化学最新文献

Sensitive and accurate detection and imaging of different microRNAs (miRNAs) in cancer cells hold great promise for early disease diagnosis. Herein, a DNA tetrahedral scaffold (DTS)-corbelled autonomous-motion (AM) molecular machine based fluorescent sensing platform was designed for simultaneous detection of two types of miRNAs (miRNA-21 and miRNA-155) in HeLa cells. Locking-strand-silenced DNAzymes (P:L duplex) were firstly grafted at the loop of target-analogue-embedded double-stem hairpin substrates (TDHS) of DTS, making the sensor in a "signal off" state due to the closely distance between modified fluorophores (FAM and Cy5) with the corresponding quenchers (BHQ1 and BHQ2). The detection of miRNA-21 and miRNA-155 was mainly based on the activation of locking-strand-silenced DNAzymes, cleaving hairpin DNA into single-strand DNA segments, accompanying with the release of modified fluorophores and the signal recovery (signal on). Upon the cyclical stimulation of miRNA targets in such AM molecular machine, sensitive detection of miRNA-21 and miRNA-155 was realized in this self-feedback circuit (SFC) with the detection limit down to 38.8 aM and 27.1 aM, respectively. Moreover, the analytical performance was greatly improved for miRNAs imaging in cancer cells with enhanced tumor cell recognition ability, excellent stability in virtue of DTS, indicating a potential analytical tool in early cancer diseases diagnosis.

Porous carbons with large surface area (>3000 m²/g) and heteroatom dopants have shown great promise as electrode materials for zinc ion hybrid capacitors. Centralized mesopores are effective to accelerate kinetics, and edge nitrogen can efficiently enhance pseudocapacitive capability. It is a great challenge to engineer centralized mesopores and edge nitrogen in large-surface-area porous carbons. Herein, a strategy of melamine-boosted K₂CO₃ activation is proposed to prepare edge-nitrogen-doped hierarchical porous carbons (ENHPCs). KOCN generated by K₂CO₃ reacting cyano groups (-CN) couples with K₂CO₃ activation engineers large-surface-area porous carbon. KCN in-situ generated by KOCN etching carbon atoms plays a template role in constructing centralized mesopores. Edge-nitrogen skeleton is formed by g-C₃N₄ losing -CN, and then in-situ integrated into porous carbon skeleton. The efficiency of melamine-boosted K₂CO₃ activation reaches the highest at a melamine/lignin mass ratio of 0.5, where the optimized ENHPCs (ENHPC-0.5) have a large surface area of 3122 m²/g, a mesopore architecture (2.8 nm) with a mesoporosity of 60.5 % and a moderate edge-N content of 1.9 at.%. ENHPC-0.5 cathode displays a high capacitance of 350F/g at 0.1 A/g, an excellent rate capability of 129F/g at 20 A/g and a robust cycling life. This work provides a novel strategy to prepare heteroatom-doped high-surface-area porous carbons for zinc ion hybrid capacitors.

Modern microelectronics industries urgently require dielectric materials with low thermal expansion coefficients, low dielectric constants, and minimal dielectric loss. However, the design principles of materials with low dielectric constants and low thermal expansion are contradictory. In this study, a new diamine monomer containing a dibenzocyclooctadiene unit (DBCOD-NH₂) was designed and synthesized, which was subsequently polymerized with high fluorine content 4,4'-hexafluoroisopr-opylidene diphthalic anhydride and 4,4'-diamino-2,2'-bis(trifleoromethyl)biphenyl to obtain a series of fluorinated polyimides (PIs). Due to the unique conformational transition of the eight-membered carbon ring, the resulting PI can reach a low averaging thermal expansion coefficient (CTE) of only 12.27 ppm/K over 5-150 ℃ with a size change rate of only 0.16 %. Surprisingly, the synergistic effect of DBCOD-NH₂ with the other two monomers enhances the dielectric performance of the PIs. At an electric field frequency of 10 MHz, the dielectric constant (D_k) and the dielectric loss (D_f) can be reduced to as low as 2.61 and 0.00194, respectively. The strategy used herein largely tackles the challenge of balancing low D_k with low CTE. Furthermore, these PI films also exhibit good thermal stability (with 5 wt% weight loss temperatures ranging from 453 to 537 ℃ in N₂, and glass transition temperatures of 305-337 ℃) and robust mechanical properties (with a tensile modulus of 1.88-2.29 GPa and an elongation at break of 6.36-8.11 %). The combination of low thermal expansion and excellent dielectric properties renders these PIs highly promising for applications in the microelectronics and telecommunications industries.

The simultaneous generation of hydrogen (H₂) and the oxidative transformation of organic molecules through photocatalytic processes represents a highly promising dual-purpose strategy. This approach obviates the necessity for sacrificial agents while augmenting catalytic efficiency, thereby facilitating the integrated production of high-value chemicals and renewable energy carriers. Polymeric carbon nitride (PCN) has emerged as a leading candidate among coupled photocatalysts. Nevertheless, PCN's efficacy is constrained by the inefficient separation of charges and the functional limitations of its active sites. Herein, the incorporation of P-N₃ groups into PCN introduces active sites with pronounced charge asymmetry, resulting in strong local charge polarization. This asymmetric charge distribution, mediated by the P-N₃ groups, significantly enhances exciton dissociation. Remarkably, the P-N₃-modified narrow-dimensional fragmented carbon nitride (P-CNNS) achieves an 85 % conversion rate for 4-MBA with nearly 100 % selectivity, and a hydrogen evolution rate of 27.9 mmol g^-1 (with Pt as a co-catalyst), representing 6.2 times higher than that of bulk carbon nitride (BCN). The charge-polarized sites facilitate the transfer of electrons, which is a pivotal process in the activation of 4-methoxybenzyl alcohol (4-MBA). Additionally, these sites serve as adsorption sites, facilitating the oxidation of 4-MBA into anisaldehyde (AA). This work underscores the potential of non-metallic site catalysts for a wide range of coupled photocatalytic applications.

An idea of using ion-exchanger salt containing optically active cations to prepare ion-selective membranes is proposed. Although the presence of an ion-exchanger in the composition of neutral ionophore based sensors is necessary, the choice of available salts for cation-selective sensors preparation, is usually limited to sodium or potassium compounds. In this work we propose application of an alternative salt, using a cation optically active both in absorption and emission mode as a mobile one. Thus, coloured ion-selective membranes can be obtained. This in turn opens new possibilities of monitoring the state of the receptor layer as well as allows direct analytical application of ion-selective membranes in simple optical mode with all benefits related to eliminating the necessity of using reference electrodes. As a model system Nile blue derivative of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion-exchanger was prepared and used to obtain potassium or calcium selective sensors. Selective exchange of ions between the membrane and solution, leading to an increase in optical signal of the solution, can be used to quantify the presence of analyte ions. Thus the sensor pretreatment process is becoming a source of analytical information. The applicability of this approach was verified in determining the presence of potassium ions in the vast majority of interfering ions, e.g. present as impurities in the reagent grade calcium chloride. The resulting potassium ions contents was well comparable with values obtained in course of ICP-MS approach.

Enzyme immobilization techniques are crucial for enhancing enzyme stability and catalytic efficiency. Traditional methods such as physical adsorption and simple covalent binding often fail to maintain enzyme activity and stability. In this study, an innovative multi-level immobilization strategy was proposed to achieve efficient targeted immobilization of nuclease P1 (NP1) by fine-tuning the surface microenvironment. Molecular simulation results revealed that the distinctive electrostatic distribution and the specific placement of basic amino acids, such as lysine, on the NP1 surface caused dopamine to preferentially adsorb on areas away from NP1's active site. This selective adsorption facilitated the directed immobilization of NP1, while the positively charged environment generated by the co-deposited surface further enhanced NP1's adsorption capacity. This multilevel modification was found to significantly optimize the physicochemical environment of the immobilized surface through surface characterization and enzymatic testing. This strategy greatly improves enzyme activity (3590.0 U/mg), stability, and reusability (70 % after 10 cycles). In particular, NP1 on this surface exhibited an optimal Michaelis constant (K_m) of 34.0 mM and a maximum reaction rate of 5.5 mM min^-1, demonstrating the remarkable effect of the modification strategy in enhancing the enzyme catalytic performance. The present study provides an efficient and stable immobilization platform for enzyme catalytic applications by precisely modulating the surface microenvironment and the oriented immobilization strategy, which has an important potential for practical applications. This stable and reusable NP1 platform allows for efficient DNA/RNA cleavage, facilitating its application in industrial biocatalysis, biomedical enzyme-based processes, and biosensors.

This study examined the changing character of the last honours of those who died of COVID-19 in Kashmir and the life experiences of the families of the deceased. A semi-structured interview schedule was used to collect information from 21 participants. Using qualitative data analysis approaches, five key themes were identified vis-à-vis the impact of COVID-19 on burial rituals and customs; effects on bereaved families, shades of grief, bereavement care, community response, and coping with loss. Based on examining the pandemic-induced changes related to customs and rituals around death, the study found that the bereaved family members were in danger of marginalization, economic burdens, psychological traumas, and overall reduced quality of life. This study would be a credible addition to the existing literature on death practices as there is a shortage of research on funeral rituals during the post-pandemic period in Kashmir.

Mercury (II) ions (Hg²⁺) are a significant source of heavy metal contamination in groundwater, posing a serious threat to human health and the environment. Therefore, there is an urgent need for the development of a new detection technique with high sensitivity for monitoring Hg²⁺ in contaminated groundwater. Here, we developed a signal amplifying MOF-based probe (NXS@ZIF-8) for on-site and ultrasensitive dual-channel portable detection of Hg²⁺ in groundwater. The successful grafting of the fluorescent probe (NXS) onto ZIF-8 effectively enhanced the enrichment of the NXS probe, thereby amplifying the detection signal for Hg²⁺. Upon exposure to Hg²⁺, NXS@ZIF-8 quickly emits fluorescent signals, which can be easily detected using portable laser-induced fluorescence spectrometers (LIFs) with a low detection limit of 0.30 ppb. Importantly, the platform enables on-site detection of Hg²⁺ in groundwater samples and direct on-site and in-situ detection of Hg²⁺ in contaminated groundwater, achieving acceptable results. Furthermore, NXS@ZIF-8 was fabricated as a paper-based sensor and integrated into a portable smartphone device for visual detection of Hg²⁺ in contaminated groundwater. This work presents an approach for on-site, in-situ and highly sensitive portable detection of heavy metals in contaminated groundwater, eliminating the need for access to specialized laboratory equipment.