Phosphorus doped carbon nanodots particles based on pomegranate peels for highly active dehydrogenation of sodium borohydride in methanol

Here, the carbon nanodots were successfully synthesized from pomegranate peels (PPCD). This obtained PPCD was treated by a hydrothermal process with phosphoric acid for P doping (P doped PPCD) and used as a metal-free catalyst to obtain hydrogen(H₂) from sodium borohydride (NaBH₄) methanolysis for the first time. The characteristics of the samples obtained by ultraviolet, fluorescence, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Inductively coupled plasma mass spectrometry (ICP-MS) analyses were examined. NaBH₄ concentration effect, temperature effect and catalyst reusability experiments were carried out. Using 10 mg of the catalyst with 2.5% NaBH₄, an HGR value of 13000 mL min^?1g^?1 was obtained. The activation energy (Ea) for the P-doped PPCD catalyst was 30.96 kJ mol^?1.     

CdS量子点/CdTe纳米棒光电极制备及其光电性能研究

本文利用化学沉积法和射频溅射法成功实现了CdS量子点/CdTe纳米棒复合光电极的制备。通过X射线粉末衍射(XRD)、扫描电镜(SEM)、紫外-可见吸收光谱(UV-vis)和电化学工作站分别对获得的光电极进行了结构、形貌和光电性能的表征;结果表明,所获得的光电极由CdS量子点和CdTe一维纳米棒组成,其中CdTe纳米棒沿着(111)择优方向定向生长。在不同CdS量子点厚度的光电极的电化学表征结果中,我们发现了由CdS的压电效应引起的新颖的热释电现象,并在25 cycle CdS QDs的光电极测试中获得了最好的结果,开路电压为0.49 V,短路电流为71.09 μA,其I-t曲线的开光比为6。我们在研究过程中还发现了热释电引起的电流反向现象,这一特性对于未来提高光电器件的性能具有重要的意义。     

Preparation and employment of carbon nanodots to improve electron extraction capacity of polyethylenimine interfacial layer for polymer solar cells

The performance of polymer solar cells is substantially enhanced by introducing carbon nanodots as additives in polyethylenimine buffer layer. The most pronounced effect is observed in one type of device with the average power conversion efficiencies increased from 5.78% to 7.56% after the addition of carbon nanodots at an optimal concentration in the interfacial layer, which is mainly attributed to the enhanced light trapping and electron transfer in the devices. Besides the light-harvesting and electron transport capacity improvement, the addition of carbon nanodots can also increase exciton generation and dissociation, leading to a high electron mobility. This study demonstrates a facile approach for enhancing the efficiencies of polymer solar cells.     

‘Beautiful’ unconventional synthesis and processing technologies of superconductors and some other materials

Abstract

Superconducting materials have contributed significantly to the development of modern materials science and engineering. Specific technological solutions for their synthesis and processing helped in understanding the principles and approaches to the design, fabrication and application of many other materials. In this review, we explore the bidirectional relationship between the general and particular synthesis concepts. The analysis is mostly based on our studies where some unconventional technologies were applied to different superconductors and some other materials. These technologies include spray-frozen freeze-drying, fast pyrolysis, field-assisted sintering (or spark plasma sintering), nanoblasting, processing in high magnetic fields, methods of control of supersaturation and migration during film growth, and mechanical treatments of composite wires. The analysis provides future research directions and some key elements to define the concept of ‘beautiful’ technology in materials science. It also reconfirms the key position and importance of superconductors in the development of new materials and unconventional synthesis approaches.     

Size‐Controlled Soft‐Template Synthesis of Carbon Nanodots toward Versatile Photoactive Materials

Size‐controlled soft‐template synthesis of carbon nanodots (CNDs) as novel photoactive materials is reported. The size of the CNDs can be controlled by regulating the amount of an emulsifier. As the size increases, the CNDs exhibit blue‐shifted photoluminescence (PL) or so‐called an inverse PL shift. Using time‐correlated single photon counting, ultraviolet photoelectron spectroscopy, and low‐temperature PL measurements, it is revealed that the CNDs are composed of sp² clusters with certain energy gaps and their oleylamine ligands act as auxochromes to reduce the energy gaps. This insight can provide a plausible explanation on the origin of the inverse PL shift which has been debatable over a past decade. To explore the potential of the CNDs as photoactive materials, several prototypes of CND‐based optoelectronic devices, including multicolored light‐emitting diodes and air‐stable organic solar cells, are demonstrated. This study could shed light on future applications of the CNDs and further expedite the development of other related fields.     

Low voltage bipolar resistive switching in self-assembled PVDF nanodot network in capacitor like structures on Au/Cr/Si with Hg as a top electrode

In this letter, resistive switching phenomena in self-assembled nanodot network of Polyvinylidene fluoride (PVDF) polymer in a capacitor geometry of Hg/PVDF/Au/Cr/Si is investigated. A stable & bipolar resistive switching with a set voltage ranging from 0.35 V to 0.9 V & reset voltage with a range of −0.08 V to −0.25 V is detected. A practical resistance ratio between HRS and LRS of 10–25 may have great potential in organic memories. Possible mechanism for the bipolar switching is discussed with the filament type conduction mechanism. Furthermore, the low voltage switching is elucidated with the high current density associated filament formation and it is explicated using the parallel resistor model.     

Unravelling charge carrier dynamics in protonated g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> interfaced with carbon nanodots as co-catalysts toward enhanced photocatalytic CO<Subscript>2</Subscript> reduction: A combined experimental and first-principles DFT study

In this work,we demonstrated the successful construction of metal-free zerodimensional/two-dimensional carbon nanodot (CND)-hybridized protonated g-C3N4 (pCN) (CND/pCN) heterojunction photocatalysts by means of electrostatic attraction.We experimentally found that CNDs with an average diameter of 4.4 nm were uniformly distributed on the surface of pCN using electron microscopy analysis.The CND/pCN-3 sample with a CND content of 3 wt.％ showed the highest catalytic activity in the CO2 photoreduction process under visible and simulated solar light.Thisprocess results in the evolution of CH4 and CO.The total amounts of CH4 and CO generated by the CND/pCN-3 photocatalyst after 10 h of visible-light activity were found to be 29.23 and 58.82 μmol·gcatalyst-1,respectively.These values were 3.6 and 2.28 times higher,respectively,than the amounts generated when using pCN alone.The corresponding apparent quantum efficiency (AQE) was calculated to be 0.076％.Furthermore,the CND/pCN-3 sample demonstrated high stability and durability after four consecutive photoreaction cycles,with no significant decrease in the catalytic activity.The significant improvement in the photoactivity using CND/pCN-3 was attributed to the synergistic interaction between pCN and CNDs.This synergy allows the effective migration of photoexcited electrons from pCN to CNDs via wellcontacted heterojunction interfaces,which retards the charge recombination.This was confirmed by photoelectrochemical measurements,and steady-state and time-resolved photoluminescence analyses.The first-principles density functional theory (DFT) calculations were consistent with our experimental results,and showed that the work function of CNDs (5.56 eV) was larger than that of pCN (4.66 eV).This suggests that the efficient shuttling of electrons from the conduction band of pCN to CNDs hampers the recombination of electron-hole pairs.This significantly increased the probability of free charge carriers reducing CO2 to CH4 and CO.Overall,this study underlines the importance of understanding the charge carrier dynamics of the CND/pCN hybrid nanocomposites,in order to enhance solar energy conversion.     

One‐Step Synthesis of Superbright Water‐Soluble Silicon Nanoparticles with Photoluminescence Quantum Yield Exceeding 80%

Fluorescent silicon nanoparticles (SiNPs) have shown potential applications in bioimaging/biolabelling, sensing, and nanomedicine/cancer therapy due to their superior properties such as excellent photostability, low cytotoxicity, and versatile surface modification capability. Here, a simple, high‐yield, and one‐pot method is developed to prepare superbright, water‐soluble, and amine‐functionalized SiNPs with photoluminescence quantum yield (PLQY) comparable to fluorescent II–VI semiconductor quantum dots (QDs) but with much lower cytotoxicity. By introducing a commercially available amine‐containing silane molecule, N‐[3‐(trimethoxysilyl)propyl]ethylenediamine (DAMO), water‐soluble SiNPs are prepared with PLQY of 82.4% via a microwave‐assisted method. To the best of our knowledge, this is the highest PLQY value ever reported for water‐soluble fluorescent SiNPs. The silicon element in our SiNPs is mainly four‐valent silicon and thus these SiNPs may also be termed as oxidized silicon nanospheres or silica nanodots. We have also demonstrated the importance of the silane structure (e.g., a suitable amine content) on the photoluminescence property of the prepared SiNPs. As revealed by the time‐resolved photoluminescence technique, the highest PLQY value of DAMO SiNPs is correlated with their monoexponential decay with a relatively long fluorescence lifetime. In addition, the potential use of these SiNPs has also been demonstrated for fluorescent patterning/printing and ion sensing (including Cu²⁺ and Hg²⁺).