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The present study reports the localization and interaction of thioglycolic acid (TGA) capped CdTe quantum dots (TGA@CdTe QDs) within the extracellular matrix (ECM) of Haematococcus pluvialis (Chlorophyceae) microalgae (HPM) after an incubation period of 5 min. Changes in the Raman spectrum of HPM induced by the adsorption of the TGA@CdTe QDs are successfully found by using naked gold anisotropic structures as nano-sensors for surface-enhanced Raman scattering (SERS effect). Raman spectroscopy results show that TGA@CdTe QDs interact with the biomolecules present in the ECM. Sample preparation and characterization by complementary techniques such as confocal and electron microscopy are also used to confirm the presence and localization of the nanoparticles in the algae. This research shows new evidence on early accumulation of QDs in plant cells and would further improve our understanding about their environmental impact., (© The Author(s) 2016.)

CdTe quantum dots (QDs) are widely used in bio-applications due to their size and highly efficient optical properties. However internalization mechanisms thereof for the variety of freshly extracted, not cultivated human cells and their specific molecular interactions remains an open topic for discussion. In this study, we assess the internalization mechanism of CdTe quantum dots (3.3 nm) capped with thioglycolic acid using non cultivated oral epithelial cells obtained from healthy donors. Naked gold nanoparticles (40 nm) were successfully used as nanosensors for surface-enhanced Raman spectroscopy to efficiently identify characteristic Raman peaks, providing new evidence indicating that the first interactions of these QDs with epithelial cells occurred preferentially with aromatic rings and amine groups of amino acid residues and glycans from trans-membrane proteins and cytoskeleton. Using an integrative combination of advanced imaging techniques, including ultra-high resolution SEM, high resolution STEM coupled with EDX spectroscopy together with the results obtained by Raman spectroscopy, it was determined that thioglycolic acid capped CdTe QDs are efficiently internalized into freshly extracted oral epithelial cells only by facilitated diffusion, distributed into cytoplasm and even within the cell nucleus in three minutes., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrochemical impedance spectroscopy was used to analyze 10 µm thickness TiO2 films containing 250 nm TiO2 nanoparticles (NPs) with anatase crystalline phase deposited on FTO substrates. The TiO2 films were sensitized with CdSe quantum dots (QDs) (4.5 nm) and decorated with Au nanoparticles (NPs) (7 nm) and poly-3-octylthiophene (P3OT) in three different configurations, namely TiO2/QDs, TiO2/Au/QDs, and TiO2/Au/QDs/P3OT. The characteristic absorption bands for each component, TiO2. P3OT, CdSe QDs, and Au NPs, are centered at 338 nm (3.67 eV), 459 nm (2.7 eV), 552 nm (2.24eV), and 517 nm (2.40 eV), respectively. The UV-Vis spectrum of the composite film TiO2/Au/QDs/P3OT shows clear absorption peaks from 338 to 700 nm. Equivalent circuits were proposed for the different configuration interfaces to fit experimental impedances. The results suggest that the introduction of Au NPs into the TiO2/Au/QDs films strongly reduces resistance to the electron flux from QDs to TiO2 and increases the overall charge transport. Meanwhile, P3OT in the TiO2/Au/QD/P3OT films promotes hole transport and increases the capacitance with the electrolyte, reducing the electron leakage and improving the fill-factor and the final light energy conversion efficiency. [ABSTRACT FROM AUTHOR]

In this work, we explore the development of Yb 3+ -Er 3+ co-doped ZrO 2 nanoparticles to coat on TiO 2 /CdS/ZnS configuration to boost the photoconversion efficiency of quantum dot sensitized solar cells. Photovoltaic measurement results indicate that the Yb 3+ -Er 3+ :ZrO 2 layer on TiO 2 /CdS/ZnS configuration offer a remarkable enhancement in open circuit voltage (593 mV) and fill factor (68.7%). This results proves that it is possible to increase the 55% of photoconversion efficiency (3.0%) in the CdS-based QDSSCs effectively by incorporating the Yb 3+ -Er 3+ :ZrO 2 layer. Electrochemical impedance spectroscopy measurements confirm further the suppressed charge recombination process after coating with the Yb 3+ -Er 3+ :ZrO 2 layer. [ABSTRACT FROM AUTHOR]

Solution-processed mesoscopic oxide semiconductor-based materials offer potentially low-cost and high stability alternative for next generation of solar cells, and metallic nanoparticles had shown to be a good alternative to improve specific parameters in such kind of devices. In the present work, it is showed the systematic study of the effect of electrophoretic gold nanospheres (Au NPs) with cadmium sulfide Quantum Dots (CdS QDs) sensitized TiO 2 solar cells. Au NPs were added by electrophoretic deposition at several times (0.5, 2.5 and 7.5 minutes) and CdS QDs were deposited by a Successive Ionic Layer Absorption and Reaction (SILAR) method. Electrophoretic deposition allowed to significantly decrease the Au NPs deposition times respect previously reported methods. The results show that Au NPs reduce the photocurrent (from 9.85 to 9.44 mA/cm 2 ) at the same time that increase the open circuit voltage (V oc ) (from 575 to 618 mV) and the Fill Factor (FF) (from 46 to 51%) which result in a final increase of the photoconversion efficiency (η) (from 2.63 to 2.96% for 0.5 min of deposit). A systematic characterization permitted to identify the origin of the variations observed in the solar cell parameters with and without Au NPs. Incident Photon to Current conversion efficiency (IPCE) demonstrate that the Au NPs reduces the amount of light that reach the CdS QDs and Impedance Spectroscopy (IS) analysis, indicates a downshift in the TiO 2 conduction band (CB) and decreases the recombination processes, resulting in the observed increase in the FF and V oc . [ABSTRACT FROM AUTHOR]

Highlights • PCE of CdS QDSSC from 2.8% to 3.7% was obtained by solvent modified SILAR approach. • Enhanced PCE is due to increase in light absorption & reduction of recombination rate. • An optimized CdS QDSSC can act as the base for most efficient multilayered QDSSC. Abstract CdS quantum dot sensitized solar cells were fabricated using a solvent modified successive ionic layer adsorption and reaction (SILAR) method. The power conversion efficiency (PCE) of the device (TiO 2 /CdS/ZnS) fabricated by the modified SILAR was increased from 2.8% to a maximum of 3.70%. This was achieved by the use of ethanol in the cadmium precursor solution and methanol in the washing step, instead of the ethanol or methanol solutions used in both steps in the conventional SILAR method. The ethanol – methanol SILAR method enhanced the photovoltaic parameters of the QDSSC by increasing the light absorption and reducing the recombination rate of electrons in the device determined by UV–Vis absorbance spectroscopy and electrochemical impedance spectroscopy. These effects were mainly attributed at the better wettability of ethanol with the TiO 2 surface against the use of methanol or water and the higher solubility of Na 2 S in methanol instead of ethanol in the washing step, resulting in more homogeneous distribution of S−2 ions to react with the already adsorbed Cd2+ cations. [ABSTRACT FROM AUTHOR]

A series of colloidal quantum dots (QDs) of CdS, ZnS, and the ternary chalcogenide Cd 1−x Zn x S were synthesized by a nanoemulsion method, using a sonication probe as shearing power source. Quantum dots with diameters between 4 and 5 nm and cubic crystal structure were obtained and measured by HRTEM and XRD. In all cases, homogeneous solid solutions were obtained, as revealed by Vegard's Law, except with Cd 0.39 Zn 0.61 S. Optical properties of colloidal QDs were measured; the absorption edge is blue shifted, as the content of Zn increases, and showed a quantum confinement. Different emitted colors under UV light was observed, from dark brown with CdS to deep blue with ZnS. QDs of Cd 0.39 Zn 0.61 S show a white photoluminescence. Photoluminescence of the colloidal QDs is due to the combination of the direct band emissions and the trap emissions. [ABSTRACT FROM AUTHOR]

The effect of the Cu 2 O and CdS QD particles on the photoconversion efficiency of the TiO 2 solar cell was analyzed. The Cu 2 O particles were synthesized using the chemical reduction method, and the CdS QDs were prepared using the SILAR method. The JV curves indicated that the photocurrent of the TiO 2 /ZnS solar cell was 0.04 ​mA/cm2, while the introduction of Cu 2 O particles in the TiO 2 /Cu 2 O/ZnS configuration showed that the cell exhibited a photocurrent forty times higher, of 1.82 ​mA/cm2. With the introduction of CdS QD in the following TiO 2 /Cu 2 O/CdS/ZnS and TiO 2 /CdS/ZnS/Cu 2 O solar cell configurations, the current increased to 5.34 ​mA/cm2 and 5.57 ​mA/cm2, respectively, being three times higher compared to TiO 2 /Cu 2 O/ZnS. Although the values of FF and V oc decreased in the TiO 2 solar cells sensitized with Cu 2 O and CdS, probably due to the introduction of new defects, the photogenerated current increased significantly. These results lead to an improvement in photoconversion efficiency, η=0.38% for TiO 2 /Cu 2 O/CdS/ZnS and η ​= ​0.65% for TiO 2 /CdS/ZnS/Cu 2 O which is due to an increase in the absorption range. Cu 2 O particles contribute as a sensitizer probably improves the alignment of the conduction band between the different materials and the defect passivation effect of CdS on the surface of TiO 2. [Display omitted] • Cu 2 O particles and CdS QDs increase photocurrent of 1.82 ​mA/cm2 until 5.57 ​mA/cm2. • Photoconversion efficiency was 0.65% and 0.34% in solar cells. • Cu 2 O particles contribute as sensitizer in the red region of the light spectrum. [ABSTRACT FROM AUTHOR]

We report a novel and simple method for the synthesis of high quality PbS colloidal quantum dots (CQDs) by controlled precipitation between Pb2+ cations and S2− anions inside aqueous nanodroplets that are generated by an ultrasonic bath operated at 35 ​kHz frequency. The synthesized PbS CQDs have cubic crystal structure with an average particle size of 6.8 ​nm, a size dispersion of 15% and an optical band gap of 0.72 ​eV. PbS CQDs were deposited uniformly by electrophoretic method on a TiO 2 photoelectrode applying 200 ​V for 60 ​min and used as photosensitizers in a TiO 2 solar cell. Their photovoltaic parameters were studied under 1 sun illumination. Remarkably, we obtain power conversion efficiencies similar to those found in TiO 2 sensitized solar cells made with high quality PbS CQDs synthesized by hot injection method. High quality PbS colloidal quantum dots synthesized by ultrasonic bath and their use as photosensitizers in a TiO 2 solar cell. Image 1 • High quality PbS colloidal quantum dots synthesized by ultrasonic bath. • PbS CQD have cubic crystal structure and 6.8 ​± ​1.02 ​nm nanoparticle size. • Quantum dot sensitized solar cells are fabricated with the PbS CQD. • PCE is similar to solar cells made with hot injection PbS CQD. [ABSTRACT FROM AUTHOR]