Self-Organized Tubular Structures as Platforms for Quantum Dots

Abstract

The combination of top-down and bottom-up approaches offers great opportunities for the production of complex materials and devices. We demonstrate this approach by incorporating luminescent CdSe-ZnS nanoparticles into macroscopic tube structures that form as the result of externally controlled self-organization. The 1-2 mm wide hollow tubes consist of silica-supported zinc oxide/hydroxide and are formed by controlled injection of aqueous zinc sulfate into a sodium silicate solution. The primary growth region at the top of the tube is pinned to a robotic arm that moves upward at constant speed. Dispersed within the injected zinc solution are 3.4 nm CdSe-ZnS quantum dots (QDs) capped by DHLA-PEG-OCH3 ligands. Fluorescence measurements of the washed and dried tubes reveal the presence of trapped QDs at an estimated number density of 10(10) QDs per millimeter of tube length. The successful inclusion of the nanoparticles is further supported by electron microscopy and energy dispersive X-ray spectroscopy, with the latter suggesting a nearly homogeneous QD distribution across the tube wall. Exposure of the samples to copper sulfate solution induces quenching of about 90% of the tubes' fluorescence intensity. This quenching shows that the large majority of the QDs is chemically accessible within the microporous, about 15-μm-wide tube wall. We suggest possible applications of such QD-hosting tube systems as convenient sensors in microfluidic and related applications.

From Chemical Gardens to Chemobrionics

“…58 In these experiments, luminescent nanoparticles were dispersed in the injected zinc sulfate solution. The otherwise hydrophobic particles were modified by ligand exchange with dihydrolipoic acid appended with poly(ethylene glycol) prior to injection.…”

Self-organization in precipitation reactions far from the equilibrium

“…( J and K ) Emission spectrum (J) and transmission electron microscopy (K) image of quantum dot (QD)–functionalized zinc oxide/hydroxide tubes [adapted with permission from Makki et al . ( 34 )]. ( L ) Postsynthetic processing of copper hydroxide tube to produce various copper-based materials [adapted with permission from Uechi et al .…”

“…For example, Makki et al . reported the trapping of CdSe/ZnS quantum dots during tube growth ( 34 ). After synthesis, the trapped particles were chemically accessible to solutes in the surrounding solution, as demonstrated by experiments that quenched the photoluminescence of the dots with Cu(II) ions ( Fig.…”

“…By comparison, the impact of this research on materials synthesis has remained relatively small so far, which, in our opinion, is not due to fundamental limitations but rather reflect limited effort. However, several recent advances have opened new and exciting horizons: periodic precipitation has been scaled down to nano- and micropatterns with a remarkable degree of control ( 33 ), chemical gardens have been functionalized with quantum dots ( 34 ) and constrained to quasi–two-dimensional layers ( 35 ), and biomorphs have been rationally designed into complex biomimetic structures ( 36 ). These and other results provide important stepping stones toward one of the ultimate goals of “Materials by Design”: programming chemical reactions in space and time to spontaneously assemble the desired complex products.…”

Diffúzió- és áramlásvezérelt csapadékmintázatok vizsgálata

“…A buborékkal vezérelt módszer alkalmas a csapadékmembránok tanulmányozására és általa kontrollálható a csövek falának összetétele [70], ahogyan Roszol és Steinbock a szilikát-réz-hidroxid és a szilikátcink-hidroxid rendszerben leírták [71]. A módszer továbbfejlesztésre került Makki és Steinbock által oly módon, hogy lehetőség nyílt a függőleges irányú csőnövekedés sebességének szabályozására [72], melyet alkalmaztak a lumineszcens CdSe-ZnS nanorészecskék beépítésére szilikát tartalmú cink-oxid/hidroxid csövekbe [73]. A fémionok beadagolása megfelelő áramlási sebesség alkalmazásával lehetővé teszi, hogy ellenőrzött és reprodukálható módon állítsunk elő üreges csöveket.…”