Narrow and symmetric emission spectrum, continuous excitation spectrum, high quantum yields and resistance to photobleaching are outstanding advantages semiconductor nanoparticles exhibit ideally compared to conventional fluorescent dyes. However, it is still a challenge to replace existing organic fluorophores and develop a tool for imaging and site-specific drug delivery. In this presentation, we demonstrate the chemistry and spectroscopy of homogeneously alloyed nanocrystals and nanocrystal-doped protein microspheres, emitting the IR and near-infra red as tools for bio-imaging, and drug delivery, respectively. In addition, nanoparticles are studied as energy donors to photosensitizer phthalocyanine dyes, which have proven potential for photodynamic therapy.
Having been hibernated for almost 50 years, research in thermoelectric materials is beginning to regain activity because of the recent advances in nanoscience and nanotechnology. Thermoelectric is an old topic, which was discovered as early as 1821 by Thomas Johann Seebeck. During the following 120 years, great advances in both the theories and experiments were achieved. Since the 1950s, studies in thermoelectric have developed very little, because of the painful difficulties in elevating the efficiency of these kinds of materials. The efficiency of thermoelectric materials is determined by a dimensionless parameter--figure of merit (ZT), given by ZT = S2σT/κ where T is the temperature, S is the thermoelectric power (or Seebeck coefficient), σ is the electrical conductivity, and κ is the thermal conductivity. The best commercially available thermoelectric materials nowadays have a ZT around 1.0, which can be only used in some special cases. To be competitive to the kitchen refrigerators or air-conditioners, a ZT ⩾ 3 at room temperature is required. Recently, some exciting results indicated that higher ZT values can be realized by nanoengineering of these materials. Both theoretical calculations and experimental modulations have shown the promising potentials in the elevation of the efficiency of thermoelectric materials.
Photodynamic therapy (PDT) is an emerging therapy for cancer treatment that shows the greater selectivity towards the malignant cells. Semiconductor nanoparticles are a novel class of photosensitizers with properties that are not easily available with conventional PDT reagents. Their potential properties such as improved luminescence, resistance to photobleaching, and the possibility to modify the surface chemically make them suitable candidates for PDT. In this report, we discuss the synthesis of ternary CdSe1-x Tex nanoparticles along with well known CdSe QDs and their potential in generating the singlet oxygen state by Foerster Resonance Energy Transfer (FRET) to a PDT reagent or by direct triplet-triplet energy transfer to molecular oxygen.
The relaxation dynamics of Cu2O and Cu1.8S quantum dots (QDs) are compared via time-resolved femtosecond pump probe experiments. It is found that Cu2O shows extremely long-lived excited states on the microsecond time scale and Cu1.8S exhibits much shorter lifetimes in the picosecond time regime. While copper sulfide systems are described in the literature as p-type direct band gap materials, the Cu2O system is direct band gap, however it has a forbidden lowest-energy state. These differences are expressed in the different lifetimes displayed in the time-resolved femtosecond and nanosecond measurements. Moreover, it is confirmed by photoluminescence spectroscopy that reveals that only the Cu1.8S QDs show efficient PL and the Cu2O QDs do not luminescence. In all of the systems, carrier trapping is probably the lifetime limiting process for the conduction band edge depopulation.
Cardiolipin is a unique phospholipid containing two phosphatidyl glycerol moieties and four fatty acids per molecule. It
is found exclusively in the mitochondrial inner membrane and at the contact sites between the inner and outer
membranes. The acridine derivative, nonyl-acridine orange (NAO), is a highly specific probe of cardiolipin, with a
binding affinity approximately two orders of magnitude greater than that for binding to other anionic phospholipids. We
recently reported that when NAO is bound in the mitochondria of human prostate cancer PC-3 cells and activated at 488
nm, NAO could transfer fluorescence resonance energy to the phthalocyanine photosensitizer Pc 4. This observation
indicates that one site of Pc 4 binding is very near to NAO and therefore very near to cardiolipin. The average distance
between the two fluorophores was calculated to be 7 nm. In the present study, we have extended the observation to the
endogenously synthesized photosensitizer, protoporphyrin IX, an intermediate in heme biosynthesis that is used for
photodynamic therapy of several types of malignant and non-malignant conditions. Protoporphyrin IX is generated in
the mitochondria but is known to bind to other cellular sites as well, especially the endoplasmic reticulum. The ability of
this molecule to accept resonance energy from NAO in cells is consistent with a localization of at least some of the
molecules in the mitochondria either on the inner membrane, the site of cardiolipin, or within about 10 nm of it. Since
protoporphyrin IX binds with high affinity to the peripheral benzodiazepine receptor, a component of the permeability
transition pore complex that forms at contact sites between the inner and outer membranes, our observations provide
evidence for the close association of several critical molecules for mitochondrial functions and suggest that cardiolipin
may be an early oxidative target during PDT with at least two photosensitizers.