RSC Advances

Fernández-Herrera, María A.; Barroso-Flores, Joaquín; Merino, Gabriel

doi: 10.1039/d3ra05117jpmid: N/A

This study examines the stability and protonation properties of four potential azahomocubanes. Through high-level ab initio computations, we find that 9-azahomocubane is the most stable isomer, closely followed by 5-azahomocubane, 1-azahomocubane, and 2-azahomocubane. However, understanding the stability of the systems with a nitrogen atom incorporated into a highly constrained polycyclic environment extends beyond mere bond angles or hybridization considerations. Strain energy analysis reveals that azahomocubanes experience less strain compared to their carbon congeners. An exploration of multiple solvents shows that their impact on relative energies and geometries is negligible. On the other hand, among the four isomers, 2-azahomocubane exhibits the highest tendency for protonation. Basicity, as assessed through the minimum electrostatic potential, correlates well with protonation affinities.

Xu, Yuehua; Li, Dongze; Zeng, Qiang; Sun, He; Li, Pengfei

doi: 10.1039/d3ra05079cpmid: 37731832

Utilizing two-dimensional (2D) heterostructures in photocatalysis can enhance optical ab-sorption and charge separation, thereby increasing solar energy conversion efficiency and tackling environmental issues. Density functional theory (DFT) was employed in this study to investigate the structural and optoelectronic properties of the AgBr/SiH van der Waals (vdW) heterostructures. All three configurations (A1, A2, and A3) were stable, with direct bandgaps of 1.83 eV, 0.99 eV, and 1.36 eV, respectively. The type-II band alignment in these structures enables electrons to be transferred from the SiH layer to the AgBr layer, and holes to move in the opposite direction. In the ultraviolet region, the optical absorption coefficients of the A1, A2, and A3 configurations are approximately 4.0 × 105 cm−1, significantly higher than that of an isolated AgBr monolayer (2.4 × 104 cm−1). In the visible light region, the A1 configuration has an absorption coefficient of 4 × 104 cm−1, higher than that of an isolated AgBr (2.2 × 104 cm−1). The band edges of the A1 configuration satisfy the redox potential for photocatalytic water splitting at pH 0–7. When the biaxial tensile strain is 5% for the A2 configuration and 2% for the A3 configuration, it can allow photocatalytic water splitting from half-reactions without strain to photocatalytic overall water splitting at pH 0–7. With a 5% biaxial tensile strain in the visible light region, the A1 and A3 configurations experience a rise in the maximum absorption coefficient of 5.7 × 104 cm−1 and 4.6 × 104 cm−1, respectively. The findings indicate that the AgBr/SiH vdW heterostructure configurations could be utilized in photocatalytic water-splitting processes with great potential.

Nukunudompanich, Methawee; Suzuki, Kazuma; Kameda, Keisuke; Manzhos, Sergei; Ihara, Manabu

doi: 10.1039/d3ra05547gpmid: 37727315

The mechanism of perovskite film growth is critical for the final morphology and, thus, the performance of the perovskite solar cell. The nano-roughness of compact TiO2 (c-TiO2) fabricated via the spray pyrolysis method had a significant effect on the perovskite grain size and perovskite solar cell performance in this work. While spray pyrolysis is a low-cost and straightforward deposition technique suitable for large-scale application, it is influenced by a number of parameters, including (i) alcoholic solvent precursor, (ii) spray temperature, and (iii) annealing temperature. Among alcoholic solvents, 2-propanol and 1-butanol showed a smooth surface without any large TiO2 particles on the surface compared to EtOH. The lowest roughness of the c-TiO2 layer was obtained at 450 °C with an average perovskite grain size of around 300 nm. Increased annealing temperature has a positive effect on the roughness of TiO2. The highest efficiency of the solar cell was achieved by using 1-butanol as the solvent. The decrease in the nano roughness of c-TiO2 promoted larger perovskite grain sizes via a relative decrease in the nucleation rate. Therefore, controlling the spray pyrolysis technique used to deposit the c-TiO2 layer is a promising route to control the surface nanoroughness of c-TiO2, which results in an increase in the MAPbI3 grain size.

Doyle, Bradley; Madden, Leigh A.; Pamme, Nicole; Jones, Huw S.

doi: 10.1039/d3ra03742hpmid: N/A

The study of naturally circulating drug metabolites has been a focus of interest, since these metabolites may have different therapeutic and toxicological effects compared to the parent drug. The synthesis of metabolites outside of the human body is vital in order to conduct studies into the pharmacological activities of drugs and bioactive compounds. Current synthesis methods require significant purification and separation efforts or do not provide sufficient quantities for use in pharmacology experiments. Thus, there is a need for simple methods yielding high conversions whilst bypassing the requirement for a separation. Here we have developed and optimised flow chemistry methods in glass microfluidic reactors utilising surface-immobilised enzymes for sulfonation (SULT1a1) and glucuronidation (UGT1a1). Conversion occurs in flow, the precursor and co-factor are pumped through the device, react with the immobilised enzymes and the product is then simply collected at the outlet with no separation from a complex biological matrix required. Conversion only occurred when both the correct co-factor and enzyme were present within the microfluidic system. Yields of 0.97 ± 0.26 μg were obtained from the conversion of resorufin into resorufin sulfate over 2 h with the SULT1a1 enzyme and 0.47 μg of resorufin glucuronide over 4 h for UGT1a1. This was demonstrated to be significantly more than static test tube reactions at 0.22 μg (SULT1a1) and 0.19 μg (UGT1a1) over 4 h. With scaling out and parallelising, useable quantities of hundreds of micrograms for use in pharmacology studies can be synthesised simply.

Li, Ren; Zhang, Lei; Wang, Yi; Bai, Jinbo; Li, Xiaolin; Zhang, Chunmei

doi: 10.1039/d3ra04270gpmid: 37731826

Fe–N–C material, known for its high efficiency, cost-effectiveness, and environmental friendliness, is a promising electrocatalyst in the field of the oxygen reduction reaction (ORR). However, the influence of defects and coordination structures on the catalytic performance of Fe–N–C has not been completely elucidated. In our present investigation, based on density functional theory, we take an Fe adsorbed graphene structure containing a 5–8–5 divacancy (585DV) defect as a research model and investigate the influence of the coordination number of N atoms around Fe (Fe–NxC(4−x)) on the ORR electrocatalyst behavior in alkaline conditions. We find that the Fe–N4 structure exhibits superior ORR catalytic performance than other N coordination structures Fe–NxC4−x (x = 0–3). We explore the reasons for the improved catalytic performance through electronic structure analysis and find that as the N coordination number in the Fe–NxC(4−x) structure increases, the magnetic moment of the Fe single atom decreases. This reduction is conducive to the ORR catalytic performance, indicating that a lower magnetic moment is more favorable for the catalytic process of the ORR within the Fe–NxC(4−x) structure. This study is of great significance for a deeper understanding of the structure–performance relationship in catalysis, as well as for the development of efficient ORR catalysts.

Zhang, Jianen; Chen, Mingjun; Ren, Xiaojie; Shi, Weicai; Yin, Tao; Luo, Tao; Lan, Youshi; Li, Xu; Guan, Li

doi: 10.1039/d3ra05031apmid: N/A

The influence of sp2- and sp3-hybridized carbon coexisting in carbon cores on fluorescence characteristics of carbon dots (CDs) was revealed by density functional theory calculations. Based on the constructed coronene-like structures, the fluorescence emission spectra, transition molecular orbital pairs and several physical quantities describing the distribution of electrons and holes were investigated. The results indicate that due to the interaction between sp2 and sp3 carbon atoms, two main factors including the hyperconjugative effect and the separation of sp2 domain by sp3 carbon atoms can regulate the fluorescence wavelength. By analyzing the transition molecular orbital pairs, it was found that the fluorescence wavelength has a close correlation with the conjugation length, suggesting that the conjugation length can predict the shift of the emission spectra of CDs. The theoretical results provide a comprehensive understanding of fluorescence mechanism and help to synthesize CDs with expected fluorescence wavelength.

Ayoup, Mohammed Salah; Wahby, Yasmin; Abdel-Hamid, Hamida; Abu-Serie, Marwa M.; Ramadan, Sherif; Barakat, Assem; Teleb, Mohamed; Ismail, Magda M. F.

doi: 10.1039/d3ra04029apmid: 37736568

Selective induction of breast cancer apoptosis is viewed as the mainstay of various ongoing oncology drug discovery programs. Passerini scaffolds have been recently exploited as selective apoptosis inducers via a caspase 3/7 dependent pathway. Herein, the optimized Passerini caspase activators were manipulated to synergistically induce P53-dependent apoptosis via modulating the closely related P53-MDM2 signaling axis. The adopted design rationale and synthetic routes relied on mimicking the general thematic features of lead MDM2 inhibitors incorporating multiple aromatic rings. Accordingly, the cyclization of representative Passerini derivatives and related Ugi compounds into the corresponding diphenylimidazolidine and spiro derivative was performed, resembling the nutlin-based and spiro MDM-2 inhibitors, respectively. The study was also extended to explore the apoptotic induction capacity of the scaffold after simplification and modifications. MTT assay on MCF-7 and MDA-MB231 breast cancer cells compared to normal fibroblasts (WI-38) revealed their promising cytotoxic activities. The flexible Ugi derivatives 3 and 4, cyclic analog 8, Passerini adduct 12, and the thiosemicarbazide derivative 17 were identified as the study hits regarding cytotoxic potency and selectivity, being over 10-folds more potent (IC50 = 0.065–0.096 μM) and safer (SI = 4.4–18.7) than doxorubicin (IC50 = 0.478 μM, SI = 0.569) on MCF-7 cells. They promoted apoptosis induction via caspase 3/7 activation (3.1–4.1 folds) and P53 induction (up to 4 folds). Further apoptosis studies revealed that these compounds enhanced gene expression of BAX by 2 folds and suppressed Bcl-2 expression by 4.29–7.75 folds in the treated MCF-7 cells. Docking simulations displayed their plausible binding modes with the molecular targets and highlighted their structural determinants of activities for further optimization studies. Finally, in silico prediction of the entire library was computationally performed, showing that most of them could be envisioned as drug-like candidates.

Chen, Wei-Cheng; Qi, Xiaoding

doi: 10.1039/d3ra05191apmid: 37731828

BiFe1−2xMnxMgxO3 (BFMM, x = 0−8%) was mixed with exfoliated g-C3N4 (GCN) to form a composite for establishing an S-scheme heterojunction for photodegradation. BFMM was synthesized by sol–gel method, and showed a decreased band gap from 2.24 eV to 1.75 eV as x increased from 0% to 7%, allowing a more efficient absorption of sunlight. GCN was prepared by thermal polymerization of melamine and then exfoliated to form nanosheets by sulfur acid in order to increase the specific surface area and thus increase reaction sites. A composite with a weight ratio of BFMM/GCN equal to 1 : 3 was prepared by sintering the powder mixture at 300 °C. Such a composite showed a greatly improved efficiency in photodegradation of methylene blue, which was over 6 times faster than pristine BiFeO3, and the Mn/Mg co-doping improved the efficiency by 48%. The Mott–Schottky plots showed that both GCN and BFMM are n-type semiconductors with flat-band potentials of −0.79 and +0.11 V (vs. NHE), respectively. So, the band alignment allowed the S-scheme to work, leading to an efficient separation of photogenerated electrons and holes, which was confirmed by the greatly increased photocurrents measured with the composites.

Wang, Haoxiang; Tang, Chengli; Xu, Jun

doi: 10.1039/d3ra05232jpmid: 37727318

Flexible humidity sensors have found new applications in diverse fields including human healthcare, the Internet of Things, and so on. In this paper, a highly sensitive humidity sensor based on carboxymethyl cellulose@graphene and conductive adhesive tape was developed. The sensor was constructed on conductive tape which acted as both of the flexible substrate and the electrode to transmit electronic signals. A carboxymethyl cellulose@graphene composite was assembled on the substrate as the sensing layer by a simple spreading method in a 3-D printed groove mold. The sensitive material was characterized for its morphology, composition, crystalline phase, and hydrophilicity by SEM, EDS, XRD, and contact angle measurements. The effect of graphene on the sensitivity was investigated in detail by adjusting the doping concentration. Humidity sensing performance was tested in different relative humidity levels. The rapid responses under different respiratory conditions demonstrated their practical usability in continuous respiration monitoring and recognition of respiratory status. The conductive mechanism of the sensing film was studied by complex impedance spectroscopy under different relative humidity levels. A rational sensing mechanism was proposed integrating ionic conduction, electron conduction and swelling behavior of the carboxymethyl cellulose@graphene composite.

Kiani, Rana; Steimecke, Matthias; Alqaisi, Marah; Bron, Michael; Sebastiani, Daniel; Partovi-Azar, Pouya

doi: 10.1039/d3ra02980hpmid: N/A

Optimization of lithium–sulfur batteries highly depends on exploring and characterizing new cathode materials. Sulfur/carbon copolymers have recently attracted much attention as an alternative class of cathodes to replace crystalline sulfur. In particular, poly(sulfur-n-1,3-diisopropenylbenzene) (S/DIB) has been under considerable experimental and theoretical investigations, promising a good performance in mitigating the so-called shuttle effect. Here, combining ab initio Raman spectroscopy simulations with experimental measurements, we show that S/DIB copolymers containing short and long sulfur chains are distinguishable based on their Raman activity in 400–500 cm−1. This frequency range corresponds to S–S stretching vibrations and is only observed in the Raman spectra of those copolymers with longer sulfur chains. The results reported in this study have direct applications in identification and characterization of general sulfur/carbon copolymers with different sulfur contents.