Controlling the charge transfer flow at the graphene/pyrene-nitrilotriacetic acid interface

The fabrication of highly efficient bio-organic nanoelectronic devices is still a challenge due to the difficulty in interfacing the biomolecular component to the organic counterparts. One of the ways to overcome this bottleneck is to add a self-assembled monolayer (SAM) in between the electrode and the biological material. The addition of a pyrene-nitrilotriacetic acid layer to a graphene metal electrode enhances the charge transfer within the device. Our theoretical calculations and electrochemical results show that the formation of a pyrene-nitrilotriacetic acid SAM enforces a direct electron transfer from graphene to the SAM, while the addition of the Ni2+ cation and imidazole reverses the charge transfer direction, allowing an atomic control of the electron flow, which is essential for a true working device. © 2018 The Royal Society of Chemistry

Design and synthesis of heteroleptic ruthenium (II) complexes and their applications in nanocrystalline TiO 2 solar cells

Two ruthenium complexes, [Ru II(L2)(dcbpy)(NCS) 2] Ru II(4,5-diazafluoren-9-one)(4,4 '-dicarboxy-2,2 '-bipyridyl)-di(thiocyanate) [K30] and [Ru(dcbpy) 3] Ru IItris(4,4'-dicarboxy-2,2'-bipyridyl) [K303] have been synthesized and used in dye sensitized solar cells. The ruthenium complexes have been characterized by elemental analyses, FT-IR, UV-Vis, cyclic voltammetry and 1H NMR spectral methods. The performance of this complexes as charge transfer photosensitizer in nc-TiO 2 based dye sensitized solar cells is studied under standard AM 1.5 sunlight and by using an electrolyte consisting of 0.6 M N-methyl-N-butyl imidazolium iodide (BMII), 0.1 M LiI, 0.05 M I 2, 0.5 M 4-tert-butyl pyridine (TBP) in acetonitrile. Notably, the photo-to-electrical conversion efficiency of the DSSCs sensitized with [K30] and [K303] reaches 3.45%, and 6.33%, and the DSSC sensitized with [K303] shows better photovoltaic performances (Jsc = 19.58 mA/cm 2, Voc = 570 mV and FF = 0.58) than [K30]. © 2012 Elsevier B.V. All rights reserved

The effect of annealing of ZnSe nanocrystal thin films in air atmosphere

The zinc selenide (ZnSe) nanocrystal thin films have been prepared on glass substrates by chemical bath deposition at 80 degrees C. The ZnSe films have been annealed in an air atmosphere at 373, 473, 573, 673 and 773 K for 1 h. The crystallographic structure and size of the crystallites, dislocation density, number of crystallites per unit surface area and strain have been studied by X-ray diffraction on as-deposited and annealed films. The surface morphology of ZnSe coated thin films obtained at different annealing temperatures has been elucidated by AFM studies. The optical properties of the films have been investigated by recording the transmission spectra. It has been observed that the energy band gap decreases upon annealing temperature. The conductivity measurements have been carried out using four probe methods. It is observed that the conductivity and activation energy change upon annealing temperature

Reliability of the Bates‐Jensen wound assessment tool for pressure injury assessment: The pressure ulcer detection study

The Bates-Jensen Wound Assessment Tool (BWAT) is used to assess wound healing in clinical practice. The purpose of this study was to evaluate BWAT use among nursing home residents with pressure injury. Findings and reliability estimates from the BWAT related to pressure injury characteristics (stage, anatomic location) and natural history (resolved, persisted) among 142 ethnically and racially diverse residents are reported. In this prospective 16-week study, 305 pressure injuries among 142 participants (34% prevalence) are described by stage, anatomic location, and BWAT scores. Visual and subepidermal moisture assessments were obtained from sacrum, buttock, ischial, and heel ulcers weekly. Participants were 14% Asian, 28% Black, 18% Hispanic, 40% White with a mean age of 78 ± 14 years, and were 62% female; 80% functionally dependent (bed mobility extensive/total assistance) and at risk (Braden Scale score 14 ± 2.7). The reliability coefficient for BWAT score (all participants, all anatomic locations) was high (r = 0.90; p < 0.0001; n = 1,161 observations). Weighted Kappas for characteristics ranging from 0.46 (skin color surrounding wound) to 0.79 (undermining) were consistent for all participants. BWAT scores showed strongest agreement coefficients for stage 4 pressure injury (r = 0.69), pressure injuries among Asian and White ethnicity/racial groups (r = 0.89, and r = 0.91, respectively), and sacrum anatomic location (r = 0.92) indicating scores are better correlated to fair skin tones. Lower agreement coefficients were demonstrated for stage 2 pressure injury (r = 0.38) and pressure injuries among African American and Hispanic ethnicity/racial groups (r = 0.88 and 0.87, respectively). BWAT scores were significantly different by pressure injury stage (F = 496.7, df = 6, p < 0.001) and anatomic location (F = 33.76, df = 8, p < 0.001). BWAT score correlated with pressure injury natural history (ulcer resolved 18.4 ± 7.4, ulcer persisted 24.9 ± 10.0; F = 70.11, df = 2, p < 0.001), but not with comorbidities. The BWAT provides reliable, objective data for assessing pressure injury healing progress

A study of the electronic and physical properties of SnO2 thin films as a function of substrate temperature

In this work, tin dioxide (SnO2) thin films were prepared at various substrate temperatures (380–440 °C, in steps of 20 °C) on glass substrates by the Spray Pyrolysis Method. X-ray Diffraction (XRD) measurements revealed that the SnO2 thin films were formed in a tetragonal crystallized structure. The electronic structure of the tin dioxide thin films that were prepared at several substrate temperatures were investigated with the collected X-ray Absorption Spectroscopy (XAS) data. The crystal structure analysis was also supported by the Extended X-ray Absorption Fine Structure (EXAFS) data analysis extracted from the X-ray Absorption Fine Structure (XAFS) data. Unstable crystal behaviors were detected in the samples due to metastable SnO structure formations as a result of phase transitions from the SnO to SnO2 structure during the annealing processes. Clear information on the atomic displacements in the samples as a picture of the crystal mechanism was obtained from the analysis of EXAFS data. The SnO2 thin films were found to exhibit high transmittance (average 90%) in the 400–1100 nm interval. The thickness of the SnO2 thin film (t) and refractive index (n) were calculated from transmittance spectra in the visible region using envelope method. The direct energy band gaps of the films obtained were 4.01–4.09 eV. Atomic force microscope (AFM) measurements were performed in order to investigate the surface roughness of the SnO2 thin films. © 2019 Elsevier Ltd and Techna Group S.r.l.FBA–2017–7829This work was supported by the University of Cukurova [Project Number FBA–2017–7829 ]

Graphene-Based Conductive Interfaces

A major bottleneck in the fabrication of efficient bio-organic nanoelectronic devices resides in the strong charge recombination that is present at the different interfaces forming the complex system. An efficient way to overcome this bottleneck is to add a self-assembled monolayer (SAM) of molecules between the biological material and electrode that promotes an efficient direct electron transfer while minimizing wasteful processes of charge recombination. In this work, the presence of a pyrene-nitrilotriacetic acid layer carrying different metal centers as the SAM is physisorbed on graphene is fully described by means of electrochemical analysis, field-emission scanning electron microscopy, photoelectrochemical characterization, and theoretical calculations. Our multidisciplinary study reveals that the metal center holds the key role in the efficient electron transfer at the interface. While Ni2+ is responsible for the electron transfer from the SAM to graphene, Co2+ and Cu2+ force an opposite transfer from graphene to SAM. Moreover, since Cu2+ inhibits the electron transfer due to a strong charge recombination, Co2+ seems to be the transition metal of choice for the efficient electron transfer.C1 [Osella, Silvio; Trzaskowski, Bartosz] Univ Warsaw, Ctr New Technol, Chem & Biol Syst Simulat Lab, Banacha 2C, PL-02097 Warsaw, Poland.[Kargul, Joanna] Univ Warsaw, Ctr New Technol, Solar Fuels Lab, Banacha 2C, PL-02097 Warsaw, Poland.[Kiliszek, Malgorzata; Harputlu, Ersan] Mersin Univ, Adv Technol Res & Applicat Ctr, Ciftlikkoy Campus, TR-33343 Yenisehir, Mersin, Turkey.[Unlu, Cumhur G.] Pamukkale Univ, Dept Biomed Engn, TR-20070 Denizli, Turkey.[Ocakoglu, Kasim] Tarsus Univ, Fac Technol, Dept Energy Syst Engn, TR-33400 Tarsus, Turkey

Orientation of photosystem i on graphene through cytochrome: C 553 leads to improvement in photocurrent generation

We report the fabrication of an oriented bioelectrode of photosystem I (PSI) on single-layer graphene (SLG). This bioelectrode demonstrates improved photocurrent generation, which can be directly attributed to the molecular conductive interface formed by cytochrome c553 (cyt c553) promoting the uniform orientation of PSI with its donor side towards the electrode. The conductive interface between PSI-cyt c553 and SLG is facilitated by a monolayer composed of ?-?-stacked pyrene functionalized with the Ni-NTA moiety, which binds the His6-tagged cyt c553. The surface uniformity of the PSI protein orientation in the electrode structure is evidenced by cross-sectional scanning electron microscopy and fluorescence microscopy, with the latter also proving the efficient electronic coupling between majority of the PSI complexes and graphene. With the uniform organization of the biological photoactive layer, photocurrents are generated at the open circuit potential, which can be further increased when a negative potential is applied. Indeed, at the highest applied negative potential (-0.3 V), over 5-fold increase in the cathodic photocurrent for the PSI complexes conjugated via cyt c553 to the SLG substrate is observed compared with that obtained for the randomly oriented structure where PSI is physisorbed on graphene. These results indicate the key role of a strictly defined orientation of photoactive proteins on electrodes for proper electron transfer and substantial improvement in photocurrent generation in the present or similar bioelectrode architectures. © 2018 The Royal Society of Chemistry

Plasmonic enhancement of photocurrent generation in a photosystem I-based hybrid electrode

We experimentally demonstrate that oriented assembly of red algal photosystem I (PSI) reaction centers on a plasmonically active Silver Island Film (SIF) leads to strong enhancement of both the fluorescence intensity and photocurrent generated upon illumination. PSI complexes were specifically attached to a monolayer of graphene deposited on the SIF layer. The results of comprehensive fluorescence microscopy point to the critical role of the SIF layer in enhancing the optical response of PSI, as we observe increased emission intensity. Hence, importantly, the strong increase of photocurrent generation demonstrated for the biohybrid electrodes can be directly associated with the plasmonic enhancement of the optical and electrochemical functionalities of PSI. The results also indicate that the graphene layer is not diminishing the influence of the plasmonic excitations in SIF on the absorption and emission of PSI. © The Royal Society of Chemistry 2020