Local pH environment has been considered to be a potential biomarker for tumor diagnosis because solid tumors contain highly acidic environments. A pH‐sensing nanoprobe based on surface‐enhanced Raman scattering (SERS) using nanostars under near‐infrared excitation has been developed for potential biomedical applications. To theoretically investigate the effect of protonation state on SERS spectra of p‐mercaptobenzoic acid (pMBA), we used the density functional theory (DFT) with the B3LYP functional to calculate Raman vibrational spectra of pMBA‐Au/Ag complex in both protonated and deprotonated states. Vibrational spectral bands were assigned with DFT calculation and used to investigate SERS spectral changes observed from experiment when varying pH value between five and nine. The SERS peak position of pMBA at ~1580 cm−1 was identified to be a novel pH‐sensing index, which has small but noticeable downshift with pH increase. This phenomenon is confirmed and well‐explained with theoretical simulation. The study demonstrates that SERS is a sensitive tool to monitor minor structural changes due to local pH environment, and DFT calculations can be used to investigate Raman spectra changes associated with minor differences in molecular structure. Copyright © 2013 John Wiley & Sons, Ltd.

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Hyperspectral remote sensing can be used to effectively identify contaminated elements in soil. However, in the field of monitoring soil heavy metal pollution, hyperspectral remote sensing has the characteristics of high dimensionality and high redundancy, which seriously affect the accuracy and stability of hyperspectral inversion models. To resolve the problem, a gradient boosting regression tree (GBRT) hyperspectral inversion algorithm for heavy metal (Arsenic (As)) content in soils based on Spearman’s rank correlation analysis (SCA) coupled with competitive adaptive reweighted sampling (CARS) is proposed in this paper. Firstly, the CARS algorithm is used to roughly select the original spectral data. Second derivative (SD), Gaussian filtering (GF), and min-max normalization (MMN) pretreatments are then used to improve the correlation between the spectra and As in the characteristic band enhancement stage. Finally, the low-correlation bands are removed using the SCA method, and a subset with absolute correlation values greater than 0.6 is retained as the optimal band subset after each pretreatment. For the modeling, the five most representative characteristic bands were selected in the Honghu area of China, and the nine most representative characteristic bands were selected in the Daye area of China. In order to verify the generalization ability of the proposed algorithm, 92 soil samples from the Honghu and Daye areas were selected as the research objects. With the use of support vector machine regression (SVMR), linear regression (LR), and random forest (RF) regression methods as comparative methods, all the models obtained a good prediction accuracy. However, among the different combinations, CARS-SCA-GBRT obtained the highest precision, which indicates that the proposed algorithm can select fewer characteristic bands to achieve a better inversion effect, and can thus provide accurate data support for the treatment and recovery of heavy metal pollution in soils.

Perovskite quantum dots (PeQDs) have emerged as a new kind of nanomaterial in various applications, especially light-emitting diodes (LEDs). However, the synthesis of PeQDs is relatively complicated and the electron transport layer (ETL) is usually fabricated in a vacuum because of the dissolution of PeQDs films in organic solvents, which will increase the difficulty and cost in mass production. Here, a simple one-step "ultrasonic bath" treatment to synthesis PeQDs is adopted and applied into the PeQDs-LEDs. Meanwhile, an all-solution process is developed to fabricate PeQDs-LEDs based on the solvent engineering strategy. By using methyl acetate (MeOAc) as the solvent of ETL, the all-solution-processed PeQDs-LEDs exhibit bright luminance with the maximum current efficiency of 3.26 cd/A. This work is simple and easy to be scaled up, which will pave a new way to the low-cost all-solution processable PeQDs-LEDs.

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Conductors with high conductivity and stretchability are the crucial components of smart wearable electronics. However, most of the reported conductors have disadvantages of single function, high energy consumption, which seriously limit their application in wearable electronics. Here, a kind of stretchable (up to 373%), highly conductive (the same order of magnitude as commercial metal wire), and multifunctional sheath‐core fibers based on liquid metal that can be continuously fabricated in large quantity through a coaxial wet‐spinning process are reported. The simple preparation method of the fibers can realize continuous and mass production (1 m min–1 in the laboratory). When the fibers are used as an electric heater, the temperature can reach 58 °C at 0.6 V and the heating rate is obviously faster than the ambient temperature under infrared light. When the fibers are used as a wearable sensor, the tiny force of 0.001 cN can be detected and objects at less than 40 cm can be detected without contact. The stretchable fibers with high electric conductivity may provide strong supports for the commercialization of wearable electronics and pave the way toward full‐fledged multifunctional wearable sensors.

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We report in this paper direct observation of redox-induced uptake of a charged species in micelles with a complex coacervate core, using a system consisting of negatively charged iron-coordination polymers and positively charged-b-neutral block co-polyelectrolytes. Neutral, charge-balanced micelles are first prepared by stoichiometric mixing of the oppositely charged components. Upon a redox stimulus, the micelles develop excess charges, which (as proposed in our previous work) most likely lead to sequestration of oppositely charged species, as the charge balance has to be restored. In this work we verify this prediction by using a rigid, rod-like iron coordination polymer, namely, the positively charged MEPE, as the species to be taken up. After uptake of this rigid cargo, the morphology of the micelles was found to transform from spheres to banana-shaped bundles and fibers, which clearly indicate the uptake of MEPE in the micellar core. Our result proves that the redox stimulus indeed induces excess charges in the core, which forces the self-assembled particles to change both composition and shape. As an interesting example of "adaptive self-assembly", our findings also pave the way to novel redox-triggered uptake and release systems.