Nanoscale Confinement and Fluorescence Effects of Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas

Many key chemical and biochemical reactions, particularly in living cells, take place in confined space at the mesoscopic scale. Toward understanding of physicochemical nature of biomacromolecules confined in nanoscale space, in this work we have elucidated fluorescence effects of a light harvesting complex LH2 in nanoscale chemical environments. Mesoporous silicas (SBA-15 family) with different shapes and pore sizes were synthesized and used to create nanoscale biomimetic environments for molecular confinement of LH2. A combination of UV-vis absorption, wide-field fluorescence microscopy, and in situ ellipsometry supports that the LH2 complexes are located inside the silica nanopores. Systematic fluorescence effects were observed and depend on degree of space confinement. In particular, the temperature dependence of the steady-state fluorescence spectra was analyzed in detail using condensed matter band shape theories. Systematic electronic-vibrational coupling differences in the LH2 transitions between the free and confined states are found, most likely responsible for the fluorescence effects experimentally observed

Intergradation of UiO‐66 Nanoparticles with Expanded Graphite for Electrocatalytic Determination of Nitrite and L‐Cysteine

Abstract In this study, metal–organic framework (MOF) nanoparticles of UiO‐66 are integrated with expanded graphite (EG) (UiO‐66/EG) by a facile solvothermal approach. The advantages of this nanocomposite UiO‐66/EG overcome the poor electronic conductivity and slow diffusion of MOFs for their electrochemical applications. Through electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical techniques, the morphology, surface area, and physicochemical properties of this UiO‐66/EG nanocomposite are characterized. The UiO‐66/EG nanocomposite exhibits superior sensing performance over the UiO‐66 and EG when used for nitrite and L‐cysteine determination. This includes less positive oxidation potentials and enhanced oxidation currents. Using the UiO‐66/EG nanocomposite, the nitrite oxidation peak current is linear with a concentration range of 0.20 μm to 13.15 mm with the lowest limit of detection (LOD) of 0.06 μm (S/N = 3). Meanwhile, superior performance is demonstrated for L‐cysteine monitoring, where the oxidation peak current is linear over the L‐cysteine concentration in the range of 0.5–250 μm and of 0.25–3.50 mm and a LOD of 0.28 μm (S/N = 3). This UiO‐66/EG/GCE nanocomposite is successfully exploited to detect nitrite in food samples and to measure L‐cysteine in juice samples. Therefore, the proposed sensing platform enables the fabrication of high‐performance electrochemical sensors to accurately quantify nitrite and L‐cysteine in complex matrixes

Graphene nanoplatelets supported metal nanoparticles for electrochemical oxidation of hydrazine

Graphene nanoplatelets have been applied as the support to electrodeposit monometallic Au and Pd nanoparticles as well as bimetallic Au–Pd nanoparticles. These nanoparticles have been characterized with scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical techniques. They are further utilized as the catalysts for electrochemical oxidation of hydrazine. The oxidation peak potential is −0.35 and 0.53 V (vs. SCE) when monometallic Pd and Au nanoparticle are used as the catalysts. When bimetallic nanoparticles are applied as the catalyst, their composition affects the peak potential and peak current for the oxidation of hydrazine. Higher oxidation current is achieved when bimetallic Au–Pd nanoparticles with an atomic ratio of 3:1 are deposited on graphene nanoplatelets. Metal nanoparticle-loaded graphene nanoplatelets are thus novel platforms for electrocatalytic, electroanalytical, environmental, and related applications. Keywords: Graphene nanoplatelets (GNPs), Metal nanoparticles, Electrochemical oxidation of hydrazine, Electrodepositio