Surface modifications of ZnO quantum dots for bio-imaging

Abstract

The wide bandgap and large exciton binding energy of ZnO may generate new applications in bio-imaging after careful surface modifications. Formation of chemically pure ZnO colloidal nanocrystals with controlled size without unwanted by-products or agglomeration has been the major challenge to fully utilize ZnO's unique properties. In this research, colloidal ZnO nanocrystals were synthesized by a soft chemical method. Particle size and colloidal stability were controlled by capping agents. Influences of the surface modifications on particle size, size distribution and photoluminescence properties were investigated. Pure ZnO showed high intensity UV emission and very low intensity in the visible range, indicating good surface morphology of the ZnO nanoparticles with little surface defects. Transmission electron microscopy (TEM) analysis revealed that the capped crystals were close to spherical shape with single-crystal size about 6 nm. X-ray diffraction (XRD) analyses revealed single-phase ZnO nanoparticles. For bio-imaging, emission in visible wavelength range is preferred. Both TiO 2 and SiO 2 were effective in shifting the emission peak to the visible range with high intensity. Optimum capping thickness is 0.5 nm. ZnO-TiO 2 quantum dots (QDs) showed good bio-imaging capability on plant cells. Quantum yields of the pure ZnO and TiO 2 capped ZnO were measured and compared to commercial fluorescence materials.

Mass spectrometric study of Ar/NH3 surface wave plasma utilized for surface functionalization of ZnO nanoparticles

“…16,17) To make the ZnO NPs suitable for bioimaging applications, their surface should firstly be treated. [18][19][20][21] ZnO NP functionalization has already been carried out employing several different chemical methods, proving the possibility of binding linkers to the surface of NPs, which serve as further connection points for organic and inorganic dyes 22,23) and different kinds of molecules. 24,25) Usually, this type of functionalization is time-consuming and the high cost of the chemicals used is also a serious issue.…”

ZnO quantum dots modified bioactive glass nanoparticles with pH-sensitive release of Zn ions, fluorescence, antibacterial and osteogenic properties

“…2c), confirming the presence of ZnO QDs crystals in ZnO-BGN. 39 Notably, BGN showed an emission peak in the range of violet light (B440 nm), which could be attributed to the defect pair consisting of a dioxasilirane and a silylene center in the heated silica-based particles. 40 As a comparison, ZnO-BGN showed an interesting PL spectrum, in which three PL peaks at B410, 480, and 520 nm could be observed.…”

“…This phenomenon has been found in previous studies on the combination of ZnO and silica-based nanoparticles. 41,42 The strongest peak located at B410 nm in the violet range was induced by the presence of ZnO QDs, 39 while the emergence of other two peaks in the blue (B480 nm) and green range (B520 nm) could be related to the change in OH groups on the samples 39,43 and the spherical shape of BGN causing multiple scattering of excitation light, 42 respectively.…”

Synthesis, Self-assembly and Optoelectronic Properties of Monodisperse ZnO Quantum Dots

“…Meulenkamp has reported a synthetic process with the highest temperature at only room temperature to make as-prepared ZnO QDs at a size of 3-6nm [29]. In typical preparation of ZnO QDs, zinc acetate dehydrate (Zn(CH 3 COO) 2 ·2H 2 O) or purity zinc acetate (Zn(CH 3 COO) 2 ) was mostly chosen as Zn precursor, while it is much more flexible to choose other reagents as oxygen source, such as lithium hydroxide (LiOH) [4][5][6][7][8], sodium hydroxide (NaOH) [9][10][11][12][13], Monoethanolamine (MEA) [14,15], Diethylene Glycol (99.5% DEG, ethylenediamine-tetra-acetic acid (EDTA)) [16,17], Triethanolamine (TEA) [18] and water [19,20]. Various alcohols like ethanol [4-8,12,14,], propanol [9][10][11][12][13]19,20] were used as solvents.…”

“…Applications of QDs on biology, photovoltaic devices, solar cells, sensors and QD-LEDs also have gained great interest in their relative research fields [3][4][5][6][7]. Much effort has been devoted to fabricating and developing compound semiconductor QDs, such as CdSe, CdTe, GaAs, InAs, InP, ZnS and ZnO [8][9][10][11][12][13][14]. A number of synthetic approaches have been used to fabricate those QDs, such as sol-gel [15], hydrothermal growth [16], thermal decomposition [17], pulsed laser ablation [18], flame spray pyrolysis [19], etc.…”