Accurate wavelet thresholding method for ECG signals.

Current wavelet thresholding methods for cardiogram signals captured by flexible wearable sensors face a challenge in achieving both accurate thresholding and real-time signal denoising. This paper proposes a real-time accurate thresholding method based on signal estimation, specifically the normalized ACF, as an alternative to traditional noise estimation without the need for parameter fine-tuning and extensive data training. This method is experimentally validated using a variety of electrocardiogram (ECG) signals from different databases, each containing specific types of noise such as additive white Gaussian (AWG) noise, baseline wander noise, electrode motion noise, and muscle artifact noise. Although this method only slightly outperforms other methods in removing AWG noise in ECG signals, it far outperforms conventional methods in removing other real noise. This is attributed to the method's ability to accurately distinguish not only AWG noise that is significantly different spectrum of the ECG signal, but also real noise with similar spectra. In contrast, the conventional methods are effective only for AWG noise. In additional, this method improves the denoising visualization of the measured ECG signals and can be used to optimize other parameters of other wavelet methods to enhancing the denoised periodic signals, thereby improving diagnostic accuracy.

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.

A Fast and Easy-To-Go Method for the Preparation of Au Nanocluster and Its Application for Fe(III) Cation Sensing.

In this article, we reported the synthesis and characterization of gold nanoclusters (AuNCs) with a diameter of ∼2 nm. A simple method of microwave-assisted reaction was applied here, with L-cysteine as both reducing agent and stabilizer. The resulting AuNCs were analyzed by means of TEM, XPS, DLS, and IR. Their photophysical performance was then analyzed in detail, including UV-vis absorption, emission, quantum yield, and lifetime. Efficient red emission was observed from these AuNCs, originating from ligand-to-metal nanoparticle core charge transfer (LMNCT). This red emission was found quenchable by Fe(III) cations. The corresponding quenching curve and sensing performance were discussed. An effective working region of 0-80 µM with an LOD of 3.9 µM was finally observed. Their quenching mechanism was revealed as Fe(III) energy competing for the LMNCT process. The novelty and advancement of this work is the simple synthesis and impressive sensing performance, including wide working region, good linearity, and selectivity.