Reduction of N , N -dimethylcarboxamides to aldehydes by sodium hydride-iodide composite

A new and concise protocol for selective reduction of N,N‐dimethylamides into aldehydes was established using sodium hydride (NaH) in the presence of sodium iodide (NaI) under mild reaction conditions. The present protocol with the NaH‐NaI composite allows for reduction of not only aromatic and heteroaromatic but also aliphatic N,N‐dimethylamides with wide substituent compatibility. Retention of α‐chirality in the reduction of α‐enantioriched amides was accomplished. Use of sodium deuteride (NaD) offers a new step‐economical alternative to prepare deuterated aldehydes with high deuterium incorporation rate. The NaH‐NaI composite exhibits unique chemoselectivity for reduction of N,N‐dimethylamides over ketones.MOE (Min. of Education, S’pore)EDB (Economic Devt. Board, S’pore)Accepted versio

Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides

New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2 ). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2 )∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H-Zn-Cl)2 is the key species for the production of amines.Ministry of Education (MOE)Accepted versionThis work was supported by funding from Nanyang Technological University (NTU) (for S.C.), the Singapore Ministry of Education (Academic Research Fund Tier 1: RG10/17 for S.C.), and Takeda Science Foundation (for R.T.). Computations were performed using Research Center for Computational Science at Okazaki, Japan. We thank Prof. Subodh G. Mhaisalkar (School of Materials Science and Engineering, NTU) and Prof. Han Sen Soo (School of Physical and Mathematical Sciences, NTU) for the assistance in powder X‐ray diffraction (XRD) experiments

A Novel Method for Food Market Regulation by Emotional Tendencies Predictions from Food Reviews Based on Blockchain and SAEs

As a part of food safety research, researches on food transactions safety has attracted increasing attention recently. Food choice is an important factor affecting food transactions safety: It can reflect consumer preferences and provide a basis for market regulation. Therefore, this paper proposes a food market regulation method based on blockchain and a deep learning model: Stacked autoencoders (SAEs). Blockchain is used to ensure the fairness of transactions and achieve transparency within the transaction process, thereby reducing the complexity of the trading environment. In order to enhance the usability, relevant Web pages have been developed to make it more friendly and conduct a security analysis for using blockchain. Consumers’ reviews after the transactions are finished can be used to train SAEs in order to perform emotional tendencies predictions. Compared with different advanced models for predictions, the test results show that SAEs have a better performance. Furthermore, in order to provide a basis for the formulation of regulation strategies and its related policies, case studies of different traders and commodities have also been conducted, proving the effectiveness of the proposed method

Enabling Efficient Folding and High-Resolution Crystallographic Analysis of Bracelet Cyclotides

Cyclotides have attracted great interest as drug design scaffolds because of their unique cyclic cystine knotted topology. They are classified into three subfamilies, among which the bracelet subfamily represents the majority and comprises the most bioactive cyclotides, but are the most poorly utilized in drug design applications. A long-standing challenge has been the very low in vitro folding yields of bracelets, hampering efforts to characterize their structures and activities. Herein, we report substantial increases in bracelet folding yields enabled by a single point mutation of residue Ile-11 to Leu or Gly. We applied this discovery to synthesize mirror image enantiomers and used quasi-racemic crystallography to elucidate the first crystal structures of bracelet cyclotides. This study provides a facile strategy to produce bracelet cyclotides, leading to a general method to easily access their atomic resolution structures and providing a basis for development of biotechnological applications

MXene nanosheets functionalized with Cu atoms for urea adsorption in aqueous media

Ti3C2Tx MXene is an emerging family of two-dimensional materials, and because of its large specific surface area, it has potential for many applications. Herein, a new application using Cu-doped MILD (minimally intensive layer delamination) synthesized Ti3C2Tx MXene for urea removal is demonstrated. The doping of Cu on MXene results in an increase in its affinity for urea adsorption as compared to the pristine MILD synthesized MXene due to the formation of the Cu−urea complex. Previous computational studies have shown that the adsorption energies of urea on the MXene surface can be improved in the presence of Cu. The valence state of Cu in the doped MILD synthesized MXene, which binds on to the surface via Ti−O−Cu linkage, is between 0 and +1 as verified by XAS and XPS. As the optimal urea adsorption occurs on Cu as a single atom site, an increase in Cu doping on MXene does not increase urea removal due to Cu agglomeration. Looking at the adsorption behaviour, it seems that Cu-doped MXene follows the monolayer adsorption on homogenous surface model.Ministry of Education (MOE)Submitted/Accepted versionWe would like to acknowledge the Ministry of Education Research Scholarship, Singapore, for supporting the project

Photocatalytic degradation of methylene blue Using N-doped ZnO/carbon dot (N-ZnO/CD) nanocomposites derived from organic soybean

This study reports on successful synthesis of carbon dots (CDs), nitrogen-doped zinc oxide (N-ZnO), and N-ZnO/CD nanocomposites as photocatalysts for degradation of methylene blue. The first part was the synthesis of CDs utilizing a precursor from soybean and ethylenediamine as a dopant by a hydrothermal method. The second part was the synthesis of N-ZnO with urea as the nitrogen dopant carried out by a calcination method in a furnace at 500 °C for 2 h in an N2 atmosphere (5 °C min-1). The third part was the synthesis of N-ZnO/CD nanocomposites. The characteristics of CDs, N-ZnO, and N-ZnO/CD nanocomposites were analyzed through Fourier transform infrared (FTIR), UV-vis absorbance, photoluminescence (PL), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), thermal gravimetry analysis (TGA), field-emission scanning electron microscopy energy-dispersive spectroscopy (FESEM EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analysis. Based on the HR-TEM analysis, the CDs had a spherical shape with an average particle size of 4.249 nm. Meanwhile, based on the XRD and HR-TEM characterization, the N-ZnO and N-ZnO/CD nanocomposites have wurtzite hexagonal structures. The materials of N-ZnO and N-ZnO/CD show increased adsorption in the visible light region and low energy gap E g. The E g values of N-ZnO and N-ZnO/CDs were found to be 2.95 and 2.81 eV, respectively, whereas the surface area (S BET) values 3.827 m2 g-1 (N-ZnO) and 3.757 m2 g-1(N-ZnO/CDs) belonged to the microporous structure. In the last part, the photocatalysts of CDs, N-ZnO, and N-ZnO/CD nanocomposites were used for degradation of MB (10 ppm) under UV-B light irradiation pH = 7.04 (neutral) for 60 min at room temperature. The N-ZnO/CD nanocomposites showed a photodegradation efficiency of 83.4% with a kinetic rate of 0.0299 min-1 higher than N-ZnO and CDs. The XRD analysis and FESEM EDS of the N-ZnO/CDs before and after three cycles confirm the stability of the photocatalyst with an MB degradation of 58.2%. These results have clearly shown that the N-ZnO/CD nanocomposites could be used as an ideal photocatalytic material for the decolorization of organic compounds in wastewater.Published versionThe authors are grateful for the financial support from KEMENRISTEK DIKTI, Republic Indonesia, DRPM-PTM 2022 program with contract number of 097/E5/PG.02.00.PT/ 2022 and thankful for the School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore, for help to conducting the XPS and HR-TEM analysis of the photocatalyst materials in this study

High-performance semi-transparent perovskite solar cells with over 22% visible transparency: pushing the limit through MXene interface engineering

Semi-transparent perovskite solar cells (ST-PSCs) have attracted enormous attention recently due to their potential in building-integrated photovoltaic. To obtain adequate average visible transmittance (AVT), a thin perovskite is commonly employed in ST-PSCs. While the thinner perovskite layer has higher transparency, its light absorption efficiency is reduced, and the device shows lower power conversion efficiency (PCE). In this work, a combination of high-quality transparent conducting layers and surface engineering using 2D-MXene results in a superior PCE. In situ high-temperature X-ray diffraction provides direct evidence that the MXene interlayer retards the perovskite crystallization process and leads to larger perovskite grains with fewer grain boundaries, which are favorable for carrier transport. The interfacial carrier recombination is decreased due to fewer defects in the perovskite. Consequently, the current density of the devices with MXene increased significantly. Also, optimized indium tin oxide provides appreciable transparency and conductivity as the top electrode. The semi-transparent device with a PCE of 14.78% and AVT of over 26.7% (400-800 nm) was successfully obtained, outperforming most reported ST-PSCs. The unencapsulated device maintained 85.58% of its original efficiency after over 1000 h under ambient conditions. This work provides a new strategy to prepare high-efficiency ST-PSCs with remarkable AVT and extended stability.Nanyang Technological UniversityNational Research Foundation (NRF)Submitted/Accepted versionThis research was supported by grants from the National Research Foundation, Prime Minister’s Office, Singapore, under its Campus of Research Excellence and Technological Enterprise (CREATE) program. T.C.S. and M.F. acknowledge the support from Nanyang Technological University under its start-up grant (M4080514) and the National Research Foundation (NRF), Singapore, under its NRF Investigatorship (NRF-NRFI-2018-04)

Can the Helium-detonation Model Explain the Observed Diversity of Type Ia Supernovae?

We study a sample of 16 Type Ia supernovae (SNe Ia) having both spectroscopic and photometric observations within 2–3 days after the first light. The early B − V colors of such a sample tend to show a continuous distribution. For objects with normal ejecta velocity (NV), the C ii λ6580 feature is always visible in the early spectra, while it is absent or very weak in the high-velocity (HV) counterpart. Moreover, the velocities of the detached high-velocity features (HVFs) of the Ca II near-IR triplet (CaIR3) above the photosphere are found to be much higher in HV objects than in NV objects, with typical values exceeding 30,000 km s−1 at 2–3 days. We further analyze the relation between the velocity shift of late-time [Fe II] lines (v[Fe II]) and host galaxy mass. We find that all HV objects have redshifted v[Fe II], while NV objects have both blue- and redshifted v[Fe II]. It is interesting to point out that the objects with redshifted v[Fe II] are all located in massive galaxies, implying that HV and a portion of NV objects may have similar progenitor metallicities and explosion mechanisms. We propose that, with a geometric/projected effect, the He-detonation model may account for the similarity in birthplace environment and the differences seen in some SNe Ia, including B − V colors, C II features, CaIR3 HVFs at early times, and v[Fe II] in the nebular phase. Nevertheless, some features predicted by He-detonation simulation, such as the rapidly decreasing light curve, deviate from the observations, and some NV objects with blueshifted nebular v[Fe II] may involve other explosion mechanisms