Recent Progress in Dye‐Sensitized Solar Cells Using Nanocrystallite Aggregates

Nanocrystallite aggregates are spherical assemblies of nanometer‐sized crystallites and feature a size on the order of sub‐micrometers. This paper reports and summarizes recent progress in nanocrystallite aggregates for applications in dye‐sensitized solar cells. It emphasizes that nanocrystallite aggregates are a promising class of materials with the capability to generate light scattering, enhance electron transport, retain high specific surface area for dye adsorption, and facilitate electrolyte diffusion while serving as the photoelectrode film of a dye‐sensitized solar cell. In the Perspectives section, it is suggested that optimization of the porosity of the aggregates, the facets of nanocrystallites forming the aggregates, and the structure of photoelectrode film could possibly lead to breakthroughs in improving the power conversion efficiency of the current state‐of‐the‐art dye‐sensitized solar cells.     

Preparation of novel authentication film by screen printing of anthocyanin biomolecular extract: Thermochromism and vapochromism

Novel thermochromic and vapochromic paper substrates were prepared via screen printing with anthocyanin extract in the presence of ferrous sulfate mordant, resulting in multi-stimuli responsive colorimetric paper sheets. Environmentally friendly anthocyanin extract was obtained from red-cabbage (Brassica oleracea var. capitata L.) to function as spectroscopic probe in coordination with ferrous sulfate mordant. Pink anthocyanin/resin nanocomposite films immobilized onto paper surface were developed by well-dispersion of anthocyanin extract as a colorimetric probe in a binding agent without agglomeration. As demonstrated by CIE colorimetric studies, the pink (λ_max = 418 nm) film deposited onto paper surface turns greenish-yellow (λ_max = 552 nm) upon heating from 25 to 75°C, demonstrating new thermochromic film for anti-counterfeiting applications. The thermochromic effects were investigated at different concentrations of the anthocyanin extract. Upon exposure to ammonia gas, the color of the anthocyanin-printed sheets changes rapidly from pink to greenish-yellow, and then immediately returns to pink after taking the gaseous ammonia stimulus away, demonstrating vapochromic effect. The current sensor strip showed a detection limit for ammonia gas in the range 50–300 ppm. Both thermochromism and vapochromism showed high reversibility without fatigue. In addition to studying the rheological properties of the prepared composites, the morphological and mechanical properties of the printed cellulose substrates were also studied.     

A Lipid Requirement for Photosystem I Activity in Heptane-extracted Spinach Chloroplasts

A lipid requirement for photosystem I activity in Spinacia oleracea chloroplasts has been characterized. The transfer of electrons from tetramethyl-p-phenylenediamine through the chloroplast photosystem to viologen dye was used as an assay of photosystem I activity. Activity is diminished by prolonged heptane extraction and is partially restored by readdition of the extracted lipid. Extracted chloroplasts require plastocyanin for maximal restoration of activity. The effect of lipid extract in restoration is partially replaced by triglycerides containing unsaturated, C₁₈ fatty acids. Various potential redox carriers which occur naturally in chloroplasts do not substitute for extracted lipid. Galacto-lipids, sulfolipids, and phospholipids are not involved in the restoration of activity.     

MoS2‐Based All‐Purpose Fibrous Electrode and Self‐Powering Energy Fiber for Efficient Energy Harvesting and Storage

Here an all‐purpose fibrous electrode based on MoS₂ is demonstrated, which can be employed for versatile energy harvesting and storage applications. In this coaxial electrode, ultrathin MoS₂ nanofilms are grown on TiO₂ nanoparticles coated carbon fiber. The high electrochemical activity of MoS₂ and good conductivity of carbon fiber synergistically lead to the remarkable performances of this novel composite electrode in fibrous dye‐sensitized solar cells (showing a record‐breaking conversion efficiency of 9.5%) and high‐capacity fibrous supercapacitors. Furthermore, a self‐powering energy fiber is fabricated by combining a fibrous dye‐sensitized solar cell and a fibrous supercapacitor into a single device, showing very fast charging capability (charging in 7 s under AM1.5G solar illumination) and an overall photochemical‐electricity energy conversion efficiency as high as 1.8%. In addition, this wire‐shaped electrode can also be used for fibrous Li‐ion batteries and electrocatalytic hydrogen evolution reactions. These applications indicate that the MoS₂‐based all‐purpose fibrous electrode has great potential for the construction of high‐performance flexible and wearable energy devices.     

不同溶剂和保存条件对尾叶悬钩子花色素苷提取及稳定性的影响

对尾叶悬钩子(Rubus caudifolius Wuzhi)鲜果中花色素苷的提取条件、主要化学组分及pH值、温度、没食子酸和Al^3 对其颜色及稳定性的影响进行了分析探讨。结果表明,尾叶悬钩子花色素苷的主要组分可能为矢车菊素-3-葡萄糖苷;pH值和温度影响该花色素苷的色泽及其稳定性,随着pH值和温度的增加,其分解加剧,且花色素苷的分解均遵循动力学一级反应规律;添加不同浓度的Al^3 ,色素溶液的吸光值有所升高,显示出有一定的增色效应,但Al^3 和没食子酸对贮藏期间花色素苷的稳定性及色泽均无明显效果。     

Pollen protein synthesis and control of incompatibility in Brassica

Summary Excised but otherwise intact cabbage (Brassica oleracea var. capitata) stigmas release a watersoluble substance which selectively inhibits germination of self-but not cross-pollen. The inhibitory effect on self-pollen germination is dependent on both the concentration of stigma extract and on the time of addition. Low concentrations of stigma extract inhibit when present from the start (zero time additions) of pollen imbibition, whereas high concentrations do not. High concentrations inhibit when stigma extracts are added 1 to 2 minutes after the start of pollen imbibition, but germination is increasingly less inhibited when additions are delayed 2 to 4 minutes. Similar inhibition kinetics are also observed with delayed additions of cordycepin and cycloheximide. Stigma extracts selectively inhibit leucine-¹⁴C incorporation into proteins of self-pollen. We conclude that germination does not require protein synthesis whereas the regulation of self-incompatibility does.Department of Vegetable Crops Publication No. VC 718.     

Spray Deposition of Silver Nanowire Electrodes for Semitransparent Solid‐State Dye‐Sensitized Solar Cells

Transparent top electrodes for solid‐state dye‐sensitized solar cells (ssDSCs) allow for fabrication of mechanically stacked ssDSC tandems, partially transparent ssDSCs for building integration, and ssDSCs on metal foil substrates. A solution‐processed, highly transparent, conductive electrode based on PEDOT:PSS [poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)] and spray‐deposited silver nanowires (Ag NWs) is developed as an effective top contact for ssDSCs. The electrode is solution‐deposited using conditions and solvents that do not damage or dissolve the underlying ssDSC and achieves high performance: a peak transmittance of nearly 93% at a sheet resistance of 18 Ω/square – all without any annealing that would harm the ssDSC. The role of the PEDOT:PSS in the electrode is twofold: it ensures ohmic contact between the ssDSC 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)9,9′‐spirobifluorene (Spiro‐OMeTAD) overlayer and the silver nanowires and it decreases the series resistance of the device. Semitransparent ssDSCs with D35 dye fabricated using this Ag NW/PEDOT:PSS transparent electrode show power conversion efficiencies of 3.6%, nearly as high as a reference device using an evaporated silver electrode (3.7%). In addition, the semitransparent ssDSC shows high transmission between 700–1100 nm, a necessity for use in efficient tandem devices. Such an electrode, in combination with efficient ssDSCs or hybrid perovskite‐sensitized solar cells, can allow for the fabrication of efficient, cost‐effective tandem photovoltaics.     

Recent Advances and Emerging Trends in Photo‐Electrochemical Solar Energy Conversion

Photo‐electrochemical (PEC) solar energy conversion offers the promise of low‐cost renewable fuel generation from abundant sunlight and water. In this Review, recent developments in photo‐electrochemical water splitting are discussed with respect to this promise. State‐of‐the‐art photo‐electrochemical device performance is put in context with the current understanding of the necessary requirements for cost‐effective solar hydrogen generation (in terms of solar‐to‐hydrogen conversion efficiency and system durability, in particular). Several important studies of photo‐electrochemical hydrogen generation at p‐type photocathodes are highlighted, mostly with protection layers (for enhanced durability), but also a few recent examples where protective layers are not needed. Recent work with the widely studied n‐type BiVO₄ photoanode is detailed, which highlights the needs and necessities for the next big photoanode material yet to be discovered. The emerging new research direction of photo‐electrocatalytic upgrading of biomass substrates toward value‐added chemicals is then discussed, before closing with a commentary on how research on PEC materials remains a worthwhile endeavor.     

STUDIES ON PENETRATION OF DYES WITH GLASS ELECTRODE : IV. PENETRATION OF BRILLIANT CRESYL BLUE INTO NITELLA FLEXILIS

Glass electrode measurements of the pH value of the sap of Nitella show that cresyl blue in form of free base penetrates the vacuoles and raises pH value of the sap to about the same degree as the free base of the dye added to the sap in vitro, while the dye salt dissolved in the sap does not alter its pH value. It is proved conclusively that the increase in the pH value of the sap is due only to the presence of the dye and not to some other alkaline substance. Spectrophotometric measurements show that the dye which penetrates the vacuole is chiefly cresyl blue. When the protoplasm is squeezed into the sap, the pH value of the sap is higher than that of the pure sap. Such a mixture behaves very much like the sap in respect to the dye.     

Oxidative degradation of Amaranth dye by a new genus Kerstersia sp.

A dye-decolorizing bacterium was isolated from a coconut coir sample and identified as a new genus Kerstersia sp. by various biochemical tests and 16S rRNA gene sequencing. This bacterium was capable of degrading sulfonated azo dye Amaranth aerobically at 40?°C and pH 7.0. Tests conducted on intracellular crude enzyme extract identified an oxygen insensitive azoreductase. The optimum dye-decolorizing activity at pH 7.0 and 40?°C for the decolorization of dye was 0.091?U mL^?1 (μ_max 0.522?mg h^?1). The K_s 104.51?μM^?1 has been evaluated by plotting Lineweaver–Burk plot for the Amaranth dye. The dye degraded products were extracted and characterized by TLC, diazotization and Carbylamines test, which indicated that Amaranth was biotransformed into non-toxic aromatic metabolite without amine group.     

Geogrid‐Inspired Nanostructure to Reinforce a CuxZnySnzS Nanowall Electrode for High‐Stability Electrochemical Energy Conversion Devices

Inspired by geogrids commonly applied in construction engineering to reinforce side slopes and retaining walls, the use of a “nano‐geogrid” to reinforce a Cu_x Zn_y Sn_z S (CZTS) nanowall electrode for application in electrochemical reactions is demonstrated. The CZTS nanowall electrode reinforced by the nano‐geogrid (denoted as NWD) shows not only remarkable mechanical and electrochemical stability but also considerable electrochemical performances. The NWD demonstrated as a counter electrode in a dye‐sensitized solar cell shows a power conversion efficiency of 7.44 ± 0.04%, comparable with the device using Pt as electrode, and also significantly improves device stability as compared with that afforded by an electrode comprising a CZTS nanowall without the nano‐geogrid (denoted as NOD). In addition, applying the NWD electrode as a cathode in photo‐electrochemical hydrogen evolution reactions (HERs) yields a photocurrent density of ?10 mA cm^?2 at ?0.162 V (vs RHE) under AM 1.5 illumination. Moreover, when HERs are conducted under extreme conditions, the NWD electrode remains intact, whereas the NOD electrode is completely peeled off after 10 min of reaction. Therefore, the concept of using a mimetic rational nanostructure could pave the way for the possibility of improving the performance and stability of various devices.     

Anthocyanins inhibit peroxyl radical-induced apoptosis in Caco-2 cells

The antioxidant activity of anthocyanins has been well characterized in vitro; many cases has been postulated to provide an important exogenous mediator of oxidative stress in the gastrointestinal tract. The objective of this study was to evaluate the efficacy of anthocyanin protection against peroxyl radical (AAPH)-induced oxidative damage and associated cytotoxicity in Caco-2 colon cancer cells. Crude blackberry extracts were purified by gel filtration column to yield purified anthocyanin extracts that were composed of 371 mg/g total anthocyanin, 90.1% cyanidin-3-glucoside, and 4.9 mmol Trolox equivalent/g (ORAC) value. There were no other detectable phenolic compounds in the purified anthocyanin extract. The anthocyanin extract suppressed AAPH-initiated Caco-2 intracellular oxidation in a concentration-dependent manner, with an IC₅₀ value of 6.5 ± 0.3 μg/ml. Anthocyanins were not toxic to Caco-2 cells, but provided significant (P < 0.05) protection against AAPH-induced cytotoxicity, when assessed using the CellTiter-Glo assay. AAPH-induced cytoxicity in Caco-2 cells was attributed to a significant (P < 0.05) reduction in the G1 phase and increased proportion of cells in the sub G1 phase, indicating apoptosis. Prior exposure of Caco-2 cells to anthocyanins suppressed (P < 0.05) the AAPH-induced apoptosis by decreasing the proportion of cells in the sub-G1 phase, normalized the proportion of cells in other cell cycle phases. Our results show that the antioxidant activity of anthocyanins principally attributed to cyanidin-3-O-glucoside and common to blackberry, are effective at inhibiting peroxyl radical induced apoptosis in cultured Caco-2 cells.     

The Effect of Hole Transport Material Pore Filling on Photovoltaic Performance in Solid‐State Dye‐Sensitized Solar Cells

A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid‐state dye‐sensitized solar cells (ss‐DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss‐DSCs improve with the pore filling fraction (PFF) of the HTM, 2,2’,7,7’‐tetrakis‐(N, N ‐di‐ p ‐methoxyphenylamine)9,9’‐spirobifluorene(spiro‐OMeTAD). The mechanisms through which the improvement of photovoltaic characteristics takes place were studied with transient absorption spectroscopy and transient photovoltage/photocurrent measurements. It is shown that as the spiro‐OMeTAD PFF is increased from 26% to 65%, there is a higher hole injection efficiency from dye cations to spiro‐OMeTAD because more dye molecules are covered with spiro‐OMeTAD, an order‐of‐magnitude slower recombination rate because holes can diffuse further away from the dye/HTM interface, and a 50% higher ambipolar diffusion coefficient due to an improved percolation network. Device simulations predict that if 100% PFF could be achieved for thicker devices, the efficiency of ss‐DSCs using a conventional ruthenium‐dye would increase by 25% beyond its current value.     

Mesoporous TiO2 Beads Offer Improved Mass Transport for Cobalt‐Based Redox Couples Leading to High Efficiency Dye‐Sensitized Solar Cells

Overcoming ionic diffusion limitations is essential for the development of high‐efficiency dye‐sensitized solar cells based on cobalt redox mediators. Here, improved mass transport is reported for photoanodes composed of mesoporous TiO₂ beads of varying pore sizes and porosities in combination with the high extinction YD2‐o‐C8 porphyrin dye. Compared to a photoanode made of 20 nm‐sized TiO₂ particles, electrolyte diffusion through these films is greatly improved due to the large interstitial pores between the TiO₂ beads, resulting in up to 70% increase in diffusion‐limited current. Simultaneously, transient photocurrent measurements reveal no mass transport limitations for films of up to 10 μm thickness. In contrast, standard photoanodes made of 20 nm‐sized TiO₂ particles show non‐linear behavior in photocurrent under 1 sun illumination for a film thickness as low as 7 μm. By including a transparent thin mesoporous TiO₂ underlayer in order to reduce optical losses at the fluorine‐doped tin oxide (FTO)‐TiO₂ interface, an efficiency of 11.4% under AM1.5G 1 sun illumination is achieved. The combination of high surface area, strong scattering behavior, and high porosity makes these mesoporous TiO₂ beads particularly suitable for dye‐sensitized solar cells using bulky redox couples and/or viscous electrolytes.     

Triblock‐Terpolymer‐Directed Self‐Assembly of Mesoporous TiO2: High‐Performance Photoanodes for Solid‐State Dye‐Sensitized Solar Cells

A new self‐assembly platform for the fast and straightforward synthesis of bicontinuous, mesoporous TiO₂ films is presented, based on the triblock terpolymer poly(isoprene ‐ b ‐ styrene ‐ b ‐ ethylene oxide). This new materials route allows the co‐assembly of the metal oxide as a fully interconnected minority phase, which results in a highly porous photoanode with strong advantages over the state‐of‐the‐art nanoparticle‐based photoanodes employed in solid‐state dye‐sensitized solar cells. Devices fabricated through this triblock terpolymer route exhibit a high availability of sub‐bandgap states distributed in a narrow and low enough energy band, which maximizes photoinduced charge generation from a state‐of‐the‐art organic dye, C220. As a consequence, the co‐assembled mesoporous metal oxide system outperformed the conventional nanoparticle‐based electrodes fabricated and tested under the same conditions, exhibiting solar power‐conversion efficiencies of over 5%.     

9-Aminoacridine, a fluorescent probe of the thiamine carrier in yeast cells

The uptake of 9-aminoacridine is studied in the yeast Saccharomyces cerevisiae by fluorescence and absorbance measurements of the dye. Uptake of the dye proceeds via two pathways. One pathway consists of a diffusion of the non-protonated form. At high pH (7.5) this pathway is the predominant one, and the dye distributes between the cell inner and the medium according to the ratio of the proton concentrations in the two compartments. In other words, at high pH 9-aminoacridine behaves as a probe of the H⁺ gradient across the yeast cell membrane. At low external pH (4.5) a second pathway is involved. Much greater accumulation ratios for the dye are observed than can be accounted for by the H⁺ gradient across the membrane. The transport system predominantly responsible for the great accumulation of the dye appears to be inducible, to require metabolic energy and to be saturable. This transport system is competitively inhibited by thiamine, and also by dibenzyldimethylammonium and thiaminedisulfide, two specific inhibitors of the thiamine carrier in the yeast. On the other hand, the thiamine uptake by the yeast cells is competitively inhibited by 9-aminoacridine. In addition, uptake of 9-aminoacridine is greatly reduced in the thiamine transport-negative mutant of S. cerevisiae, PT-R2. It is concluded that at low pH 9-aminoacridine is taken up by yeast via the thiamine carrier of the cell and that, consequently, the dye may be applied as a probe of this transport system.     

Rational Design of Metal Oxide–Based Cathodes for Efficient Dye‐Sensitized Solar Cells

Recently, there is an urgent need for alternative energy resources due to the nonrenewable nature of fossil fuels and increasing CO₂ greenhouse gas emissions. The photovoltaic technologies which directly utilize the abundant and sustainable solar energy are critical. Among various photovoltaic devices (solar cells), dye‐sensitized solar cells (DSSCs) have gained increasing attention due to their high efficiency and easy fabrication process in the past decade. The cathode is a critical part in DSSCs while the benchmark Pt cathode suffers from high cost and scarcity. Thus, the development of alternative Pt‐free cathodes has attracted significant attention with the aim to heighten the cost competitiveness of DSSCs. Among various cathodes, metal oxides are of growing interest due to their superior activity, robust stability, and low cost. Simple oxides such as WO₃ and SnO₂ are used as cathodes for DSSCs. Considering the fixed atomic environment in simple oxides, complex oxides are more attractive as cathodes because of their more flexible physical and chemical properties. This review attempts to present the rational design of simple/complex metal oxide–based cathodes in DSSCs and then to provide useful guidance for the future design of Pt‐free cathodes. The demonstrated design strategies can be extended to other electrocatalysis‐based applications.     

Nitrogen‐Doped CNx/CNTs Heteroelectrocatalysts for Highly Efficient Dye‐Sensitized Solar Cells

The use of polydopamine as a nitrogen containing precursor to generate catalytically active nitrogen‐doped carbon (CN_x) materials on carbon nanotubes (CNTs) is reported. These N‐doped CN_x/CNT materials display excellent electrocatalytic activity toward the reduction of triiodide electrolyte in dye‐sensitized solar cells (DSSCs). Further, the influence of various synthesis parameters on the catalytic performance of CN_x/CNTs is investigated in detail. The best performing device fabricated with the CN_x/CNTs material delivers power conversion efficiency of 7.3%, which is comparable or slightly higher than that of Pt (7.1%) counter electrode‐based DSSC. These CN_x/CNTs materials show great potential to address the issues associated with the Pt electrocatalyst including the high cost and scarcity.     

Prospects for conserving biodiversity in Amazonian extractive reserves

Non‐timber forest product (NTFP) extraction is a popular alternative to timber extraction that figures prominently in efforts to utilize tropical forests sustainably. But the ability to conserve biodiversity through NTFP management, particularly in extractive reserves in Amazonia, has remained untested. We found that intensive management of Euterpe oleracea (Palmae) fruit, one of the most important extractive products in the Amazon, has substantial impacts on biodiversity, whereas moderate management does not. We mimicked traditional levels of fruit harvest in a replicated experiment over one fruiting season. High‐intensity harvest (75% of fruits removed) reduced avian frugivore species diversity by 22%. Low‐intensity harvest (40% of fruits removed), however, had no effect on diversity. On a larger scale, we found that forests with enriched densities of E. oleracea supported more fruit‐eating birds but fewer non fruit‐eating birds than non‐enriched forests. Taken together, these results suggest that intensive NTFP management to meet market demands may trigger substantial ecological impacts, at least at the level of our study. E. oleracea harvest should be limited where conservation of biodiversity is a goal.