Rapid and tunable growth of well-ordered hexagonal nanoporous anodic aluminum oxide (AAO) structure by two step high temperature anodization

In this study, we have developed a swift and well-ordered growth of the Anodic Aluminum Oxide (AAO) nanoporous structure by two-step high temperature anodization of pure Aluminum substrate. The pre-anodization surface treatment of the aluminum substrate assists in the formation of well-organized nanoporous structures. The two-step anodization process was performed in 0.3 M of oxalic acid at 20 °C for 40 V and 45 V to obtain tunable pore diameters. The high temperature of the electrolyte solution helps in the rapid growth of the AAO nanoporous structure. The top surface image of AAO shows a well-ordered nanoporous structure with an average pore diameter of 70 nm at 40 V and 100 nm at 45 V. The SEM cross sectional view also illustrates the well-ordered nano channel and the elemental mapping elaborates the presence of aluminum and oxygen. The thickness of the AAO nanoporous structure was determined by using SEM for three anodization time spans (20, 24 and 28 hours), in which an increasing trend was observed. The fabricated AAO has a higher thickness and a well-ordered nanoporous structure that shows it can be used as a template for fabricating nanostructured materials.

2-photon-fabricated nano-fluidic traps for extended detection of single macromolecules and colloids in solution

The analysis of nanoscopic species, such as proteins and colloidal assemblies, at the single-molecule level has become vital in many areas of fundamental and applied research. Approaches to increase the detection timescales for single molecules in solution without immobilising them onto a substrate surface and applying external fields are much sought after. Here we present an easy-to-implement and versatile nanofluidics-based approach that enables increased observational-timescale analysis of single biomacromolecules and nanoscale colloids in solution. We use two-photon-based hybrid lithography in conjunction with soft lithography to fabricate nanofluidic devices with nano-trapping geometries down to 100 nm in height. We provide a rigorous description and characterisation of the fabrication route that enables the writing of nanoscopic 3D structures directly in photoresist and allows for the integration of nano-trapping and nano-channel geometries within micro-channel devices. Using confocal fluorescence burst detection, we validated the functionality of particle confinement in our nano-trap geometries through measurement of particle residence times. All species under study, including nanoscale colloids, α-synuclein oligomers, and double-stranded DNA, showed a three to five-fold increase in average residence time in the detection volume of nano-traps, due to the additional local steric confinement, in comparison to free space diffusion in a nearby micro-channel. Our approach thus opens-up the possibility for single-molecule studies at prolonged observational timescales to analyse and detect nanoparticles and protein assemblies in solution without the need for surface immobilisation.

Role of Host-Guest Interaction in Understanding Polymerisation in Metal Organic Frameworks

<div>Metal-organic frameworks, MOFs, offer an effective templet for</div><div>polymerisation of polymers with precisely controlled structures</div><div>within the sub-nanometre scales. However, synthetic difficulties</div><div>such as monomer infiltration, detailed understanding of polymerisation</div><div>mechanisms within the MOF nano-channels and the</div><div>mechanism for removing the MOF template post polymerisation</div><div>have prevented wide scale implementation of polymerisation in</div><div>MOFs. This is partly due to the significant lack in understanding</div><div>of the energetic and atomic-scale intermolecular interactions</div><div>between the monomers and the MOFs. Consequently in this study,</div><div>we explore the interaction of varied concentration of styrene,</div><div>and EDOT, at the surface and in the nano-channel of Zn2(1,4-</div><div>ndc)2(dabco), where 1,4-ndc = 1,4-naphthalenedicarboxylate</div><div>and dabco = 1,4-diazabicyclo[2.2.2]octane. Our results showed</div><div>that the interactions between monomers are stronger in the</div><div>nano-channels than at the surfaces of the MOF. Moreover, the</div><div>MOF-monomer interactions are strongest in the nano-channels</div><div>and increases with increase in the number of monomers. However,</div><div>as the number of monomer increases, the monomers turn to bind</div><div>more strongly at the surface leading to a potential agglomeration</div><div>of the monomers at the surface.</div>

Role of Host-Guest Interaction in Understanding Polymerisation in Metal Organic Frameworks

<div>Metal-organic frameworks, MOFs, offer an effective templet for</div><div>polymerisation of polymers with precisely controlled structures</div><div>within the sub-nanometre scales. However, synthetic difficulties</div><div>such as monomer infiltration, detailed understanding of polymerisation</div><div>mechanisms within the MOF nano-channels and the</div><div>mechanism for removing the MOF template post polymerisation</div><div>have prevented wide scale implementation of polymerisation in</div><div>MOFs. This is partly due to the significant lack in understanding</div><div>of the energetic and atomic-scale intermolecular interactions</div><div>between the monomers and the MOFs. Consequently in this study,</div><div>we explore the interaction of varied concentration of styrene,</div><div>and EDOT, at the surface and in the nano-channel of Zn2(1,4-</div><div>ndc)2(dabco), where 1,4-ndc = 1,4-naphthalenedicarboxylate</div><div>and dabco = 1,4-diazabicyclo[2.2.2]octane. Our results showed</div><div>that the interactions between monomers are stronger in the</div><div>nano-channels than at the surfaces of the MOF. Moreover, the</div><div>MOF-monomer interactions are strongest in the nano-channels</div><div>and increases with increase in the number of monomers. However,</div><div>as the number of monomer increases, the monomers turn to bind</div><div>more strongly at the surface leading to a potential agglomeration</div><div>of the monomers at the surface.</div>

Two-dimensional metal-organic framework with perpendicular one dimensional nano-channel as precise polysulfides sieves for high efficient lithium−sulfur batteries

Even were regarded as one of the most promising energy storage devices, lithium–sulfur batteries are still suffering from severe “shuttle effects” which hind their further applications. In this work, a...

Direct Numerical Simulation of Nano Channel Flows at Low Reynolds Number

The governing equations of viscous fluid flow are generally represented by Navier–Stokes (NS) equations. The output of Navier Stokes equations is in essence velocity vector from which rest of the flow parameters can be calculated. It is essentially a riotous task, sometimes it becomes so unmanageable that fluid flow over simplest topologies under low Reynold’s numbers also needs the most powerful supercomputing facility to solve, if needed to model the fluid and its behavior under the turbulent conditions the best way out is to solve the averaged NS equations. However in the process of averaging Reynolds introduced certain new terms such as Reynolds Stresses. Therefore it is required to close the system of equations by relating the unknown variables with known ones. Hence we have turbulence models. Direct Numerical Simulation (DNS) is a method of solving NS equations directly that is by forfeiting the need of turbulence models as the equations are not averaged. However originally direct numerical simulation procedure does not need of additional closure equations, it is essential to have very fine grid elements and should be estimated for exceptionally small time steps to achieve precise solutions. In the present chapter an interesting flow through nano-channel problem has been discussed using the indispensable mathematical technique of computational fluid dynamics (CFD) which is DNS.