Confidential multiple-input multiple-output optical camera communication aided by a two-dimensional pilot.

Optical camera communication (OCC) has attracted increased attention for its inherent security advantage. However, there still exists the risk of eavesdropping on the broadcasting channel of OCC. To achieve confidential communication, we propose the confidentiality-interference dual light-emitting diode (LED) communication (CIDLC) scheme at the transmitter (TX) and elimination of interference (EI) scheme at the receiver (RX). Meanwhile, interference signals refer to the bit shift of confidential signals. Further, we propose the two-dimensional pilot-aided channel estimation (2D-PACE) scheme to enhance the reliability of multiple-input multiple-output (MIMO) OCC. Experiment results validate the effectiveness of our schemes, which guarantee confidentiality while performing well at a 2 m non-line-of-sight (NLOS) distance. Finally, the communication-illumination integration OCC is constructed via the energy equalization coding (EEC) scheme.

Morphology Engineering of BiVO4 with CoOx Derived from Cobalt-containing Polyoxometalate as Co-catalyst for Oxygen Evolution.

Bismuth vanadate (BiVO4 ) as a metal oxidation semiconductor has stimulated extensive attention in the photocatalytic water splitting field. However, the poor transport ability and easy recombination of charge carriers limit photocatalytic water oxidation activity of pure BiVO4 . Herein, the photocatalytic activity of BiVO4 is enhanced via adjusting its morphology and combination co-catalyst. First, the Cu-BiVO4 was synthesized by copper doping to control the growth of {110} facet of BiVO4 , which is regarded for the separation of photo-generated charge carriers. Then the CoOx in-situ generated from K6 [SiCoII (H2 O)W11 O39 ] ⋅ 16H2 O was photo-deposited on Cu-BiVO4 surface as co-catalyst to speed up reaction kinetics. Cu-BiVO4 @CoOx hybrid catalyst shows highest photocatalytic activity and best stability among all the prepared catalysts. Oxygen evolution is about 34.6 µmol in pH 4 acetic acid buffer under 420 nm LED irradiation, which is nearly 20 times higher than that of pure BiVO4 . Apparent quantum efficiency (AQE) in 1 h and O2 yield are 1.83% and 23.1%, respectively. O2 evolution amount nearly maintains the original value even after 5 cycles.