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De novo design of organic photocatalysts: bithiophene derivatives for the visible-light induced C-H functionalization of heteroarenes
摘要： Herein, we report the de novo synthesis and characterization of a series of substituted bithiophene derivatives as novel inexpensive organic photocatalysts. DFT calculations were used to predict a priori their absorption spectra and redox potentials, which were then confirmed with empirical data. The photocatalytic activity of this novel class of organic photoredox catalyst was demonstrated in two visible-light mediated strategies for the C-H functionalization of heteroarenes. The implementation of these strategies in a continuous-flow photo-microreactor afforded moderate to excellent yields within few minutes of reaction time. Due to their straightforward synthesis, low cost and good photocatalytic properties we believe that the proposed bithiophene derivatives could be employed as a new class of organic photoredox catalysts.
关键词： Organic photocatalysts,C-H functionalization,Photoredox catalysis,DFT calculations,Continuous flow catalysis
更新于2025-09-04 15:30:14
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Omnidirectional sub-bandgap photo-detection using functionalized moulded composite flexible platforms
摘要： The substrate is an optically functional component of a thin film organic optoelectronic device. In the well-known context of photovoltaics, the functionality of substrate is relatively simple – that of a broadband transmittance which allows almost all the incoming light into the absorber. A less explored idea is that of incorporating other optical functionalities in the substrate bulk. Such unconventional design can help surpass the performance limitations of commonly available optoelectronic materials to achieve novel functionality. Bulk functionalization of substrates is particularly easy when the substrates are made using moldable transparent materials which allow mixing of optically functional materials into a composite substrate bulk. In this paper, the example of photonic-upconversion is considered as a representative optical function, to make organic photo-detectors which detect up-converted infrared light. By incorporating this functionality in a composite substrate two advantages are demonstrated in which the composite substrate architecture surpasses the performance of the conventional thin film device design. First, the composite substrate preserves the electronic performance of the device by spatially isolating the optical and the charge transport functions. Second, the composite architecture enables sub-bandgap photo-detection which is invariant with respect to the angle of incidence of the infrared input light, by placing the optical function before the light can encounter optically reflecting interfaces. In summary, the unconventional design employing a composite optically functional substrate can be extended to multiple optical functionalities and represents a key design finding that can enable considerably more efficient optoelectronic device designs.
关键词： Functionalization,Optoelectronic device,Moulded substrate,Composite,Up-conversion,Photodetection
更新于2025-09-04 15:30:14
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From the Bottom-Up: Toward Area-Selective Atomic Layer Deposition with High Selectivity
摘要： Bottom-up nanofabrication by area-selective atomic layer deposition (ALD) is currently gaining momentum in semiconductor processing, because of the increasing need for eliminating the edge placement errors of top-down processing. Moreover, area-selective ALD offers new opportunities in many other areas such as the synthesis of catalysts with atomic-level control. This Perspective provides an overview of the current developments in the field of area-selective ALD, discusses the challenge of achieving a high selectivity, and provides a vision for how area-selective ALD processes can be improved. A general cause for the loss of selectivity during deposition is that the character of surfaces on which no deposition should take place changes when it is exposed to the ALD chemistry. A solution is to implement correction steps during ALD involving for example surface functionalization or selective etching. This leads to the development of advanced ALD cycles by combining conventional two-step ALD cycles with correction steps in multistep cycle and/or supercycle recipes.
关键词： surface functionalization,semiconductor processing,area-selective atomic layer deposition,catalysts synthesis,selectivity,bottom-up nanofabrication,selective etching,ALD
更新于2025-09-04 15:30:14
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Fe3O4/SiO2 Core Shell Nanostructures: Preparation and Characterization
摘要： Silica coated iron oxide nanoparticles with controlled silica shell thickness were prepared by a modified St?ber method. Modification of the St?ber method consisted of changing the synthesis conditions to control the thickness of the SiO2 shell. The core-shell nanoparticles were characterized by means of X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy and vibrational sample magnetometry. It was found that the shell formed after 8 hours of stirring. An increase of the tetraethoxysilane-magnetite mass ratio from 12.5 to 25.1 led to an increase of the shell thickness, whereas further increase in the tetraethoxysilane-magnetite mass ratio (from 25.1 to 37.6) led to decrease shell thickness. The core size has only insignificant influence on the shell thickness. Magnetic properties of composite particles correlate well with properties of pure magnetite nanoparticles considering dilution of magnetic particles by silica. Obtained results can be used for fabrication of silica shell with controlled thickness on the surface of different sized magnetite nanoparticles.
关键词： FTIR,iron oxide,surface functionalization,silica coated,nanoparticles
更新于2025-09-04 15:30:14
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Tuning the Electronic Structure of Hydrogen-Decorated Silicene
摘要： The effects of strain, charge doping, and external electric field on the electronic structure of a free-standing silicene layer decorated by hydrogen atoms are studied by first-principles density functional theory. Various phases, including insulating, metallic, spin-polarized, and half-metallic have been found, depending on these external factors. The most efficient way of switching the system between these phases is charge doping. The character of the energy gap of the H/silicene system can also be modified, and for charged or for strained systems, the originally indirect gap can be tuned to become direct. The obtained results are very promising in view of the silicene functionalization and potential applications of silicene in the fields of spintronics and optoelectronics.
关键词： density functional theory (DFT),silicene,functionalization
更新于2025-09-04 15:30:14
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Efficient synthesis of high solid content emulsions of AIE polymeric nanoparticles with tunable brightness and surface functionalization through miniemulsion polymerization
摘要： Efficient production and flexible surface functionalization are important developing directions for the synthesis of polymeric nanomaterials. In this work, aggregation-induced emission (AIE) polymeric nanoparticles (PNPs) were efficiently synthesized by encapsulating a model AIE luminogen, tetraphenylethylene (TPE), within a polymeric matrix via miniemulsion polymerization. The AIE PNPs with similar emission and particle properties were synthesized in a wide solid content range of 8–40 wt%. The particle size and photoluminescence intensity of AIE PNPs could be flexibly tuned by synthetic parameters including the surfactant content and TPE content. Furthermore, the surface carboxyl- and amino-functionalization of AIE PNPs were conveniently achieved through copolymerization of styrene and functional monomers methacrylic acid and 2-aminoethyl methacrylate hydrochloride, respectively, in miniemulsions. The surface functionalization extent could be facilely tuned by the content of functional monomers. This miniemulsion polymerization based technique could be a feasible and efficient method to prepare AIE PNPs with versatile surface functionalization, tunable brightness, and controllable particle properties for the applications in biodetection, bioimaging, etc.
关键词： high solid content,miniemulsion polymerization,Aggregation-induced emission,AIE polymeric nanoparticles,surface functionalization
更新于2025-09-04 15:30:14
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High-Performance PEDOT:PSS/Hexamethylene Diisocyanate-Functionalized Graphene Oxide Nanocomposites: Preparation and Properties
摘要： Graphene oxide (GO) has emerged as an ideal ?ller to reinforce polymeric matrices owing to its large speci?c surface area, transparency, ?exibility, and very high mechanical strength. Nonetheless, functionalization is required to improve its solubility in common solvents and expand its practical uses. In this work, hexamethylene diisocyanate (HDI)-functionalized GO (HDI-GO) has been used as ?ller of a conductive polymer matrix, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The nanocomposites have been prepared via a simple solution casting method, and have been characterized by scanning electron microscopy (SEM), UV–Vis and Raman spectroscopies, X-ray diffraction (XRD), thermogravimetric analysis (TGA), tensile tests, and four-point probe measurements to get information about how the HDI-GO functionalization degree (FD) and the HDI-GO concentration in the nanocomposite in?uence the ?nal properties. SEM analysis showed a very homogenous dispersion of the HDI-GO nanosheets with the highest FD within the matrix, and the Raman spectra revealed the existence of very strong HDI-GO-PEDOT:PSS interactions. A gradual improvement in thermal stability was found with increasing HDI-GO concentration, with only a small loss in transparency. A reduction in the sheet resistance of PEDOT:PSS was found at low HDI-GO contents, whilst increasing moderately at the highest loading tested. The nanocomposites showed a good combination of stiffness, strength, ductility, and toughness. The optimum balance of properties was attained for samples incorporating 2 and 5 wt % HDI-GO with the highest FD. These solution-processed nanocomposites show considerably improved performance compared to conventional PEDOT:PSS nanocomposites ?lled with raw GO, and are highly suitable for applications in various ?elds, including ?exible electronics, thermoelectric devices, and solar energy applications.
关键词： hexamethylene diisocyanate,PEDOT:PSS,functionalization degree,nanocomposite,optical transmittance,sheet resistance,graphene oxide,mechanical properties
更新于2025-09-04 15:30:14