A Light‐Resistant Organic Sensitizer for Solar‐Cell Applications

Finely tuned : A stable dye‐sensitized solar cell that contains a molecularly engineered organic dye has been prepared. The efficiency of the cell remains at 90 % after 1000 h of light soaking at 60 °C. The remarkable stability of the cell is also reflected in the open‐circuit voltage value (V_oc), short‐circuit photocurrent‐density value (J_sc), and the fill factor, which also show barely no decline (see picture).

     

Molecular Design of D‐π‐A Type II Organic Sensitizers for Dye Sensitized Solar Cells

Four new type II organic dyes with D‐π‐A structure (donor‐π‐conjugated‐acceptor) and two typical type II sensitizers based on catechol as reference dyes are synthesized and applied in dye sensitized solar cells (DSCs). The four dyes can be adsorbed on TiO₂ through hydroxyl group directly. Electron injection can occur not only through the anchoring group (hydroxyl group) but also through the electron‐withdrawing group (? CN) located close to the semiconductor surface. Experimental results show that the type II sensitizers with a D‐π‐A system obviously outperform the typical type II sensitizers providing much higher conversion efficiency due to the strong electronic push‐pull effect. Among these dyes, LS223 gives the best solar energy conversion efficiency of 3.6%, with J_sc=7.3 mA·cm^?2, V_oc=0.69 V, FF=0.71, the maximum IPCE value reaches 74.9%.     

Quasi‐One‐Dimensional Electronic Systems Formed from Boron Dipyrromethene (BODIPY) Dyes

Synthetic strategies have been devised that allow the rational design and isolation of highly coloured boron dipyrromethene (BODIPY) dyes that absorb across much of the visible region. Each dye has an aryl polycycle (usually pyrene or perylene) connected to the central BODIPY core through a conjugated tether at the 3,5‐positions. Both mono‐ and difunctionalised derivatives are accessible, in certain cases containing both pyrene and perylene residues. For all new compounds, the photophysical properties have been recorded in solution at ambient temperature and in a glassy matrix at 77 K. The presence of the aryl polycycle(s) affects the absorption and emission maxima of the BODIPY nucleus, thereby confirming that these units are coupled electronically. Indeed, the band maxima and oscillator strengths depend on the conjugation length of the entire molecule, whereas there is no sign of fluorescence from the polycycle. As a consequence, the radiative rate constant tends to increase with each added appendage. The nature of the linkage (styryl, ethenyl, or ethynyl) also exerts an effect on the photophysical properties and, in particular, the absorption spectrum is perturbed in the region of the aryl polycycle. The perylene‐containing BODIPY derivatives absorb over a wide spectral range and emit in the far‐red region in almost quantitative yield. A notable exception to this generic behaviour is provided by the anthracenyl derivative, which exhibits charge‐transfer absorption and emission spectra in weakly polar media at ambient temperature. Regular BODIPY‐like behaviour is restored in a glassy matrix at 77 K. Overall, these new dyes represent an important addition to the range of strongly absorbing and emitting reagents that could be used as solar concentrators.     

Development and characterization of new insulin containing polysaccharide nanoparticles

A nanoparticle insulin delivery system was prepared by complexation of dextran sulfate and chitosan in aqueous solution. Parameters of the formulation such as the final mass of polysaccharides, the mass ratio of the two polysaccharides, pH of polysaccharides solution, and insulin theorical loading were identified as the modulating factors of nanoparticle physical properties. Particles with a mean diameter of 500 nm and a zeta potential of approximately −15 mV were produced under optimal conditions of DS:chitosan mass ratio of 1.5:1 at pH 4.8. Nanoparticles showed spherical shape, uniform size and good shelf-life stability. Polysaccharides complexation was confirmed by differential scanning calorimetry and Fourier transformed infra-red spectroscopy. An association efficiency of 85% was obtained. Insulin release at pH below 5.2 was almost prevented up to 24 h and at pH 6.8 the release was characterized by a controlled profile. This suggests that release of insulin is ruled by a dissociation mechanism and DS/chitosan nanoparticles are pH-sensitive delivery systems. Furthermore, the released insulin entirely maintained its immunogenic bioactivity evaluated by ELISA, confirming that this new formulation shows promising properties towards the development of an oral delivery system for insulin.     

Optimizing dyes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have emerged as an important cheap photovoltaic technology. Charge separation is initiated at the dye, bound at the interface of an inorganic semiconductor and a hole-transport material. Careful design of the dye can minimize loss mechanisms and improve light harvesting. Mass application of DSSCs is currently limited by manufacturing complexity and long-term stability associated with the liquid redox electrolyte used in the most-efficient cells. In this Minireview, dye design is discussed in the context of novel alternatives to the standard liquid electrolyte. Rapid progress is being made in improving the efficiencies of such solid and quasi-solid DSSCs which promises cheap, efficient, and robust photovoltaic systems.     

A Highly Sensitive Sandwich Enzyme Immunoassay for Insulin in Human Serum Developed Using Capybara Anti-Insulin Fab' -Horseradish Peroxidase Conjugate

Abstract

A highly sensitive sandwich enzyme immunoassay for insulin in human serum has been developed using capybara anti-insulin serum. Capybara anti-insulin IgG-coated polystyrene balls were incubated with serum samples in the presence of 0.4 M NaCl and then with capybara anti-insulin Fab'-horseradish peroxidase conjugate.

The peroxidase activity bound to the polystyrene balls was correlated to the amount of insulin to be assayed. Serum interference was eliminated by the presence of 0.4 M NaC1, and there was no need to add insulin-free serum to a standard curve. The sensitivity was 4 nU/tube or 0.2 μU/ml of serum when 20 μ1 of serum samples was used. The recovery of insulin added to human serum was 92–97 %. The coefficients of within-assay and between-assay variations were 5.1–7.2 % and 7.6–9.2 %, respectively. The regression equation and correlation coefficient to radioimmunoassay were Y(EIA)=0.91×(RIA)-2.4 and 0.97 (n=76), respectively.     

Separation techniques in radioimmunoassays for digoxin and insulin

Ohne Zusammenfassung

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Separation techniques in radioimmunoassays for digoxin and insulin

     

A dyadic sensitizer for dye solar cells with high energy-transfer efficiency in the device.

A new bichromophoric dyad based on an alkyl-functionalized aminonaphthalimide as energy-donor chromophore and [Ru(dcbpy)2(acac)]Cl (dcbpy=4,4'-dicarboxybipyridine, acac=acetylacetonato) as energy acceptor and sensitizing chromophore is synthesized. Efficient quenching of the donor-chromophore emission is observed in solution, presumably due to resonant energy transfer. This dyad is then used as a sensitizer in a dye solar cell. By comparing the spectral properties of transparent dye solar cells sensitized with the dyad and [Ru(dcbpy)2(acac)]Cl, it is possible to demonstrate that photons absorbed by the donor moiety also contribute significantly to the generation of current. Instead of using acceptor luminescence as a probe, enhanced photocurrent generation is employed to estimate the energy-transfer efficiency. Fitting theoretical to experimental external quantum efficiency functions gives a value for the energy-transfer efficiency of 85 %. Evaluation of the maximum output power of dye solar cells sensitized with the dyad and [Ru(dcbpy)2(acac)]Cl showed, under selective illumination at the absorption maximum of the donor chromophore, that the introduction of the energy-donor moiety leads to a significant increase in the monochromatic maximum output power under blue illumination. This result demonstrates the usefulness of energy transfer for the generation of current in dye-sensitized solar cells.     

A theoretical study of explosive sensitizers

Quantum chemical calculations at the HF/6-31G^* and B3LYP/6-31G^* levels have been performed on five explosive sensitizers, ethyl nitrate (EN), n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN) and tetraethylene glycol dinitrate (TEGDN). Theoretical study has made a detailed molecular-level investigation of the title compounds. Based on the Mulliken populations and bond lengths, the fission of the O₂–N₃ can be acceptable reasonably. Charge distribution analysis indicates that the five nitrates produce NO₂ gas during the dissociation of the O₂–N₃ weak bond. We also order the relative thermal stability of five nitrates on the basis of frontier orbital energy (E _HOMO, E _LUMO) and energy gap (ΔE = E _HOMO − E _LUMO).     

A SENSITIZED PHOTOINITIATION SYSTEM ——BIS (7-DIETHYLAMINO COUMARIN ) KETONE-3 AND DIPHENYLIODONIUM SALT COMBINATION

Bis (7-diethylaminocoumarin) ketone- 3(DACK) and diphenyliodonium salt (DPIO)combination as an effective photoinitiation system for radical polymerization has been investigated. The sensitized photolysis of DACK/DPIO leads to bleaching of DACK and decomposition of DPIO to generate initiating radical species. The electron transfer sensitization occurs mainly from the triplet state of DACK. The photobleaching obeyed a second-order kinetics and the rate constant was evaluated to be 31.3mol~(-1)·1·s~(-1) Photopolymerization of MMA initiated by DACK/DPIO was carried out in acetonitrile solution. The polymerization rate was found to be proportional to the concentration of DACK, DPIO and MMA with the exponents of 0.34, 0.40 and 1.0 respectively. The initiated efficiency is comparable to those of small molecular ketones.The sensitized photoinitiation mechanism has been discussed.