Polymer dots with nonconjugated groups that are facile to synthesize and environmentally friendly generally attract substantial interest. However, their fluorescence-emitting mechanisms are not clear. In this paper, nonconjugated polymer dots (N-PDs) are synthesized by amidation reaction between polyethylenimine (PEI) and citric acid (CA), then self-assemble into rice-like dots in aqueous phase with a high fluorescence quantum yield. Such nitrogen-containing nonconjugated compounds N-PDs are believed to be inherently fluorescent, and the reported reasons for fluorescence-emitting are discussed. Importantly, these N-PDs can be used as an excellent fluorescent probe to detect Cu2+ and ClO– in aqueous solutions. Cu2+ could combine with the PEI moiety of the N-PDs to form a copper amine complex and then quench the fluorescence by an internal filtration effect. ClO– could oxidize the hydroxyl groups on the surface of the N-PDs to form a positive charge, blocking electron transfer between the hydroxyl groups and the chromophore groups. Finally, the sensor was successfully applied to the detection of Cu2+ and ClO– in environmental water samples.

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Narrow-bandwidth luminescent materials are already used in optoelectronic devices, superresolution, lasers, imaging, and sensing. The new-generation carbon fluorescence nanomaterials—carbon dots—have attracted considerable attention due to their advantages, such as simple operation, environmental friendliness, and good photoelectric performance. In this work, two narrower-bandwidth (21 and 30 nm) emission graphene quantum dots with long-wavelength fluorescence were successfully prepared by a one-step method, and their photoluminescence (PL) peaks were at 683 and 667 nm, respectively. These red-emitting graphene quantum dots were characterized by excitation wavelength dependence of the fluorescence lifetimes, and they were successfully applied to spectral and spatial superresolved sensing. Here, we proposed to develop an infrared spectroscopic sensing configuration based on two narrow-bandwidth-emission graphene quantum dots. The advantage of the method used is that spectroscopic information was extracted without using a spectrometer, and two narrow-bandwidth-emission graphene quantum dots were simultaneously excited to achieve spatial separation through the unique temporal “signatures” of the two types of graphene quantum dots. The spatial separation localization errors of the graphene quantum dots (GQDs-Sn and GQDs-OH) were 1 pixel (10 nm) and 3 pixels (30 nm), respectively. The method could also be adjusted for nanoscope-related applications in which spatial superresolved sensing was achieved.

matrices can show their unique intrinsic features. [5][6][7] Many hybrid composites and devices with excellent performance often require high doping concentration of functional materials. However, high doping ratio tends to result in adverse effects such as dropped transmittance caused by Rayleigh scattering, [8] weakened optoelectronic and mechanical performance. [9,10] Therefore, maintaining the intrinsic properties of nanoparticles while improving the doping concentration of nanomaterials becomes an urgent subject. There are two approaches to limit nanomaterials in substrates: physical dispersion and chemical dispersion. Physical dispersion of guest materials in host matrices is a conventional approach to prepare hybrid composites. Due to the weak physical interaction, the performance usually is impaired. Compared with physical dispersion, the covalent bond can prevent the phase separation existing in hybrid materials. [11] Among these ways, sol-gel method is a helpful technique to modify nanomaterials and prepare nano-or macroscale organic-inorganic hybrid materials such as glasses, ceramics, films, coatings, fibers, and powders. [12] Silane coupling agents or organosilicon polymers (silicone oil, resin, rubber, etc.) are introduced in the route based on the advantages of simultaneously possessing hydrophilic and lipophilic groups. First, they can elevate the dispersibility of nanomaterials in solutions. Second, they successfully link organic and inorganic phases with covalent bonds. Third, the introduction of silicon promotes the radiation recombination of electron/hole pairs through providing different surface states. There are five empty d orbitals of a silicon atom, where can be occupied by electrons of connected atoms or functional groups to form a dπ-pπ bond. [13] Owing to the above features, the hybrid materials inherit the superiorities of organosilanes: excellent resistance against high temperature; [14] stability under UV radiation; [15] lower surface tension, lower surface energy, and more prominent film-forming ability. [13] Since the discovery in 2004, carbon dots (CDs) have become promising issues due to their outstanding optical properties, such as high quantum yield (QY), photobleaching resistance, upconversion photoluminescence (PL). [16][17][18][19][20] In previous works, a concept of one-step prefunctionalization was brought up, using citric acid and long-chain amino-silanes as starting materials to prepare silane-functionalized CDs (SiCDs). [18] These types of CDs represent either "silane-functionalized carbon dots" or Nanomaterials usually manifest unique properties in solutions but will be undermined in the solid state. It is necessary to incorporate them into substrates or hybrid them with other functional materials for multiple devices and applications. Though there are a variety of methods to inherit their intrinsic properties like fluorescent and mechanical performance, most nanohybrid materials would lose their transparency irreversibly when construct solid-state devices. As a hot t...