ChemNanoMat最新文献

The synthesis of a nanocomposite material consisting of Cu nanoparticles encapsulated in halloysite nanotubes (Cu@Hal) was achieved by the reduction of Cu(NO₃)₂ ⋅ 3H₂O with sodium ascorbate/sodium borohydride in an aqueous suspension of trisodium citrate and halloysite. The nanocomposite was found to be an effective heterogeneous catalyst for the multicomponent copper catalyzed azide-alkyne cycloaddition reaction (CuAAC). A variety of terminal alkynes reacted with benzyl halides and sodium azide in the presence of Cu@Hal in water. In situ formation of the organic azides afforded the corresponding 1,4-disubstituted 1,2,3-triazoles regioselectivily, in excellent yields. The catalyst was easily recovered and recycled without loss of activity with low metal leaching.

Excessive ultraviolet (UV) radiation causes a series of adverse effects on human skin, such as erythema and tanning due to the produce of endogenous melanin of human skin. Inspired by the self-defense mechanism of human skin to prevent UV radiation damage, we construct a natural and biocompatible Carb@PDA−L sunscreen hydrogel by doping melanin-like L-lysine doped polydopamine (PDA−L) to biocompatible poly-γ-glutamic acid based hydrogel matrix Carb, which displays good biosafety, efficient UV shielding performance and excellent antioxidative and anti-inflammatory performance in the application of the skin protection of sun and repair after sunburn. The melanin-like PDA−L can be synthesized by the oxidative polymerization of dopamine triggered by L-lysine under alkali-free condition, which exhibits increase absorption intensity in the UV region and better reactive oxygen species removal performance compared with undoped polydopamine in the perspective of a UV absorber. Meanwhile, PDA−L, as the synthetic analogue of natural melanin, has good biosafety, which can avoid the skin oxidative damage and penetrative toxicity of the conventional sunscreen.

Electrochemical water splitting is considered to be a green and flexible strategy for the mass production of hydrogen fuel, while the high cost and insufficent activity of current cathode catalysts severely suffocate the widespread thriving of hydrogen economy. Herein, we present a bottom-up assembly strategy to the controllable construction of 2D/2D heterojunctions built from cobalt-iron selenide nanolamellas and Ti₃C₂T_x MXene nanosheets. This unique architectural design gives the resulting Co_yFe_1-ySe₂/Ti₃C₂T_x catalysts a series of interesting structural advantages, such as 2D/2D heterostructure, large active surface areas, modulated electronic structure, uniform Co_yFe_1-ySe₂ dispersion, and good electron conductivity, thereby leading to strong synergistic coupling effects. As a consequence, the optimized Co_0.7Fe_0.3Se₂/Ti₃C₂T_x electrocatalyst with an appropriate Co/Fe ratio possesses unusual hydrogen evolution properties in terms of a low overpotential of 69 mV at 10 mA cm⁻², a small Tafel slope of 51 mV dec⁻¹ and reliable long-term durability, which are more competitive than those of bare Ti₃C₂T_x, FeSe₂ and CoSe catalysts.

Localized surface plasmon resonance (LSPR) in plasmonic nanomaterials can concentrate light in the nano-dimension, leading to an enhancement of the light intensity by order of magnitude. While LSPR is a subject of extensive research in chalcogenide semiconductor nanocrystals (NCs), research on tellurium multinary chalcogenides (MnCs) remains elusive, possibly due to non-availability of the corresponding quantum dots (QDs). In this report, we show the sequential switching of plasmonic to non-plasmonic properties during the colloidal synthesis of AgInTe₂ QDs. The reaction passes through several intermediates including AgInTe₂/AgIn₅Te₈ core/shell NCs, AgInTe₂ microrods (MRs), AgInTe₂ QDs, and finally AgInTe₂ quantum dot chain (QDC). Here, the AgInTe₂/AgIn₅Te₈ core/shell NCs and AgInTe₂ QDs depict strong LSPR absorption in the visible-NIR region until ~2000 nm. We propose that small-size quantum confined and cation deficient AgInTe₂ particles are responsible for the observation of LSPR modes in both cases due to presence of the free carriers (holes). Our work on developing Te-based plasmonic MnC QDs may find significant advancement in the nanoscale light-matter interaction in semiconductor research.

Mesoporous thin films modified with nanoparticles of metal (Au) have been used for the fabrication of an ultra-microelectrode array (UMEA). For the first time, UMEAs were studied using probe beam deflection (PBD) and cyclic voltammetry. The study was carried out using the [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ couple as a redox probe. The electrochemical response is that of an array of nanoelectrodes. The effects of scan rate on the current and PBD signal profiles are discussed in the context of mass transport within the pores and at the solution-electrode interface. The study suggests that the combination of PBD and CV allows a better understanding of the mass transport phenomena in this type of UMEAs of complex architecture.

The preparation of high-quality perovskite thin films with long-term stability is the prerequisite for realizing efficient perovskite solar cells (PSCs). In this work, the effect of the bifunctional additive 1-ethyl-3-methylimidazolium acetate (EMIMAc) ionic liquid on defect passivation in perovskite films was systematically investigated. Both theoretical simulations and experimental results reveal that EMIMAc has a strong coordination interaction with the undercoordinated Pb²⁺ through the lone electron pairs of carboxyl functional groups and the electron-rich imidazole moieties, leading to a decreased deep defect density of MAPbI₃ system. Besides, EMIMAc treatment realizes energy band alignment. As a result, the photoelectric conversion efficiency (PCE) of optimized PSCs reaches 17.07 %, and the filling factor (FF) exceeded 74.91 % which is the highest FF for hole transport layer (HTL)-free carbon-based MAPbI₃ devices based on TiO₂ electron transport layer. Moreover, the unencapsulated EMIMAc-modified device maintains approximately 89 % of its initial PCE after 30 days, which demonstrates much better air stability than control devices. These results provide effective strategies for improving the efficiency and long-term stability of HTL-free carbon-based PSCs (H-C-PSCs).

The presence of shape- and size-selective catalysts in various catalytic reactions is of paramount importance. Metal-organic frameworks (MOFs) possess a distinctive characteristic of lacking in-accessible dead spaces, owing to their well-structured nature. The effective separation of active sites within MOFs is facilitated by their exceptionally high surface area, which allows for a high density of active sites per unit volume of the catalyst. In this comprehensive review article, we delve into one of the most critical and practical features of MOFs: their ability to modify and engineer the structure of these materials. This structural engineering approach enables the attainment of desired physical, chemical, and surface properties, particularly in the realm of heterogeneous catalysts. The article encompasses several key areas, including surface functionalization within MOFs, synthesis of novel enzyme-inspired MOFs, creation of mesoporous MOFs, development of porous structures utilizing MOFs, and engineering of structural limitations in MOFs. These rapidly advancing and highly applicable topics, especially in the field of heterogeneous catalysts, are thoroughly investigated and analyzed within the purview of this comprehensive review article.

Titanium dioxide nanoparticles (TiO₂ NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO₂ NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO₂ NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(III) content is positively correlated with the reactivity of TiO₂ NPs. Additionally, these Ti(III) sites could be introduced by reducing commercial TiO₂ NPs using NaBH₄. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO₂ NPs. Utilizing single-molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO₂ nanowires. Achieving sub-nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity.

The photocatalytic conversion of benzylamine into imine is promising for industrial production and environmental protection. To develop photocatalysts with desirable compositions and microstructures is key to achieve high activity and selectivity. Here we propose the immobilization of Bi₂O₂CO₃ on g-C₃N₄ for the photocatalytic conversion of benzylamine. The Bi₂O₂CO₃/g-C₃N₄ catalyst possesses improved light absorption capacity, electron transmission rate and reduced electron-hole recombination than pure Bi₂O₂CO₃. It can efficiently catalyze benzylamine coupling reaction under mild conditions, i. e., at room temperature, with air as oxidant and no additional oxidant involved. The maximum turnover frequency value of N-benzylbenzaldimine reaches 1555.3 μmol g⁻¹ h⁻¹ under this condition. The Bi₂O₂CO₃/g-C₃N₄ catalyst has potential in other photocatalytic reactions.