Novel Core/Shell Nylon 6,6/La-TMA MOF Electrospun Nanocomposite Membrane and CO2 Capture Assessments of the Membrane and Pure La-TMA MOF.

Membrane technology plays a vital, applicable, and essential role in human life and industry. The high adsorption capacity of membranes can be employed for capturing air pollutants and greenhouse gases. In this work, we tried to develop a shaped industrial form of a metal-organic framework as an adsorbent material with the ability to capture CO2 in the laboratory phase. To do so, a core/shell Nylon 6,6/La-TMA MOF nanofiber composite membrane was synthesized. This organic/inorganic nanomembrane is a kind of nonwoven electrospun fiber that was prepared using the coaxial electrospinning approach. FE-SEM, surface area calculations, nitrogen adsorption/desorption, XRD grazing incidence on thin films, and histogram diagrams were applied to assess the quality of the membrane. This composite membrane as well as pure La-TMA MOF were assessed as CO2 adsorbent materials. The CO2 adsorption abilities of the core/shell Nylon 6,6/La-TMA MOF membrane and pure La-TMA MOF were as high as 0.219 and 0.277 mmol/g, respectively. As a result of preparing the nanocomposite membrane from microtubes of La-TMA MOF, the %A of the micro La-TMA MOF (% 43.060) increased to % 48.524 for Nylon 6,6/La-TMA MOF.

Mediator-Free Self-Powered Bioassay for Wide-Range Detection of Dissolved Carbon Dioxide.

Electrochemical sensors for the dissolved CO2 (dCO2) measurement have attracted great interest because of their simple setup and the resulting low costs. However, the developed sensors suffer from the requirement of the external electrical power supply throughout the sensing. Here, the fabrication and evaluation of a self-powered biosensor based on biofuel cells (BFCs) for dCO2 measurements are described. In this device, AuNPs-multiwalled carbon nanotubes/GOx-modified carbon paper (CP) served as a bioanode for the oxidation of glucose, while imine-linked covalent triazine framework (I-CTF)-modified CP was employed as the cathode for the reduction of Fe(CN)63-. I-CTF is a porous organic polymer with a high CO2 capture capacity. Voltammetry and electrochemical impedance spectroscopy confirmed that the electron transfer of Fe(CN)63- on the I-CTF-modified electrode decreases after contacting I-CTF with dCO2. In the designed BFC, by capturing CO2 by the I-CTF-modified cathode, a significant decrease in open-circuit voltage (EOCV) of the BFC was observed, which can be used for the sensitive measurement of dCO2. In addition to the self-powering feature, the EOCV of the BFC sensor can be restored when the captured CO2 is desorbed from the I-CTF-modified cathode by increasing the temperature of the cathode. Finally, the BFC is integrated into a circuit containing a matching capacitor; the charges generated by the BFC are accumulated on the capacitor, and then the instantaneous current is quickly detected using a switching regulator and a digital multimeter. Under optimal conditions, the instantaneous current of the BFC sensor was found to sensitively respond to dCO2 in a wide concentration range from 1.3 × 10-5 to 0.252 atm with a low detection limit of 5 × 10-6 atm.

Large Suspended Monolayer and Bilayer Graphene Membranes with Diameter up to 750 µm.

In this paper ultra clean monolayer and bilayer Chemical Vapor Deposited (CVD) graphene membranes with diameters up to 500 µm and 750 µm, respectively have been fabricated using Inverted Floating Method (IFM) followed by thermal annealing in vacuum. The yield decreases with size but we show the importance of choosing a good graphene raw material. Dynamic mechanical properties of the membranes at room temperature in different diameters are measured before and after annealing. The quality factor ranges from 200 to 2000 and shows no clear dependence on the size. The resonance frequency is inversely proportional to the diameter of the membranes. We observe a reduction of the effective intrinsic stress in the graphene, as well as of the relative error in the determination of said stress after thermal annealing. These measurements show that it is possible to produce graphene membranes with reproducible and excellent mechanical properties.

A miniature gas analyzer made by integrating a chemoresistor with a microchannel.

A microfluidic channel is integrated with a tin oxide-based generic gas sensor on a PMMA (polymethyl methacrylate) substrate to fabricate a miniature gas analyzer. The analyte gas diffuses along the air-filled channel to affect the sensor installed in a microcavity positioned at the end of the channel. Analyte diffusion rates, experimentally estimated based on the temporal responses received from the sensor, are connected to the analyte's interactions with the channel walls as well as its diffusivity in air. The analyte-related information is extracted from the recorded responses and used for analyte recognition. A single PMMA channel of 80 µm × 3 mm × 50 mm dimensions facilitates the correct classification of single component contaminants each introduced in a wide concentration range in air. The device is also shown to identify 15 ppm of 2-butanol in air contaminated with 1500 ppm of 1-butanol. The gas analyzer fabricated based on this concept is durable, inexpensive, handheld and suitable for a variety of applications.

Gas analysis by monitoring molecular diffusion in a microfluidic channel.

Despite the increasing industrial and domestic demand for gas analyzers, the unmanageable size and cost of the available devices prevent them from fulfilling this pervasive need. In this paper, we demonstrate that, monitored by a generic gas sensor, the progress rate of a gaseous analyte's free diffusion through an air-filled centimeter-long microfluidic channel yields sufficient information for gas recognition. The installation of additional channels made from different materials provides more uncorrelated information, enabling more detailed gas analyses. This device classifies gases based on their physical features at room temperature, namely, diffusivity and interaction (physisorption/desorption) with channel walls. This process does not degrade the gas discriminating element of the instrument. Our prototype, featuring a 50 mm long 50 µm bore borosilicate glass channel, successfully differentiated between 24 analytes, including four butanol isomers, and estimated the compositions of their binary and ternary gas mixtures dispersed in air at different concentration levels. The findings presented here are directly applicable to the production of a new inexpensive, compact, portable, and durable generation of artificial olfaction system whose performance is almost entirely independent of the utilized gas sensor's drift.