Then, the mixture was shifted into a dialysis membrane (MWCO of 3,000) learn more against pure water to remove surplus PEG2000N. Characterization To determine the size and morphology, RNase A@C-dots were characterized by high-resolution transmission electron microscopy (HR-TEM, JEM-2100 F, 200 kV, JEOL Ltd., Tokyo, Japan). The samples for TEM/HR-TEM were made by simply dropping

aqueous solution of the C-dots onto a 300-mesh copper grid casted with a carbon film. UV–Vis absorption spectra of the C-dots were measured with a Varian Cary 50 LY3039478 spectrophotometer (Varian Inc., Palo Alto, CA, USA). Fluorescence excitation and emission spectra of RNase A@C-dots were recorded on a Hitachi FL-4600 spectrofluorimeter (Hitachi Ltd., Tokyo, Japan). Zeta potential of RNase A@C-dots was measured on a Nicomp 380 ZLS zeta potential/particle sizer (PSS. Nicomp, Santa Barbara, CA, USA). X-ray photoelectron

spectroscopy (XPS) was obtained at room temperature by a Kratos Axis Ultra spectrometer selleck chemical (AXIS-Ultra DLD, Kratos Analytical Ltd., Tokyo, Japan) using a monochromated Al Kα (1486.6 eV) source at 15 kV. Fourier transform infrared (FTIR) spectra were obtained on a Nicolet 6700 spectrometer (Thermo Electron Corporation, Madison, WI, USA). The samples for FTIR measurement were prepared by grinding the dried C-dots with KBr together and then compressed into thin pellets. X-ray diffraction (XRD) profiles of the C-dot powders were recorded on a D/MAX 2600 PC (Rigaku, Tokyo, Japan) equipped with graphite monochromatized Cu Kα (λ = 0.15405 nm) radiation at a scanning speed of 4°/min in the range from 10° to 60°. Time-resolved fluorescence intensity decay of RNase A@C-dots was performed on a LifeSpec II (Lifetime only, Edinburgh Instruments, Livingston, UK). The sample was excited

by 380-nm laser, and the decay was measured in a time scale of 0.024410 ns/channel. Quantum yield measurement To assess the quantum yield of RNase A@C-dots, quinine sulfate in 0.1 M H2SO4 (quantum yield, 54%) was used as a reference fluorescence reagent. The final results were calculated according to Equation 1 below: (1) where Φstd is the known quantum yield of the standard compound, F sample and F std stand Tideglusib for the integrated fluorescence intensity of the sample and the standard compound in the emission region from 380 to 700 nm, A std and A sample are the absorbance of the standard compound and the sample at the excitation wavelength (360 nm), and n is the refractive index of solvent (for water, the refractive index is 1.33). To minimize the reabsorption effects, UV absorbance intensities of the samples and standard compound should never exceed 0.1 at the excitation wavelength. Photoluminescence (PL) emission spectra of all the sample solutions were measured at the excitation wavelength of 360 nm. The integrated fluorescence intensity is the area under the PL curve in the wavelength from 380 to 700 nm.