Semiconductor colloidal quantum dots have been, for the past two decades, incorporated in a wide range of
applications from catalysis and optical sensors to biolabels. For this reason, simple, cheap and reproducible routes of
synthesis are the main goal of many research groups around the world. They seek the production of a very stable and
extremely quantum efficient nanocrystal that can afford rough changes in the external environment. Silica capping is
becoming a very common tool in the quest for a stable quantum dot, because of its strong and stable structure, this
material provides a great insulator to the nanocrystal from the outside. The nanocrystal surface is not chemically
favorable to the deposition of the bare silica shell, what demands a bifunctional molecule that provides the linkage
between the core and the shell. In this work we present a comparison between several silanization methods of thiol
capped CdSe and CdTe quantum dots, showing some simplifications of the routes and an application of the quantum dots
produced as fluorescent cell markers in acquisition of confocal microscopy images.
One of the fundamental goals in biology is to understand the interplay between biomolecules of different cells. This
happen, for example, in the first moments of the infection of a vector by a parasite that results in the adherence to the cell
walls. To observe this kind of event we used an integrated Optical Tweezers and Confocal Microscopy tool. This tool
allow us to use the Optical Tweezers to trigger the adhesion of the Trypanosoma cruzi and Trypanosoma rangeli parasite
to the intestine wall cells and salivary gland of the Rhodnius prolixus vector and to, subsequently observe the sequence
of events by confocal fluorescence microscopy under optical forces stresses. We kept the microorganism and vector cells
alive using CdSe quantum dot staining. Besides the fact that Quantum Dots are bright vital fluorescent markers, the
absence of photobleaching allow us to follow the events in time for an extended period. By zooming to the region of
interested we have been able to acquire confocal images at the 2 to 3 frames per second rate.
PbTe doped tellurite glass photonic optical fiber for non linear application were developed using rod in tube method in a
draw tower. We follow the growth kinetics of the quantum dots in the optical fiber by High Resolution Transmission
Electron Microscopy giving some results related with the growth kinetic of the same in function of time so much for
optical fiber as for the glass bulk. Absorption peak near 1500 nm as observed and it was attributed the optical resonance
due PbTe quantum dots in the core fiber.
In the past it was observed that buck ball doped glasses showed enhanced optical
nonlinearities. However, carbon nanotubes are much more stable than buck ball and
should be a better choice for that purpose. Therefore we decided to investigate the
possibility to produce carbon nanotubes doped tellurite glasses and measured their
optical nonlinearities. Tellurite glasses already have a larger nonlinearity compared to
silica, and other, glasses. We produced TeO2-ZnO tellurite family glasses doped with
multi wall Carbon Nanotube (CNT). The CNTs acquired from Carbolex were
vigorously mechanically mixed with the tellurite glass precursors and melted in
platinum crucible around 650°C in a controlled atmosphere inside an electrical induction
furnace. We used the lowest temperature possible and controlled atmosphere to avoid
the CNT oxidation. The glass melt was cast in a stainless steel and thermally treated at
300°C for 5 hours to relieve internal stresses. The samples were than cutted and
polished to perform the optical characterization. We measured refractive index and
thermo physical properties, such as vitreous transition Tg, crystallization onset Tx and
melting Tf temperatures. Raman spectroscopy showed the possible presence of CNTs.
A new polymeric open optical fiber with a star cross section from extruded PMMA grains was
developed. We have painted the external surface of this fiber with the Europium chelate or
Antracene. We have observed the typical luminescence of these compounds when excited with
nanosecond 355 nm pulsed laser. These results show that the developed fiber presents potentialities
for optical sensing.
We have been able to produce soft glass conventional core-clad and micro-structured fibers using rod-and-tube and stack-and-draw method respectively. The stack-and-draw technique shows several difficulties when used with soft glasses, that we managed to avoid using two different lead and alkaline glasses. Non commercial glasses and fibers were thermo-mechanically and optically characterized.
We produced a PbTe quantum dot core doped optical fiber with tellurite glasses intended to be used in highly nonlinear ultrafast optical devices capable to operate at the optical communication window at 1300 and 1500 nm wavelength region. Attenuation peaks of the optical fiber depends on the heat treatment time as expected for dots growth and covered the whole mid infrared region near 1500 nm. The optical fiber preform was made with the rod-in-tube method and the fiber was produced with a 4 m high Heatway drawing tower. The optical fiber core can be heavily doped because tellurite glasses solubility for PbTe quantum dots is order of magnitude higher than borosilicate and phosphate glasses, for example. In order to match all the requirements for core-clad optical fibers we studied undoped and doped tellurite glasses optical and thermophysical properties as a function of the glass composition. We also followed the growth kinetics of the quantum dots by High Resolution Transmission Electron Microscopy in the bulk glass matrix and the optical fiber.