Tzarara López-Luke

Brilliant blue, green and orange–red emission band on Tm3+-, Tb3+- and Eu3+-doped ZrO2 nanocrystals

Tm3+-, Tb3+- and Eu3+-doped ZrO2 nanocrystals were prepared by a facile precipitation method with a hydrothermal process. Structural characterization showed a crystallite size ranging from 30 to 40 nm, and monoclinic and tetragonal zirconia phases were observed depending on the dopant concentration. The monoclinic phase was dominant for 0.5 mol% of Tb3+ and Eu3+, and the tetragonal phase was 100% stabilized for 2 mol% of Tm3+ and Tb3+. The structure of emission bands associated with Eu3+ confirms the substitution of Zr4+ located at C1 and D2h symmetry sites for the monoclinic and tetragonal phases. The emission of three primary colours, red, green and blue, was obtained from Eu3+, Tb3+ and Tm3+, respectively, which makes this nanophosphor an excellent candidate for use in photonics applications. The emitted signal was analysed as a function of ion concentration and the optimum concentration was determined.

Glucose detection using SERS with multi-branched gold nanostructures in aqueous medium

Gold nanoparticles (AuNPs), multi-branched gold nanoparticles (MBGNs), and silica-coated MBGNs (MBGNs-silica) were studied for rhodamine B (RB) and α-glucose detection at low concentration. The MBGNs SPR band in the NIR, which is tunable, is useful for SERS that was demonstrated using rhodamine B and α-glucose as probe molecules with detection limits of 50 pM and 5 mM (90 mg dL−1), respectively, much lower than that using regular AuNPs. The SERS signals of RB and α-glucose using MBGNs-silica are further enhanced with respect to AuNPs and MBGNs, which is attributed to the aggregation of the MBGNs and a stronger interaction. In the case of α-glucose, the functionalization process performed to both, α-glucose molecules and MBGNs, improves the interaction and allows measurements at low concentration.

Current improvement in hybrid quantum dot sensitized solar cells by increased light-scattering with a polymer layer

We investigate the effect of the incorporation of a material with efficient electron transport into a Hybrid Quantum Dot Sensitized Solar Cell (HyQDSSC). The performance of different quantum dot sensitized solar cells is compared with a cell containing poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) with structure TiO2/PbS/PFN/CdS/ZnS. The photoconversion efficiency, as compared to our reference samples, was enhanced in some cases by approximately 45%, while the short-circuit current increased by up to 100% after the incorporation of PFN. The deposition order of the different components was crucial in achieving these improvements. Diffuse reflectance and impedance spectroscopy were used to study the behaviour of the cells. The observed enhancements are attributed to increased light scattering in the active layer, better charge transport, and a decrease in charge recombination and transport resistance.

Operating Mechanisms of Mesoscopic Perovskite Solar Cells through Impedance Spectroscopy and J–V Modeling

The performance of perovskite solar cell (PSC) is highly sensitive to deposition conditions, the substrate, humidity, and the efficiency of solvent extraction. However, the physical mechanism involved in the observed changes of efficiency with different deposition conditions has not been elucidated yet. In this work, PSCs were fabricated by the antisolvent deposition (AD) and recently proposed air-extraction antisolvent (AAD) process. Impedance analysis and J-V curve fitting were used to analyze the photogeneration, charge transportation, recombination, and leakage properties of PSCs. It can be elucidated that the improvement in morphology of perovskite film promoted by AAD method leads to increase in light absorption, reduction in recombination sites, and interstitial defects, thus enhancing the short-circuit current density, open-circuit voltage, and fill factor. This study will open up doors for further improvement of device and help in understanding its physical mechanism and its relation to the deposition methods.

Labeling of HeLa cells using ZrO2:Yb3+-Er3+ nanoparticles with upconversion emission

Abstract. This work reports the synthesis, structural characterization, and optical properties of ZrO2:Yb3+-Er3+ (2–1 mol%) nanocrystals. The nanoparticles were coated with 3-aminopropyl triethoxysilane (APTES) and further modified with biomolecules, such as Biotin-Anti-rabbit (mouse IgG) and rabbit antibody-AntiKi-67, through a conjugation method. The conjugation was successfully confirmed by Fourier transform infrared, zeta potential, and dynamic light scattering. The internalization of the conjugated nanoparticles in human cervical cancer (HeLa) cells was followed by two-photon confocal microscopy. The ZrO2:Yb3+-Er3+ nanocrystals exhibited strong red emission under 970-nm excitation. Moreover, the luminescence change due to the addition of APTES molecules and biomolecules on the nanocrystals was also studied. These results demonstrate that ZrO2:Yb3+-Er3+ nanocrystals can be successfully functionalized with biomolecules to develop platforms for biolabeling and bioimaging.

SERS and integrative imaging upon internalization of quantum dots into human oral epithelial cells

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.

SERS-active Au/SiO2 clouds in powder for rapid ex vivo breast adenocarcinoma diagnosis.

In the present work, we report a dry-based application technique of Au/SiO2 clouds in powder for rapid ex vivo adenocarcinoma diagnosis through surface-enhanced Raman scattering (SERS); using low laser power and an integration time of one second. Several characteristic Raman peaks frequently used for the diagnosis of breast adenocarcinoma in the range of the amide III are successfully enhanced by breading the tissue with Au/SiO2 powder. The SERS activity of these Au/SiO2 powders is attributed to their rapid rehydration upon contact with the wet tissues, which promotes the formation of gold nanoparticle aggregates. The propensity of the Au/SiO2 cloud structures to adsorb biomolecules in the vicinity of the gold nanoparticle clusters promotes the necessary conditions for SERS detection. In addition, electron microscopy, together with elemental analysis, have been used to confirm the structure of the new Au/SiO2 cloud material and to investigate its distribution in breast tissues.

Interaction of TGA@CdTe Quantum Dots with an Extracellular Matrix of Haematococcus pluvialis Microalgae Detected Using Surface-Enhanced Raman Spectroscopy (SERS).

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.

Photovoltaic study of quantum dot-sensitized TiO2/CdS/ZnS solar cell with P3HT or P3OT added

Within the body of research aimed at improving the photovoltaic performance of quantum dot-sensitized solar cells (QDSSC), poly-3-alkyl thiophenes have been commonly used in hybrid photovoltaic devices. The roles of poly(3-hexylthiophene) (P3HT) and of poly(3-octylthiophene) (P3OT) on hybrid QDSSC were investigated in the present work. To this end, CdS and ZnS QDs were deposited by successive ionic layer adsorption and reaction method on TiO2 mesoporous film. The polymers were added by drop-casting method giving the configurations TiO2/CdS/ZnS/P3HT and TiO2/CdS/ZnS/P3OT. Results showed that the polymer covers the TiO2/CdS/ZnS surface enough to protect it from contact with the polysulfide electrolyte, while electrochemical impedance spectroscopy measurements indicated that when P3HT and P3OT were employed, the recombination resistance increased and the transport resistance decreased, causing the improvement of the open circuit voltage and fill factor, respectively.Graphical Abstract

Evaluation of bacterial presence in the root canal by Raman spectroscopy: a preliminary study

The aim of this work is to present a potential diagnostic technique for bacterial presence at the entrance and inside the root canal of endodontically treated first molars based on Raman spectroscopy. A hollow core photonic crystal fiber probe was introduced inside the root canal to guide and collect the excitation and the Raman signals, respectively. Spectral features indicating differences between normal dentin and dentin with moderate and severe bacterial infection, at the entrance of the root canal, have been clearly detected as changes in the intensity ratios of the (960 cm−1/1451 cm−1) Raman bands and the intensity ratios between the bending and stretching modes of carbonate (1034 cm−1 and 1072 cm−1), respectively; these changes in the intensity ratios are common indicators of demineralization due to the presence of a bacterial infection. Raman signals of dentin with high bacterial presence exhibited a large shift (23 cm−1) for the stretching mode carbonate band together with changes in the collagen I band (1243 cm−1). Raman peaks assigned to specific membrane proteins of bacteria and organic elements were found inside the root canal by using a hollow core photonic crystal fiber probe. The presence of these Raman bands is found to be higher in the case of severe bacterial infection. This is the first Raman spectroscopy study that shows in parallel the bacterial presence within the root canal and the changes that occur in the dental tissue demonstrating the potential of this technique to assess decay of dentin inside the root canal.