The peak fluorescence emission of conventional fluorophores such as organic dyes and inorganic quantum dots is independent of the excitation wavelength. In contrast, the position of the peak fluorescence of graphene oxide (GO) in a polar solvent is heavily dependent on the excitation wavelength. The present work has discovered that the strong excitation wavelength dependent fluorescence in GO is originated from the "giant red-edge effect", which breaks Kasha's rule. When GO sheets are present in a polar solvent, the solvation dynamics slow down to the same time scale as the fluorescence due to the local environment of the GO sheet. Consequently, the fluorescence peak of GO broadens and red-shifts up to 200 nm with an increase in the excitation wavelength. The giant red-edge effect of GO disappears in a nonpolar solvent, leading to a narrow fluorescence peak that is independent of the excitation wavelength. Discovery of the underlying strong excitation wavelength dependent fluorescence mechanism provides guidelines for the design of graphene oxide-based optical devices.

20 nm sized Co 3 O 4 nanoparticles are in-situ grown on the chemically reduced graphene oxide (rGO) sheets to form a rGO-Co 3 O 4 composite during hydrothermal processing. The rGO-Co 3 O 4 composite is employed as the pseudocapacitor electrode in the 2 M KOH aqueous electrolyte solution. The rGOCo 3 O 4 composite electrode exhibits a specific capacitance of 472 F/g at a scan rate of 2 mV/s in a twoelectrode cell. 82.6% of capacitance is retained when the scan rate increases to 100 mV/s. The rGOCo 3 O 4 composite electrode shows high rate capability and excellent long-term stability. It also exhibits high energy density at relatively high power density. The energy density reaches 39.0 Wh/kg at a power density of 8.3 kW/kg. The super performance of the composite electrode is attributed to the synergistic effects of small size and good redox activity of the Co 3 O 4 particles combined with high electronic conductivity of the rGO sheets.

An ultrasensitive fluorescent sensor based on the quantum dot/DNA/gold nanoparticle ensemble has been developed for detection of mercury(II). DNA hybridization occurs when Hg(II) ions are present in the aqueous solution containing the DNA-conjugated quantum dots (QDs) and Au nanoparticles. As a result, the QDs and the Au nanoparticles are brought into the close proximity, which enables the nanometal surface energy transfer (NSET) from the QDs to the Au nanoparticles, quenching the fluorescence emission of the QDs. This nanosensor exhibits a limit of detection of 0.4 and 1.2 ppb toward Hg(II) in the buffer solution and in the river water, respectively. The sensor also shows high selectivity toward the Hg(II) ions.

Chemically modified graphene oxide (GO) sheets exhibit three ''fingerprinting'' photoluminescent (PL) peaks, which originate from the s* / n, p* / p and p* / n electronic transitions between the antibonding and the bonding molecular orbitals. The three PL peaks are associated with the C-OH, the aromatic C]C and the C]O functional groups in the GO sheets, respectively. The relative intensities of the three PL peaks are modulated by varying the oxygen-containing functional groups. The three PL emission peaks exhibit a red-shift with an increase in the excitation wavelength. The difference between the emission peak and the excitation wavelength shows a constant Stokes shift of 53.3 nm, 112.

Three different nanostructures of CuO (wires, platelets, and spindles) have been synthesized by one precursor. First, Cu(OH) 2 nanowires have been prepared by a two-step, template-free, wet chemical approach. And then the transformation from the 1D Cu(OH) 2 nanostructures to a variety of novel CuO nanostructures has been realized by thermal dehydration of the as-prepared Cu(OH) 2 in solution. The electrochemical characters of the three different nanostructures are studied by their investigation of electrochemical impendance spectrum and cyclic voltammetry. A comparison of the three nanostructures showed us an attractive phenomenon, that is, the electron transfer ability of CuO nanospindles was stronger than that of CuO nanowires or nanoplatelets. We suggest the possible reason is the assembly of the nanostructrue. The electrochemical response of the as-prepared samples on H 2 O 2 is also investigated, and good application in electrochemical detecting of glucose is exhibited.

This work describes the first investigation of starch degradation during extrusion occurring at multiple structural levels and explains the effects of the thermal and mechanical energy of extrusion. Investigated samples comprised starches with a range of amylose contents and of glycerol/water plasticizer contents. Structural analysis was performed using size‐exclusion chromatography, XRD and light microscopy. The (branch) chain length distribution did not show apparent changes upon either thermal or mechanical energy treatment. Statistical analysis showed that mechanical energy played a dominant role in reducing starch molecular size and degree of starch crystallinity, while thermal energy only partially gelatinized starch granules with negligible effect on molecular size. The rigid crystallites of amylopectin in starch granules are more susceptible to shear degradation than the flexible amorphous amylose. Previous studies did not draw quantitative conclusions as to the relative importance of these two types of energy in extrusion on starch structural degradation. This mechanistic understanding from multi‐level characterization is helpful to design the processing of starch‐based biopolymers with improved functional properties.

Surface-enhanced Raman spectroscopy (SERS) has evolved from an esoteric physical phenomenon to a robust and effective analytical method recently. The need of addressing both the field enhancement and the extinction of nanoparticle suspensions, however, has been underappreciated despite its substantive impact on the sensing performance. A systematic experimental investigation of SERS enhancement and attenuation is performed in suspensions of gold nanostars, which exhibit a markedly different behavior in relation to conventional nanoparticles. The relationship is elucidated between the SERS enhancement and the localized surface plasmon resonance band, and the effect of the concentration of the gold nanostars on the signal propagation is investigated. It is shown that an optimal concentration of gold nanostars exists to maximize the enhancement factor (EF), and the maximum EF occurs when the LSPR band is blue-shifted from the excitation wavelength rather than at the on-resonance position.

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