Access to N-Difluoromethyl Amides, (Thio)Carbamates, Ureas, and Formamides.

The first efficient access to N-difluoromethyl amides, carbamates, thiocarbamates, ureas, formamides, and their derivatives is reported herein. The synthetic strategy relies on the initial synthesis and straightforward derivatization of N-CF2H carbamoyl fluorides, which were prepared through a desulfurization-fluorination of thioformamides (─NH─C(H)═S) coupled with carbonylation. The newly made N-CF2H carbonyl compounds proved to be highly robust and compatible with numerous chemical transformations and downstream derivatizations, underscoring the potential of this novel motif as a building block in complex functional molecules.

Mono or double Pd-catalyzed C-H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives.

The Pd-catalyzed annulative π-extension of 1,8-dibromonaphthalene for the preparation of fluoranthenes in a single operation has been investigated. With specific arenes such as fluorobenzenes, the Pd-catalyzed double functionalization of C-H bonds yields the desired fluoranthenes. The reaction proceeds via a palladium-catalyzed direct intermolecular arylation, followed by a direct intramolecular arylation step. As the C-H bond activation of several benzene derivatives remains very challenging, the preparation of fluoranthenes from 1,8-dibromonaphthalene via Suzuki coupling followed by intramolecular C-H activation has also been investigated to provide a complementary method. Using the most appropriate synthetic route and substrates, it is possible to introduce the desired functional groups at positions 7-10 on fluoranthenes.

Salt-Templated Nanoarchitectonics of CoSe2-NC Nanosheets as an Efficient Bifunctional Oxygen Electrocatalyst for Water Splitting.

Recently, the extensive research of efficient bifunctional electrocatalysts (oxygen evolution reaction (OER) and hydrogen evolution reaction (HER)) on water splitting has drawn increasing attention. Herein, a salt-template strategy is prepared to synthesize nitrogen-doped carbon nanosheets encapsulated with dispersed CoSe2 nanoparticles (CoSe2-NC NSs), while the thickness of CoSe2-NC NSs is only about 3.6 nm. Profiting from the ultrathin morphology, large surface area, and promising electrical conductivity, the CoSe2-NC NSs exhibited excellent electrocatalytic of 10 mA·cm-2 current density at small overpotentials of 247 mV for OER and 75 mV for HER. Not only does the nitrogen-doped carbon matrix effectively avoid self-aggregation of CoSe2 nanoparticles, but it also prevents the corrosion of CoSe2 from electrolytes and shows favorable durability after long-term stability tests. Furthermore, an overall water-splitting system delivers a current density of 10 mA·cm-2 at a voltage of 1.54 V with resultants being both the cathode and anode catalyst in alkaline solutions. This work provides a new way to synthesize efficient and nonprecious bifunctional electrocatalysts for water splitting.

Design and Embedded Implementation of Secure Image Encryption Scheme Using DWT and 2D-LASM.

In order to further improve the information effectiveness of digital image transmission, an image-encryption algorithm based on 2D-Logistic-adjusted-Sine map (2D-LASM) and Discrete Wavelet Transform (DWT) is proposed. First, a dynamic key with plaintext correlation is generated using Message-Digest Algorithm 5 (MD5), and 2D-LASM chaos is generated based on the key to obtain a chaotic pseudo-random sequence. Secondly, we perform DWT on the plaintext image to map the image from the time domain to the frequency domain and decompose the low-frequency (LF) coefficient and high-frequency (HF) coefficient. Then, the chaotic sequence is used to encrypt the LF coefficient with the structure of "confusion-permutation". We perform the permutation operation on HF coefficient, and we reconstruct the image of the processed LF coefficient and HF coefficient to obtain the frequency-domain ciphertext image. Finally, the ciphertext is dynamically diffused using the chaotic sequence to obtain the final ciphertext. Theoretical analysis and simulation experiments show that the algorithm has a large key space and can effectively resist various attacks. Compared with the spatial-domain algorithms, this algorithm has great advantages in terms of computational complexity, security performance, and encryption efficiency. At the same time, it provides better concealment of the encrypted image while ensuring the encryption efficiency compared to existing frequency-domain methods. The successful implementation on the embedded device in the optical network environment verifies the experimental feasibility of this algorithm in the new network application.

Design of highly selective and stable CsPbI3 perovskite catalyst for photocatalytic reduction of CO2 to C1 products.

Finding efficient photocatalytic carbon dioxide reduction catalysts is one of the core issues in addressing global climate change. Herein, the pristine CsPbI3 perovskite and doped CsPbI3 perovskite were evaluated in carbon dioxide reduction reaction (CO2RR) to C1 products by using density functional theory. Free energy testing and electronic structure analysis methods have shown that doped CsPbI3 exhibits more effective catalytic performance, higher selectivity, and stability than undoped CsPbI3. Additionally, it is discovered that CsPbI3 (100) and (110) crystal surfaces have varied product selectivity. The photo-catalytic effectiveness is increased by the narrower band gap of Bi and Sn doped CsPbI3, which broadens the absorption spectrum of visible light and makes electron transport easier. The calculation results indicate that Bi doped CsPbI3 (100) and CsPbI3 (110) crystal faces exhibit good selectivity towards CH4, with free energy barriers as low as 0.55 eV and 0.58 eV, respectively. Sn doped CsPbI3 (100) and CsPbI3 (110) crystal planes exhibit good selectivity for HCOOH and CH3OH, respectively. The results indicate that the Bi and Sn doped CsPbI3 perovskite catalyst can further improve the CO2 photocatalytic activity and high selectivity for C1 products, making it a suitable substrate material for high-performance CO2RR.

Advances in MXene surface functionalization modification strategies for CO2 reduction.

MXenes, 2D transition metal carbides and nitrides, show great potential in electrocatalytic CO2 reduction reaction (ECO2RR) applications owing to their tunable structure, abundant surface functional groups, large specific surface area and remarkable conductivity. However, the ECO2RR has a complex pathway involving various reaction intermediates. The reaction process yields various products alongside a competitive electrolytic water-splitting reaction. These factors limit the application of MXenes in ECO2RRs. Therefore, this review begins by examining the functionalized modification of MXenes to enhance their catalytic activity and stability via the regulation of interactions between carriers and the catalytic centre. The review firstly covers the synthesis methods and characterisation techniques for functionalized MXenes reported in recent years. Secondly, it presents the methods applied for the functionalized modification of carriers through surface loading of single atoms, clusters, and nanoparticles and construction of composites. These methods regulate the stability, active sites, and metal-carrier electronic interactions. Finally, the article discusses the challenges, opportunities, pressing issues, and future prospects related to MXene-based electrocatalysts.

Pyrolysis Characteristics and Non-Isothermal Kinetics of Integrated Circuits.

Due to the complexity of components and high hazard of emissions, thermochemical conversions of plastics among waste-integrated circuits (ICs) are more favorable compared with the common treatment options of electronic waste (E-waste), such as chemical treatment and burning. In this study, the waste random-access memory, as the representative IC, was used to investigate the thermal degradation behaviors of this type of E-waste, including a quantitative analysis of pyrolysis characteristics and non-isothermal kinetics. The results show that the pyrolysis of the ICs can be divided into three different decomposition stages. The pyrolysis temperature and gas atmosphere play an important role in the pyrolysis reaction, and the heating rate greatly affects the rate of the pyrolysis reaction. The non-isothermal kinetic parameters and reaction mechanisms of ICs are determined using the Friedman method, Coats and Redfern (CR) method, and Kissinger method. The results show that the actual average activation energy of the pyrolysis reaction of ICs should be between 170 and 200 kJ·mol-1. The optimally fitting model for the ICs pyrolysis is the three-step parallel model consisting of the random nucleation model (Am) and reaction order model (Cn).

High-quality restoration image encryption using DCT frequency-domain compression coding and chaos.

With the arrival of the age of big data, the amount and types of data in the process of information transmission have increased significantly, and the full-disk encryption mode used by traditional encryption algorithms has certain limitations of the times. In order to further improve the bandwidth efficiency of digital images in the transmission process and the information effectiveness of digital image transmission, this paper proposes an algorithm of high-quality restoration image encryption using DCT frequency-domain compression coding and chaos. Firstly, the image hash value is used for the generation of an encryption key with plaintext correlation, then lightweight chaos is generated based on the key to obtain a pseudo-random sequence. Secondly, the image is partitioned into subblock, and converted from time domain into frequency domain by employing Discrete Cosine Transform (DCT) on each block, then perform quantization operation based on frequency domain information to obtain DCT coefficient matrix. Thirdly, the direct current (DC) coefficients and alternating current (AC) coefficients are extracted in the DCT coefficient matrix and compressed by different encoding methods to obtain two sets of bitstream containing DC coefficient and AC coefficient information. Fourthly, permute the DC coefficient bit stream by the chaotic sequence, and reconstruct it with the AC coefficient bit stream to obtain the frequency domain ciphertext image. Finally, the chaotic sequence is used to diffuse ciphertext, and the processed hash value is hidden in the ciphertext to obtain the final ciphertext. The theoretical and experimental analysis showed that the key length reaches 341 bits, and the PSNR value of the restored image is close to 60, all of which satisfy the theoretical value. Therefore, the algorithm has the characteristics of high compression rate, high-quality image restoration large key space, strong plaintext sensitivity, strong key sensitivity and so on. Our method proposed in this paper is expected to provide a new idea for confidential and secure communication in the age of big data.

The mechanism of 2-chlorobiphenyl oxidative degradation by nanoscale zero-valent iron in the presence of dissolved oxygen.

It has recently been demonstrated that the addition of nanoscale zero-valent iron (nZVI) to oxygen-containing water or soil aquifers results in the oxidation of organic compounds. However, there has been little insight about the generation of the reactive oxygen species (ROS) that play a vital role in the transformation of contaminants in the presence of nZVI. This study investigated (i) the degradation of 2-chlorobiphenyl (2-CB) by nZVI; (ii) the generation and role of ROS in this process. Under anaerobic and aerobic conditions, the removal efficiency of 2-CB was 65.5 and 59.4%, respectively, after 4 h at a pH of 5.0. The results demonstrated that both the reductive and oxidative processes account for 2-CB degradation under aerobic conditions. Hydroxyl radicals (·OH) generated by nZVI at low pH could efficiently degrade 2-CB, the main reductive dechlorination product was biphenyl. Two other hydroxylation products (2-chlorophenol and 2-hydroxybiphenyl) were also examined. There was a higher degradation efficiency of 2-CB under acidic conditions than basic conditions because more ·OH was generated by nZVI. The presence of natural organic matters (NOMs), including humic acid (HA), salicylic acid (SA), galic acid (GA), and tannic acid (TA), increased the degradation efficiency of 2-CB (k values ranged from 0.0041 to 0.0042 min-1), because NOMs can mediate the electron transfer from the nZVI surface to O2, and facilitate the production of Fe2+ and H2O2 that subsequently form ·OH. The mechanisms of these processes have provided new insights into the role of nZVI in the transformation of organic compounds.