The first direct‐current triboelectric generator (DC‐TEG) based on sliding electrification for harvesting mechanical energy from rotational motion is reported. The DC‐TEG consists of two rotating wheels and one belt for connecting them, which are made of distinctly different triboelectric materials with a specific requirement. During the rotation, the contact‐induced electrification and the relative sliding between the two wheels and the belt can induce a continuous increase of the accumulated positive and negative triboelectric charges at the two rotating wheels, respectively, resulting in a Corona discharge and producing the observed current through an external load. The DC‐TEG can deliver an open‐circuit voltage of larger than 3200 V and a maximum power of 100 μW under an external load of 60 MΩ at a rotational speed of 1000 r min –1 . By designing a point metal discharge electrode near the accumulated positive charges on the metal wheel, the instantaneous short‐circuit current can be up to 0.37 mA. The DC‐TEG can be utilized as a direct power source to light up 1020 serially connected commercial light‐emitting diodes (LEDs) and the produced energy can also be stored in a capacitor for other uses. This work presents a DC‐TEG technology to harvest mechanical energy from rotational motion for self‐powered electronics.
Introduction Lead is a naturally occurring metal with highly toxic effects on humans, particularly children, who are particularly vulnerable to its long-lasting adverse impacts. Patient concerns This report presents the case of a 10-year-old boy with a 10-month history of recurrent vomiting. No organic lesions were identified. However, the symptoms were inconsistent with cyclic vomiting syndrome (CVS), given the presence of growth retardation, vitamin D deficiency, bilateral cervical lymphadenopathy, academic difficulties, and impaired concentration. Diagnosis Detailed history-taking revealed proximity to a lead mining facility. Blood lead level (BLL) was significantly elevated (382 μg/L), confirming chronic lead poisoning. Interventions Chelation therapy with dimercaptosuccinic acid (DMSA) was administered for 19 days at a 350 mg/m 2 dose per administration. Outcomes Following treatment, BLL decreased to 168 µg/L, accompanied by significant improvement in vomiting and abdominal pain. Conclusion Pediatric lead poisoning should be considered in the differential diagnosis of children presenting with cyclic vomiting and neurological symptoms, due to its diagnostic complexity.
Using the white line intensities, electron energy-loss spectroscopy in a transmission electron microscope has been employed to characterize the valence conversion and oxygen vacancies in La1−xCaxMnO3−y. For a nominal doping composition x=0.33, the ratio of Mn4+ to Mn3+ is determined to be more than 0.25 but less than 0.5, and the content of oxygen vacancy y is no more than 0.065 (equivalent to 2.2 at. % of the oxygen content). At ymax=0.065, 60% of the residual charge introduced by Ca doping is balanced by the conversion of Mn3+to Mn4+ and 40% by oxygen vacancy.
©2000 Materials Research Society. The original publication is available at: http://www.mrs.org/
Piezoelectric semiconductors, such as ZnO and GaN, demonstrate multiproperty coupling effects toward various aspects of mechanical, electrical, and optical excitation. In particular, the three-way coupling among semiconducting, photoexcitation, and piezoelectric characteristics in wurtzite-structured semiconductors is established as a new field, which was first coined as piezo-phototronics by Wang in 2010. The piezo-phototronic effect can controllably modulate the charge-carrier generation, separation, transport, and/or recombination in optical-electronic processes by modifying the band structure at the metal-semiconductor or semiconductor-semiconductor heterojunction/interface. Here, the progress made in using the piezo-phototronic effect for enhancing photodetectors, pressure sensors, light-emitting diodes, and solar cells is reviewed. In comparison with previous works on a single piezoelectric semiconducting nanowire, piezo-phototronic nanodevices built using nanowire arrays provide a promising platform for fabricating integrated optoelectronics with the realization of high-spatial-resolution imaging and fast responsivity.
A novel nanocage structure derived from carboxymethyl-β-cyclodextrins (CMCDs) intercalated in layered double hydroxides (LDHs), whose gates can be controlled by the process of swelling/drying the CMCD−LDH, has been prepared. Furthermore, the extent of opening of this nanocage structure can be controlled by swelling in different solvents. Dodecylbenzene (DDB) as the guest molecule has been incorporated into the nanocage structure through two different routes: intercalation of CMCD in the LDH followed by inclusion of DDB (intercalation−inclusion method) and inclusion of DDB in CMCD followed by intercalation of the host−guest complex into the LDH (inclusion−intercalation method). For the convenience of using this nanocage as an absorbent and storage vessel for neutral guest, films of the resulting composite materials (CMCD−LDH) were fabricated by the method of solvent evaporation on glass substrates. The structures, chemical compositions, morphologies, and physicochemical properties of the materials were fully studied. Moreover, the effects of the combined confinement of both the LDH layers and the cyclodextrin cavity on the encaged guest were investigated. Compared with the confinement effect produced by cyclodextrin only, this double-confinement imposes stronger restrictions on the mobility of the guest molecule, which leads to a blue shift of the fluorescence spectrum and increases the decay time of the guest. Therefore, this structured nanocage might have potential applications as adsorbents, synergistic agents, and storage vessels for neutral molecules.
Ceria nanoparticles are a widely used nanomaterial for applications in catalysts, fuel cell, and microelectronics. An important factor that influences the performance of CeO2 is the particle shape. In this paper, a systematic study has been carried out to determine the shapes of CeO2 nanoparticles. For particles in the size range of 3−10 nm, the particle shape is dominated by truncated octahedral that is defined by the {100} and {111} facets. The fastest growth of the nanoparticles along 〈100〉 results in the disappearance of the {100} facets; thus, the large size CeO2 particles are dominated by the octahedral shape with flat surfaces. The nanoparticles agglomerate by minimizing the interface energy with the formation of a lattice matched "coherent interface". The faceted shape also results in the textured distribution of nanoparticles deposited onto a substrate surface, with a preferred orientation of [110]. These structural characteristics are likely to affect their performance in technological applications.
