Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril

Abstract

Este trabalho apresenta uma rota alternativa para a preparação de nanodiscos de iodeto de chumbo (ca. 50-340 × 7Å, diâmetro × espessura) utilizando o macrocíclico cucurbit [7]urila como molde de síntese e agente estabilizante. Estas nanopartículas apresentam um deslocamento para o azul de gap óptico consistente com seu tamanho reduzido e confinamento quântico 1D. Suas espessuras são compatíveis com a de uma camada de iodeto de chumbo esfoliado, indicando que cucurbit [7]urila impede a formação de estruturas lamelares e limita o crescimento das nanopartículas. A estrutura, a morfologia e as propriedades destes discos foram verificadas por difratometria de raios X em pó (XRD), espectroscopia no UV-Visível, microscopia de força atômica (AFM), microscopia eletrônica de varredura com análise de fluorescência de raios X por dispersão de energia (SEM-EDS) e microscopia eletrônica de transmissão de alta resolução (HRTEM).This work presents an alternative route for the preparation of heavy metal iodide nanoparticles, particularly lead iodide nanodisks (ca. 50-340 × 7 Å, diameter × thickness), using the macrocycle cucurbit [7]uril as a synthetic template and stabilizing agent. These nanoparticles exhibit an opticalgap blue shift consistent with their small size and 1D quantum confinement. Their thicknesses are compatible with an exfoliated single layer of lead iodide, indicating that cucurbit [7]uril, preventing the stacking and formation of tactoids, thus limiting nanoparticles growth in the z direction. The structure, morphology and properties of these disks were analyzed by X-ray powder diffractometry (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy with analysis of energy dispersive X-ray fluorescence (SEM-EDS) and high resolution transmission electron microscopy (HRTEM).Keywords: lead iodide, cucurbit [7]uril, synthetic template, nanodisks, quantum confinement IntroductionLead iodide is a lamellar solid consisting of layers of metal and iodide ions united by covalent bonds. Weak van der Waals interactions hold these layers together in a three dimensional sandwich-like semiconductor. This structure can be described as a hexagonal close-packed array of iodide anions with alternate layers of octahedral interstices occupied by lead(II) cations. Therefore, each layer can be described as a I-Pb-I sequence layer.1 Very interesting materials can be obtained by diminishing the PbI 2 particle size to the nanoscale in order to favor the appearance of new properties resultant of quantum confinement, such as those observed in zero-dimensional solids, quantum dots and other N-dimensional, quantumconfined nanomaterials. Quantum dots encounter many applications in several technological fields such as sensor devices and anti-counterfeiting systems, illumination (as high efficiency white-light emitting diodes), medicine (as cellular markers), lasers, solar cells and others.2-5 Another important property of lead iodide is its ability to form intercalation compounds with many chemical species, ...

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

“…CB[ n ]s are also not toxic, cheap and resistant to microorganisms, which makes them excellent candidates to replace cyclodextrins for most applications. Our own contribution to this field includes the stabilization of reactive species and drug carriers, and the use of CB[ n ] as structural elements in hybrid composites, as templates for nanoparticle synthesis, or to develop special catalysts and coatings, sensors and specialty polymers . Their ability to host a wide range of substrates is mainly due to the hydrophobicity of the inner cavity lacking hydrogen bond donor/acceptor moieties.…”

“…It is well known that CB[ n ]s may act as growth regulators during nanoparticle synthesis . They usually bind by adsorption onto the particle surface and prevent the indefinite growth of metals and oxides for example.…”

“…It is well known that CB[n]s may act as growth regulators during nanoparticle synthesis. 25,26 They usually bind by adsorption onto the particle surface and prevent the indefinite growth of metals and oxides for example. Trabolsi and his group have used this property to prepare arrays of CB [7] surface-modified magnetic iron oxide nanoparticles using 1,1 ′ -diphenyl-4,4 ′ -bipyridinium (DPV) as a linker between adjacent nanoparticles forming dual host (2:1) ternary caviplexes (Fig.…”

Synthesis and characterization of high-quality PbI $$_{2}$$ 2 nanopowders from depleted SLA accumulator anode and cathode

“…A challenging issue presently faced in materials synthesis is the problem of controlling the mesoscopic anisotropy in inorganic materials. Extensive studies of the influence of purity of precursor PbI 2 powders on single bulk crystal growth have reported varying degrees of success in the literature [5]. Examples of currently used methods that yield micro-or nano-PbI 2 structures are low temperature colloidal process [6], reverse micelles method [7], vapor-transporting method [8], hydrothermal [9] and vapor deposition [2].…”

Comparative studies of optical absorption, photoluminescence and EPR spectra of PbMnI2 bulk layers and nanocrystals

“…Recently, a number of research works have been reported on the synthesis of the low-dimensional structures of PbI 2 by chemical and physical methods with different shapes. For example, colloidal [7][8][9], solgel [10,11], reverse micells [12], hydrothermal techniques [13,14] and so on were employed for growth of the PbI 2 nanostructures in the form of nanoplates, nanodisks, nanorods, nanodots, nanobelts and nanobelts bundles. All these structures demonstrate anisotropy of properties and a strong exciton confinement.…”