Muhammad Yousuf

Highly Selective and Stable Carbon Dioxide Uptake in Polyindole-Derived Microporous Carbon Materials

Adsorption with solid sorbents is considered to be one of the most promising methods for the capture of carbon dioxide (CO₂) from power plant flue gases. In this study, microporous carbon materials used for CO₂ capture were synthesized by the chemical activation of polyindole nanofibers (PIF) at temperatures from 500 to 800 °C using KOH, which resulted in nitrogen (N)-doped carbon materials. The N-doped carbon materials were found to be microporous with an optimal adsorption pore size for CO₂ of 0.6 nm and a maximum (Brunauer-Emmett-Teller) BET surface area of 1185 m(2) g(-1). The PIF activated at 600 °C (PIF6) has a surface area of 527 m(2) g(-1) and a maximum CO₂ storage capacity of 3.2 mmol g(-1) at 25 °C and 1 bar. This high CO₂ uptake is attributed to its highly microporous character and optimum N content. Additionally, PIF6 material displays a high CO₂ uptake at low pressure (1.81 mmol g(-1) at 0.2 bar and 25 °C), which is the best low pressure CO₂ uptake reported for carbon-based materials. The adsorption capacity of this material remained remarkably stable even after 10 cycles. The isosteric heat of adsorption was calculated to be in the range of 42.7-24.1 kJ mol(-1). Besides the excellent CO₂ uptake and stability, PIF6 also exhibits high selectivity values for CO₂ over N₂, CH₄, and H₂ of 58.9, 12.3, and 101.1 at 25 °C, respectively, and these values are significantly higher than reported values.

Precise tuning of cationic cyclophanes toward highly selective fluorogenic recognition of specific biophosphate anions

Cationic cyclophanes with bridging and spacer groups possess well-organized semirigid cavities and are able to encapsulate and stabilize anionic species through diverse molecular interactions. We highlight the precise tuning of functionalized cyclophanes toward selective recognition of AMP, GTP, and pyrophosphate (PPi) using fluorescence, NMR spectroscopy, and density functional theory (DFT).

Accelerated Bone Regeneration by Two-Photon Photoactivated Carbon Nitride Nanosheets

Human bone marrow-derived mesenchymal stem cells (hBMSCs) present promising opportunities for therapeutic medicine. Carbon derivatives showed only marginal enhancement in stem cell differentiation toward bone formation. Here we report that red-light absorbing carbon nitride (C3N4) sheets lead to remarkable proliferation and osteogenic differentiation by runt-related transcription factor 2 (Runx2) activation, a key transcription factor associated with osteoblast differentiation. Accordingly, highly effective hBMSCs-driven mice bone regeneration under red light is achieved (91% recovery after 4 weeks compared to 36% recovery in the standard control group in phosphate-buffered saline without red light). This fast bone regeneration is attributed to the deep penetration strength of red light into cellular membranes via tissue and the resulting efficient cell stimulation by enhanced photocurrent upon two-photon excitation of C3N4 sheets near cells. Given that the photoinduced charge transfer can increase cytosolic Ca2+ accumulation, this increase would promote nucleotide synthesis and cellular proliferation/differentiation. The cell stimulation enhances hBMSC differentiation toward bone formation, demonstrating the therapeutic potential of near-infrared two-photon absorption of C3N4 sheets in bone regeneration and fracture healing.

Selective detection of guanosine-5′-triphosphate and iodide by fluorescent benzimidazolium-based cyclophanes

New fluorescent benzimidazolium-based receptors selectively display the effective fluorescence quenching effect for biologically important anions, GTP and I(-), in aqueous solution of physiological pH 7.4. These affinities can be attributed to the strong ionic H-bonding along with additional interactions of fluorophore moieties with the nucleic base of GTP and I(-).

High-Affinity-Assisted Nanoscale Alloys as Remarkable Bifunctional Catalyst for Alcohol Oxidation and Oxygen Reduction Reactions

A key challenge in developing fuel cells is the fabrication of low-cost electrocatalysts with high activity and long durability for the two half-reactions, i.e., the methanol/ethanol oxidation reaction (MOR/EOR) and the oxygen reduction reaction (ORR). Herein, we report a conductivity-enhanced bifunctional electrocatalyst of nanoscale-coated Pt-Pd alloys on both tin-doped indium (TDI) and reduced graphene oxide (rGO), denoted as Pt-Pd@TDI/rGO. The mass activities of Pt in the Pt-Pd@TDI/rGO hybrid toward MOR, EOR, and ORR are 2590, 1500, and 2690 mA/mg, respectively. The ORR Pt specific activity and mass activity of the electrocatalyst are 17 and 28 times larger, respectively, than commercial Pt/C catalysts. All these remarkable catalytic performances are attributed to the role of TDI in enhancing the catalytic activity by protecting Pt from oxidation as well as rapid mass/charge transfer due to the synergistic effect between surface Pt-Pd alloys and TDI/rGO.

Turn‐On Ratiometric Fluorescent Probe for Selective Discrimination of Cr3+ from Fe3+ in Aqueous Media for Living Cell Imaging

Pyrene-based turn-on ratiometric fluorescent probe 1 demonstrates high sensitivity and exceptional selectivity toward Cr(3+) in the presence of other metals, including Fe(3+) in aqueous media. Interaction of Cr(3+) with probe 1 brings pyrene moieties close enough to have better aligned π-π stacking, thus enhancing the excimer peak many fold. On the other hand, the interaction of Fe(3+) with probe 1 brings forth a negligible difference in stacking, resulting in an insignificant change in fluorescence intensity. Exceptional selectivity of probe 1 with Cr(3+) over Fe(3+) and other metals has been confirmed by theoretical studies in addition to experimental results. Imaging of HeLa cells observed by confocal fluorescence microscopy reveals that probe 1 can be used to monitor Cr(3+) in live cells to map its subcellular distribution.

An efficient non-reaction based colorimetric and fluorescent probe for the highly selective discrimination of Pd0 and Pd2+ in aqueous media

A novel anthraquinone-imidazole based colorimetric and fluorogenic probe 1 is synthesized, which can discriminate the oxidation states of palladium (Pd0 and Pd2+) by naked eye with high selectivity in aqueous media owing to the difference in coordination within the right sized pocket of the probe molecule. The experimental results (fluorescence, UV/Vis and 1H NMR spectroscopy) aided by density functional theory (DFT) calculations reveal that charge transfer (CT) is the main cause of the selective detection of the oxidation states of palladium. In the 1–Pd2+ complex, which is deficient in electrons, all the electron transitions represent electron transfers from the probe molecule to the central metal atom i.e. partial ligand-to-metal transition excitation while electronically filled Pd0 shows electron transfers from the metal atom to the probe ligand i.e. partial metal-to-ligand transition excitation.

Halides with Fifteen Aliphatic C-H···Anion Interaction Sites.

Since the aliphatic C–H···anion interaction is relatively weak, anion binding using hydrophobic aliphatic C–H (Cali–H) groups has generally been considered not possible without the presence of additional binding sites that contain stronger interactions to the anion. Herein, we report X-ray structures of organic crystals that feature a chloride anion bound exclusively by hydrophobic Cali–H groups. An X-ray structure of imidazolium-based scaffolds using Cali–H···A− interactions (A− = anion) shows that a halide anion is directly interacting with fifteen Cali–H groups (involving eleven hydrogen bonds, two bidentate hydrogen-bond-type binding interactions and two weakly hydrogen-bonding-like binding interactions). Additional supporting interactions and/or other binding sites are not observed. We note that such types of complexes may not be rare since such high numbers of binding sites for an anion are also found in analogous tetraalkylammonium complexes. The Cali–H···A− interactions are driven by the formation of a near-spherical dipole layer shell structure around the anion. The alternating layers of electrostatic charge around the anion arise because the repulsions between weakly positively charged H atoms are reduced by the presence of the weakly negatively charged C atoms connected to H atoms.