Reversing Organic-Inorganic Hybrid Perovskite Degradation in Water via pH and Hydrogen Bonds.

The moisture instability of organic-inorganic hybrid perovskite solar cells has been a major obstacle to the commercialization, calling for mechanistic understanding of the degradation process, which has been under debate. Here we present a surprising discovery that the degradation is actually reversible, via in situ observation of X-ray diffraction, supported by FTIR and SEM. To isolate the hydrogen bond effect, water was replaced by methanol during the in situ experiment, revealing the decomposition to be initiated by the breakdown of N-H-I hydrogen bonds. This is followed by the step of organic iodide hydrolyzing, which can be inhibited in the neutral environment, making the whole process reversible under variable pH.

Non-invasive blood glucose measurement of 95% certainty by pressure regulated Mid-IR.

To fight against diabetes mellitus, from which more than 400 million people suffer in the world, the patients have to puncture their fingers 4-5 times a day for the blood glucose level checks when using a glucometer, causing invasive pain and the risk of infection. Therefore, non-invasive method has been urged for blood glucose monitoring, among which the mid-infrared spectroscopy (Mid-IR) response of interstitial fluid was found to be promising. However, despite the prolonged effort, the accuracy still falls below the FDA's requirement. To break this barrier which lasted for almost three decades, we discovered the finger contact pressure playing a critical role during the measurement, where the Mid-IR reading could be affected significantly by a small change of the finger posture. In addition, the Mid-IR absorption level was also found to be highly associated with individual, revealing the necessity of adjusting the calibration correlation for each patient. By imposing a certain contact pressure monitored by a pressure transducer, we were able to achieve over 95% certainty from the Mid-IR measurement of glucose concentration and 100% comparability to the "true" glucose concentration for the first time, which was mainly attributed to the morphological change of finger tissue under pressure. The previous works resulted in only about 70% accuracy on average, barely hitting 80 + %, whereas ours reaches 95%, finally exceeding the requirement of FDA.