Potential clinical applications of quantum dots

The use of luminescent colloidal quantum dots in biological investigations has increased dramatically over the past several years due to their unique size-dependent optical properties and recent advances in biofunctionalization. In this review, we describe the methods for generating high-quality nanocrystals and report on current and potential uses of these versatile materials. Numerous examples are provided in several key areas including cell labeling, biosensing, in vivo imaging, bimodal magnetic-luminescent imaging, and diagnostics. We also explore toxicity issues surrounding these materials and speculate about the future uses of quantum dots in a clinical setting

Design of Biotin-Functionalized Luminescent Quantum Dots

We report the design and synthesis of a tetraethylene glycol- (TEG-) based bidentate ligand functionalized with dihydrolipoic acid (DHLA) and biotin (DHLA—TEG—biotin) to promote biocompatibility of luminescent quantum dots (QD's). This new ligand readily binds to CdSe—ZnS core-shell QDs via surface ligand exchange. QDs capped with a mixture of DHLA and DHLA—TEG—biotin or polyethylene glycol- (PEG-) (molecular weight average ∼600) modified DHLA (DHLA—PEG600) and DHLA—TEG—biotin are easily dispersed in aqueous buffer solutions. In particular, homogeneous buffer solutions of QDs capped with a mixture of DHLA—PEG600 and DHLA—TEG—biotin that are stable over broad pH range have been prepared. QDs coated with mixtures of DHLA/DHLA—TEG—biotin and with DHLA—PEG600/DHLA—TEG—biotin were tested in surface binding assays and the results indicate that biotin groups on the QD surface interact specifically with NeutrAvidin-functionalized microtiter well plates

Good coupling between LDPC-Staircase and Reed-Solomon for the design of GLDPC codes for the Erasure Channel

International audienceIn this paper we analyze the design of Generalized LDPC-staircase (GLDPC-staircase) codes, where the base code is an LDPC-Staircase code and component codes are Reed-Solomon codes. More precisely we compare two schemes: scheme A has the property that on each check node of the base code the repair symbol generated by the LDPC code is also a Reed- Solomon repair symbol. On the opposite, with scheme B for each check node the repair symbols generated by the LDPC code are Reed-Solomon source symbols. In this work we perform a behavioral analysis of the two schemes in order to determine the best one for ITerative + Reed Solomon (IT+RS) and Maximum Likelihood (ML) decoding. To that purpose we use an asymptotic analysis using Density evolution (DE) and EXtrinsic Information Transfer techniques, as well as a finite length analysis. We show that scheme A is globally the best solution since it significantly performs better than scheme B with an (IT+RS) decoding and yields similar performance with ML decoding

GLDPC-Staircase AL-FEC codes: A Fundamental study and New results

International audienceThis paper provides fundamentals in the design and analysis of Generalized Low Density Parity Check (GLDPC)-Staircase codes over the erasure channel. These codes are constructed by extending an LDPC-Staircase code (base code) using Reed Solomon (RS) codes (outer codes) in order to benefit from more powerful decoders. The GLDPC-Staircase coding scheme adds, in addition to the LDPC-Staircase repair symbols, extra-repair symbols that can be produced on demand and in large quantities, which provides small rate capabilities. Therefore, these codes are extremely flexible as they can be tuned to behave either like predefined rate LDPC-Staircase codes at one extreme, or like a single RS code at another extreme, or like small rate codes. Concerning the code design, we show that RS codes with " quasi " Hankel matrix-based construction fulfill the desired structure properties, and that a hybrid (IT/RS/ML) decoding is feasible that achieves Maximum Likelihood (ML) correction capabilities at a lower complexity. Concerning performance analysis, we detail an asymptotic analysis method based on Density evolution (DE), EXtrinsic Information Transfer (EXIT) and the area theorem. Based on several asymptotic and finite length results, after selecting the optimal internal parameters, we demonstrate that GLDPC-Staircase codes feature excellent erasure recovery capabilities, close to that of ideal codes, both with large and very small objects. From this point of view they outperform LDPC-Staircase and Raptor codes, and achieve correction capabilities close to those of RaptorQ codes. Therefore all these results make GLDPC-Staircase codes a universal Application-Layer FEC (AL-FEC) solution for many situations that require erasure protection such as media streaming or file multicast transmission

Design of Small Rate, Close to Ideal, GLDPC-Staircase AL-FEC Codes for the Erasure Channel

International audienceThis work introduces the Generalized Low Density Parity Check (GLDPC)-Staircase codes for the erasure channel, that are constructed by extending LDPC-Staircase codes through Reed Solomon (RS) codes based on "quasi" Hankel matrices. This construction has several key benefits: in addition to the LDPC-Staircase repair symbols, it adds extra-repair symbols that can be produced on demand and in large quantities, which provides small rate capabilities. Additionally, with selecting the best internal parameters of GLDPC graph and under hy- brid Iterative/Reed-Solomon/Maximum Likelihood decoding, the GLDPC-Staircase codes feature a very small decoding overhead and a low error floor. These excellent erasure capabilities, close to that of ideal, MDS codes, are obtained both with large and very small objects, whereas, as a matter of comparison, LDPC codes are known to be asymptotically good. Therefore, these properties make GLDPC-Staircase codes an excellent AL-FEC solution for many situations that require erasure protection such as media streaming

Cathodoluminescence and photoluminescence of highly luminescent CdSe/ZnS quantum dot composites

We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSenanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-filmquantum dot composites were synthesized by electrospray organometallic chemical vapor deposition.Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window (470-650 nm) by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied

Experimental Observation of Quantum Confinement in the Conduction Band of CdSe Quantum Dots

Recent theoretical descriptions as to the magnitude of effect that quantum confinement has on he conduction band (CB) of CdSe quantum dots (QD) have been conflicting. In this manuscript, we experimentally identify quantum confinement effects in the CB of CdSe QDs for the first time. Using X-ray absorption spectroscopy, we have unambiguously witnessed the CB minimum shift to higher energy with decreasing particle size and have been able to compare these results to recent theories. Our experiments have been able to identify which theories correctly describe the CB states in CdSe QDs. In particular, our experiments suggest that multiple theories describe the shifts in the CB of CdSe QDs and are not mutually exclusive

Conjugated Polyelectrolyte‐Antibody Hybrid Materials for Highly Fluorescent Live Cell‐Imaging

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91116/1/adma_201103895_sm_suppl.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91116/2/2479_ftp.pd