DNAzyme crosslinked hydrogel: a new platform for visual detection of metal ions

We propose the use of DNAzyme as a crosslinker of hydrogel to develop a catalytic platform for the sensing of metal ions. The DNAzyme crosslinked hydrogel can undergo gel-sol transition in response to Cu(2+) ions, which enables sensitive visual detection of Cu(2+) by observing the release of pre-trapped AuNPs.     

A novel fluoride ion colorimetric chemosensor based on coumarin

A novel visible colorimetric sensor (L1) with high selectivity for fluoride ion based on coumarin has been synthesized by a simple modification of our earlier report. The chemosensor L1 shows an obvious color change from yellow to blue upon addition of fluoride ion with a large red shift of 145 nm in acetonitrile, and without interference of other anions such as Cl-, Br-, I-, NO3-, H2PO4-, HSO4-, and AcO-. The investigation of 1H NMR spectrum titration indicates the proposed mechanism is that F- first establishes a hydrogen bonding interaction with L1, and then the formation of [F-H-F]- induces deprotonation.     

K(+)-recognition capsules with squirting release mechanisms

K(+)-recognition capsules are developed to translate K(+)-recognition into a squirting release function. Upon recognition of K(+), the capsules shrink rapidly and squirt out encapsulated oil cores due to the cooperative interaction of host-guest complexation and phase transition in capsule membranes. The capsules provide a promising model for K(+)-recognition smart functional systems.     

Enhanced catalytic performance of assembled ceria necklace nanowires by Ni doping

Ceria and nickel-doped ceria necklace-like nanowires were synthesized by a facile, surfactant free method, through an unconventional assembly route. Homogeneous doping of lower-valent cations introduces elastic strain, resulting in extrinsic surface defects and higher catalytic performance in CO oxidization.     

Graphene–Pt nanocomposite for nonenzymatic detection of hydrogen peroxide with enhanced sensitivity

A sensitive hydrogen peroxide (H₂O₂) sensor was fabricated based on graphene–Pt (GN–Pt) nanocomposite. The GN–Pt was synthesized by photochemical reduction of K₂PtCl₄ on GNs, and characterized by atomic force microscope (AFM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical investigations indicated that the GN–Pt exhibited a high peak current and low overpotential towards the reduction of H₂O₂. The GN–Pt modified glass carbon electrode displayed a wide linear range (2–710 μM), low limit of detection (0.5 μM) and good selectivity for detection of H₂O₂ with a much higher sensitivity than that of Pt nanoparticles or graphene modified electrode.     

对比变分自编码器的近红外光谱测量及其在液态样品检测中的应用

近红外光谱是热门的食品检测方法之一,对于这种高维光谱数据的分析常常需采用数据降维算法提取其中的特征,然而绝大多数算法都只能针对单个数据集进行分析。虽然已有基于对比学习的对比主成分分析成功应用于不同水果表面农残的近红外光谱检测中,但是该方法只能以线性的方式组合原有特征,特征提取效果存在局限性,并且需要调节对比参数来控制背景集影响,需要消耗更大的时间成本。cVAE（contrastive variational autoencoder）是一种基于对比学习和变分自编码器的改进算法,被用于图像去噪和RNA序列分析中,它仍然具备分析多个数据集的特点,同时因为组合了神经网络的概率生成模型而具备了提取非线性隐含特征的能力。将cVAE算法应用于近红外光谱分析,建立了准确的近红外光谱数据降维模型。在实际验证中,使用cVAE算法对购买的不同品牌和批次纯牛奶中掺假三聚氰胺进行检测。结果表明,使用VAE算法只能区分出不同品牌和批次的纯牛奶,而其中是否掺假三聚氰胺这一重要信息无法表现出来;而使用cVAE算法进行数据分析时,由于添加了背景数据集分离了无关变量,能够清晰的将有无掺假三聚氰胺的样本分类。这说明了,cVAE不仅具备了cPCA（contrastive principle component analysis）在近红外光谱数据降维中的优势,而且具备提取非线性特征的能力,同时不需要调节可变参数,能够更方便地建立近红外光谱降维模型。     

从单分子到凝聚相水体系的理论描述：势能面和分子动力学最新进展

本文回顾了近十年来水体系的势能面与分子动力学理论研究的最新进展,包括水分子参与的气相反应,固体表面上的吸附与解离动力学,以及从团簇到凝聚相水的结构、振动光谱与统计力学模拟. 近年来再次发展起来的机器学习技术,例如结合置换不变多项式的神经网络,或结合基本不变量的神经网络,已被成熟应用于气相与固体表面体系的高精度势能面构造中. 对于团簇甚至凝聚相水体系,原子中心神经网络方法或基于核的高斯过程方法应用更为广泛. 此外,在多体展开框架下,在气相体系中发展起来的的方法也组成了高维度体系势函数构造的高精度方案. 当前凝聚相水体系面临的主要问题是高精度从头算数据集的积累,兼顾计算精度与效率的双杂化密度泛函是一种可能的解决方案. 在动力学理论方面,无论是化学反应截面计算还是振动光谱模拟,往往需要合理描述水分子中氢原子的量子效应,才能得到较为可靠的理论计算结果. 量子波包动力学方法已经在气相反应机理研究方面有深入的应用,也在包含数个水分子的团簇振动分析中有初步应用. 基于路径积分的分子动力学方法正在较大水团簇以及凝聚相水的结构与谱学模拟方面发挥重要作用.     

Raman phonon anomalies in Sr(Fe1-xCox)2As2

Phonon anomalies have been reported in iron-pnictide superconductors indicating a diverse interplay between different orders in the materials.Here,we report Raman scattering measurements on Sr(Fe_1-xCo_x)₂As₂(x=0 and x=0.04)single crystals in the B;symmetry with respect to a 1 Fe unit cell.Upon cooling,we observe a larger split(13 cm;)of Eg Raman phonon modes pertaining to in-plane Fe and As displacements as the crystals undergo the tetragonal-toorthorhombic structural phase transition,although a considerable split(9 cm;)has been reported in BaFe_1-xCo_x)₂As₂.Furthermore,the splitting of E;phonon modes is strongly reduced upon doping.We perform an order-parameter analysis revealing a similar doping dependence of E;phonon splitting as reported in other compounds of the 122 family,indicating these phonon anomalies widely exist in 122 iron-based superconductors and might share the same mechanisms.