We report on bulk-heterojunction hybrid solar cells based on blends of non-ligand-exchanged CdSe quantum dots (QDs) and the conjugated polymer poly(3-hexylthiophene) with improved power conversion efficiencies of about 2% under AM1.5G illumination after spectral mismatch correction. This is the highest reported value for a spherical CdSe QD based photovoltaic device. After synthesis, the CdSe QDs are treated by a simple and fast acid-assisted washing procedure, which has been identified as a crucial factor in enhancing the device performance. A simple model of a reduced ligand sphere is proposed explaining the power conversion efficiency improvement
Most of the recent developments in ultrasensitive detection of nucleic acid are based on the gold nanoparticles and carbon nanotubes as a medium of signal amplification. Here, we present an ultrasensitive electrochemical nucleic acid biosensor using the conducting polyaniline (PANI) nanotube array as the signal enhancement element. The PANI nanotube array of a highly organized structure was fabricated under a well-controlled nanoscale dimension on the graphite electrode using a thin nanoporous layer as a template, and 21-mer oligonucleotide probes were immobilized on these PANI nanotubes. In comparison with gold nanoparticle- or carbon nanotube-based DNA biosensors, our PANI nanotube array-based DNA biosensor could achieve similar sensitivity without catalytic enhancement, purification, or end-opening processing. The electrochemical results showed that the conducting PANI nanotube array had a signal enhancement capability, allowing the DNA biosensor to readily detect the target oligonucleotide at a concentration as low as 1.0 fM (approximately 300 zmol of target molecules). In addition, this biosensor demonstrated good capability of differentiating the perfect matched target oligonucleotide from one-nucleotide mismatched oligonucleotides even at a concentration of 37.59 fM. This detection specificity indicates that this biosensor could be applied to single-nucleotide polymorphism analysis and single-mutation detection.
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