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A type of carbon dot that possesses tunable fluorescence properties both in liquid and solid states was synthesized and applied to trace water detection.

Carbon dots-based room temperature phosphorescent (RTP) materials have attracted widespread attention owing to their excellent optical properties. However, there still is a challenge to fabricate carbon dots-based materials simultaneously showing long RTP lifetime and high phosphorescent quantum yield. Herein, we have designed a kind of carbon dots-silica hybrid material that can produce RTP emission with ultralong lifetime and also high phosphorescent quantum yield (1.3 s and 11.22%). Both chemical and optical analytical characterizations indicate the source of the outstanding RTP performance as the synergistic strategy of abundant electron traps, highly rigid network, and stable covalent bond. The findings provide a new design idea to achieve novel carbon dots-based RTP materials, showing broad application prospects in optical anticounterfeiting, optoelectronics, and others.

Hemin with functions such as oxygen carrying, oxygen storing, promoting redox, and performing electron transfer is important for the health of organisms. In this paper, green synthetic silicon nanoparticles (Si-NPs) were synthesized and used for free hemin detection in serum (a low limit of detection (LOD), 29.5 nM). The quenching mechanism was investigated by UV-vis absorption spectra, time-resolved luminescence decay curve, and circular dichroism (CD) spectra. It was confirmed that multiple redox centers of hemin led to intensified effective collision and increased the electron transfer rate, therefore enhancing the dynamic quenching, and it was undeniable that the inner filter effect (IFE) also played a role in the quenching.

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.

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 topic of nanomaterials in recent years, scientific works found a type of carbon dots using silane coupling agents as precursors that can overcome the shortcoming. These carbon dots, called silane-functionalized carbon dots (SiCDs), are catching increasing interest due to their versatility. Silane coupling agents endow SiCDs with the ability to disperse in solvents or polymerize with matrices by blending or covalent bonds without loss of transparency and decline of performance. The distinguishing features make SiCDs an ideal high transmittance, high doping concentration nanomaterial. The synergistic effect of SiCDs and hybridized sol-gel solid structures can not only hold the optical features of CDs but also enhance their original physical and chemical performance. This highlight focuses on the connection between SiCDs and organosilanes. Plus, preparation methods, applications, and prospective of SiCDs are mentioned.

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. Graphene nanoparticles useful for high-resolution spectroscopy and imaging have been fabricated by scientists in China and Israel. Quantum dots are nanoparticles of semiconductor that can trap electrons and their positively charged counterparts, ‘holes’. The light emitted when the electron and hole combine is notable for its high spectral purity, i.e., its very narrow range of frequencies, or colors. Zheng Xie from the Technical Institute of Physics and Chemistry in Beijing, Zeev Zalevsky from Bar-Ilan University, Ramat-Gan, and their colleagues used a simple one-pot method to synthesize graphene quantum dots that emit ultranarrow frequency light in two different shades of red. The team proposed unique configurations for using those nanoparticles for spatial and spectral superresolved sensing specifically for field called nanoscopy, to create images at a resolution beyond that achievable with a microscope. Infrared spectral and spatial imaging configurations were developed based on near-infrared graphene quantum dots with ultranarrow half-width (FWHM = 21 nm). The spectral imaging is obtained without a spectrometer and the spatial imaging exceeds the limits of resolution (superresolved imaging). The superresolved sensing is obtained due to the unique temporal and spectral properties of the quantum dot.

Here, Carbon dots (CDs) were fabricated through a simple one-step hydrothermal treatment of N-aminoethylpiperazine (AEP) and citric acid (CA). The as-prepared CDs have a bright blue emission with a quantum yield of 56%, with good water solubility, light stability and temperature sensitivity. In addition, the photoluminescence of the CDs deriving from two components was experimentally verified: one is amide molecules resulting from the reaction between AEP and CA, and the other is the carbon nucleus coming from the precursors at high temperatures. More importantly, the fluorescence intensity of the CDs is temperature-dependent, and decreasing linearly from 25 °C to 95 °C, with excellent sensitivity and recoverability. A CD/epoxy composite was prepared by doping the CDs into an epoxy resin, which exhibits superior temperature response that may be caused by the greater dielectric constant of epoxy resin. In addition, the fluorescence of the CDs can be efficiently quenched by Hg2+, and the addition of biothiols restore the quenched fluorescence of CDs. The sensor was applied to detect ions in river water and tap water and satisfied results were achieved.

In order to compute the thermal deformation of the hydrostatic thrust bearing in the heavy type CNC equipments, a numerical research concerning temperature field of multi-pad hydrostatic thrust bearing having sector cavity, rectangular cavity, Ishaped cavity and ellipse cavity is described. Three-dimensional temperature field of gap fluid between the rotation worktable and the base has been simulated by using Finite Volume Method of CFX. This study analyzes the influence of cavity shape on the bearing temperature performance according to computational fluid dynamics and lubricating theory. It has revealed its temperature distribution. The simulation results demonstrate that an improved characteristic will be affected by cavity shape easily. Through this method, the safety of a multi-pad hydrostatic thrust bearing having different cavities can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, experience and thermal deformation computation for hydrostatic thrust bearing in the heavy CNC equipments.

In this paper, non-conjugated organosilicone fluorescent nanoparticles (Si-NPs) were synthesized by the Stober method. The Si-NPs have a diameter of approximately 30 nm, uniform particle size, and a quantum yield of up to 70.6% ultra-bright blue light emission. The prepared non-conjugated siloxane fluorescent small molecule is covalently bonded to the silica matrix. The Si-NPs exhibited excellent stability in ultraviolet irradiation and a wide pH range, and their improved stable optical properties are attributable to the protection of the silica matrix. In addition, the effectiveness of Si-NPs for potential fingerprint detection on a variety of substrates is demonstrated. Clear optical/fluorescent images of the ridges and spaces with high contrast and resolution are obtained because the particle size of the obtained Si-NPs is much smaller than the width of the fingerprint ridges.

In order to solve the loading capacity of the hydrostatic thrust bearing, a numerical simulation concerning dynamic pressure of multi-pad hydrostatic thrust bearing under the different recess depth and rotating velocity is been described. Three-dimensional dynamic pressure field of gap fluid between the rotational worktable and the base has been simulated by using the Computational Fluid Dynamics. This study theoretically researches the influence of recess depth and rotating velocity on dynamic pressure of the bearing according to the lubricating theory and Finite Volume Method, and the simulation results indicate that an improved characteristic will be affected by recess depth and rotating velocity easily. Through this method, the optimal loading capacity of such products can be achieved.

This work describes a numerical simulation concerning dynamic effect of multi-pad hydrostatic thrust bearing having different recess depth in order to solve the loading capacity of the hydrostatic thrust bearing. Threedimensional pressure field of gap fluid between the rotation worktable and the base has been computed by using the Finite Volume Method. This study theoretically analyzes the influence of recess depth on dynamic effect of the bearing according to the Computational Fluid Dynamics and lubricating theory, and the simulation results indicate that an improved characteristic will be affected by recess depth easily. Through this method, the optimal loading capacity of such products can be achieved.