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Diatoms are unicellular photosynthetic algae that autonomously fabricate a porous organized biosilica shell refined in billion years of evolution. They represent an inexhaustible source of low cost, biocompatible mesoporous silica. Despite the major advances in the genomic field, studies on diatom cell biology are still hampered by a lack of cellular tools. In particular, cell staining assays of diatoms viability are still limited or not well performant. Here we provide a phosphorescent organometallic iridium complex (Ir-Fcx) suitable to act as staining agent to detect diatoms viability.
This study provides detailed information on the manufacture of III-V metal organic vapor phase epitaxy precursors through extensive literature and patent research. This data informed a cradle-to-gate life cycle assessment of these chemicals. Reported impacts include cumulative energy demand and greenhouse gas emissions. The results were interpreted to identify sources of environmental burden within the life cycle and were compared to energy demand reported in previous studies.
Comparative studies between doped conducting polymers and electrochemical deposited organometallic compounds reveals the interplay between crystalline-amorphous phases with significant contributions to the internal quantum efficiency in the OLED devices. The coexistence of the amorphous and crystalline phase in the electrodeposited film is revealed by the minor micro-crystal products which are present in the amorphous phase in thin films, while the many micro-crystals are randomly distributed in the thick films. Concerning the doped conducting polymers, the level of doping induces crystalline effects as a result of the π–π stacking between molecules, due to the Forester energy transfer processes in which the transfer rate is increased with decreasing of the distances between neighboring molecules. The crystallization processes change the emission properties of the active layers both for the luminance level and all over color, ranging from yellow to red in the case of IrQ(ppy)2 compounds.
Recently, organometal halide perovskite solar cells have passed the threshold of 20 % power conversion efficiency (PCE). While such PCE values of perovskite solar cells are already competitive to those of other photovoltaic technologies, processing of large-area devices is still a challenge. Most of the devices reported in literature are prepared by small-scale solution-based processing techniques (e.g. spin-coating). Perovskite solar cells processed by vacuum thermal evaporation (VTE), which show uniform layers and achieve higher PCE and better reproducibility, have also been presented. Regarding the co-evaporation of the perovskite constituents, this technology suffers from large differences in the thermodynamic characteristics of the two species. While the organic components evaporate instantaneously at room temperature at pressures in the range of 10−6 hPa, significantly higher temperatures are needed for reasonable deposition rates of the metal halide compound. In addition, hybrid vapor phase deposition techniques have been developed employing a carrier gas to deposit the organic compound on the previously solution-processed metal halide compound. Generally, vapor phase processes have proven to be a desirable choice for industrial large-area production. In this work, we present a setup for the direct chemical vapor phase deposition (CVD) of methylammonium lead iodide (MAPbI3) employing nitrogen as carrier gas. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements are carried out to investigate the crystal quality and structural properties of the resulting perovskite. By optimizing the deposition parameters, we have produced perovskite films with a deposition rate of 30 nm/h which are comparable to those fabricated by solution processing. Furthermore, the developed CVD process can be easily scaled up to higher deposition rates and larger substrates sizes, thus rendering this technique a promising candidate for manufacturing large-area devices. Moreover, CVD of perovskite solar cells can overcome most of the limitations of liquid processing, e.g. the need for appropriate and orthogonal solvents.
Here, we investigate the effect of divalent metal (Zn2+, Cd2+ and Hg2+) on the structural and optoelectronic properties of methylammonium lead iodide perovskite materials prepared by the two-step deposition process. The incorporation of Cd2+ significantly improved the grain size, crystallinity, and charge carrier lifetime of CH3NH3PbI3. The inclusion of Hg2+ and Zn2+ improved the grain size compare to the control sample but adversely affected the optoelectronic properties of perovskite films. The Hg- and Zn-based impurities were formed on the surface of the films, which increased the charge trap density and lead to high non-radiative recombination rate. Time resolved photoluminescence measurements indicated that the Cd and Zn point defects do not create deep-level trap states, but the Zn-modified film showed a low lifetime due to morphology changes in the film and particle segregation on the surface.
We present a study of the energy levels in a FTO/TiO2/CH3NH3PbI3/Spiro solar cell device. The measurements are performed using a novel ambient pressure photoemission (APS) technique alongside Contact Potential Difference data from a Kelvin Probe. The Perovskite Solar Cell energy band diagram is demonstrated for the device in dark conditions and under illumination from a 150W Quartz Tungsten Halogen lamp. This approach provides useful information on the interaction between the different materials in this solar cell device. Additionally, non-destructive macroscopic DC and AC Surface Photovoltage Spectroscopy (SPS) studies are demonstrated of different MAPBI3 device structures to give an indication of overall device performance. AC-SPS measurements, previously used on traditional semiconductors to study the mobility, are used in this case to characterise the ability of a perovskite solar cell device to respond rapidly to chopped light. Two different device structures studied showed very different characteristics: Sample A (without TiO2): (ITO/PEDOT:PSS/polyTPD/CH3NH3PbI3/PCBM) had ∼4 times the magnitude of AC-SPS response compared to Sample B (including TiO2): (ITO/TiO2/ CH3NH3PbI3/Spiro). This demonstrates that the carrier speed characteristics of device architecture A is superior to device architecture B. The TiO2 layer has been associated with carrier trapping which is illustrated in this example. However, the DC-SPV performance of sample B is ∼5 times greater than that of sample A. The band gap of the MAPBI3 layer was determined through DC-SPS (1.57 ± 0.07 eV), Voc of the devices measured and qualitative observations made of interface trapping by DC light pulsing. The combination of these (APS, KP, AC/DC-SPV/SPS) techniques offers a more general method for measuring the energy level alignments and performance of Organic and Hybrid Solar Cell Devices.
TMNCN (where TM = Mn2+, Fe2+, Co2+ or Ni2+) have been recently proposed as electrochemically active materials for Na-ion insertion that operate via conversion reaction. Their electrochemical performance for Na-ion batteries is presented here with an emphasis on long-term cycling. With a very low voltage for Na insertion of ∼0.1V vs Na+/Na for MnNCN, the overpotential observed in batteries of MnNCN plays a very important role in their performance, evidencing big differences in the electrochemical performance between materials produced with different nano- and micrometer particle sizes evidenced by SEM images. A more suitable voltage for the conversion reaction accompanied by less overpotential is shown by FeNCN, CoNCN and NiNCN. Despite the lower reversible capacity achieved by FeNCN (450 mAh/g) in comparison with CoNCN and NiNCN in the first cycle; the smallest first-cycle irreversible capacity (220 mAh/g) and the lower voltage plateau (0.3 V vs Na+/Na) make FeNCN a good candidate as an anode material for sodium ion batteries. The voltages of conversion reaction are correlated with the calculated enthalpies of formation suggesting that thermodynamics dominates the observed electrochemical conversion reaction.
Motivated by low cost, low toxicity, mechanical flexibility, and conformability over complex shapes, organic semiconductors are currently being actively investigated as thermoelectric (TE) materials to replace the costly, brittle, and non-eco-friendly inorganic TEs for near-ambient-temperature applications. Metal–organic frameworks (MOFs) share many of the attractive features of organic polymers, including solution processability and low thermal conductivity. A potential advantage of MOFs and MOFs with guest molecules (Guest@MOFs) is their synthetic and structural versatility, which allows both the electronic and geometric structure to be tuned through the choice of metal, ligand, and guest molecules. This could solve the long-standing challenge of finding stable, high-TE-performance n-type organic semiconductors, as well as promote high charge mobility via the long-range crystalline order inherent in these materials. In this article, we review recent advances in the synthesis of MOF and Guest@MOF TEs and discuss how the Seebeck coefficient, electrical conductivity, and thermal conductivity could be tuned to further optimize TE performance.
A new organometallic halide perovskite (OHP) synthesis method, whereby a polymer melt is used to thermodynamically drive the reaction that forms OHP crystallites, is demonstrated. The synthesis method allows for the facile encapsulation of moisture-sensitive OHP without the loss of simplicity during fabrication, which makes OHP materials so attractive for the photovoltaic industry. Degradation of OHP crystallites embedded in a polystyrene matrix was studied using UV-Vis absorbance over a period of several days. The OHP crystallites degrade as a result of the reversible nature of the reaction that forms the crystallites. After the reversion to precursors (PbI2 and CH3NH3I) the CH3NH3I irreversibly degrades  allowing the degradation to be tracked via optical interrogation. Additionally, surface morphology and elemental analysis of fabricated samples was carried out using SEM/EDS techniques.
For efficient charge separation and charge transport in optoelectronic materials,
small internal reorganization energies are desired. While many p-type organic
semiconductors have been reported with low internal reorganization energies, few
n-type materials with low reorganization energy are known. Metal phthalocyanines
have long received extensive research attention in the field of organic device
electronics due to their highly tunable electronic properties through
modification of the molecular periphery. In this study, density functional
theory (DFT) calculations are performed on a series of zinc-phthalocyanines
(ZnPc) with various degrees of peripheral per-fluoroalkyl
(-C3F7) modification. Introduction of the highly electron
withdrawing groups on the periphery leads to a lowering in the energy of the
molecular frontier orbitals as well as an increase in the electron affinity.
Additionally, all molecules studies are found to be most stable in their anionic
form, demonstrating their potential as n-type materials. However, the calculated
internal reorganization energy slightly increases as a function of peripheral
modification. By varying the degree of modification we develop a strategy for
obtaining an optimal balance between low reorganization energy and high electron
affinity for the development of novel n-type optoelectronic materials.
Zinc phthalocyanine (ZnPc) thin films were prepared by pulsed laser deposition (PLD) using KrF laser (λ = 248 nm, τ = 5 ns). The effect of laser fluence (in the region from 10 to 100 mJ/cm2) and repetition rate of 50 and 200 Hz to the film growth and its properties was investigated. The growth of ZnPc thin film was in situ monitored using transmission measurement in ultraviolet-visible spectral range. The optical properties in conjunction with density functional theory/time-dependent density functional theory calculations suggested the growth of the film in β-phase. X-ray diffraction also revealed crystalline character of the film. The electrical properties analyzed by van der Pauw method exhibited resistivity ρ ≈ 108–1010 Ω cm. Fourier transform infrared spectroscopy analyses revealed low deterioration of PLD deposited ZnPc films. We demonstrate that, by finely tuning the deposition conditions, PLD is a successful technique for fabrication of ZnPc thin films.
Ruthenium-nitrosyl (RuII(NO)) complexes are stable in the dark, but exhibit a unique photoreactivity which can lead either to a solid state isomerization from RuII(NO) to RuII(ON), or to a nitric oxide (NO·) release in solution. From our recent discovery of a high yield of isomerization (> 92%) in [RuII(py)4Cl(NO)](PF6)2, we have developed a computational strategy aimed at designing switchable nonlinear optical (NLO) material with high contrast (large difference in the on / off NLO response) in the solid state. Our synthetic targets are terpyridine based RuII chromophores in which various substituents can be introduced to adjust the NLO response which, at best, should be vanishing in the off state. Alternatively, these complexes can undergo a photo-induced NO· release in solution, a possibility which becomes increasingly appealing in relation to the discovery of the numerous biological roles of NO·, in the context of the emergence of the photodynamic therapy. A promising fluorene-terpyridine RuII(NO) complex was investigated, which could find an additional interest in relation to its capability for releasing NO· by a two-photon absorption process.
A series of fluorine appended highly conjugated fullerenes were prepared containing fluoro-α-cyanostilbene and aryl ester units. These modified PCBM dyads are fully characterized by NMR, Mass spectrometry, UV-vis, and cyclic voltammetry (Figures 1-4). It was found that the presence of fluoro-α-cyanostilbenes and esters affects the cyclic voltammetry and absorption in the UV-Vis region. The PCBA modified fullerenes significantly influences the HOMO-LUMO energy and wide absorption compared to PCBM.
Organic films with a thickness of few nanometers are potentially useful components in many practical and commercial applications such as sensors, detectors, displays and electronic circuit components. In this context, the Langmuir-Blodgett (LB) method is one the most promising techniques for preparing these films.
In this work, we report the synthesis and characterization of three new amphiphilic organometallic compounds with ferrocene units, which consist of one ferrocenyl aminocarbene with the general formula FcC=Cr(CO)5NH(CH2)15CH3, and two ferrocenyl amides with the general formula FcC=MNH(CH2)15CH3 where M = S or Se. These new derivatives have been synthesized to study the influence of long alkyl side chain and the hydrophilic head on the film organization behavior at the air-water interface.
The Langmuir-Blodgett (LB) technique was focused for building ordered nanostructures in molecular assemblies of ferrocenyl derivatives, which are apt to form a stable and transferable monolayer film. The π-A isotherm, hysteresis, Brewster angle microscopy (BAM) and film stability were used to characterize the behavior of a monolayer film at the air-water interface. Z- type LB films were prepared from molecular monolayers which were transferred onto glass substrates. These films were characterized by atomic force microscopy (AFM), UV-Visible spectra and X-ray diffraction (DRX) techniques.
By combining two types of ligands, phenylpyridine and quinoline, a new type of organometallic IrQ(ppy)2 compound has been synthesized, which exhibits two phosphorescences: green and red. Using an appropriate catalyst, the final IrQ(ppy)2 compound has a good chemical yield up to 60% and becomes a stable dual emitter at room temperature. This compound is important because it exhibits stable red emission which is limited by the quantum yield due to the low energy band gap. As a result, an overlap between the ground state and the excited state occurs due to the vibrations that increase the nonradiative transitions, destroying the red emissions. Structural characteristics of the IrQ(ppy)2 powder reveal a triclinic structure confirmed by x-ray diffraction and scanning electron microscopy images. Thermal analysis of the final compound confirms a good stability against decomposition and structural changes up to 350 °C. X-ray photoelectron spectroscopy reveals Ir–O chemical bonds and several differences between the intermediate and final compounds, such as Ir–Cl bonds. Cathodoluminescence patterns show a phosphorescent triclinic structure with a higher efficiency for the red color. Backscattering electron images prove that there is a uniform distribution of iridium ions in the IrQ(ppy)2 nanocrystals.
Fibrous polyethylene terephthalate (PET) was modified by organometallic vapor exposure to form hybrid materials with unique photoluminescent characteristics. Using a sequential vapor infiltration (SVI) process, the elongated exposures of trimethylaluminum (TMA) to PET were examined. As the infiltration temperature increased, the evidence of changes in the reaction between the organometallic vapor and the polymer was observed as well as significant changes in the infiltration depth into the polymer fiber, owing to the variation in the reaction mechanisms of the hybrid material formation. At TMA exposures of 60 °C, the mass of the polymer fiber increased by ∼55 wt%, whereas exposures at 150 °C were limited to ∼25 wt% infiltration. Photoluminescence analysis of PET after TMA infiltration shows an intensity increase of up to ∼13x and an increase in red shift with increasing infiltration temperature, attributed to the variations in the reaction mechanism to form the hybrid modification observed through the spectroscopy analysis.
Organic materials provide a unique platform for exploiting the spin of the electron—a field dubbed organic spintronics. Originally, this was mostly motivated by the notion that because of weak spin-orbit coupling, due to the small mass elements in organics and small hyperfine field coupling, organic matter typically displays a very long electron spin coherence time. More recently, however, it was found that organics provide a special class of spintronic materials for many other reasons—several of which are discussed throughout this issue. Over the past decade, there has been a growing interest in utilizing the molecular spin state as a quantum of information, aiming to develop multifunctional molecular spintronics for memory, sensing, and logic applications. The aim of this issue is to stimulate the interest of researchers by bringing to their attention the vast possibilities not only for unexpected science but also for the enormous potential for developing new functionalities and applications. The six articles in this issue deal with some of the breakthrough work that has been ongoing in this field in recent years.
Organic materials are fascinating and promising candidates for nanoscale spintronic devices and may open viable routes toward quantum computing. Previous experiments on spin transport in organic devices, through break junctions or spin valves, unveiled exciting new frontiers of molecular magnetism. However, much more effort is needed to understand the properties of organic/magnetic interfaces at a microscopic level. In this article, we show how spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM/STS) can provide unprecedented insights into organic/magnetic interfaces as an initial step toward favorably tailoring such interfaces in order to increase device efficiency. Based on the unique combination of spin-sensitivity, atomic-scale spatial resolution, and high-energy resolution, SP-STM/STS has proven to be an invaluable method for exploring spatial and bias dependences of spin-polarized currents through individual molecules as well as for revealing individual spin-split molecular orbitals interacting with ferromagnetic substrates.
Alternate aluminum and arsenic precursors were investigated for InAlAs grown by organometallic vapor phase epitaxy (OMVPE). The quality of the InAlAs growths was investigated by secondary-ion mass spectrometry (SIMS) to measure impurity concentrations. Trends are extracted from SIMS measurements for each precursor as a function of V/III ratio and growth temperature. Two arsenic precursors, arsine and tertiarybutylarsine (TBAs), were chosen to compare InAlAs growth quality. The impurity concentrations measured by SIMS decrease as the V/III ratio increases, for both arsine and TBAs growths. Impurities also decrease as growth temperature increases. Two aluminum precursors, trimethylaluminum (TMAl) and tritertiarybutylaluminum (TTBAl), were used to compare the effect of alumimum precursor on carbon and oxygen impurity levels. TMAl is widely studied in literature, though TTBAl is less common. This study represents the first report using the TTBAl precursor for InAlAs growth. Each aluminum source is used in conjunction with each aforementioned arsenic precursor in order to compare all possible precursor combinations. TMAl growths demonstrated decreasing impurities with increasing V/III ratio. TTBAl growths did not exhibit such a dependence, impurity concentrations remained virtually constant regardless of V/III ratio.
To prepare cholesteric liquid crystalline nonlinear optical materials with ability to be vitrified on cooling and form long time stability cholesteric glasses at room temperature, a series of platinum acetylide complexes modified with cholesterol has been synthesized. The materials synthesized have the formula trans-Pt(PR3)(cholesterol (3 or 4)-ethynyl benzoate)(1-ethynyl-4-X-benzene), where R = Et, Bu or Oct and X = H, F, OCH3 and CN. A cholesteric liquid crystal phase was observed in the complexes R = Et, and X = F, OCH3 and CN but not in any of the other complexes. When X = CN, a cholesteric glass was observed at room temperature which remained stable up to 130 °C, then converted to a mixed crystalline/cholesteric phase and completely melted to an isotropic phase at 230 °C. When X = F or OCH3 the complexes were crystalline at room temperature with conversion to the cholesteric phase upon heating to 190 and 230 °C, respectively. In the series X = CN, OCH3 and F, the cholesteric pitch was determined to be 1.7, 3.4 and 9.0 µ, respectively.