Transmissive Mode Laser Micro-Ablation Performance of Ammonium Dinitramide-Based Liquid Propellant for Laser Micro-Thruster.

The transmissive mode laser micro-ablation performance of near-infrared (NIR) dye-optimized ammonium dinitramide (ADN)-based liquid propellant was investigated in laser plasma propulsion using a pulse YAG laser with 5 ns pulse width and 1064 nm wavelength. Miniature fiber optic near-infrared spectrometer, differential scanning calorimeter (DSC) and high-speed camera were used to study laser energy deposition, thermal analysis of ADN-based liquid propellants and the flow field evolution process, respectively. Experimental results indicate that two important factors, laser energy deposition efficiency and heat release from energetic liquid propellants, obviously affect the ablation performance. The results showed that the best ablation effect of 0.4 mL ADN solution dissolved in 0.6 mL dye solution (40%-AAD) liquid propellant was obtained with the ADN liquid propellant content increasing in the combustion chamber. Furthermore, adding 2% ammonium perchlorate (AP) solid powder gave rise to variations in the ablation volume and energetic properties of propellants, which enhanced the propellant enthalpy variable and burn rate. Based on the AP optimized laser ablation, the optimal single-pulse impulse (I)~9.8 µN·s, specific impulse (Isp)~234.9 s, impulse coupling coefficient (Cm)~62.43 dyne/W and energy factor (η)~71.2% were obtained in 200 µm scale combustion chamber. This work would enable further improvements in the small volume and high integration of liquid propellant laser micro-thruster.

Liquid-solid phase regulating excited-state intramolecular proton transfer process of HBT-d-NO2: A QM/MM study.

The excited-state intramolecular proton transfer process of 2-(1,3-benzothiazol-2-yl)-4-[2-(4-nitrophenyl)ethynyl]phenol (HBT-d-NO2) in the different surrounding environment is investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The optimized molecular structure provides convincing evidence that the intramolecular hydrogen bond is strengthened in the first excited (S1) state. The frontier molecular orbitals observed the HBT-d-NO2 exists obvious intramolecular charge translate phenomenon. The results of the potential energy curve show that HBT-d-NO2 is difficult to undergo proton transfer in the ground (S0) state due to the high energy barrier, while it becomes easier in the S1 state in both liquid and solid phases. By comparison, the energy barrier of ESIPT in the solid phase is higher than that in the liquid phase. We can conclude that the solid phase effectively hinders the ESIPT process compared with that the liquid phase. In this work, we illustrate the influence of liquid and solid phases on the intramolecular proton transfer process, which could promote further developments in biomedical and fluorophore applications.

Interface Adhesion Property and Laser Ablation Performance of GAP-PET Double-Layer Tape with Plasma Treatment.

In the field of laser ablation micro-propulsion, the property of double-layer tape has significant impact on the propulsion performance. In this paper, low temperature plasma was used to treat the surface of polyethylene terephthalate (PET) to improve its adhesion with energetic polymer. The PET surface pre- and post-plasma treatment was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), and the enhancement mechanism of the interface adhesion was discussed. In addition, the ablation performance of the double-layer tape after the plasma treatment was studied. The results showed that the plasma etching effect increased the root mean square roughness of the PET surface from 1.74 nm to 19.10 nm. In addition, after the plasma treatment, the number of C-OH/COOH bonds and O=C-O bonds increased, which also greatly improved the adhesion between the PET and energetic polymers. In the optimization of the ablation performance, the optimal laser pulse width was about 200 µs. The optimal values of the specific impulse (Isp), impulse coupling coefficient (Cm), and ablation efficiency (η) were 390.65 s, 250.82 µN/W, and 48.01%, respectively. The optimization of the adhesion of the double-layer tape and the ablation performance lay the foundation for the engineering application of laser ablation micro-thrusters.

Photoluminescence-based sensing of ethanol gas with ultrafine WO3 nanorods.

Ultrafine one-dimensional WO3 nanorods (NRs) with diameters of 10-200 nm have been fabricated using a hydrothermal synthesis method. The optical performance of the WO3 NRs strongly depends on their various defects as well as their crystal quality. Upon exposure to trace quantities of ethanol gas, the photoluminescence (PL) spectra of these nanorod samples under ultraviolet illumination showed a large variation in intensity. WO3-NR-based ethanol gas sensing via PL spectra variation demonstrated a 100 ppm sensitivity detection limit and a wide linear detection range of 200-2000 ppm at 100°C. This outstanding optical ethanol sensing performance can be ascribed to the very large surface area to volume ratio of this material, which increases the density of active sites for ethanol adsorption and reaction with adsorbed oxygen species.

Analysis of circulating non-coding RNAs in a non-invasive and cost-effective manner.

Non-coding RNAs (ncRNAs) participate in regulation of gene expression, and are highly relevant to pathological development. They are found to be stably present in diverse body fluids, including those in the circulatory system, which can be sampled non-invasively for clinical tests. Thus, circulating ncRNAs have great potential to be disease biomarkers. However, tremendous efforts are desired to discover and utilize ncRNAs as biomarkers in clinical diagnosis, calling for technological advancement in analysis of circulating ncRNAs in biospecimens. Hence, this review summarizes the recent developments in this area, highlighting the works devoted to cancer diagnosis and prognosis. Three main directions are focused: 1) Extraction and purification of ncRNAs from body fluids; 2) Quantification of the purified circulating ncRNAs; and 3) Microfluidic platforms for integration of both steps to enable point-of-care diagnostics. These technologies have laid a solid foundation to move forward the applications of circulating ncRNAs in disease diagnosis and cure.

Redox cycling of iron by carbon dot enhanced chemiluminescence: mechanism of electron-hole induction in carbon dot.

The chemiluminescence (CL) of the Fenton system with nitrogen doped carbon dots (N-CDs) was significantly enhanced. The introduction of N-CDs improved the utilization of H2O2 and drastically enhanced the generation of ˙OH, which resulted in enhanced CL emission of the Fenton system through energy and electron transfer processes. The oxidation of N-CDs by ˙OH led to rapid incorporation of oxygen into N-CDs. The mechanism relied on the production of •OH radicals through the Fenton reaction and clearly indicated the important role of peroxide-induced redox cycling of Fe2+ ⇔ Fe3+ in the presence of N-CDs. The CL intensity of the system containing Fe2+ was higher than that containing Fe3+ because the rate of the Fe3+ reaction was much slower than that of the Fe2+ reaction. The CL signal remained constant after some time due to redox cycling, which established equilibrium, irrespective of the form of iron. This study provides a feasible approach to greatly enhance the weak CL of the Fenton system with the introduction of environmentally friendly N-CDs, and initiates an inspiring research in the domain of catalysis, CL and the mechanism of the Fenton system, which will be helpful in various applied research areas.

Ultra-weak chemiluminescence enhanced by facilely synthesized nitrogen-rich quantum dots through chemiluminescence resonance energy transfer and electron hole injection.

In this study, novel nitrogen-rich quantum dots (N-dots) were easily synthesized with a very high percentage of nitrogen (about 57%). The N-dots exhibited unique optical properties, which significantly enhanced (400 fold) the ultra-weak chemiluminescent reaction of NaIO4 with H2O2via CRET and electron hole injection.

Heterogeneous Chemiluminescence from Gas-Solid Phase Interactions of Ozone with Alcohols, Phenols, and Saccharides.

Gas-solid phase reactions between ozone (O3) and three representative solids (alcohols, phenols, and saccharides) were investigated through a heterogeneous chemiluminescence (CL) strategy. When interactions between these two species occurred at the surface of the solid powder, an obvious CL effect was obtained. This performance could be attributed to the evolution of a ROOOH intermediate, which subsequently released emissive 1O2 species. This is the first report analyzing the gas-solid phase CL performance of O3 with alcohols, phenols, and saccharides. It is believed that this strategy can be extended to applications in other gas-solid phase CL analyses utilizing the O3 system. This has also created a novel area of gas-solid CL performance; thus, relevant processes and mechanisms can be deduced and identified.

Fluorescent carbon nanoparticles: mimicking hydrogen peroxide properties in a chemiluminescence system.

Fluorescent carbon nanoparticles (FCNs), as novel luminescent reagents exhibiting hydrogen peroxide mimicking properties, can directly react with luminol, NaHCO3 and NaHSO3 in alkaline conditions to yield novel chemiluminescence, and show great potential towards further applications of ultra-weak chemiluminescence.

Peroxynitrous-acid-induced chemiluminescence detection of nitrite based on Microfluidic chip.

A chemiluminescent method for nitrite detection was developed on microfluidic chip. Carbon dots-NaNO2(-) acidified H2O2 system was adopted. Chemiluminescence (CL) spectrum of this system was detected. The radiative recombination of hole-injected and electron-injected carbon dots explained their CL property. Spiral microchannels were designed on the microfluidic chip to allow enough reaction time for the carbon dots-NaNO2-acidified H2O2 system. Carbon dots and NaNO2 were premixed in the branch microchannel, then, the mixture reacted with acidified H2O2 in spiral microchannels. Concentrations of H2SO4 and H2O2, dilution ratio of carbon dots in H2O and flow rate were optimized to obtain the best CL signals. The approach presented satisfactory linear relationship between NaNO2 concentration and CL intensity. The tolerance of metal ions in determination of 1×10(-5)M nitrite was analyzed. The nitrites in water and beverage samples were successfully analyzed on the microfluidic chip with good repeatability. The data were well accordance with the results obtained from GB 5009.33(-) 2010. This microfluidic CL detection method is believed to be a simple, automatic and agent-save approach for inorganic ion analysis.

Bisulfite induced chemiluminescence of g-C3N4 nanosheets and enhanced by metal ions.

In this work, a novel chemiluminescence (CL) phenomenon was found: a g-C3N4 nanosheets suspension was mixed with NaHSO3 solution directly to produce luminescence, and the intensity of luminescence could be obviously enhanced by some metal ions, which was distinctly different from the phenomenon that Cu(2+) ions can quench the fluorescence of g-C3N4 nanosheets as reported before.

Determination of boron in water samples by dispersive liquid-liquid microextraction based on the solidification of a floating organic drop coupled with a fluorimetric method.

In this work, a new, rapid and reliable method for the determination of boron in water samples by dispersive liquid-liquid microextraction based on the solidification of a floating organic drop (DLLME-SFO) prior to fluorescence spectra analysis was developed. As a result of its complexation with boric acid, the method relies on the enhancement of the fluorescence (λex = 350 nm, λem = 373 nm) of chromotropic acid. The influences of DLLME-SFO parameters, including the extraction solvent type and its volume, pH, the disperser solvent type and its volume, and salt effects were investigated. Under the optimized conditions, the limit of detection was 0.11 ng L(-1), with a preconcentration factor of 86 times. The calibration curve was linear in the range of 0-40 nM. The proposed method has also been successfully applied to analyze real water samples and the relative recoveries of water samples ranged from 86.9 to 93.2%.

Plasmonic luminescent core-shell nanocomposites-enhanced chemiluminescence arising from the decomposition of peroxomonosulfite.

A core-shell structure of plasmonic luminescent nanocomposite, Ni@SiO2@FITC@SiO2 (NSFS) combining the stable luminescence of fluorophore with the excellent plasmonic property of metal nanomaterials, has been synthesized through layer-by-layer assembly. The effect of NSFS on the ultraweak chemiluminescence (CL) reaction of hydrogen peroxide (H2O2) and sodium bisulfite (NaHSO3) was explored for the first time. It was found that the CL intensity from the decomposition of peroxomonosulfite was significantly enhanced by NSFS. The mechanism of the nanocomposite-enhanced CL was revealed as the coupling of chemically induced excited states of fluorescein isothiocyanate (FITC) with surface plasmons of Ni nanoparticles based on studies of CL emission spectra, electron spin resonance spectra, extinction spectra and fluorescence spectra. The work sheds new light on the characteristics of the versatile materials and gives us new insight into the optical properties of fluorophores.

Production of superoxide anion radicals as evidence for carbon nanodots acting as electron donors by the chemiluminescence method.

In this communication, a novel chemiluminescence phenomenon was observed for the as-prepared carbon nanodots (CDs) in a concentrated sodium hydroxide (NaOH) solution. The generation of superoxide anion radical (O2˙(-)) directly provides evidence for the excellent electron-donating ability of CDs.

Development of an automatic multi-channel ink-jet ejection chemiluminescence system and its application to the determination of horseradish peroxidase.

In this work, an automatic multi-channel ink-jet for chemiluminescence (CL) analysis was developed. The four-channel ink-jet device was controlled by a home-made circuit. Differing from the classic flow injection CL, the whole procedure for CL analysis was automatically completed on a hydrophobic glass side. CL reaction of luminal and hydrogen peroxide for the determination of horseradish peroxidase (HRP) was selected as an application to automatic CL analysis platform. All solutions delivered by different channels were precisely ejected to the same position of the glass slide for the CL analysis. The consumption of reaction solution was reduced to nanoliter level. The whole CL analysis could be completed in less than 4min, which was benefited from the prompt solution mixing in small size of droplet. The CL intensity increased linearly with HRP concentration in the range from 0.01 to 0.5µgmL(-1). The limit of detection (LOD) (S/N=3) was 0.005µgmL(-1). Finally, the automatic CL system could also be used for the detection of HRP in HRP-protein conjugates, which showed its practical application in immunoassay.