Controlled Synthesis And Properties Characterization Of Copper Compound

This paper is focused on controlled synthesis of copper-based inorganic nanoparticles, nanosheets,and hierarchical nanostructures through liquid-phase chemical routes. Growth mechanism,self-assembly of nanoparticles and primary property characterizations were also conducted.Investigations are based on several aspects including controlled synthesis,formation mechanism,and properties and applications. The contents mainly include preparation and formation mechanism of hierarchical transition metal oxide microspheres;controlled synthesis,fabrication mechanism,and optical or catalytic properties of composite hollow spheres,hollow naocubes,and CuI nanosheets.The aim is to study the intrinsic controlling mechanism of nanoparticls in solution and construct nanostructured materials with nanoparticles as building blocks.1.Preparation and formation mechanism of CuO hierarchical nanostructures through a chelating agent assisted aqueous solution routeCuO pricky microspheres(CPMs)were fabricated through a simple hydrothermal route at 60-180℃for a setting time using CuCl₂·2H₂O,Na₂(C₄H₄O₆)·3H₂O,and NaOH as reactants.The CPMs were composed of compressed nanothoms exhibiting tapering feature with tip size of less than 10nm.The size of the CPMs can be tuned from 100-200 nm to 4-6μm by simple adjusting the molar ratio of NaOH to Cu²⁺or reagent contentration.The morphology of the CPMs was determined by the molar ratio of tartrate to Cu²⁺cations.Reaction temperature mainly affected the formation rate of the product rather the size and morphology.The formation mechanism of the nanostructures was investigated in detail through time-dependent experiments with TEM and XRD.At first,Cu(C₄H₂O₆)^2-formed through a reversible reaction in the precursor solution that prevents the formation of precipitates.With the temperature increasing,Cu²⁺and OH^- were released and a homogeneous nucleation of Cu(OH)₂ occurred.Subsequently,Cu(OH)₂ nanoclusters dehydrated and aggregated orientedly to form CuO truck nanothorns along[010]direction due to the coordinated or absorbed tartrate anions on the crystal surface.The aggregation-based growth resulted in many defects in the inner parts and surface of the nanothorns that might supply active sites for next crystal growth.So the constant supply of Cu²⁺cations would facilitate further growth of new CuO nanothorn from the surface steps.The nucleation and crystal growth were successfully separated by controlled releasing of Cu²⁺and OH- ions through the reversible reaction of Cu²⁺cations,OH^-,and C₄H₄O₆^2-anions. We conducted further investigation with CuO as target product to clarify the formation mechanism of nanostructured oxides in solution and shed some light on the effect of the coordinated agent on the formation of the oxides.Nanostructured CuO microflowers with tunable size were prepared by heated the solution of CuCl₂·2H₂O and ammonia at 90-180℃.The CuO microflowers were composed of nanosheets with zigzag edges which were 20-40 nm in thickness and 500-800 nm in width.The formation mechanism of CuO microflowers based on the assembly of Cu(OH)₂ nanobelts was elucidated by tracking the hydrothermal process.At first,due to the layered structure of orthorhombic Cu(OH)₂ and assistant of NH₃ molecules,the Cu(OH)₂ grew preferentially to form the belt-like Cu(OH)₂ crystals.Subsequently,the dehydration of Cu(OH)₂ nanobelts occurred,leading to the formation of short CuO nanoribbons.Then the CuO nanoribbons assembled to form CuO aggregates through an oriented-assembly manner.Finally,the aggregates of CuO nanosheets developed into the CuO microflowers.The high ammonia concentration,high ratio of NH₃ to Cu²⁺(Rac)and elevated temperature were necessary for the formation of microflowers,and the ammonia concentration was critical for the morphology evolution of the particles.The effect of the products as catalyst on the decomposition of ammonium perchlorate was enhanced remarkably compared to bulk CuO and was similar with the CuO nanoparticles with size of 8-15 nm derived from the aqueous solution,which means that although enlarging the overall size of the aggregations into micrometer scale the properties of nanobuilding blocks retained excellently.These nanostructured microparticles avoid the limitations of nanoparticles,such as conglomeration and difficult to mix due to high surface energy,while retain the good catalytic property,which may supply potential applications in the future.2.PEG-assisted formation of nanosized Cu₂O Hollow structures and theis optical propertiesThe nanosized Cu₂O/PEG400 composite hollow spheres(HSs,50-80 nm in diameter) with mesoporous shells of～15-20 nm were synthesized by a poly(ethylene glycol) (PEG)-assisted wet-chemical method using CuCl₂·2H₂O and NaNO₃ as reactants.In the hollow nanostructures,the polymer content was ca.18.1 wt%,and the mean size of the component nanocrystals and the pore diameter were ca.5 and 3.8 nm, respectively.The formation of the products included two steps:at first,PEG200, CuCl₂·2H₂O and NaNO₃ reacted at 180℃for 6h to form a precursor solution,then, after cooled to room temperature the precursor solution hydrolyzed in deionized water to obtain the composite hollow spheres.During the first step,Cu(â…¡)were reduced to Cu(â… )by PEG molecular which can be proved UV-vis spectra.So PEG acts as solvent, reducing agent,and complexing agent.And in the second step poly(ethylene glycol 400)(PEG400)molecules self-assemble to form micelles which act as templates for the formation of the hollow structures.The formation of mesoporous structures is due to the oriented-aggregation of composite nanoparticles.The nanosized-composite HSs exhibited peculiar photoluminescence(PL)phenomenon with strong peaks at 414 and 436 nm and weak ones at 454,570,and 637 nm.Furthermore,the HSs showed excellent adsorption ability for methyl orange(MO)because of their composite and mesoporous shell structures.A precursor solution was prepared with CuCl₂·2H₂O and NaOH as reactants,and PEG200 as solvent,complexing agent and reducing agent.Then nanosized Cu₂O hollow nanocubes with single crystalline shells were produced directly through the hydrolysis of the precursor solution under room temperature.The length and the shell thickness of the hollow nanocubes' sides are ca.50-90 nm and ca.6-15 nm, respectively.The size of the hollow nanocubes can be tuned from 60 nm to 200 nm by simple adjusting the reagent contentration and solvents of the precursor solution. NaOH play an important role in the formation of the products,however,the detailed formation mechanism still needs further investigation.3.PEG-Assisted Fabrication of Single-Crystalline CuI Nanosheets CuI single-crystalline nanosheets have been prepared for the first time via a PEG-assisted aqueous solution route at room temperature.Certain amount of KI and sodium dodecyl benzenesulfonate(SDBS)was dissolved in PEG600 under stirring to give a clear solution and CuCl₂·2H₂O was dissolved in PEG600,too.The two solutions were mixed together to give a clear amaranth solution which was used as the precursor solution.Then the precursor solution was added into NaNO₃ solution drop by drop with a burette under stirring to generate CuI precipitate at room temperature. Raman spectra and TEM observation on the precursor solution confirmed that aâ… -Cu(â… )-PEG complex rather than Cuâ… nanoparticles formed in the precursor solution. Thus,PEG600 serve as a complex agent to prevent the formation of Cuâ… .The thickness and in-plane size of the nanosheets were ca.60-80 nm and several micrometers,respectively.The two basal surfaces of these nanosheets were(111) planes.The phase transformation temperature and the melting point decreased 8 and 12℃compared with those of the bulk Cuâ… ,respectively.The resistance of a single Cuâ… nanosheet was measured by a conductive AFM tip method,and a high conductivity of 1.996×10^-2Ω·cm and a photoconduction phenomenon were observed. As a general process this strategy can be used to prepare more 2-D nanostructures including Ag and BiOâ… .