Whispering Gallery Mode Enabled Efficiency Enhancement: Defect and Size Controlled CdSe Quantum Dot Sensitized Whisperonic Solar Cells.

A synergetic approach of employing smooth mesoporous TiO2 microsphere (SµS-TiO2)-nanoparticulate TiO2 (np-TiO2) composite photoanode, and size and defect controlled CdSe quantum dots (QD) to achieve high efficiency (η) in a modified Grätzel solar cell, quantum dot sensitized whisperonic solar cells (QDSWSC), is reported. SµS-TiO2 exhibits whispering gallery modes (WGM) and assists in enhancing the light scattering. SµS-TiO2 and np-TiO2 provide conductive path for efficient photocurrent charge transport and sensitizer loading. The sensitizer strongly couples with the WGM and significantly enhances the photon absorption to electron conversion. The efficiency of QDSWSC is shown to strongly depend on the size and defect characteristics of CdSe QD. Detailed structural, optical, microstructural and Raman spectral studies on CdSe QD suggest that surface defects are prominent for size ~2.5 nm, while the QD with size > 4.5 nm are well crystalline with lower surface defects. QDSWSC devices exhibit an increase in η from ≈0.46% to η ≈ 2.74% with increasing CdSe QD size. The reported efficiency (2.74%) is the highest compared to other CdSe based QDSSC made using TiO2 photoanode and I-/I3- liquid electrolyte. The concept of using whispering gallery for enhanced scattering is very promising for sensitized whisperonic solar cells.

Surface Engineering of PAMAM-SDB Chelating Resin with Diglycolamic Acid (DGA) Functional Group for Efficient Sorption of U(VI) and Th(IV) from Aqueous Medium.

A novel chelating resin obtained via growth of PAMAM dendron on surface of styrene divinyl benzene resin beads, followed by diglycolamic acid functionalization of the dendrimer terminal. Batch experiments were conducted to study the effects of pH, nitric acid concentration, amount of adsorbent, shaking time, initial metal ion concentration and temperature on U(VI) and Th(IV) adsorption efficiency. Diglycolamic acid terminated PAMAM dendrimer functionalized styrene divinylbenzene chelating resin (DGA-PAMAM-SDB) is found to be an efficient candidate for the removal of U(VI) and Th(IV) ions from aqueous (pH >4) and nitric acid media (>3M). The sorption equilibrium could be reached within 60min, and the experimental data fits with pseudo-second-order model. Langmuir sorption isotherm model correlates well with sorption equilibrium data. The maximum U(VI) and Th(IV) sorption capacity onto DGA-PAMAMG5-SDB was estimated to be about 682 and 544.2mgg-1 respectively at 25°C. The interaction of actinides and chelating resin is reversible and hence, the resin can be regenerated and reused. DFT calculation on the interaction of U(VI) and Th(IV) ions with chelating resin validates the experimental findings.

Synthesis of Cu-Deficient and Zn-Graded Cu-In-Zn-S Quantum Dots and Hybrid Inorganic-Organic Nanophosphor Composite for White Light Emission.

Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications.

Tumor targeting using polyamidoamine dendrimer-cisplatin nanoparticles functionalized with diglycolamic acid and herceptin.

Polymer mediated drug delivery system represents a novel promising platform for tumor-targeting with reduced systemic side effects and improved chemotherapeutical efficacy. In this study, we report the preparation and characterization of herceptin targeted, diglycolamic acid (DGA) functionalized polyamidoamine (PAMAM) dendrimer as a potent drug carrier for cisplatin. DGA dendrimers carrying cisplatin demonstrated enhanced anticancer activity when targeted with herceptin. In vitro cell line studies with herceptin-DGA-G4-cisplatin in HER-2 +ve and HER-2 -ve human ovarian cancer cell lines showed that these nanoparticles possessed remarkable features such as lower IC50 value, improved S-phase arrest, and enhanced apoptosis due to increased cellular uptake and accumulation than the untargeted DGA-G4-cisplatin and free cisplatin. Furthermore, in vivo results in SCID mice bearing SKOV-3 tumor xenografts, herceptin-DGA-G4-cisplatin, appeared to be more effective in inducing tumor regression as compared to free cisplatin. Collectively, these results indicate that herceptin targeted DGA functionalized PAMAM-cisplatin conjugates serve as better anti-tumor agents than individual therapeutic agents.

Adsorption of uranium from aqueous solution by PAMAM dendron functionalized styrene divinylbenzene.

A new polymeric chelating resin was prepared by growing third generation poly(amido)amine (PAMAMG3) dendron on the surface of styrene divinylbenzene (SDB) and characterized by FTIR, TGA and SEM. The ideal branching of dendron in the chelating resin was determined from potentiometric titration. Adsorption of uranium (VI) from aqueous solution using PAMAMG3-SDB chelating resin was studied in a series of batch experiments. Effect of contact time, pH, ionic strength, adsorbent dose, initial U(VI) concentration, dendron generation and temperature on adsorption of U(VI) were investigated. Kinetic experiments showed that U(VI) adsorption on PAMAMG3-SDB followed pseudo-second-order kinetics model appropriately and equilibrium data agreed well with the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were evaluated from temperature dependent adsorption data and the uranium adsorption on PAMAMG3-SDB was found to be endothermic and spontaneous in nature. The sticking probability value (5.303 × 10(-9)), kinetic and isotherm data reveal the chemisorption of uranium on PAMAMG3-SDB and adsorption capacity of the chelating resin was estimated to be 130.25 mg g(-1) at 298 K. About 99% of adsorbed U(VI) can be desorbed from PAMAMG3-SDB by a simple acid treatment suggesting that the chelating resin is reusable.