We prepared graphene oxide(GO) saturable absorber (SA) successfully through optical deposition method, which is a simple but effective approach to deposit various materials onto substrate under the effects of light, and investigated several factors that influence the optical deposition result of GO onto optical fiber end, including poly(methyl methacrylate) (PMMA) concentration, light intensity, light mode, and deposition time. The efficient optically deposited GO preserving its nonlinearity guaranteed by GO/PMMA composite formation was also demonstrated. The GO SA prepared by optical deposition shows superior saturable absorption property with modulation depth and nonsaturable loss of 6% and 40%, respectively.

A novel fluorescent probe for H2PO4- was designed and fabricated based on the carbon dots/Fe3+ composite. The carbon dots were synthesized by an established one-pot hydrothermal method and characterized by transmission electron microscope, X-ray diffractometer, UV-Vis absorption spectrometer and fluorescence spectrophotometer. The carbon dots/Fe3+ composite was obtained by aqueous mixing of carbon dots and FeCl3, and its fluorescence property was characterized by fluorescence spectrophotometer. The fluorescence of carbon dots was quenched by aqueous Fe3+ cations, resulting in the low fluorescence intensity of the carbon dots/Fe3+ composite. On the other hand, H2PO4- reduced the concentration of Fe3+ by chemical reaction and enhanced the fluorescence of the carbon dots/Fe3+ composite. The Stern-Volmer equation was introduced to describe the relation between the relative fluorescence intensity of the carbon dots/Fe3+ composite and the concentration of H2PO4-, and a fine linearity (R2=0.997) was found in the range of H2PO4- concentration of 0.4-12 mM.

•CdS-PMMA nanocomposite was developed by in-situ bulk polymerization for NO detection.•The fluorescence quenching mechanism relies on the interaction between NO and Cd2 +.•The fluorescence response shows a good linear reproducibility with NO concentrations.•A linear calibration is obtained in the range from 1.4 × 10− 5 to 9.3 × 10− 3 mol · L− 1 NO.A novel nitric oxide (NO) fluorescent probe CdS-poly(methyl methacrylate) (PMMA) nanocomposites with different molar ratios of CdS quantum dots (QDs) to PMMA are developed successfully via in-situ bulk polymerization method. The optical properties of CdS/PMMA nanocomposites are studied by UV–Vis absorption spectra and fluorescence (FL) spectra in detail. It is demonstrated that the optical properties from such nanocomposite solution are tuned and stabilized by simply varying the concentration of CdS in the final product. X-ray diffraction (XRD) patterns of CdS-PMMA nanocomposite with higher loading of CdS show broad pattern for cubic CdS, which has narrow particle size distribution with less than 5 nm in PMMA observed by transmission electron microscopy (TEM). The surface morphological characterization of the CdS-PMMA nanocomposite has been done through atomic force microscopy (AFM). The thermo-gravimetric analyses (TGA) and differential scanning calorimetry (DSC) confirm the enhanced thermal stability of CdS-PMMA nanocomposites than PMMA. NO can coordinate with Cd2 + as a ligand for transition metal complexes, which will cause a quenching effect on the fluorescence of CdS QDs. Therefore, a significant quenching effect on the fluorescence of the CdS-PMMA nanocomposite is observed in the presence of NO. The fluorescence responses are concentration-dependent and can be well described by the typical Stern–Volmer equation, and a linear calibration I0/I = 1.0021 + 0.1944[NO] (R2 = 0.96052) is obtained in the range from 1.4 × 10− 5 to 9.3 × 10− 3 mol/L NO with a detection limit of 1.0 × 10− 6 mol/L (S/N = 3).

A new fiber optic sensor was developed to detect nitric oxide (NO) in aqueous solution using CdSe quantum dots (QDs)/cellulose acetate (CA) as the sensitive membrane, in which CdSe QDs were embedded in CA via simple hybridized approach. Nitric oxide radical (NO) could react easily with dissolved oxygen in water and coordinate with Cd2+, so it was found a significant quenching effect on the fluorescence of the CdSe QDs in the sensitive membrane. The fluorescence responses were concentration-dependent and could be well described by the typical Stern–Volmer equation. NO concentrations were determined by the phase-modulation fluorometry using this new fiber optic sensor. Under optimum conditions, a linear calibration (R2 = 0.9908) was obtained in the range of 1.0 × 10−7 to 1.0 × 10−6 mol L−1 NO concentration with a detection limit of 1.0 × 10−8 mol L−1 (S/N = 3) by the modulation of optical phase delay observed.

We report an organic/inorganic hybridized nanocomposite consisting of a bi-functional poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl serves as a polymeric charge-transporting and second-order nonliner optical matrix, and CdS nanoparticles as photosensitizers to manifest photorefractive (PR) effect. The unpoled PVNPAK film exhibits a second harmonic generation (SHG) coefficient of 4.7 pm/V due to the possibility of self-alignment of the azo chromophore. Significant enhancement of photoconductivity is noticed with the increase of CdS nanoparticles concentration. The photorefractive property of the polymer nanocomposites were determined by two-beam coupling (TBC) experiment. The TBC gain and diffraction efficiency of 11.89 cm−1 and 3.2% were obtained for PVNPAK/CdS at zero electrical field.

A novel multifunctional inorganic−organic photorefractive (PR) poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl-CdS nanocomposites with different molar ratios of CdS to poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl (PVNPAK) were synthesized via a postazo-coupling reaction and chemically hybridized approach, respectively. The nanocomposites are highly soluble and could be obtained as film-forming materials with appreciably high molecular weights and low glass transition temperature (Tg) due to the flexible spacers. The PVNPAK matrix possesses a highest-occupied molecular orbital value of about −5.36 eV determined from cyclic voltammetry. Second harmonic generation (SHG) could be observed in PVNPAK film without any poling procedure and 4.7 pm/V of effective second-order nonlinear optical susceptibility is obtained. The CdS particles as photosensitizers had a nanoscale size in PVNPAK adopting transmission electron microscopy. The improvement of interface quality between CdS and polymer matrix is responsible for efficient photoinduced charge generation efficiency in the nanocomposites. An asymmetric optical energy exchange between two beams on the polymer composites PVNPAK-CdS/ECZ has been found even without an external field in two-beam coupling (TBC) experiment, and the TBC gain and diffraction efficiency of 14.26 cm−1 and 3.4% for PVNPAK-5-CdS/ECZ, 16.43 cm−1 and 4.4% for PVNPAK-15-CdS/ECZ were measured at a 647.1 nm wavelength, respectively.