Intense Optical Absorption Research Articles

Turning dead leaves into an active multifunctional material as evaporator, photocatalyst, and bioplastic

Large numbers of leaves fall on the earth each autumn. The current treatments of dead leaves mainly involve completely destroying the biocomponents, which causes considerable energy consumption and environmental issues. It remains a challenge to convert waste leaves into useful materials without breaking down their biocomponents. Here, we turn red maple dead leaves into an active three-component multifunctional material by exploiting the role of whewellite biomineral for binding lignin and cellulose. Owing to its intense optical absorption spanning the full solar spectrum and the heterogeneous architecture for effective charge separation, films of this material show high performance in solar water evaporation, photocatalytic hydrogen production, and photocatalytic degradation of antibiotics. Furthermore, it also acts as a bioplastic with high mechanical strength, high-temperature tolerance, and biodegradable features. These findings pave the way for the efficient utilization of waste biomass and innovations of advanced materials.

Synthesis of Self-Assembled Single Atomic Layer Gold Crystals-Goldene.

We report, for the first time, a technique to synthesize free-standing, one-atom thick 2D gold crystals (namely, goldene) and self-assembled 2D periodic arrays of goldene. High-resolution transmission electron microscopy (HRTEM) imaging of goldene revealed herringbone and honeycomb lattices, which are primarily gold surface features due to its reconstruction. Imaging of these surface-only features by a nonsurface characterization technique such as HRTEM is an unequivocal proof of the absence of three-dimensionality in goldene. Atomic force microscopy confirmed 1-2 Å thickness of goldene. High-resolution X-ray photoelectron spectroscopy (HR-XPS), selective area electron diffraction, and energy-dispersive X-ray spectroscopy confirmed the chemical identity of goldene. We discovered the phenomenon of electric field-induced self-assembly of goldene supracrystals with a herringbone structure and developed an electric field printing (e-print) technique for goldene arrays. Goldene showed a semiconductor response with a knee voltage of ∼3.2 V, and I/V spectroscopy revealed periodic room temperature Coulomb blockade oscillations. These observations are consistent with the theoretical calculations reported in the literature predicting enhanced Coulombic interactions between gold valence electrons and the nucleus in stable 2D gold. Goldene exhibited multiple, intense, and well-resolved optical absorption peaks and several fine bands across the UV-vis region, and we calculated its optical band gap to be 3.59 eV. Magnetic force microscopy measurements of goldene periodic arrays showed a ∼5 mV peak amplitude confirming its ferromagnetism. Optical and magnetic properties of goldene are consistent with those reported in the literature for 2D planar gold clusters with less than 12 atoms.

Synthesis and characterization of n-type semiconducting graft copolymers with polystyrene side chains

In this study, we synthesized and evaluated graft copolymers with polystyrene (PSt) as side chains on poly {[N,N´-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′ -bithiophene)} [P(NDI2OD-T2)], which is a typical n-type semiconducting polymer applied to in organic photovoltaics due to its intense optical absorption for the visible light, and high electron affinity. A well-controlled structure was confirmed by 1H-NMR analysis. It was found that enhanced electron mobilities in graft copolymer films were observed compared with the homopolymer. In order to clarify the role of PSt chains and the origins of the enhanced mobility, UV–vis absorption, electrochemical, morphological and thermal characteristics, and crystalline nature were investigated. As the results, it is suggested that the improved mobilities were attributed to the enhanced growth of π–π stacks, and increased crystallinity induced by PSt graft chains.

Probing High Oxygen Activity in YSZ Electrolyte

The redox behavior of terbium and praseodymium doped yttria-stabilized zirconia (YSZ) is studied. The aim is to identify spectroscopic probes and a suitable experimental procedure to monitor the oxygen activity in YSZ electrolytes in solid oxide cells with spatial resolution and at operation conditions (e.g. at high temperatures). Sintered ceramics and crystals with 0.3 to 10 at% content of Pr or Tb ions in YSZ were prepared. Upon equilibration in atmospheres from 10−20 to 100 bar PO2 around 800 °C, the majority of these rare earth ions are in the 3 + oxidation state. At oxygen pressures above 0.001 bar, the small proportion of Tb4+ and Pr4+ formed give rise to intense optical absorption around 300–500 nm and to decreased reflectance. From the reflectance measurements it is shown that the Tb4+ concentration increases as PO2 1/4, as correspond to the trapping of the holes generated upon the oxygen incorporation as Tb4+. This competitive absorption causes a decrease of the Tb3+ luminescence. A quantitative relationship of the Tb3+ luminescence intensity with PO2 at 800 °C has been found, which is compatible with the trapping model. The spatial resolution of the experimental procedure could be very roughly estimated of the order of 100 μm.

Investigation of Interaction Mechanisms of High Energy Electrons and Gamma Quantum with Aqueous Solution of Methyl Orange Dye

The level of development of modern nuclear technologies forms a request for the development of new branches of science. At the same time, chemical dosimetry methods are also being improved [1, 2]. The essence of such methods consists in the quantitative determination of the radiation-chemical damages to the molecules of a substance when it is exposed to ionizing radiation [3, 4]. Liquid and solid solutions of organic dyes have intense bands optical absorption and fluorescence in the visible region of the spectrum, which makes it possible to use them in dosimetry systems [5, 6]. The use of organic dyes makes it possible to determine the absorbed dose in the range from 10-6 to 104 M Rad [7, 8]. In this work, we studied the processes of interaction of gamma-ray and high-energy electron fluxes with an aqueous solution of the organic dye methyl orange (C14H14N3О3SNa) [9, 10]. The calculations and experiment were carried out on a resonant electron accelerator with energies up to 30 MeV. The electron beam energy was 15 MeV. A tungsten converter was used to generate gamma quanta. The thickness of the converter varied from 0 to 6 mm. We have developed a computer program in C++ to simulate the irradiation process. This program uses the Geant4 class library based on the Monte Carlo method and runs in multi-threaded mode. For calculations, the model “PhysicsList emstandard_opt3” was chosen as the most suitable one. The value of radiation damage per one incident electron and produced gamma-quantum is determined in the work. The simulation results are compared with experimental data. Based on the results obtained, conclusions were drawn about the main mechanisms leading to the decomposition of organic dye molecules, and methods for optimizing the experiment for further research were proposed.

Gold(III) Porphyrin Was Used as an Electron Acceptor for Efficient Organic Solar Cells.

The widespread use of nonfullerene-based electron-accepting materials has triggered a rapid increase in the performance of organic photovoltaic devices. However, the number of efficient acceptor compounds available is rather limited, which hinders the discovery of new, high-performing donor:acceptor combinations. Here, we present a new, efficient electron-accepting compound based on a hitherto unexplored family of well-known molecules: gold porphyrins. The electronic properties of our electron-accepting gold porphyrin, named VC10, were studied by UV–Vis spectroscopy and by cyclic voltammetry (CV) , revealing two intense optical absorption bands at 500–600 and 700–920 nm and an optical bandgap of 1.39 eV. Blending VC10 with PTB7-Th, a donor polymer, which gives rise to an absorption band at 550–780 nm complementary to that of VC10, enables the fabrication of organic solar cells (OSCs) featuring a power conversion efficiency of 9.24% and an energy loss of 0.52 eV. Hence, this work establishes a new approach in the search for efficient acceptor molecules for solar cells and new guidelines for future photovoltaic material design.

Amplifying the photovoltaic properties of azaBODIPY core based small molecules by terminal acceptors modification for high performance organic solar cells: A DFT approach

Molecular engineering of azaBODIPY based molecule was done to construct four novel small photoactive materials (SM1-SM4) by varying terminal thiophene spaced acceptors for theoretical investigation of photovoltaic properties. In the present study, DFT and TD-DFT methods using B3LYP functionalwith a basis set of 6-31G were employed to systematically evaluate wavelength, determine parameters (absorption values, first excitonic energy, LHE), charge transfer elements (fill factor FF, open circuit voltage Voc), reactivity descriptors (IP and EA) and electronic processes (FMO, DOS, TDM) of modelled molecules (SM1-SM4). All studied molecules showed intense optical absorption in the visible region (710–751 nm), strong light harvesting capability, clearly assigned HOMO-LUMO placement, and lessened exciton binding energies due to highly electron withdrawing acceptor moieties. Greater dipole moment in solution phase than in the gas phase as compared to gaseous medium indicated that these small molecules possessed good solubility in Benzonitrile solvent.The internal reorganization energy values of novel molecules suggested their reliability as efficient hole transport materials. Additionally, results interpreted through analysis of values of Voc (with PTB7-Th), and FF, anticipated an escalation of power conversion efficiency. Among all considered molecules, SM2 and SM3 emerged as promising photovoltaic materials owing to their significant optical properties, reduced band gaps, rapid exciton dissociation, and high estimated PCE. Conclusively, these supportive outcomes favor the structural amendment of small molecules through effective terminal acceptor entities which could enhance the efficiency of photovoltaic materials.

Highly efficient UV-visible-infrared light-driven photothermocatalytic steam biomass reforming to H2 on Ni nanoparticles loaded on mesoporous silica

An integration of good thermocatalytic activity, intense optical absorption and novel photoactivation on Ni nanoparticles loaded on mesoporous silica enable efficient H2 production from biomass using solar energy.

Special features of the Faraday effect in rare earth orthoaluminate TbAlO3

The luminescence excitation spectra (LES) and luminescence (fluorescence) spectra of terbium orthoaluminate TbAlO3 have been studied within the wavelength range 150–350 nm and 450–700 nm, respectively, and within the temperature range 25–300 K. Based on the results of studying the LES within the wavelength range 220–260 nm, it has been concluded that in the same range there is an intense optical absorption band due to the allowed (in the electric dipole approximation) transition 4f(8)(F76)→4f(7)5d(eg). While measuring the Faraday effect (FE) in TbAlO3 the spectral dependence of the rotation angle θ of the major axis of the polarization ellipse has been investigated for temperature 300 K over the visible and near ultraviolet (UV) spectral range 250–400 nm. From the analysis of the data of magneto-optical studies, the frequency dependence of the Verde constant of TbAlO3 in the UV spectral range has been restored. The behavior of the FE frequency dependence for the absorption band of the 220–260 wavelength indicates that there is a “paramagnetic” contribution to the Verdet constant caused by allowed (in the electric dipole approximation) transitions occurring from the Stark sublevels of the ground 7F6 multiplet to the states of the mixed excited configuration 4f(7)5d of the rare-earth Tb3+ ion in orthoaluminate.

Improved CsPbBr3 visible light photodetectors via decoration of sputtered au nanoparticles with synergistic benefits

AbstractOwing to the intense carrier recombination and limited optical absorption, the as‐fabricated CsPbBr3 visible light photodetectors (PDs) are far from practical application. In this work, we have demonstrated performance‐improved metal‐semiconductor‐metal (MSM) structured CsPbBr3 visible light PDs realized by the decoration of sputtered Au nanoparticles (NPs). It showed that the Au NPs on the CsPbBr3 exhibited synergistic benefits including improving the photogenerated charge carriers’ lifetime and enhancing the optical absorption of the CsPbBr3, both of which are fundamental factors for the performance‐improved PDs. Electrical characterizations showed that localized Schottky junctions formed at the Au NPs/CsPbBr3 interface. In addition, optical investigations showed that effective resonant coupling occurred between the localized surface plasmon resonance effects of Au NPs and excitons in the CsPbBr3. As a result, the on‐off switching of the Au‐decorated CsPbBr3 photodetector increased by 13 times compared with that of the pristine one. Meanwhile, the peak photo sensitivity of the CsPbBr3 photodetector was increased from 0.088 to 0.61 A W‐1 after the decoration of Au NPs. It is believed that the results shown in this work will provide pathways for fabricating high‐performance CsPbBr3 PDs and other similar devices in the future.

Coordination mechanism of cyanine dyes on the surface of core@active shell β-NaGdF4:Yb3+,Er3+ nanocrystals and its role in enhancing upconversion luminescence

The sensitization of lanthanide-doped upconversion nanocrystals (UCNCs) using organic dyes with a broad and intense optical absorption is an interesting approach for efficient excitation-energy harvesting and enhancing the upconversion luminescence.

Synthesis and characterization of new nonfullerene electron acceptors with a chrysene core

The utilization of non-fullerene acceptors has greatly promoted the development of organic photovoltaics in past few years. Herein, two new non-fullerene small-molecule electron acceptors, CRIC and CRIC-4F, with a four-fused-rings containing chrysene core, are designed and synthesized. Benefiting from the rigid and planar chrysene segment, these two acceptors exhibit strong intramolecular π electron transition with intense optical absorption from 550 to 750 nm. Both molecules present deep lowest unoccupied molecular orbital (LUMO) energy levels at around −4.0 eV, thereby making them suitable to employ as electron acceptors. In combination with electron donor J52-2F, organic solar cells based on CRIC achieved a decent power conversion efficiency (PCE) of 6.12% with a low energy loss of 0.59 eV owning to their complementary absorption, higher energy levels, and reduced charge recombination, thus surpassing the J52-2F:CRIC-4F based counterpart (PCE = 5.61%). This work demonstrates that chrysene derivatives are potential acceptors for applications in organic photovoltaics with low energy losses.

Surfactant-Stripped Micelles for NIR-II Photoacoustic Imaging through 12 cm of Breast Tissue and Whole Human Breasts.

Surfactant-stripped micelles are formed from a commercially available cyanine fluoroalkylphosphate (CyFaP) salt dye and used for high contrast photoacoustic imaging (PAI) in the second near-infrared window (NIR-II). The co-loading of Coenzyme Q10 into surfactant-stripped CyFaP (ss-CyFaP) micelles improves yield, storage stability, and results in a peak absorption wavelength in the NIR-II window close to the 1064 nm output of Nd-YAG lasers used for PAI. Aqueous ss-CyFaP dispersions exhibit intense NIR-II optical absorption, calculated to be greater than 500 at 1064 nm. ss-CyFaP is detected through 12 cm of chicken breast tissue with PAI. In preclinical animal models, ss-CyFaP is visualized in draining lymph nodes of rats through 3.1 cm of overlaid chicken breast tissue. Following intravenous administration, ss-CyFaP accumulates in neoplastic tissues of mice and rats bearing orthotopic mammary tumors without observation of acute toxic side effects. ss-CyFaP is imaged through whole compressed human breasts in three female volunteers at depths of 2.6-5.1 cm. Taken together, these data show that ss-CyFaP is an accessible contrast agent for deep tissue PAI in the NIR-II window.

Solvothermally-synthesized tin-doped indium oxide plasmonic nanocrystals spray-deposited onto glass as near-infrared electrochromic films

Nanocrystals of semiconducting, highly-doped metal oxides present localized surface plasmon resonance properties responsible for intense optical absorption in the near-infrared (NIR) spectral range. These features make them strong candidates for designing “new generation”, spectrally-selective electrochromic smart windows and other optoelectronic devices. In the present study, nanocrystals of tin-doped indium oxide (ITO) are solvothermally-synthesized in benzyl alcohol. Their structure, morphology and composition are assessed by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, while their optical plasmonic behavior is evidenced by means of VIS-NIR spectrometry and electron energy loss spectroscopy coupled to scanning transmission electron microscopy. Remarkably, the latter setup allows for the value-added acquisition of high-resolution mappings and quantifications of the nanocrystals individual plasmon responses at both surface and bulk levels. Inks of ITO nanocrysals are then spray-coated onto glass to act as NIR-modulating plasmonic electrochromic layers. ITO dispersions are straightforwardly deposited from low toxic media (isopropanol) according to a room-temperature procedure implying no harsh chemical or thermal post-treatment – only a mild drying step at 100 °C for 10 min. Finally, in situ spectroelectrochemical measurements completed on the films immersed in liquid electrolyte show appreciable NIR contrasts (up to 40%) upon electrochemical charge/discharge, together with a >80% VIS transmittance.

P- and n-Channel Photothermoelectric Conversion Based on Ultralong Near-Infrared Wavelengths Absorbing Polymers

Organic materials absorbing near-infrared (NIR) light are very attractive for the fabrication of optoelectronic devices. In this study, we developed an ultralow energy gap copolymer TzQI-TDPP composed of thiadiazoloquinoxalinimide (TzQI) and thiophene-flanked diketopyrrolopyrrole (TDPP) repeat units. TzQI-TDPP has a nearly identical narrow energy gap (0.60 eV) to that of the p-channel thienoisoindigo-based homopolymer PTII. Both polymers exhibit broad and intense optical absorption in the NIR-II light window (1000–1700 nm). Examination of charge polarity using field-effect transistors indicates p-channel conduction for PTII and n-channel-dominant ambipolar conduction for TzQI-TDPP with moderate mobilities, in which a thin film of TzQI-TDPP displayed air-stable n-channel performance with a persistent mobility of over 0.003 cm2 V–1 s–1 after 30 days. In addition, we explored the photothermal (PT) and thermoelectric (TE) effects in the NIR-II light window by fabricating a photothermoelectric device. Both polymers exhibit PT conversion efficiencies of ∼30%, and the TE effect is observed in p-channel PTII and n-channel TzQI-TDPP. Notably, the PTII and TzQI-TDPP films display excellent photostability during on–off irradiating light cycles, indicating prominent NIR light detection. Our work not only provides a set of p-channel and n-channel-dominant ambipolar polymers with ultralow energy gaps but also demonstrates their underlying structure–property correlations based on electronic structures and their promising potential in applications utilizing NIR-II light.

Magnetically amplified photothermal therapies and multimodal imaging with magneto-plasmonic nanodomes

Nanotherapies require new ways for controlling and improving the delivery of the therapeutic agents to the site of action to maximize their efficacy and minimize the side effects. This control is particularly relevant in photothermal treatments to reduce the required light intensity and amount of injected nanoparticles, and to minimize necrotic cell deaths. Here we present a novel concept for multifunctional nanobiomedical agents: magneto-plasmonic (MP) nanodomes for magnetically guided and amplified photothermal therapies and as contrast agents for multimodal imaging. The MP nanodomes are composed of a Fe/Au bilayer semi-shell deposited on a 100nm diameter fluorescent polystyrene nanosphere, which gather a unique combination of straightforward functionalization, high colloidal stability, very strong ferromagnetic behavior and intense optical absorption efficiency in the near infrared. We show that the photothermal conversion efficiency of the Fe/Au nanodomes with high Fe ratios is substantially larger than pure plasmonic Au nanodomes and the state-of-art plasmonic nanoheaters, i.e. Au nanorods and nanoshells, by merging strong optical absorption, minimized scattering and low optical anisotropy. Remarkably, the effective magnetophoretic concentration of the Fe/Au nanodomes at the illumination region enables large local increase of the optically induced temperature rise. The Fe semishell also provides very intense T2 contrast in nuclear magnetic resonance, which is at least 15-fold larger per particle than commercial iron oxide contrast agents. Moreover, the fluorescent polystyrene nanosphere and the Au semishell integrate valuable fluorescent and X-ray contrasts, respectively, which we have used to assess the nanodomes internalization by cancer cells. The MP nanodomes are nontoxic to cells even in the case of magnetophoretic local enrichment with initially high particle concentration (100μg/mL). Remarkably, we demonstrate amplified local photothermal treatments by the magnetic enrichment of the nanodomes at the illumination region, which enables reaching nearly 100% reduction of cell viability with low particle concentration (10μg/mL) and mild NIR laser intensity (5W/cm2). These results highlight the high potential of MP nanodomes for magnetically guided and amplified photothermal therapies.

Tunable Optoelectronic Properties of Triply Bonded Carbon Molecules with Linear and Graphyne Substructures

In this paper we present a detailed computational study of the electronic structure and optical properties of triply-bonded hydrocarbons with linear, and graphyne substructures, with the aim of identifying their potential in opto-electronic device applications. For the purpose, we employed a correlated electron methodology based upon the Pariser-Parr-Pople model Hamiltonian, coupled with the configuration interaction (CI) approach, and studied structures containing up to 42 carbon atoms. Our calculations, based upon large-scale CI expansions, reveal that the linear structures have intense optical absorption at the HOMO-LUMO gap, while the graphyne ones have those at higher energies. Thus, the opto-electronic properties depend on the topology of the {graphyne substructures, suggesting that they can be tuned by means of structural modifications. Our results are in very good agreement with the available experimental data.

Photophysical Characterization and BSA Interaction of Direct Ring Carboxy Functionalized Symmetrical squaraine Dyes

A series of far-red sensitive symmetrical squaraine dyes bearing direct –COOH functionalized indole ring were synthesized, characterized and subjected to photophysical investigations. These symmetrical squaraine dyes were then subjected to investigate their interaction with bovine serum albumin (BSA) in Phosphate buffer solutions. All the squaraine dyes under investigation exhibit intense and sharp optical absorption mainly in the far-red wavelength region from 550 nm -700 nm having very high molar extinction coefficients from 1.3 × 105 dm3.mol−1.cm−1. A very small Stokes shift of 10-17 nm indicates the rigid conformational structure of squaraine chromophore. Interaction of these dyes with BSA leads to not only enhanced emission intensity but also bathochromically shifted absorption maximum due to formation of dye-BSA conjugate. These dyes bind strongly with BSA having about an order of magnitude higher binding constant as compared to the reported squaraine dyes. Amongst the symmetrical squaraine dyes investigated in this work one bearing substituents like trifluorobutyl as alkyl chain at N-position of indole ring and carboxylic acid on benzene ring at the terminal (SQ-26) exhibited highest association with the BSA having very high binding constant 8.01 × 106 M−1.

Star-shaped electron acceptors containing a truxene core for non-fullerene solar cells

Abstract A series of new electron acceptors containing a truxene core with intense optical absorption were synthesized and used for non-fullerene organic solar cells. Due to the weak electron-donating characteristic of truxene core and thereby weak intramolecular charge transfer interaction from electron-donating core to electron-withdrawing end groups, the resulting new acceptors show relatively wide optical band-gap and high-lying lowest unoccupied molecular orbitals (LUMOs), which consequently lead to complementary light spectra with narrow band-gap donor polymers and high open circuit voltage (Voc) in solar cells. Particularly, Tr(Hex)6-3BR, a star-shaped planar acceptor, produced the highest power conversion efficiency of 2.1% with a high Voc of 1.02 V when blended with PTB7-Th.

Facile synthesis of novel ZnFe2O4/CdS nanorods composites and its efficient photocatalytic reduction of Cr(VI) under visible-light irradiation

ZnFe2O4/CdS composites were successfully prepared by a facile process. The obtained samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), diffuse reflection spectroscopy (DRS), Raman spectroscopy and photoluminescence (PL). Under visible light irradiation, ZnFe2O4/CdS composite shows higher photocatalytic activity in the Cr(VI) reduction, relative to the pure CdS and ZnFe2O4. The enhanced photocatalytic performance was ascribed to the intimate contact interfaces and matching band potentials between CdS and ZnFe2O4, and can be related to the efficient transfer and separation of the electron-hole pairs. It was found that the modification of ZnFe2O4 did not affect the morphology of CdS. The result of PL test indicated a lower intensity, and effective separation of photogenerated electron-hole pairs. In addition, the ZnFe2O4/CdS composites showed more intense optical absorption than that of pure CdS and ZnFe2O4. Through the analysis of experiment results, a reasonable photocatalytic mechanism over ZnFe2O4/CdS photocatalysts was also proposed.