10−17), the Na2S solution with a high pH value (12) also played a positive role in promoting the reactivity of the precursor by converting the Zn(OH)2 into more reactive ZnO22− on the template surface. In the later core-removing step, ammonia solution was used instead of the widely used NaOH or KOH [30,31]. Due to the strong coordination ability of NH3, the core-removing duration can be dramatically reduced. Moreover, the good volatility and solubility of ammonia make it easier to be evacuated from the final product. PL measurements were performed for optical characterization of the hollow ZnS shell powder. The sample is photoexcited at 350 nm. As shown in Fig. 5f, two major peaks can be observed, one at 466 nm caused by sulfur bond dangling at the interface of ZnS grains, the other at about 548 nm, which may be originated from surface states and various point defects. The strong-defect-related signal implies that ZnS nanoshells contain more defects.


Template Route to Chemically Engineering Cavities at Nanoscale: A Case Study of Zn(OH)(2) Template.

Wu D, Jiang Y, Liu J, Yuan Y, Wu J, Jiang K, Xue D - Nanoscale Res Lett (2010)

a Zn(OH)2 coated with a layer of ZnS, b core/shell structure after reacted with ammonia for 10 min, c low-magnification SEM image and d TEM image of hollow ZnS octahedra. e XRD patterns of the products generated during the process, f PL spectrum of ZnS shell obtained under an ultraviolet excitation at 350 nm
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Figure 5: a Zn(OH)2 coated with a layer of ZnS, b core/shell structure after reacted with ammonia for 10 min, c low-magnification SEM image and d TEM image of hollow ZnS octahedra. e XRD patterns of the products generated during the process, f PL spectrum of ZnS shell obtained under an ultraviolet excitation at 350 nm
Mentions: Two strategies were applied to fabricate different octahedral hollow structures by using Zn(OH)2 as templates. Transition metal sulfides were prepared through a facile chemical conversion. Zn(OH)2 templates were directly immersed into 0.20 M Na2S solution, leading to core/shell Zn(OH)2/ZnS structures (Fig. 5a), which were clearly observed after an ammonia treatment for 10 min (Fig. 5b). The diameter of the core/shell structure is almost unchanged. Figure 5c shows the low magnified SEM image, the diameter of hollow structure is 3–4 μm. From the inset of Fig. 5c, a broken part can be seen. The hole can serve as the entrance for sensitive materials such as medicine molecules or proteins. The corresponding TEM image is depicted in Fig. 5d. The interior of the products is completely hollowed and the shell is comprised of numerous nanoparticles. The whole conversion process was recorded by XRD patterns (Fig. 5e). After the core was thoroughly removed, only ZnS diffraction peaks existed with cell constant a = 5.406 Å which is consistent with the standard value (JCPDS Card No. 05-0566). In order to promote the chemical conversion, high solubility Zn5(CO3)2(OH)6 was used as a sacrificing template instead of ZnO. For the same purpose, a thioglycolic acid-assisted route was also used to activate the Zn2+ on the surface of inert ZnO template [28,29]. In our case, except the well solubility of Zn(OH)2 (Ksp = 1.2 × 10−17), the Na2S solution with a high pH value (12) also played a positive role in promoting the reactivity of the precursor by converting the Zn(OH)2 into more reactive ZnO22− on the template surface. In the later core-removing step, ammonia solution was used instead of the widely used NaOH or KOH [30,31]. Due to the strong coordination ability of NH3, the core-removing duration can be dramatically reduced. Moreover, the good volatility and solubility of ammonia make it easier to be evacuated from the final product. PL measurements were performed for optical characterization of the hollow ZnS shell powder. The sample is photoexcited at 350 nm. As shown in Fig. 5f, two major peaks can be observed, one at 466 nm caused by sulfur bond dangling at the interface of ZnS grains, the other at about 548 nm, which may be originated from surface states and various point defects. The strong-defect-related signal implies that ZnS nanoshells contain more defects.

Bottom Line: The rudimental Zn(OH)(2) core is eliminated with ammonia solution.In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process.Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
A size-controlled Zn(OH)(2) template is used as a case study to explain the chemical strategy that can be executed to chemically engineering various nanoscale cavities. Zn(OH)(2) octahedron with 8 vertices and 14 edges is fabricated via a low temperature solution route. The size can be tuned from 1 to 30 μm by changing the reaction conditions. Two methods can be selected for the hollow process without loss of the original shape of Zn(OH)(2) template. Ion-replacement reaction is suitable for fabrication of hollow sulfides based on the solubility difference between Zn(OH)(2) and products. Controlled chemical deposition is utilized to coat an oxide layer on the surface of Zn(OH)(2) template. The abundant hydroxyl groups on Zn(OH)(2) afford strong coordination ability with cations and help to the coating of a shell layer. The rudimental Zn(OH)(2) core is eliminated with ammonia solution. In addition, ZnO-based heterostructures possessing better chemical or physical properties can also be prepared via this unique templating process. Room-temperature photoluminescence spectra of the heterostructures and hollow structures are also shown to study their optical properties.

No MeSH data available.


Related in: MedlinePlus