Eye-Visible Oxygen Sensing via In-Situ Synthesizing Blue-Emitting Cu(I) Cluster in Red-Emitting COF: Characterization and Performance.

Covalent organic frameworks (COFs) have shown virtues of well-defined and uniform pores with structural diversity, including the shape, size and even chemical nature of pores. These features are excellent for the application of O2 gas optical sensors. In this paper, two oxygen probes based on halogen-bridged Cu cluster were in-situ synthesized in the micropores of COFs, to allow a uniform distribution. The resulting composite samples were characterized in detail to confirm the successful probe loading. The doping level was determined as ~22%. The halogen-bridged Cu clusters showed blue emission peaking at ~440 nm, while COF host showed red emission peaking at 630 nm. These halogen-bridged Cu clusters had long emissive lifetime of ~6.7 µs and high emission quantum yield of 0.30 in pure N2 atmosphere. Given pure O2 atmosphere, lifetime and quantum yield were quenched to 2.5 µs and 0.11, showing oxygen-sensing possibility. A linear oxygen-sensing calibration curve was observed, with sensitivity of 12.25, response time of 13 s and recovery time of 38 s. Sample emission color was changed from blue to red when testing atmosphere was changed from pure N2 to pure O2, which was detectable by eyes.

Ionic modification on COF with rare earth ions for the selective optical sensing and removal of picronitric acid.

In this work, we reported a modified COF material for trinitrophenol (TPA) ratiometric sensing and removal. Here a cationic covalent organic framework (C-COF) was prepared as host, while two Tb(III)-based ions were doped into C-COF as probe by ionic exchange reaction with probe loading level of ∼15%. In the absence of TPA, weak Tb(III) emission (489 nm, 545 nm, 585 nm) and bright red COF emission were observed (633 nm). The addition of TPA increased Tb(III) emission and decreased COF emission, following linear response within TPA concentration region of 0-9 µM. Their limit of detection values were determined as 0.9 µM and 4.5 µM, respectively. Corresponding working equations were fitted as I/I0 = 1.225 + 6.914 × 105 M-1[TPA], R2 = 0.997 for TbCF3-COF and I/I0 = 1.063 + 9.222 × 104 M-1 [TPA], R2 = 0.993 for TbDBM-COF. TbCF3-COF showed better sensing performance than TbDBM-COF, due to its suitable ligand triplet energy level. Their sensing mechanism was revealed as dopant "replacement", where dopant molecules loaded in COF micropore were replaced by TPA molecules, accompanied with energy competing on Tb(III) 5D4 level, showing ratiometric signals. Good selectivity and removal capacity (∼7.4 wt%) for TPA were achieved.

Gliding grasping analysis and hybrid force/position control for unmanned aerial manipulator system.

In this paper, considering the control difficulty of the unmanned aerial manipulator (UAM) interacting with environments, a force analysis during gliding grasping and a hybrid force/position control strategy are proposed for the UAM to enhance control performances during dynamic gliding grasping respectively. First, the instantaneous contact force during the gliding grasping is analyzed by the impulse and momentum theorem, and some factors affecting grasping performance are considered to complete an analysis of grasping force including the irregular shape of the object, the object scrolling, and geometrically asymmetric grasping. Meanwhile, the mass of the grasping object and the inertia tensor are considered unknown bounded items. As a benefit, an accurate dynamics model of the UAM gliding grasping is guaranteed. Second, a hybrid force/position controller based on an adaptive neural network estimator is adopted for UAM to overcome both internal disturbances and external disturbances. The proposed method stability is analyzed through the Lyapunov stability theory. Finally, through a dynamic gliding grasping simulation, the effectiveness and superiority of the proposed scheme are verified.

Enhancing the settling time estimation of fixed-time stability and applying it to the predefined-time synchronization of delayed memristive neural networks with external unknown disturbance.

This paper concentrates on the global predefined-time synchronization of delayed memristive neural networks with external unknown disturbance via an observer-based active control. First, a global predefined-time stability theorem based on a non-negative piecewise Lyapunov function is proposed, which can obtain more accurate upper bound of the settling time estimation. Subsequently, considering the delayed memristive neural networks with disturbance, a disturbance-observer is designed to approximate the external unknown disturbance in the response system with a Hurwitz theorem and then to eliminate the influence of the unknown disturbance. With the help of global predefined-time stability theorem, the predefined-time synchronization is achieved between two delayed memristive neural networks via an active control Lyapunov function design. Finally, two numerical simulations are performed, and the results are given to show the correctness and feasibility of the predefined-time stability theorem.