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A simple method to synthesize low-cost carbon modified TiO <sub/>2</sub> counter electrodes for high-efficiency dye-sensitized solar cells
摘要： Low cost and stable counter electrodes (CE) for dye-sensitized solar cells (DSSC) are promising for widespread use. In this paper, we report a simple and effective method to synthesize carbon modified TiO2 (TiO2/C) thin film as an abundant low cost CE for high-efficiency DSSC. The TiO2 paste layer contained organic compound was deposited on FTO glass substrate by a screen-printing method. When annealing the TiO2 paste layer at 450–550 °C under Ar flow, these organic compounds are decomposed to carbon to form carbon coated TiO2 nanoparticles. When used as a CE of DSSCs, the experimental results point out that the photoelectric conversion efficiency of DSSCs was obviously improved to near that of the referenced Pt CE. For TiO2/C is one of the cheapest and most stable materials, this TiO2/C can be used as a low cost CE for large scale high efficient DSSCs.
关键词： carbon nano materials,solar energy materials,counter electrode,dye-sensitized solar cell
更新于2025-11-14 17:04:02
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Novel honey mediated green synthesis of Graphene@Ag Nanocomposite and its two-dimensional application in photovoltaic and anti-microbial activity
摘要： The green and facile method were successfully employed for the fabrication of Graphene/Ag nanocomposite (Gr@AgNCs) with graphite oxide (GO) as graphene precursor and AgNO3 as precursor for Ag nanoparticles. Honey was used as a reducing and stabilizing agentwhich is known to be environment-friendly in nature. The characterization of synthesized Gr@AgNCs was done using x-ray diffraction (XRD),scanning electron microscopy (SEM),Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectra (RS),Thermogravimetric analysis (TGA), and UV analysis. The results showed that Honey effectively reduced GO to graphene and silver ions to silver nanoparticles (AgNPs) which makes present synthesis more suitable for synthesizing other metals like gold (Au) on graphene sheets. This active synthesis perhaps can have wide applications in medical, technological and industrial ?eld. In addition to this, enhanced antimicrobial activity of silver nanoparticles (AgNPs) was retained in the Gr@AgNCs along with the photovoltaic activity signifyingtheir potential use as a graphene-based nanomaterial.
关键词： antimicrobial activity,honey,graphene,nano materials,graphene oxide,photovoltaic activity
更新于2025-09-23 15:19:57
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Output energy enhancement in a dual-wavelength Q-switched fiber laser based on a ternary MoWSe2 saturable absorber
摘要： As a novel ternary selenide-based transition metal dichalcogenide (TMD), few-layered molybdenum tungsten selenide (MoWSe2) was fabricated using liquid phase exfoliation method and applied in a Q-switched fiber laser as a saturable absorber. Dual-wavelength operation was achieved with the increase of pumping strength. The shortest pulse width and the maximum repetition rate were monitored to be 1.53 μs and 85.71 kHz, corresponding to a maximum single pulse energy and peak power of 151.4 nJ and 98.91 mW, respectively. The results indicate ternary MoWSe2 could be a promising candidate in Q-switched laser applications.
关键词： Saturable absorber,MoWSe2 nano-materials,Q-switched fiber laser
更新于2025-09-19 17:13:59
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Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers
摘要： Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.
关键词： four-dimensional (4D) functional nano-materials,nano-optics,non-paraxial light fields,self-assembled monolayers (SAMs),polarization nano-tomography
更新于2025-09-12 10:27:22
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Graphene oxide on laser-induced graphene filters for antifouling, electrically conductive ultrafiltration membranes
摘要： Laser-induced graphene (LIG) is a three-dimensional porous carbon material prepared by direct laser writing with a CO2 laser on various polymers in an ambient atmosphere, leading to electrically conductive, low fouling coatings. Recently, LIG has been synthesized on porous supports, which led to highly permeable and porous separation filters and LIG composites have greatly improved the stability. On the other hand, graphene oxide (GO) has emerged as a promising 2D nanomaterial to coat porous or non-porous polymer membrane supports resulting in separation membranes with enhanced separation and surface properties. Here, we report a robust, hybrid LIG-GO membrane fabricated by filtration and crosslinking of GO onto the LIG membrane support, generating ultrafiltration membranes with tailored performance. Increasing the amount of crosslinked GO on the LIG surface resulted in increased rejection of bovine serum albumin (BSA) up to 69%, and bacterial rejection was increased from 20 to 99.9%, which agreed with the measured molecular weight cut-off determination that approached ~ 90 kDa as the GO content increased. Higher flux recovery ratios and lower BSA adsorption were seen with LIG-GO membranes, and the hybrid membranes showed comparatively good antifouling. These composite membranes showed 83% less biofilm growth compared to a typical polymer ultrafiltration membrane under non-filtration condition. Noteworthy is that the LIG supporting layer maintained its electrical conductivity and the LIG-GO membrane used as electrodes showed complete elimination of bacterial viability with potent antimicrobial killing effects when treated with mixed bacterial culture. In cross-flow filtration, LIG-GO membranes with 3V anodic electric field showed 11% improvement of flux as compared to typical polymer ultrafiltration membrane. The LIG-GO membranes expand possibilities for the use of LIG in membrane separation applications, especially ultrafiltration.
关键词： Biofilm,Graphene oxide,Nano-materials,Ultrafiltration,Laser-induced graphene
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Measuring Charge Distribution in Nanoscale Magnesium Aluminate Spinel by Electron Energy-Loss Spectroscopy and Electron Holography
摘要： Charge distribution resulting in the formation of a space charge zone (SCZ) in ionic materials has a critical role on functional properties [1]. Even though significant advances in theoretical models have been accomplished, experimental evidence in nanoscale granular materials is indirect. Here, we investigated the distribution of cations and defects on the formation of a SCZ in a nanoscale granular model system of non-stoichiometric MgO?nAl2O3 (MAS, n= 0.95 and 1.07). The SCZ was investigated experimentally by electron energy-loss spectroscopy (EELS) and off-axis electron holography (OAEH). EEL spectra were collected along directions perpendicular to grain boundaries (GB’s), from which the magnesium-to-aluminum relative cation concentrations were calculated, as presented in Fig.1. We found that regardless of annealing processes, the vicinity of GB’s of the Mg rich spinel has excess Mg+2 cations while the vicinity of GB’s of the Al rich spinel has excess of Al+3 cations. Additionally, the cation distribution shows strong dependency on the grain size. For non-stoichiometric MAS, cation concentration is proportional to the defect concentration, because deviation from stoichiometry results in adjacent defects that compensate for the electric charge [2, 3, 4]. In both materials, the cation distribution is inhomogeneous for grains smaller than 40 nm. For larger grains, the defect concentration approaches the bulk value at the center of the grain. Furthermore, excess of Mg (Al) cations at the vicinity of the GB decreased with increase of grain size. Maier et al. [1] calculated that for grain size at the scale of the Debye length (estimated at 9nm for non-stoichiometric MAS studied here [7]), the GC is no longer electrically neutral, instead influenced by accumulation or depletion of charge at the boundaries. Due to the lack of accurate values for defect formation energy [5, 6], we applied OAEH to measure directly the electrostatic charge distribution in nano-sized MAS. We show that charge distribution and the buildup of electrostatic potential between GB and core are linked to the spatial distribution of defects rather than the overall composition of MAS (Fig. 2). At the vicinity of GB’s, excess Mg+2 or Al+3 cations accumulate depending on the composition, the magnitude of which increases with decreasing grain size. Indeed, the potential distributions show the relation between the excess cation species, grain size and the Debye length, in agreement with theoretical models [1].
关键词： Lattice ordering,Electron holography,Ionic nano-materials,Electron energy loss spectroscopy,Space charge potential
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Laser induced yellowing of stonework: a combined TEM imaging and STEM-EELS study on model samples
摘要： Nd-YAG Q-Switched laser devices operating at 1064 nm have been considered in the 1990s as the most promising tool for cleaning stone sculptures, and more particularly eliminating indurated black gypsum crusts. However, the spreading of this laser technology has been undermined because of the yellow hue it occasionally conveys to the cleaned surfaces as seen on Figure 1. Especially in France, this yellowing effect is considered as a major esthetic issue by conservators and the laser technique has gradually disappeared from the restoration sites. This discoloration issue remains partly unexplained: a currently admitted hypothesis states that the iron containing compounds present in the black crusts would transform, upon laser irradiation, into yellow iron-rich nanophase(s) that would re-deposit on the cleaned substrate. To verify this hypothesis, model black crusts have been elaborated by mixing hematite α-Fe2O3 and gypsum CaSO4.2H2O in different proportions. The model crusts were irradiated using a Nd-YAG QS laser resulting in ablation of numerous particles in a visible smoke and the color of the samples shifted instantaneously from red to a bright yellow. Transmission electron microscopy (TEM) has been used to characterize the morphology of the nanostructures generated by the laser, both in the smoke and on the surface of the samples as observed in Figure 2. In addition, the chemical composition of the neo-formed nanophases was determined by aberration corrected scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) and high angle annular dark field imaging (HAADF) as seen on Figure 3. It was found that both the surface of the samples and the ablated micro-materials are covered by an irregular nano-film and by dispersed spherical nanoparticles, all containing iron and oxygen. These results ascertain the link between the yellowing effect and the presence of iron containing nanophases after irradiation.
关键词： EELS,TEM,STEM,nano materials,iron,yellowing,laser
更新于2025-09-11 14:15:04