Flexible supercapacitors (SCs) are an emergent and promising technology for next-generation energy storage devices. However, low energy densities hindered their practical applications. Two-dimensional (2D) nanosheets can exhibit excellent electrochemical charge storage properties due to their short ion-diffusion distance and rich electroactive sites with multiple valence states. Herein, we report the direct growth of mesoporous 2D zinc cobaltite nanosheets on a flexible carbon cloth substrate (Zn–Co–O@CC) with an average thickness of ∼45 nm by a facile hydrothermal method at low temperature. The Zn–Co–O@CC electrode displays a high capacitance of 1750, 1573.65 and 1434.37 F g⁻¹ at a current density of 1.5 A g⁻¹ in LiCl, NaCl and KCl neutral aqueous electrolytes, respectively, with excellent rate capabilities at high current densities and demonstrates good cycling stability (>94%) for up to 5000 cycles. Moreover, highly flexible asymmetric supercapacitor (ASC) devices have been fabricated using Zn–Co–O@CC as a positive electrode and bimetallic organic framework (MOF)-derived nanoporous carbon polyhedra (NPC@CC) as a negative electrode (Zn–Co–O@CC//NPC@CC). The as-fabricated ASC can operate at a large potential window of 0.0–2.0 V and shows outstanding energy storage performance by delivering an ultra-high energy density of 117.92 W h kg⁻¹ at a power density of 1490.4 W kg⁻¹ with a cycling stability of 94% after 5000 charge/discharge cycles. To the best of our knowledge, the achieved energy storage performance of the ASC device is very competitive and the highest among all binary metal oxides, carbonaceous materials, and MXene-based SCs and ASCs to date. The applied strategy to fabricate SCs is capable of enhancing both electrochemical activity and cycling stability, and can be readily applied to other metal oxide-based SCs.

We propose a double image encryption by using random binary encoding and gyrator transform. Two secret images are first regarded as the real part and imaginary part of complex function. Chaotic map is used for obtaining random binary matrix. The real part and imaginary part of complex function are exchanged under the control of random binary data. An iterative structure composed of the random binary encoding method is designed and employed for enhancing the security of encryption algorithm. The parameters in chaotic map and gyrator transform serve as the keys of this encryption scheme. Some numerical simulations have been made, to demonstrate the performance this algorithm.

We demonstrate that hollow Gaussian beams can be obtained from Fourier transform of the differentials of a Gaussian beam, and thus they can be generated by spatial filtering in the Fourier domain with spatial filters that consist of binomial combinations of even-order Hermite polynomials. A typical $4f$ optical system and a Michelson interferometer type system are proposed to implement the proposed scheme. Numerical results have proved the validity and effectiveness of this method. Furthermore, other polynomial Gaussian beams can also be generated by using this scheme. This approach is simple and may find significant applications in generating the dark hollow beams for nanophotonic technology.

Graphene oxide–silver (Ag–GO) nanocomposite has emerged as a vital antibacterial agent very recently. In this work, we report a facile one step route of Ag–GO nanocomposite formation excluding the aid of surfactants and reductants and was successfully applied to negative Escherichia Coli (E coli) to investigate antibacterial activity by varying doze concentration. The successful formation of Ag–GO nanocomposite via facile one step route was confirmed using Fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy. The absorption spectra (peak ~ 300 nm) for GO and the (peak ~ 420 nm) for silver nanoparticles were observed. XRD study confirmed the formation of Ag–GO nanocomposite while atomic force microscopy (AFM) showed crumbled GO sheets decorated with Ag nanoparticles. It was observed that the functional groups of GO facilitated the binding of Ag nanoparticles to GO network and enhanced the antibacterial activity of the nanocomposite.