Numerical Study of Plasmonic Effects of Ag Nanoparticles Embedded in the Active Layer on Performance Polymer Organic Solar Cells

In this paper, the light absorption in the active layer of polymer solar cells (OPV) by using plasmonic nanocrystals with a hexagonal lattice structure is investigated. To study the relationship between the performance of the OPV solar cell and its active layer, a three-dimensional model of its morphology is utilized. Therefore, the three-dimensional (3D) finite-difference time-domain method and Lumerical software were used to measure the field distribution and light absorption in the active layer in terms of wavelength. OPV solar cells with bilayer and bulk heterojunction structured cells were designed using hexagonal lattice crystals with plasmonic nanoparticles, as well as core–shell geometry to govern a design to optimize light trapping in the active layer. The parameters of shape, material, periodicity, size, and the thickness of the active layer as a function of wavelength in OPV solar cells have been investigated. A very thin active layer and an ultra-thin shell were used to achieve the highest increase in optical absorption. The strong alternating electromagnetic field around the core–shell plasmonic nanoparticles resulting from the localized surface plasmon resonance (LSPR) suggested by the Ag plasmonic nanocrystals increased the intrinsic optical absorption in the active layer poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM). Based on the photovoltaic results, the short circuit current ranged from 19.7 to 26.7 mA/cm².

     

Isolation and characterization of the oxygen-evolving photosystem II complex from the economical red alga <Emphasis Type="Italic">Bangia fusco-purpurea</Emphasis>

The highly pure and active photosystem II (PSII) complex was isolated from Bangia fusco-purpurea (Dillw) Lyngb., an important economic red alga in China, through two steps of sucrose density gradient ultracentrifugation and characterized by the room absorption and fluorescence emission spectra, DCIP (2,6-dichloroindophenol) reduction, and oxygen evolution rates. The PSII complex from B. fusco-purpurea had the characteristic absorption peaks of chlorophyll (Chl) a (436 and 676 nm) and typical fluorescence emission peak at 685 nm (Ex = 436 nm). Moreover, the acquired PSII complex displayed high oxygen evolution (139 μmol O₂/(mg Chl h) in the presence of 2.5 mM 2,6-dimethybenzoqinone as an artificial acceptor and was active in photoreduction of DCIP (2,6-dichloroindophenol) by DPC (1,5-diphenylcarbazide) at 163 U/(mg Chl a h). SDS-PAGE also suggested that the purified PSII complex contained four intrinsic proteins (D1, D2, CP43, and CP47) and four extrinsic proteins (33-kD protein, 20-kD protein, cyt c-550, and 14-kD protein).     

4‐Cyano‐α‐methyl‐l‐phenylalanine as a Spectroscopic Marker for the Investigation of PeptaibioticMembrane Interactions

Two analogs of the ten‐amino acid residue, membrane‐active lipopeptaibiotic trichogin GA IV, mono‐labeled with 4‐cyano‐α‐methyl‐L ‐phenylalanine, a potentially useful fluorescence and IR absorption probe of the local microenvironment, were synthesized by the solid‐phase methodology and conformationally characterized. The single modification was incorporated either at the N‐terminus (position 1) or near the C‐terminus (position 8) of the peptide main chain. In both cases, the replaced amino acid was the equally helicogenic α‐aminoisobutyric acid (Aib) residue. We performed a solution conformational analysis by use of FT‐IR absorption, CD, and 2D‐NMR spectroscopies. The results indicate that both labeled analogs essentially maintain the overall helical propensity of the naturally occurring lipopeptaibiotic. Peptide? membrane interactions were assessed by fluorescence and ATR‐IR absorption techniques. Analogies and differences between the two peptides were highlighted. Taken together, our data confirm literature results that some of the spectroscopic parameters of the 4‐cyanobenzyl chromophore are sensitive markers of the local microenvironment.     

Probiotic <Emphasis Type="Italic">Bacillus coagulans</Emphasis> GBI-30, 6086 Improves Protein Absorption and Utilization

Probiotics offer numerous health benefits, including digestive and immune health. Improved digestive health is linked to a more efficient absorption of important nutrients from our diet. This review focused on the rationale of using the probiotic Bacillus coagulans GBI-30, 6086 to aid protein absorption and utilization. B. coagulans GBI-30, 6086 can withstand the acidic environment of the stomach to reach the intestine where it germinates. Once active in the small intestine after germination, it has been shown to aid the digestion of carbohydrates and proteins. Co-administration of B. coagulans GBI-30, 6086 with protein has been shown to increase protein absorption and to maximize the health benefits associated with protein supplementation.     

A bacteriophytochrome regulates the synthesis of LH4 complexesin <Emphasis Type="Italic">Rhodopseudomonas palustris</Emphasis>

The non-sulphur purple bacterium Rhodopseudomonas palustris contains five pucAB genes for peripheral light-harvesting complexes. Bacteria grown under high-light conditions absorb at 800 and 850 nm but in low-light the 850 nm peak is almost absent and LH2 complexes are replaced by LH4. The genome contains six bacteriophytochromes (Bph). Bphs sense light in the red/far-red through a reversible Pr to Pfr transformation that controls gene expression. Bph3 (RPA1537) controls the expression of a cluster of photosynthetic genes, however most of the peripheral light harvesting complex genes are outside of this region. The pucAB-d genes encode LH4 peptides and are near two Bphs (RPA3015, RPA3016). We have characterised three Bphs and show that Bph4 RPA3015 and Bph3 RPA1537 have different dark stable states. It is known that Bph3 is active in its red absorbing Pr form and suggests a working hypothesis that Bph4 is active in the Pfr state. We show that LH4 expression can be induced with red light at the Pr absorption maximum (708 nm) of Bph4. The property of light transmission of water maybe an important factor in understanding this adaptation. Bph4 can sense the reduction in light intensity indirectly through an increase in ratio of transmitted red/far-red light. The red right activated Bph4 regulates the synthesis of LH4 which concentrates bacteriochlorophyll a pigment absorption at 800 nm to exploit a recovery in water light transmission in this region.     

Plasmonic Perovskite Solar Cells Utilizing Au@SiO<Subscript>2</Subscript> Core-Shell Nanoparticles

The role of Au@SiO₂ core-shell nanoparticles on optical properties of perovskite solar cells has been explored using both the theoretical computations and the experiments. A quasi-static model is used to study the surface plasmon resonances (SPRs) of Au@SiO₂ core-shell nanospheres. Au@SiO₂ core-shell nanoparticles, with varying shell thickness and core radius, were assumed to be embedded in methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite active layer. Enhanced absorption in the active layer is obtained due to the near-field plasmonic effect of the embedded core-shell nanoparticles. Theoretical modelling shows that a shell thickness of 1 nm and core diameter of 20 nm provide absorption enhancement in the orange-red region of the electromagnetic spectrum. Experiments performed using ～20-nm-sized Au@SiO₂ core-shell nanoparticles (with a shell thickness of ～1 nm) clearly demonstrate the enhanced absorption and the resulting enhancement in photocurrent due to the plasmonic effects. An efficiency enhancement of over 18 % is obtained for the best plasmonic perovskite solar cell containing Au@SiO₂ nanoparticles in Au@SiO₂-TiO₂ weight ratio of ～1 %. Incident photon-to-current conversion efficiency (IPCE) data also showed enhancement in photocurrent for the plasmonic device. The quasi-static modelling approach provides a good correlation between theory and experiment.     

From Binary to Ternary: Improving the External Quantum Efficiency of Small‐Molecule Acceptor‐Based Polymer Solar Cells with a Minute Amount of Fullerene Sensitization

Ternary blend is proved to be a potential contender for achieving high efficiency in organic photovoltaics, which can apparently strengthen the absorption of active layer so as to better harvest light irradiation. Much of the previous work in ternary polymer solar cells focuses on broadening the absorption spectrum; however, a new insight is brought to study the third component, which in tiny amounts influents the small‐molecule acceptor‐based device performance. Without contributing to complementing the absorption, a minute amount of fullerene derivative, Bis‐PC₇₀BM, can effectively play an impressive role as sensitizer in enhancing the external quantum efficiency of the host binary blend, especially for polymeric donor. Detailed investigations reveal that the minute addition of Bis‐PC₇₀BM can realize morphology modification as well as facilitate electron transfer from polymeric donor to small molecule acceptor via cascade energy level modulation, and therefore lead to an improvement in device efficiency.     

The soluble [NiFe]-hydrogenase from<Emphasis Type="Italic"> Ralstonia eutropha</Emphasis> contains four cyanides in its active site,one of which is responsible for the insensitivity towards oxygen

Infrared spectra of ¹⁵N-enriched preparations of the soluble cytoplasmic NAD⁺-reducing [NiFe]-hydrogenase from Ralstonia eutropha are presented. These spectra, together with chemical analyses, show that the Ni-Fe active site contains four cyanide groups and one carbon monoxide molecule. It is proposed that the active site is a (RS)₂(CN)Ni(-RS)₂Fe(CN)₃(CO) centre (R=Cys) and that H₂ activation solely takes place on nickel. One of the two FMN groups (FMN-a) in the enzyme can be reversibly released upon reduction of the enzyme. It is now reported that at longer times also one of the cyanide groups, the one proposed to be bound to the nickel atom, could be removed from the enzyme. This process was irreversible and induced the inhibition of the enzyme activity by oxygen; the enzyme remained insensitive to carbon monoxide. The Ni-Fe active site was EPR undetectable under all conditions tested. It is concluded that the Ni-bound cyanide group is responsible for the oxygen insensitivity of the enzyme.Abbreviations BV benzyl viologen - DCIP 2,6-dichlorophenol-indophenol - EXAFS extended X-ray absorption fine structure - FTIR Fourier transform infrared - MV methyl viologen - SH soluble NAD⁺-reducing hydrogenase - XAS X-ray absorption spectroscopy     

Occurrence and induction of a ultraviolet‐absorbing substance in the cyanobacterium Fischerella muscicola TISTR8215

The filamentous cyanobacterium Fischerella muscicola TISTR8215 was tested for the presence of ultraviolet (UV)‐absorbing mycosporine‐like amino acids (MAAs) and their induction by UV radiation. Reverse‐phase high performance liquid chromatographic coupled with photodiode‐array detection studies revealed the presence of a MAA having an absorption maximum at 332 nm and a retention time of around 16.1 min. Based on absorption maximum, the compound was designated as M‐332. This is the first report for the occurrence of a MAA and its inducibility as influenced by UV radiation in Fischerella strains studied so far. Photosynthetically active radiation (PAR) had no significant impact on MAA induction. PAR + UV‐A radiation significantly induced the synthesis of M‐332; however, PAR + UV‐A + UV‐B radiation conferred highest impact on MAA synthesis. The cultures exposed to alternate light and dark conditions showed the induction of M‐332 synthesis mostly during the light period in contrast to the decreased levels of M‐322 during the dark period suggesting a circadian induction of its synthesis. Overall results indicate that F. muscicola may protect itself from deleterious short wavelength UV radiation by synthesizing the photoprotective compounds particularly during summer time in its natural brightly‐lit habitats.     

Role of Exogenous Nitric Oxide in Alleviating Iron Deficiency Stress of Peanut Seedlings (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

A greenhouse hydroponic experiment was performed to evaluate how peanut seedlings (Arachis hypogaea L.) responded to iron (Fe) deficiency stress in the presence of sodium nitroprusside (SNP), a nitric oxide (NO) donor. The results showed that Fe deficiency inhibited peanut plant growth, decreased chlorophyll and active Fe concentrations, and dramatically disturbed ion balance. The addition of 50, 100, 250, and 500 µM SNP, significantly promoted the absorption of Fe in the cell wall, cell organelles, and soluble fractions, increased the concentrations of active Fe and chlorophyll in peanut plants, and alleviated the excess absorption of manganese (Mn) and copper (Cu) induced by Fe deficiency. In addition, SNP also significantly increased the activities of superoxide dismutase, peroxidase, and catalase, which is beneficial to inhibit the accumulation of malondialdehyde and reactive oxygen species. Addition of 250 µM SNP had the most significant alleviating effect against Fe-deficiency stress, and after 15 days of treatment, the plants with the 250 µM SNP treatment achieved comparable NO levels with those grown under optimal nutrition conditions. However, the effects of SNP were reversed by addition of hemoglobin (Hb, a NO scavenger). These results suggest that NO released from SNP decomposition was responsible for the effect of SNP-induced alleviation on Fe deficiency.     

Facile Metal Coordination of Active Site Imprinted Nitrogen Doped Carbons for the Conservative Preparation of Non‐Noble Metal Oxygen Reduction Electrocatalysts

Iron‐ or cobalt‐coordinated heteroatom doped carbons are promising alternatives for Pt‐based cathode catalysts in polymer‐electrolyte fuel cells. Currently, these catalysts are obtained at high temperatures. The reaction conditions complicate the selective and concentrated formation of metal–nitrogen active sites. Herein a mild procedure is introduced, which is conservative toward the carbon support and leads to active‐site formation at low temperatures in a wet‐chemical metal‐coordination step. Active‐site imprinted nitrogen doped carbons are synthesized via ionothermal carbonization employing Lewis‐acidic Mg²⁺ salt. The obtained carbons with large tubular porosity and imprinted N₄ sites lead to very active catalysts with a half‐wave potential (E_1/2) of up to 0.76 V versus RHE in acidic electrolyte after coordination with iron. The catalyst shows 4e^? selectivity and exceptional stability with a half‐wave potential shift of only 5 mV after 1000 cycles. The X‐ray absorption fine structure as well as the X‐ray absorption near edge structure profiles of the most active catalyst closely match that of iron(II)phthalocyanine, proving the formation of active and stable FeN₄ sites at 80 °C. Metal‐coordination with other transition metals reveals that Zn–N_x sites are inactive, while cobalt gives rise to a strong performance increase even at very low concentrations.     

Application of the general fluid circuit theory to the chloride-bromide-deuterium oxide experiment

The general fluid circuit theory of active chloride absorption is applied to an experiment in which chloride, bromide, and deuterium oxide were simultaneously absorbed from the lower ileum, chloride only moving against a concentration gradient. The conclusion is reached that the constant for active absorption of deuterium oxide is equal, within reasonable limits of error, to the constant for active chloride absorption in accordance with the assumption that the absorption of water carries chloride out of the intestinal lumen without changing its concentration.     

Preparation and <Emphasis Type="Italic">In vitro</Emphasis> Evaluation of Ethosomal Total Alkaloids of <Emphasis Type="Italic">Sophora alopecuroides</Emphasis> Loaded by a Transmembrane pH-Gradient Method

A novel transmembrane pH gradient active loading method to prepare alkaloids binary ethosomes was developed in this work. Using this novel method, binary ethosomes containing total alkaloids extracted from Sophora alopecuroides (TASA) were prepared successfully at the temperature below the phase transition temperature (Tc) of the phosphatidyl choline (PC). Several factors affecting this method were investigated. The qualities of the TASA binary ethosomes were characterized by the shape, particle size, and encapsulation efficiency (EE). The percutaneous absorption study of TASA binary ethosomes was performed using confocal laser scanning microscopy and Franz diffusion cells. The results showed that more than 90% sophoridine, 47% matrine, 35% sophocarpine, and 32% lemannine in TASA were entrapped within 1 h at 40°C, with an efficiency improvement of 8.87, 8.10, 7.63, and 7.78-fold than those observed in passive loading method. Transdermal experiments showed that the penetration depth and fluorescence intensity of Rhodamine B from binary ethosome prepared by pH gradient active loading method were much greater than that from binary ethosome prepared by passive loading method or hydroalcoholic solution. These results suggested transmembrane pH gradient active loading method may be an effective method to prepare alkaloids ethosomal systems at the temperatures below the Tc of PC.     

Morphofunctional changes in the small intestine epithelium of the frog <Emphasis Type="Italic">Rana temporaria</Emphasis> in the course of hibernation

The structure and function of small intestine epithelium have been studied in overwintering frogs at various stages of hibernation. Experiments on the in vitro absorption of arginine vasotocin (AVT) have shown that the epithelium ability for absorption of this nonapeptide without hydrolysis persists during hibernation. However, there is a decline in AVT absorption observed in January–February and later on (as compared with that in October–December) which is most pronounced in March–April. Changes in the epithelial structure appear by midwinter and are growing towards spring. In April–May, enterocyte height decreased by 33%, microvilli length by 40%, and number of mitochondria by 57% relative to the values at the beginning of hibernation. The absence of signs of breakdown attests to the adaptive nature of the observed changes. The dynamics of the studied parameters reveals morphological and functional plasticity of small intestinal epithelium in Rana temporaria over the hibernation period.     

Loss Mechanisms in Thick‐Film Low‐Bandgap Polymer Solar Cells

Polymer bulk heterojunction solar cells based on low bandgap polymer:fullerene blends are promising for next generation low‐cost photovoltaics. While these solution‐processed solar cells are compatible with large‐scale roll‐to‐roll processing, active layers used for typical laboratory‐scale devices are too thin to ensure high manufacturing yields. Furthermore, due to the limited light absorption and optical interference within the thin active layer, the external quantum efficiencies (EQEs) of bulk heterojunction polymer solar cells are severely limited. In order to produce polymer solar cells with high yields, efficient solar cells with a thick active layer must be demonstrated. In this work, the performance of thick‐film solar cells employing the low‐bandgap polymer poly(dithienogermole‐thienopyrrolodione) (PDTG‐TPD) was demonstrated. Power conversion efficiencies over 8.0% were obtained for devices with an active layer thickness of 200 nm, illustrating the potential of this polymer for large‐scale manufacturing. Although an average EQE > 65% was obtained for devices with active layer thicknesses > 200 nm, the cell performance could not be maintained due to a reduction in fill factor. By comparing our results for PDTG‐TPD solar cells with similar P3HT‐based devices, we investigated the loss mechanisms associated with the limited device performance observed for thick‐film low‐bandgap polymer solar cells.     

High‐Performance Platinum‐Perovskite Composite Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Battery

Constructing highly active electrocatalysts with superior stability at low cost is a must, and vital for the large‐scale application of rechargeable Zn–air batteries. Herein, a series of bifunctional composites with excellent electrochemical activity and durability based on platinum with the perovskite Sr(Co_0.8Fe_0.2)_0.95P_0.05O_3?δ (SCFP) are synthesized via a facile but effective strategy. The optimal sample Pt‐SCFP/C‐12 exhibits outstanding bifunctional activity for the oxygen reduction reaction and oxygen evolution reaction with a potential difference of 0.73 V. Remarkably, the Zn–air battery based on this catalyst shows an initial discharge and charge potential of 1.25 and 2.02 V at 5 mA cm^?2, accompanied by an excellent cycling stability. X‐ray photoelectron spectroscopy, X‐ray absorption near‐edge structure, and extended X‐ray absorption fine structure experiments demonstrate that the superior performance is due to the strong electronic interaction between Pt and SCFP that arises as a result of the rapid electron transfer via the Pt? O? Co bonds as well as the higher concentration of surface oxygen vacancies. Meanwhile, the spillover effect between Pt and SCFP also can increase more active sites via lowering energy barrier and change the rate‐determining step on the catalysts surface. Undoubtedly, this work provides an efficient approach for developing low‐cost and highly active catalysts for wider application of electrochemical energy devices.     

Absorption of arginine-vasopressin and arginine-vasotocin in small intestine of the frog <Emphasis Type="Italic">Rana temporaria</Emphasis>

Experiments in vitro demonstrated a partial absorption of arginine-vasopressin (AVP) in the frog small intestine. Dynamics and efficiency of the nonapeptide absorption are studied with use of hydroosmotic method of recording of the osmotic permeability of the frog urinary bladder epithelium and immunoenzyme analysis. In the process of absorption there were preserved intactness of the hormone cyclic structure and its physiological activity, like in the case of the arginine-vasotocine (AVT) absorption. The AVP absorption increased at its administration into the gut with inhibitor of proteases. By methods of immunoelectron and immunofluorescent microscopy with use of polyclonal antibody to AVP, location of the label to the hormone was shown in the enterocyte cytoplasm. Thus, there was obtained a morphological evidence for the AVP absorption and transepithelial transfer in the frog small intestine. These data enlarge the concept of the poorly studied properties of the absorbing epithelium of the vertebrate intestine with respect to absorption of intact molecules of polypeptides.     

Active Absorption of Amino-acids in the Rectum of the Desert Locust (<Emphasis Type="Italic">Schistocerca gregaria</Emphasis>)

ALTHOUGH the concentration of amino-acids in the haemolymph of insects is high compared with that in most other groups of animals, there has been no rigorous demonstration that amino-acids are actively transported across any membrane system within the class Insecta. Treherne¹ established that ingested amino-acids are absorbed largely in the midgut of the desert locust by simple diffusion down a concentration gradient created by absorption of water and ions and Ramsay² concluded that the high concentrations of amino-acids in the secretion of the Malpighian tubules of the stick insect were the result of passive diffusion across the tubular epithelium. Because most of the water and essential solutes secreted by the Malpighian tubules are reabsorbed in the rectum of most insects³, selective retention and regulation of haemolymph amino-acids seem likely^2,4–6. Evidence for active reabsorption of amino-acids in the rectum has been sparse and inconclusive^1,2,5.     

Unraveling the <Emphasis Type="Italic">Helicobacter pylori</Emphasis> UreG zinc binding site using X-ray absorption spectroscopy (XAS) and structural modeling

Abstract  

The pathogenicity of Helicobacter pylori depends on the activity of urease for pH modification. Urease activity requires assembly of a dinickel active site that is facilitated in part by GTP hydrolysis by UreG. The proper functioning of Helicobacter pylori UreG (HpUreG) is dependent on Zn(II) binding and dimerization. X-ray absorption spectroscopy and structural modeling were used to elucidate the structure of the Zn(II) site in HpUreG. These studies independently indicated a site at the dimer interface that has trigonal bipyramidal geometry and is composed of two axial cysteines at 2.29(2) ?, two equatorial histidines at 1.99(1) ?, and a solvent-accessible coordination site. The final model for the Zn(II) site structure was determined by refining multiple-scattering extended X-ray absorption fine structure fits using the geometry predicted by homology modeling and ab initio calculations.     

1,25-Dihydroxyvitamin D3 increases the expression of the CaT1 epithelial calcium channel in the Caco-2 human intestinal cell line

Background  

The active hormonal form of vitamin D (1,25-dihydroxyvitamin D) is the primary regulator of intestinal calcium absorption efficiency. In vitamin D deficiency, intestinal calcium absorption is low leading to an increased risk of developing negative calcium balance and bone loss. 1,25-dihydroxyvitamin D has been shown to stimulate calcium absorption in experimental animals and in human subjects. However, the molecular details of calcium transport across the enterocyte are not fully defined. Recently, two novel epithelial calcium channels (CaT1/ECaC2 and ECaC1/CaT2) have been cloned and suggested to be important in regulating intestinal calcium absorption. However, to date neither gene has been shown to be regulated by vitamin D status. We have previously shown that 1,25-dihydroxyvitamin stimulates transcellular calcium transport in Caco-2 cells, a human intestinal cell line.