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This study explored the feasibility of enhancing cellulose functionalities by using media milling to reduce the size of cellulose particles, and assayed various physicochemical and physiological properties of the resulting cellulose. Cellulose has been recognized as dietary fiber by USFDA due to its health benefits. However, its properties like low degradability, stiff texture, and insolubility in water limits its applicability in foods. Milling reduced the volume mean size of cellulose from 25.7 µm to 0.9 µm, which in turn increased the specific surface area (36.78-fold), and swelling capacity (9-fold). Conversely, a reduction in the bulk density (1.41 to 1.32 g/mL) and intrinsic viscosity (165.64 to 77.28 mL/g) were found. The milled cellulose also had significantly enhanced capacity for holding water and binding bile acids and sugars. Moreover, the size reduction also resulted in increased fermentability of cellulose into short chain fatty acids using three human fecal microflora samples. The increase in production of acetate (2880.60%), propionate (2738.52%), and butyrate (2865.89%) after fermentation of cellulose for 24 h were significantly enhanced by size reduction. With these improved characteristics, the milled cellulose might have beneficial physiological effects including laxation as well as reduced blood cholesterol and glucose attenuation.

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In this paper, the transformation process from Au8 to Au25 nanoclusters (NCs) is investigated with steady state fluorescence spectroscopy and time-resolved fluorescence spectroscopy at various reaction temperatures and solvent diffusivities. Results demonstrate that Au8 NCs, protected by bovine serum albumin, transform into Au25 NCs under controlled pH values through an endothermic reaction with the activation energy of 74 kJ mol(-1). Meanwhile, the characteristic s-shaped curves describing the formation of Au25 NCs suggest this process involves a diffusion controlled growth mechanism.

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Upconversion fluorescence has been frequently cited as an important feature in carbon nanodots (CNDs) and graphene quantum dots (GQDs); and some mechanisms and potential applications have been proposed. Contrary to such a general belief, we demonstrate in this report no observable upconversion fluorescence based on five different synthesized CNDs and GQDs. We confirm that the so-called upconversion fluorescence actually originates from the normal fluorescence excited by the leaking component from the second diffraction in the monochromator of the fluorescence spectrophotometer. Upconversion fluorescence can be identified by measuring the excitation intensity dependence of the fluorescence.

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Super-small Au8 nanoclusters have shown great potential to be used in bioimaging, biosensors and catalysis. Understanding the fluorescence origin and the spectral broadening mechanism is of critical importance for the applications. Here we investigate the fluorescence origin and the spectral broadening mechanism using steady state and ultrafast time-resolved spectroscopy. For the first time we clearly elucidate the broad fluorescence of Au8 nanoclusters consisting of an intrinsic band from the Au8 core and an extrinsic band from the surface fluorophores. The emission energy of the intrinsic band is in accord with the rule of E/N(1/3) and the spectral broadening originates from ultrafast dephasing due to effective electron-electron scattering. The extrinsic band has a much larger bandwidth due to massive surface fluorophores; it is the dominant mechanism for spectral broadening in Au8. In contrast to the jellium model predictions, the overall fluorescence exhibits excitation wavelength dependence.

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Glutathione-protected Au25 clusters (Au25@GSH) are prospective for biological applications due to their biocompatibility and near infrared fluorescence. The weak electron-phonon coupling, however, restricts their applications in bioanalysis and therapeutics. Here we modify the properties of Au25@GSH by changing their ligands. The temperature dependent fluorescence shows that conjugation with different ligands results in modified temperature behavior. In particular, Au25@GSH-MPA evidently exhibits enhanced phonon coupling, therefore, resulting in a decrease in the emission energy and an increase in bandwidth upon increasing temperatures. The enhanced phonon coupling in modified Au25@GSH sheds new light on the future application of nanoclusters from early diagnosis towards therapeutics.

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Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles is a powerful tool for chemical and biological sensing experiments. In this study, we observed LSPR shifts of 11-mercaptoundecanoic acid modified gold nanorods (GNR-MUA) for the pH range of 6.41 to 8.88. We proposed a mechanism involving changes of the dipole moment after protonation/deprotonation carboxylic groups of 11-mercaptoundecanoic acid (MUA) which plays an important role by modulating LSPR around the functionalized GNR. Such a stable and easily prepared GNR-MUA has potential to become one of the most efficient and promising pH nanosensors to study intra- or extra-cellular pH in a wide range of chemical or biological systems.

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We investigated systematically the temperature dependence of the spectral properties such as the band gap, bandwidth and fluorescence intensity of CdSe/CdS dot-in-rod nanocrystals. These asymmetry nanoparticles were synthesized by seeded growth techniques with band alignment of the type-I and quasi type-II with initial core sizes of 3.3 and 2.3 nm, respectively. With increasing temperature the band gap decreases and bandwidth increases, largely due to exciton-phonon scattering. Anomalous variations of the band gap and bandwidth were observed at 200-240 K, and the variations are attributed to the anisotropic strain in the CdSe/CdS interface due to temperature dependent lattice mismatch. The integrated intensity of fluorescence shows two variation regimes. In the low temperature regime, the intensity remained roughly constant due to the temperature dependent carrier mobility and trapping by the defect states in the CdS shell. However, in the higher temperature regime, the intensity decreased quickly due to thermal/phonon assisted escape from the CdSe dot. The barrier depths are estimated to be about 557 and 285 meV for type-I and quasi type-II samples, respectively.