A novel anode material for sodium-ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few-layered MoS 2 by a one-pot spray pyrolysis process is prepared. The fi rst discharge/charge capacities of the composite microspheres are 797 and 573 mA h g −1 at a current density of 0.2 A g −1. The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g −1 is 322 mA h g −1 .The Coulombic effi ciency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS 2 -graphene composite microspheres may be attributed to the reduced stacking of the MoS 2 layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS 2 layers relaxes the strain and lowers the barrier for Na + insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling.
Taking advantage of the high impermeability property of graphene and the sharp surface plasmon resonance (SPR) curve of silver, we numerically demonstrate that SPR imaging biosensors with a graphene-on-silver substrate can be used to achieve the dramatically high sensitivity as well as to prevent silver oxidation. Results of our numerical study show that a silver substrate with a few graphene layers can significantly increase the imaging sensitivity, compared to the conventional gold-film-based SPR imaging biosensor. In particular, single layered graphene deposited on the 60-nm thick silver film amplifies the SPR imaging signal more than three times. Therefore, the proposed SPR substrate could potentially open a new possibility of SPR imaging detection for sensitive and high-throughput assessment of multiple biomolecular interactions.
Yolk-shell-structured MoSe₂ microspheres were prepared via a simple selenization process of MoO₃ microspheres. The yolk-shell-structured MoSe₂ and MoO₃ microspheres delivered initial discharge capacities of 527 and 465 mA h g(-1) in the voltage range of 0.001-3 V vs. Na/Na(+) at a current density of 0.2 A g(-1), respectively, and their discharge capacities after 50 cycles were 433 and 141 mA h g(-1), respectively. The yolk-shell-structured MoSe₂ microspheres also exhibited outstanding high rate capabilities. The hierarchical yolk-shell structure comprised of wrinkled nanosheets facilitated fast Na-ion and electron kinetics, and buffered the large volume changes encountered during cycling.
Counterfeit medicines are a fundamental security problem. Counterfeiting medication poses a tremendous threat to patient safety, public health, and the economy in developed and less developed countries. Current solutions are often vulnerable due to the limited security levels. We propose that the highest protection against counterfeit medicines would be a combination of a physically unclonable function (PUF) with on-dose authentication. A PUF can provide a digital fingerprint with multiple pairs of input challenges and output responses. On-dose authentication can verify every individual pill without removing the identification tag. Here, we report on-dose PUFs that can be directly attached onto the surface of medicines, be swallowed, and digested. Fluorescent proteins and silk proteins serve as edible photonic biomaterials and the photoluminescent properties provide parametric support of challenge-response pairs. Such edible cryptographic primitives can play an important role in pharmaceutical anti-counterfeiting and other security applications requiring immediate destruction or vanishing features.
A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic composite particles of FeO and rGO containing 71% (rGO-FeO-M1), 36% (rGO-FeO-M2), and 18% (rGO-FeO-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-FeO composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-FeO-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure FeO and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-FeO-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and FeO may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward Vibrio fischeri than commercial pure FeO particles.
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