Selective Electrocatalytic Oxidation of Biomass‐Derived 5‐Hydroxymethylfurfural to 2, 5‐Diformylfuran: from Mechanistic Investigations to Catalyst Recovery

The catalytic transformation of bio-derived compounds, specifi-cally 5-hydroxymethylfurfural (HMF), into value-added chemi-cals may provide sustainable alternatives to crude oil andnatu-ral gas-based products. HMF can be obtained from fructoseand successfully converted to 2,5-diformylfuran (DFF) by an en-vironmentally friendlyorganic electrosynthesis performed in anElectraSyn reactor, using cost-effective and sustainable graph-ite (anode) and stainless-steel (cathode) electrodes in an undi-vided cell, eliminating the need for conventionalpreciousmetal electrodes. In this work, the electrocatalysis of HMF isperformed by using green solvents such as acetonitrile, g-vale-rolactone, as well as PolarClean, which is used in electrocataly-sis for the first time. The reaction parameters and the synergis-tic effects of the TEMPOcatalyst and2,6-lutidine base are ex-plored both experimentally and through computationmodel-ing. The molecular design and synthesis of asize-enlarged C3-symmetric tris-TEMPO catalystare also performed to facilitate asustainable reactionwork-up through nanofiltration. The ob-tained performanceisthen compared with those obtained byheterogeneous TEMPO alternatives recov ered by using an ex-ternal magnetic field and microf iltration. Resultsshow that thisnew methodofelectrocatalytic oxidation of HMF to DFF canbe achieved with excellent selectivity,good yield, and excellent catalyst recovery

Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers

Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16 eV), (0.70-1.58 eV) and (0.22-0.96 eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules. (C) 2017 Published by Elsevier B.V

Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers

Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16 eV), (0.70-1.58 eV) and (0.22-0.96 eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules

Interaction of Nucleobases and Aromatic Amino Acids with Graphene Oxide and Graphene Flakes

In this work, we have studied interactions of nucleobases and aromatic amino acids with graphene (G) and graphene oxide (GO) flakes by ab initio density functional theory (DFT). It is evident from the results that GO complexes are stabilized by hydrogen bonding interactions whereas G complexes are stabilized by π–π interactions, leading to enhanced binding energies for GO complexes compared to G complexes. Moreover, time-dependent DFT (TD-DFT) calculations for the optical properties reveal that the GO nanoflakes and GO–nucleobase composite absorb visible light in the range of 400–700 nm, which may be useful for light-emitting devices. The insights obtained from our study will be useful to understand the role of GO flakes as carriers in targeted drug delivery and biosensors

Controlling the orientation of nucleobases by dipole moment interaction with graphene/h-BN interfaces

The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing and manipulating atomic and molecular entities. In this paper, with the aid of density functional theory, we demonstrate the adsorption characteristics of DNA nucleobases at different interfaces of 2D hybrid nanoflakes of graphene and h-BN. The interfaces provide stronger binding to the nucleobases in comparison to pure graphene and h-BN nanoflakes. It is also revealed that the individual dipole moments of the nucleobases and nanoflakes dictate the orientation of the nucleobases at the interfaces of the hybrid structures. The results of our study point towards a possible route to selectively control the orientation of individual molecules in biosensors

Defected and functionalized Germanene-based nanosensors under sulfur comprising gas exposure

Efficient sensing of sulfur containing toxic gases like HS and SO is of the utmost importance due to the adverse effects of these noxious gases. Absence of an efficient 2D-based nanosensor capable of anchoring HS and SO with feasible binding and an apparent variation in electronic properties upon the exposure of gas molecules has motivated us to explore the promise of a germanene nanosheet (Ge-NS) for this purpose. In the present study, we have performed a comprehensive computational investigation by means of DFT-based first-principles calculations to envisage the structural, electronic, and gas sensing properties of pristine, defected, and metal substituted Ge-NSs. Our initial screening has revealed that although interaction of SO with pristine Ge-NSs is within the desirable range, HS binding however falls below the required values to guarantee an effective sensing. To improve the binding characteristics, we have considered the interactions between HS and SO with defected and metal substituted Ge-NS. The systematic removals of Ge atoms from a reasonably large super cell lead to monovacancy, divacancies, and trivacancies in Ge-NS. Similarly, different transition metals like As, Co, Cu, Fe, Ga, Ge, Ni, and Zn have been substituted into the monolayer to realize substituted Ge-NS. Our van der Waals corrected DFT calculations have concluded that the vacancy and substitution defects not only improve the binding characteristics but also enhance the sensing propensity of both HS and SO. The total and projected density of states show significant variations in electronic properties of pristine and defected Ge-NSs before and after the exposure to the gases, which are essential in constituting a signal to be detected by the external circuit of the sensor. We strongly believe that our present work would not only advance the knowledge towards the application of Ge-NS-based sensing but also provide motivation for the synthesis of such efficient nanosensor for HS and SO based on Ge monolayer

Defected and Functionalized Germanene-based Nanosensors under Sulfur Comprising Gas Exposure

Efficient sensing of sulfur containing toxic gases like H2S and SO2 is of the utmost importance due to the adverse effects of these noxious gases. Absence of an efficient 2D-based nanosensor capable of anchoring H2S and SO2 with feasible binding and an apparent variation in electronic properties upon the exposure of gas molecules has motivated us to explore the promise of a germanene nanosheet (Ge-NS) for this purpose. In the present study, we have performed a comprehensive computational investigation by means of DFT-based first-principles calculations to envisage the structural, electronic, and gas sensing properties of pristine, defected, and metal substituted Ge-NSs. Our initial screening has revealed that although interaction of SO2 with pristine Ge-NSs is within the desirable range, H2S binding however falls below the required values to guarantee an effective sensing. To improve the binding characteristics, we have considered the interactions between H2S and SO2 with defected and metal substituted Ge-NS. The systematic removals of Ge atoms from a reasonably large super cell lead to monovacancy, divacancies, and trivacancies in Ge-NS. Similarly, different transition metals like As, Co, Cu, Fe, Ga, Ge, Ni, and Zn have been substituted into the monolayer to realize substituted Ge-NS. Our van der Waals corrected DFT calculations have concluded that the vacancy and substitution defects not only improve the binding characteristics but also enhance the sensing propensity of both H2S and SO2. The total and projected density of states show significant variations in electronic properties of pristine and defected Ge-NSs before and after the exposure to the gases, which are essential in constituting a signal to be detected by the external circuit of the sensor. We strongly believe that our present work would not only advance the knowledge towards the application of Ge-NS-based sensing but also provide motivation for the synthesis of such efficient nanosensor for H2S and SO2 based on Ge monolayer