Synthesis and optical properties of two new PPV derivatives embedded on the surface of PbS nanocrystals (original) (raw)
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Preparation and optical studies of PbS nanoparticles
In the present report formation of nano-sized PbS in MA/octene-1 copolymer matrix at 80 C temperature is being reported. A size and distribution of particles were observed in AFM results and the images are correlated with the results on X-ray diffraction measurements. The structure and phase of the PbS nanoparticles were characterized by X-ray diffraction (XRD). XRD studies reveal that as-synthesized PbS nanoparticles are in single phase cubic structure and the grain size have been calculated 10–15 nmfrom XRD results. The size distribution was further supported by UV/Vis absorption and photoluminescence (PL) spectroscopy of the colloid nanoparticles. The obtained nanocomposites show an emission peak at 418 nm.
Synthesis and Optical Properties of Thiol-Stabilized PbS Nanocrystals
Langmuir, 2005
Thiol-capped water-soluble PbS nanocrystals (NCs) stabilized with 1-thioglycerol, dithioglycerol, or a mixture of 1-thioglycerol/dithioglycerol (TGL/DTG) were prepared via one-stage synthesis at room temperature. We found that NCs stabilized with a TGL/DTG mixture show efficient and stable infrared photoluminescence centered in the second "biological window" (1050-1200 nm). Under optimized conditions, full width at half-maximum of the PL emission peak was from 70 to 100 nm. PbS NCs were stable to precipitation and aggregation for the time period from 2 to 3 months when stored in the dark under room temperature. Room-temperature photoluminescence quantum efficiency of NCs was from 7 to 10%. When NCs were stored at 37°C, their PL emission red-shifted, consistent with the NC growth. Recent progress in the use of PbS NCs includes their electroluminescence in a polymer matrix, 15 room-temperature optical gain in a glass matrix, 16 and, most recently, room-temperature optical gain in solutionprocessed PbS NC films. 17 In addition, PbS quantum dots are expected to have promising third-order nonlinear optical properties. Previous aqueous-based syntheses of PbS nanoparticles employed water-soluble polymer stabilizers: poly(vinyl alcohol), poly(vinyl pyrrolidone), gelatin, and DNA. These synthetic routes, however, did not produce PbS NCs with good optical properties, such as absorption or luminescent emission. More recently, PbS NCs with tunable size and good optical properties have been obtained by an organometallic method; 20 the drawback of this approach however was the use of organic solvents and high-temperature reaction conditions.
Correlation between structural and optical properties of PbS nanocrystals
Journal of Crystal Growth, 1996
PbS semiconductor nanocrystals have been synthesized in order to study the modifications of their optical properties in relation to their size. The synthesis has been carried out by using the techniques of colloid chemistry. A fast evolution of the optical absorption spectrum has been noticed following synthesis. Immediately after the synthesis reaction, the samples exhibit a structured absorption spectrum with three well-defined excitonic peaks. Within a few minutes, the peaks progressively disappear and a structureless spectrum occurs. A procedore of stabilization of the colloids has been set up in order to allow the study of the structural and optical properties at different stages of their evolution. Fiber-like nanocrystals (2.5 x 25 nm) and platelets have been found in the early stages of the synthesis and nearly cubic nanocrystals (13 nm) are found in later stages of evolution.
Synthesis, optical and morphological characterization of MPA-capped PbSe nanocrystals
Physica B: Condensed Matter, 2014
This work focuses on the synthesis and characterization of 3-mercaptopropionic acid-capped PbSe nanocrystals (NCs) using an aqueous synthetic protocol. The synthesis was carried out at room temperature and resulted in uniform NCs. The as-synthesized NCs were characterized using photoluminescence spectroscopy, HR-TEM and X-Ray diffraction. They showed a perfect Gaussian peak at 1203 nm with average diameters of r 3 nm and diffraction patterns consistent with rock-salt structure of PbSe NCs.
Journal of Physical Chemistry C, 2009
Colloidal photoluminescent (PL) PbS nanocrystals have attracted a lot of attention in various applications such as bioimaging and optical telecommunications due to their tunable bandgap in the near-infrared region of the electromagnetic spectrum. Hot-injection processes seem to be the best to engineer high-quality PbS nanocrystals. However, there is a limited body of literature documented on the syntheses, with little information on synthetic parameters affecting the optical properties of the product. Moreover, small PbS nanocrystals with large bandgap greater than 1.38 eV (ca. 900 nm) and narrow bandwidth are rarely reported, due to the fact that high-temperature growth in hot-injection processes leads to large nanocrystals rapidly. This manuscript deals with our noninjection and low temperature approach to small PbS nanocrystal ensembles with bandgap in wavelength shorter than 900 nm and with narrow bandwidth; the growth temperature can be as low as room temperature. For our noninjection approach, systematic study was performed on synthetic parameters affecting the growth, with the growth temperature in the range of 30-120°C and octadecene (ODE) as a reaction medium. Different acids including oleic aicd (OA) were explored as surface ligands, while two lead source compounds, which are lead oxide (PbO) and lead acetate, and three S source compounds, which are bis(trimethylsilyl)sulfide ((TMS) 2 S), thioacetamide (TAA), and elemental sulfur (S), were investigated. Generally, a solution of a lead precursor in ODE was first prepared via a reaction of a Pb-source compound and an acid; afterward, this solution was mixed with a S-source solution in ODE at room temperature. The use of (TMS) 2 S and OA bestows high-quality PbS nanocrystals, regarding narrow bandwidth of bandgap absorption and photoemission, without storage in dark for digestive and Ostwald ripening leading to selffocusing; in addition to the various acids and Pb and S source compounds explored, feed molar ratios of acid-to-Pb and Pb-to-S, as well as reactant concentrations were thoroughly investigated. Low acid-to-Pb and high Pb-to-S feed molar ratios together with high-reactant concentrations favor the formation of small PbS nanocrystals; meanwhile, from one synthetic batch, the growth of PbS nanocrystals in size is tunable mainly via temperature in addition to growth periods. The PbS nanocrystals exhibit bandwidth (full width at halfmaximum) as narrow as ca. 100 nm with growth temperature of 70°C. Thus, our noninjection approach features easy handling with high reproducibility and high-quality PbS nanocrystals with large bandgap but narrow bandwidth. Finally, bandgap engineering of our as-synthesized PbS nanocrystals was performed straightforwardly at room temperature via the mixing of a solution of Cd oleate in ODE; significant blueshift of bandgap absorption and photoemission with enhanced PL efficiency was accomplished.