Hollow SiO2/TiO2 nanoparticles decorated with Ag nanoparticles (NPs) of controlled size (Ag@HNPs) were fabricated in order to enhance visible‐light absorption and improve light scattering in dye‐sensitized solar cells (DSSCs). They exhibited localized surface plasmon resonance (LSPR) and the LSPR effects were significantly influenced by the size of the Ag NPs. The absorption peak of the LSPR band dramatically increased with increasing Ag NP size. The LSPR of the large Ag NPs mainly increased the light absorption at short wavelengths, whereas the scattering from the SiO2/TiO2 HNPs improved the light absorption at long wavelengths. This enabled the working electrode to use the full solar spectrum. Furthermore, the SiO2 layer thickness was adjusted to maximize the LSPR from the Ag NPs and avoid corrosion of the Ag NPs by the electrolyte. Importantly, the power conversion efficiency (PCE) increased from 7.1 % with purely TiO2‐based DSSCs to 8.1 % with HNP‐based DSSCs, which is an approximately 12 % enhancement and can be attributed to greater light scattering. Furthermore, the PCEs of Ag@HNP‐based DSSCs were 11 % higher (8.1 vs. 9.0 %) than the bare‐HNP‐based DSSCs, which can be attributed to LSPR. Together, the PCE of Ag@HNP‐based DSSCs improved by a total of 27 %, from 7.1 to 9.0 %, due to these two effects. This comparative research will offer guidance in the design of multifunctional nanomaterials and the optimization of solar‐cell performance. 相似文献
Thanks to thermogenesis in the presence of an alternating magnetic field, magnetic nanoparticles could play a promising role in local heating in vivo. However, the flexible control of thermogenesis for the given nanomaterials remains challenging. Here, we propose that the thermogenesis of assembled magnetic nanoparticles can be controlled by orientation of the film relative to an external field. This idea arises from the principle of energy conservation that is formulated by Poynting′s theorem in electromagnetics. We firstly prove that the thermogenesis of magnetic nanoparticles under an alternating magnetic field is directly related to the energy flux of the field rather than to the field′s intensity. Then, alteration of the orientation can lead to different incident electromagnetic energies for the nanoparticle film, where the cross‐section of the energy absorption plays a crucial role. We developed a method to directly measure the complex susceptibility of an assembled film to confirm this point. This work could be of great importance for applications based on the electromagnetic energy conversion of nanomaterials. 相似文献
This communication reports the first gold nanoparticles (NPs) chirally functionalized with optically active helical substituted polyacetylene (the resulting hybrid particles are defined as Au@PPA NPs). The novel nanoparticles consist of gold as core and optically active helical poly(N‐propargylamide) as shell and show considerable optical activity derived from helical poly(N‐propargylamide) chains with predominantly one‐handed screw sense. The Au@PPA NPs are prepared by a three‐step approach: i) a thiol‐containing N‐propargylamide monomer [Mth, HC≡CCH2NHCO(CH2)10SH] is synthesized and characterized with FTIR and1HNMR spectroscopy and elemental analysis; ii) a copolymer (poly(Mth‐co‐Mch)) was prepared by starting from monomer Mth and another chiral N‐propargylamide monomer (Mch); poly(Mth‐co‐Mch) formed helical conformations and showed optical activities; and, iii) Au@PPA NPs are prepared from hydrogen tetrachloroaurate (III) and poly(Mth‐co‐Mch) through a one‐spot procedure by using LiBH4 as reducing agent. The as‐obtained hybrid nanoparticles are characterized by FTIR spectroscopy, TEM, UV‐vis absorption and circular dichroism (CD) techniques. UV‐vis and CD measurements demonstrated the remarkable optical activity of the Au@PPA NPs. More interestingly, the Au@PPA NPs show much stronger UV‐vis and CD sigals when compared to the corresponding orginal helical copolymer, poly(Mth‐co‐Mch). The chiral hybrid nanoparticles demonstrate different absorption toward (R)‐(+)‐ and (S)‐(−)‐1‐phenylethylamines, preferentially adsorbing the (S)‐isomer.
(1) Background: Astrocytes, the most abundant cell type in the central nervous system, are essential to tune individual-to-network neuronal activity. Senescence in astrocytes has been discovered as a crucial contributor to several age-related neurological diseases. Here, we aim to observe if astrocytes demonstrate senescence in the process of brain aging, and whether they bring adverse factors, especially harm to neuronal cells. (2) Methods: In vivo, mice were housed for four, 18, and 26 months. An in vitro cell model of aged astrocytes was constructed by serial passaging until passage 20–25, and those within 1–5 were invoked as young astrocytes. Meanwhile, an oxidative induced astrocyte senescence model was constructed by H2O2 induction. (3) Results: In vitro aged astrocytes all showed manifest changes in several established markers of cellular senescence, e.g., P53, P21, and the release of inflammatory cytokine IL-6 and SA-β-gal positive cells. Results also showed mitochondrial dysfunction in the oxidative stress-induced astrocyte senescence model and treatment of berberine could ameliorate these alterations. Two types of senescent astrocytes’ conditioned medium could impact on neuron apoptosis in direct or indirect ways. (4) Conclusions: Senescent astrocyte might affect neurons directly or indirectly acting on the regulation of normal and pathological brain aging. 相似文献
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