CdSe/ZnS Nanocrystals with Dye-Functionalized Polymer Ligands Containing Many Anchor Groups

Scanning near-field optical microscopy using semiconductor nanocrystals as a local fluorescence and fluorescence resonance energy transfer source

Local fluorescence probes based on CdSe semiconductor nanocrystals were prepared and tested by recording scanning near-field optical microscopy (SNOM) images of calibration samples and fluorescence resonance energy transfer SNOM (FRET SNOM) images of acceptor dye molecules inhomogeneously deposited onto a glass substrate. Thousands of nanocrystals contribute to the signal when this probe is used as a local fluorescence source while only tens of those (the most apical) are involved in imaging for the FRET SNOM operation mode. The dip-coating method used to make the probe enables diminishing the number of active fluorescent nanocrystals easily. Prospects to realize FRET SNOM based on a single…

CdSe/ZnS-Nanokristalle mit farbstoffmarkierten Polymerliganden mit mehrfachen Ankergruppen

Rotaļa-vidējā pirmsskolas vecuma bērnu saskarsmes prasmju sekmētāja

Darba autore: Inga Potapova Darba zinātniskā vadītāja: Dr. Paed. Antra Randoha Pētnieciskā darba temats: ”Rotaļa-vidējā pirmsskolas vecuma bērnu saskarsmes prasmju sekmētāja.” Pētījuma mērķis: Izzināt un praktiski pētīt vidējā pirmsskolas vecuma bērnu saskarsmes prasmju sekmēšanas iespējas rotaļās. Pētījuma uzdevumi: 1. analizēt dažādu autoru pedagoģisko, psiholoģisko literatūru par vidējā pirmsskolas vecuma bērnu saskarsmes prasmju attīstību rotaļās; 2. praktiski pētīt un analizēt bērna saskarsmes prasmju attīstību rotaļās; 3. apkopot rezultātus un izdarīt secinājumus. Pētījuma hipotēze: saskarsmes prasmes noritēs veiksmīgi, ja pedagogs sekmēs to attīstību ievērojot bērna vecuma un individ…

Semiconductor Nanocrystals with Multifunctional Polymer Ligands

In this letter, we describe the preparation of a versatile polymer ligand, which can be attached to CdSe/ZnS semiconductor nanocrystals via a phase transfer reaction. The ligand is based on a chain of reactive esters, which can, in principle, be substituted by any compound containing amino-functionalities. The polymer/nanocrystal complexes are characterized in terms of structure and photostability.

Fluorescence Decay Time of Single Semiconductor Nanocrystals

We present fluorescence decay measurements of single ZnS covered CdSe nanocrystals. It is shown that the fluorescence decay time is fluctuating during the investigation leading to a multiexponential decay even for a single nanocrystal. In combination with measurements of the fluorescence blinking behavior we find that a high fluorescence intensity is correlated with a long fluorescence decay time. This is consistent with a model of fluctuating nonradiative decay channels leading to variable dynamic quenching processes of the excited state.

<title>Probing the interactions of single CdSe quantum dots with their local environment</title>

The fluorescence blinking of single CdSe/ZnS nanocrystals under different experimental conditions is investigated. We show that the blinking process is very sensitive to the particle environment even if the nanocrystals are covered with a few monolayers of ZnS. Especially the presence of oxygen leads to a shortening of the on-times but leaves the off-times almost unaffected. Therefore, oxygen which is adsorbed to the surface might act as a scavenger for photo generated electrons and leaves the particle in its (positively charged) dark state.