Luminescence Dynamics of Single Self-Assembled Chains of Förster (FRET)-Coupled CdSe Nanoplatelets

Self-assembled linear chains of CdSe nanoplatelets are known to exhibit highly efficient Förster resonant energy transfer (FRET) leading to fast exciton diffusion between platelets. Here, we compare the luminescence decay dynamics of single nanoplatelets, clusters of a few platelets, and self-assembled chains. As the number of stacked platelets is increased, we show that the luminescence decay becomes faster, which can be interpreted as the FRET-mediated effect of quenchers: excitons may diffuse to nearby quenchers so that their decay rate is increased. On the other hand, a minor slow decay component is also observed for single platelets, corresponding to trapping-detrapping mechanisms in nearby trap states. The contribution of the slow component is enhanced for the platelet chains. This is consistent with a FRET-mediated trapping mechanism where the excitons would diffuse from platelet to platelet until they reach a trap state. Finally, we develop toy models for the FRET-mediated quenching and trapping effects on the decay curves and analyze the relevant parameters.

Quantum dot-imprinted polymers with size and shell-selective recognition properties

The emergence of nanotechnology has stimulated a great deal of research to detect engineered nanoparticles spread out in the environment. We address this issue here by designing quantum dot-imprinted polymers for the speciation of nanoparticles based on their size, shape and surface chemistry.

Correction: Quantum dot-imprinted polymers with size and shell-selective recognition properties

Correction for ‘Quantum dot-imprinted polymers with size and shell-selective recognition properties’ by S. Gam-Derouich et al., Chem. Commun., 2015, DOI: 10.1039/c5cc05203c.

Controlling spontaneous emission with plasmonic optical patch antennas

We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk separated from a planar gold layer by a few tens of nanometers thick dielectric layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending on the antenna geometry. Considering the double dipole structure of the emitters, this corresponds to a Purcell factor up to 80 for dipoles perpendicular to the disk.

Emission characterization of a single CdSe-ZnS nanocrystal with high temporal and spectral resolution by photon-correlation Fourier spectroscopy

We report a spectroscopic study of single colloidal CdSe/ZnS nanocrystals at low temperature. We use photon-correlation Fourier spectroscopy, a technique based on measuring the correlations of the intensities detected at the outputs of a Michelson interferometer. Spectral diffusion over a few microeV is evidenced, on a typical time scale of 200 micros. A time resolution as high as 20 micros is obtained, and an upper limit of 6.5 microeV emission linewidth is measured, corresponding to a coherence time of at least 200 ps, similar to the values for epitaxial quantum dots.

Measurement of the radiative and nonradiative decay rates of single CdSe nanocrystals through a controlled modification of their spontaneous emission

We present a simple method to measure the radiative and nonradiative recombination rates of individual fluorescent emitters at room temperature. By placing a single molecule successively close and far from a dielectric interface and simultaneously measuring its photoluminescence decay and its orientation, both the radiative and nonradiative recombination rates can be determined. For CdSe nanocrystals, our results demonstrate that the fluorescence quantum efficiency, determined at the single-molecule level, is 98% in average, far above the value expected from conventional ensemble experiments. The bidimensional nature of the transition dipole is also directly evidenced from a single-particle measurement.

Potential for polysialylated form of neural cell adhesion molecule-mediated neuroplasticity within the gonadotropin-releasing hormone neurosecretory system of the ewe

The GnRH neurosecretory system undergoes marked structural and functional changes throughout life. The initial goal of this study was to examine the neuroanatomical relationship between GnRH neurons and a glycoprotein implicated in neuroplasticity, the polysialylated form of neural cell adhesion molecule (PSA-NCAM). Using dual label immunocytochemistry in conjunction with confocal microscopy, we determined that fibers, terminals, and perikarya of GnRH neurons in adult ovariectomized ewes are intimately associated with PSA-NCAM. In the preoptic area, intense PSA-NCAM immunoreactivity was evident around the periphery of GnRH cell bodies. The second goal of this study was to determine whether PSA-NCAM expression associated with GnRH neurons varies in conjunction with seasonal changes in the activity of the GnRH neurosecretory system in ovariectomized ewes treated with constant release implants of estradiol. During the breeding season when reproductive neuroendocrine activity was enhanced, the expression of PSA-NCAM immunoreactivity associated with GnRH neurons was significantly greater than that during anestrus when GnRH secretion was reduced. This difference, which occurred despite an unchanging ovarian steroid milieu, was not observed in preoptic area structures devoid of GnRH immunoreactivity, suggesting that the seasonal change is at least partially specific to the GnRH system. The close association between PSA-NCAM and GnRH neurons and the change in this relationship in conjunction with seasonal alterations in GnRH secretion provide anatomical evidence that this molecule may contribute to seasonal remodeling of the GnRH neurosecretory system of the adult.

Surgical treatment of small cell lung cancer

From 1970 till 1989, 30 patients underwent surgical resection for small cell lung cancer (SCLC). The 5-year survival in stage I patients was 31%, in stage II 17% and in stage III the projected 5-year survival was 9%. Among N2 patients there were only 25% survivors after 1 year and none after 2 years. The first group of 15 patients (1970-1979) received no adjuvant chemotherapy in contrast to the second group of 15 patients (1980-1989). The overall 5-year survival for the first group was 13% and the estimated 5-year survival for the second group was 27%. In stage I SCLC, the 5-year survival was 12% and 60%, respectively. These results confirm that surgery may lead to long-term survival in stage I and possibly stage II SCLC, with better prognosis in stage I when adjuvant chemotherapy is added.

Amiodarone and the development of ARDS after lung surgery

An evaluation of amiodarone as prophylactic treatment for supraventricular tachyarrhythmias after pulmonary surgery was stopped because of a high incidence of the adult respiratory distress syndrome (ARDS) after a pneumonectomy. Retrospective analysis of all cases of resection for pulmonary neoplasm in our hospital between 1987 and 1991 indicates that amiodarone may be implicated in the development of ARDS after lung surgery.

The effect of D-penicillamine on lung function parameters (diffusion capacity) in rheumatoid arthritis

Sequential lung function tests were performed on 28 rheumatoid arthritis (RA) patients who were treated with D-penicillamine (total of 101 treatment years) and on 42 control RA patients who were not treated or who were treated with NSAIDs, chloroquine, gold salts, corticosteroids, salazopyrine or methotrexate. A decline in lung function parameters was found in both groups, although it was only significant for the carbon monoxide diffusing capacity corrected for lung volume (DLCO/VL). This decrease in DLCO/VL was less pronounced in the D-penicillamine group (mean -6.9%) than in the control group (mean -11.3%). This difference could not be attributed to smoking, which was more frequent in the control group. When reviewing only the patients with an initial DLCO/VL < 80% of the predicted value and having, with some exceptions, chest X-ray abnormalities, we even observed an amelioration in the mean DLCO/VL in the D-penicillamine group, in contrast with a deterioration in the control group (+5.1% versus -5.6%).

Oxidative injury to erythrocytes, cell rigidity and splenic hemolysis in hemodialyzed patients before and during erythropoietin treatment

The oxidative injury to erythrocytes, red blood cell (RBC) rigidity and splenic hemolysis was assayed in 17 chronically hemodialyzed patients before and during recombinant erythropoietin (EPO) treatment. When a stable hematocrit between 30 and 35% had been established for at least 4 months, a statistically significant increase in RBC volume, hemoglobin concentration, hematocrit, reticulocyte count, and several RBC enzymes (2,3-diphosphoglycerate, glucose 6-phosphate dehydrogenase, pyruvate kinase, hexokinase) was noted. This indicated significant RBC rejuvenation under the influence of EPO. However, no significant improvement in the RBC oxidative sensitivity, RBC deformability, splenic RBC volume, slow mixing splenic RBC volume, and the intrasplenic RBC transit time could be disclosed. These data confirm the existence of an extra-erythrocytic factor in uremic plasma, which is partly responsible for a reduced RBC life span in hemodialysis patients despite EPO treatment.