In this work, we have developed a general methodology for constructing an activatable biosensor utilizing a thermoresponsive polymer and two-dimensional nanosheet. We have demonstrated the detection of four different types of biological compounds using the smart PEGMA (poly(ethylene glycol) methyl ether methacrylate), oligonucleotides, and graphene oxide nanoassembly. The activity of the functional nanodevice is controlled with a thermo-switch at 39 °C. In this design, the nanosized graphene oxide serves as a template for fluorophore labeled probe oligonucleotides while quenching the fluorescence intensities dramatically. On the other hand, the PEGMA polymer serves as an activatable protecting layer covering the graphene oxide and entrapping the probe oligonucleotides on the surface. The PEGMA polymers are hydrophobic above their lower critical solution temperature (LCST) and therefore interact strongly with the hydrophobic surface of graphene oxide, creating a closed configuration (OFF state) of the nanodevice. However, once the temperature decreases below the LCST, the polymer undergoes conformational change and becomes hydrophilic. This opens up the surface of the graphene oxide (open configuration, ON state), freeing the encapsulated payload on the surface. We have tuned the activity of the nanodevice for the detection of a sequence-specific DNA, miR-10b, thrombin, and adenosine. The activity of our functional system can be decreased by ∼80% with a thermo-switch at 39 °C. Our approach can be extended to other antisense oligonucleotide, aptamer, or DNAzyme based sensing strategies.

This study reports, for the first time, the fabrication of electrospun Cu 2 ZnSnS 4 (CZTS) nanofibers using metal acetate precursors. Viscous poly(vinyl pyrrolidone) (PVP) solution containing acetate or chloride salts of copper, zinc, and tin was electrospun onto a conductive substrate. The PVP nanofibers that have a mixture of metal salts were annealed at elevated temperatures. After calcination, these nanofibers were treated with the sulfur source and then annealed again in order to generate CZTS nanofibers. The CZTS nanofibers generated from acetate and chloride salts were characterized and compared. Belt-like and wire-like nanofibers were obtained when using metal acetate and chloride precursors, respectively.

Low-cost activated carbon (AC) samples obtained from waste coffee grounds were used for CO 2 and CH 4 adsorption. ACs were prepared by chemical activation and carbonized at three different temperatures. AC carbonized at 800 • C showed a relatively high surface area (582.92 m 2 g −1) and high adsorption capacities of 2.6 mmol g −1 and 1.1 mmol g −1 at 25 • C for CO 2 and CH 4 , respectively. Adsorbent samples were prepared by loading of Fe 3+ metal ions onto ACs and their adsorption capacities were compared with those of nonloaded ACs. As expected, the loading of Fe 3+ metal ions increased the adsorption capacities at all temperatures and the adsorption capacity of Fe 3+-loaded AC carbonized at 800 • C was 3.1 mmol g −1 for CO 2 and 1.2 mmol g −1 for CH 4 at 25 • C. The isosteric heats of adsorption were calculated at 0-35 • C with the range of 20-35 kJ mol −1 and 18-23 kJ mol −1 for CO 2 and CH 4 , respectively. According to our findings, bio-based ACs can be used as an effective and alternative adsorbent for capturing different gas molecules.

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This study involves the preparation and catalytic properties of anatase titanium dioxide nanofibers (TiO2 NFs) supported gold nanoparticles (Au NPs) using a model reaction based on the reduction of 4-nitrophenol (NP) into 4-aminophenol (AP) by sodium borohydride (NaBH4). The fabrication of surfactant-free Au NPs was performed using pulsed laser ablation in liquid (PLAL) technique. The TiO2 NFs were fabricated by a combination of electrospinning and calcination process using a solution containing poly(vinyl pyrolidone)(PVP) and titanium isopropoxide. The adsorption efficiency of laser-generated surfactant-free Au NPs to TiO2 NF supports as a function of pH was analyzed. Our results show that the electrostatic interaction mainly controls the adsorption of the nanoparticles. Au NPs/TiO2 NFs composite exhibited good catalytic activity for the reduction of 4-NP to 4-AP. The unique combination of these materials leads to the development of highly efficient catalysts. Our heterostructured nanocatalysts possibly form an efficient path to fabricate various metal NP/metal-oxide supported catalysts. Thus the applications of PLAL-noble metal NPs can widely broaden.

In the present study, we successfully prepared two different electrospun polyacrylonitrile (PAN) based-activated carbon nanofiber (ACNF) composites by incorporation of well-distributed Fe 2 O 3 and Co 3 O 4 nanoparticles (NPs). The influence of metal oxide on the structural, morphological, and textural properties of final composites was thoroughly investigated. The results showed that the morphological and textural properties could be easily tuned by changing the metal oxide NPs. Even though, the ACNF composites were not chemically activated by any activation agent, they presented relatively high surface areas (S BET ) calculated by Brunauer–Emmett–Teller (BET) equation as 212.21 and 185.12 m 2 /g for ACNF/Fe 2 O 3 and ACNF/Co 3 O 4 composites, respectively. Furthermore, the ACNF composites were utilized as candidate adsorbents for CO 2 and CH 4 adsorption. The ACNF/Fe 2 O 3 and ACNF/Co 3 O 4 composites resulted the highest CO 2 adsorption capacities of 1.502 and 2.166 mmol/g at 0 °C, respectively, whereas the highest CH 4 adsorption capacities were obtained to be 0.516 and 0.661 mmol/g at 0 °C by ACNF/Fe 2 O 3 and ACNF/Co 3 O 4 composites, respectively. The isosteric heats calculated lower than 80 kJ/mol showed that the adsorption processes of CO 2 and CH 4 were mainly dominated by physical adsorption for both ACNF composites. Our findings indicated that ACNF-metal oxide composites are useful materials for designing of CO 2 and CH 4 adsorption systems.