A Non-Contact Original-State Online Real-Time Monitoring Method for Complex Liquids in Industrial Processes

Failures are very common during the online real-time monitoring of large quantities of complex liquids in industrial processes, and can result in excessive resource consumption and pollution. In this study, we introduce a monitoring method capable of non-contact original-state online real-time monitoring for strongly coated, high-salinity, and multi-component liquids. The principle of the method is to establish the relationship among the concentration of the target substance in the liquid (C), the color space coordinates of the target substance at different concentrations (L¹, a¹, b¹), and the maximum absorption wavelength (λ_max); subsequently, the optimum wavelength λ_T of the liquid is determined by a high-precision scanning-type monitoring system that is used to detect the instantaneous concentration of the target substance in the flowing liquid. Unlike traditional monitoring methods and existing online monitoring methods, the proposed method does not require any pretreatment of the samples (i.e., filtration, dilution, oxidation/reduction, addition of chromogenic agent, constant volume, etc.), and it is capable of original-state online real-time monitoring. This method is employed at a large electrolytic manganese plant to monitor the Fe³⁺ concentration in the colloidal process of the plant’s aging liquid (where the concentrations of Fe³⁺, Mn²⁺, and (NH₄)₂SO₄ are 0.5–18 mg·L⁻¹, 35–39 g·L⁻¹, and 90–110 g·L⁻¹, respectively). The relative error of this monitoring method compared with an off-line laboratory monitoring is less than 2%.     

Scleral Lens Sensor for Ocular Electrolyte Analysis

The quantitative analysis of tear analytes in point-of-care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na⁺, K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0–8.0. Crown ether derivatives exhibit selectivity to Na⁺ and K⁺ ions within detection ranges of 0–100 and 0–50 mmol L⁻¹, and selectivities of 15.6 and 8.1 mmol L⁻¹, respectively. A 1,2 bis(o-aminophenoxy)ethane-N,N,-N',N'-tetraacetic-acid-based probe allows Ca²⁺ ion sensing with 0.02–0.05 mmol L⁻¹ sensitivity within 0.50–1.25 mmol L⁻¹ detection range. 5-Oxazolecarboxylic acid senses Mg²⁺ ions, exhibiting a sensitivity of 0.10–0.44 mmol L⁻¹ within the range of 0.5–0.8 mmol L⁻¹. The N-(2-methoxyphenyl)iminodiacetate Zn²⁺ ion sensor has a sensitivity of 1 µmol L⁻¹ within the range of 10–20 µmol L⁻¹. The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light-emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.     

Room temperature photoluminescence studies of nitrided InP(100) surfaces

The evolution of thin InN overlayer grown on InP (100) rich In substrate was investigated at room temperature by photoluminescence method versus the duration of nitridation process. The main important parameters were the duration of the process, and the angle of the reactive nitrogen flow. The nitridation was performed by a glow discharge source (GDS). The correlations between the electronic properties, gathered from photoluminescence (PL) measurements, and the chemical composition of InN–InP interfaces, derived from Auger electron spectroscopy (AES) were found. AES revealed that the nitridation process proceeds quickly in time showing self-limiting behavior. It is more effective for grazing nitrogen flux. The interface state density distributions, N_SS(E), were determined via advanced computer-aided analysis of dependencies of band edge PL efficiency, Y_PL, versus excitation light intensity, Φ. The analysis showed that the substrates were well passivated with N_SS(E) minima on the order of 5·10¹¹ cm^− 2 eV^− 1_. The nitrogen flux angle during the nitridation was found to have an influence on Y_PL(Φ) spectra. In all analyzed cases the grazing nitrogen flux generated the interface with slightly improved N_SS(E) distribution. Finally, the behavior of Y_PL versus Φ and N_SS(E) was precisely examined.     

Stoichiometric and non-stoichiometric films in the Si–O–N system: mechanical,electrical, and dielectric properties

A novel low-temperature (600–850 °C), chemical vapor deposition method, involving a simple reaction between disiloxane (H₃Si–O–SiH₃) and ammonia (NH₃), is described to deposit stoichiometric, Si₂N₂O, and non-stoichiometric, SiO_xN_y, silicon oxynitride films (5–500 nm) on Si substrates. Note, the gaseous reactants are free from carbon and other undesirable contaminants. The deposition of Si₂N₂O on Si (with (1 0 0) orientation and a native oxide layer of 1 nm) was conducted at a pressure of 2 Torr and at extremely high rates of 20–30 nm min⁻¹ with complete hydrogen elimination. The deposition rate of SiO_xN_y on highly-doped Si (with (1 1 1) orientation but without native oxide) at 10⁻⁶ Torr was ∼1.5 nm min⁻¹, and achieved via the reaction of disiloxane with N atoms, generated by an RF source in an MBE chamber. The phase, composition and structure of the oxynitride films were characterized by a variety of analytical techniques. The hardness of Si₂N₂O, and the capacitance–voltage (C–V) as a function of frequency and leakage current density–voltage (J_L–V) characteristics were determined on MOS (Al/Si₂N₂O/SiO/p-Si) structures. The hardness, frequency-dispersionless dielectric permittivity (K), and J_L at 6 V for a 20 nm Si₂N₂O film were determined to be 18 GPa, 6 and 0.05–0.1 nA cm⁻², respectively.     

Emerging artificial nitrogen cycle processes through novel electrochemical and photochemical synthesis

The nitrogen cycle is an important part of the global biogeochemical cycle, while the human activities have already caused a severe imbalance of the global nitrogen cycle. In this review, we proposed a new generation of artificial nitrogen cycle via electrochemical and photocatalytic reactions. In details, the N₂ from the air, NO₃⁻/NO₂⁻ containing wastewater, nitrogen oxides from vehicle emission are all able to be utilized as a nitrogen source for the synthesis of NH₃ under ambient conditions. The oxidation of NH₃, N₂ and nitrogen oxides can all achieve the aim of obtaining NO₃⁻. Hydrazine can also be synthesized electrochemical and photochemical reactions. Utilizing electrochemical and photocatalytic processes enables to eliminate the hazardous of nitrogen-containing organic chemicals, and some inorganic nitrogen polluted wastewater. More importantly, coupling N-based reaction with other reaction like CO₂ reduction enables to synthesize some high-value chemicals such as urea. Then we highlighted some recent achievements in these reactions and proposed some future potential developing directions. The results and funding of this work may help us develop highly efficient catalysts and strategies for the artificial nitrogen cycle, repairing the broken nitrogen cycle balance.     

Calibration of ultrahigh vacuum gauge from 10−9 Pa to 10−5 Pa by the two-stage flow-dividing system

A new two-stage flow-dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂. This system is designed based on the techniques for our previously developed calibration system in the range from 10⁻⁷ Pa to 10⁻² Pa. Three modifications were performed to extend the calibration pressure to a lower range. The relative standard uncertainty of the generated pressure (k = 1) is in the range from 2.3% to 2.6%, from 10⁻⁹ Pa to 10⁻⁵ Pa. The characteristics of ultrahigh vacuum gauges were also examined by using this system. The stabilities of the pressure reading, the linearity, the temperature dependence, and the long-term stability were examined. These results show that the calibration of ultrahigh vacuum gauges is possible in the range from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂ with the uncertainty of about 6.0% (k = 2) by this new system.     

Mechanisms of reactive sputtering of indium I: Growth of InN in mixed Ar-N2 discharges

Optical absorption and emission spectroscopies were used for in situ investigations of process occuring in the plasma and at the electrode-gas interfaces which control the reactive sputter etching of indium targets and the reactive deposition of InN films in mixed Ar-N₂ glow discharges. The sputtering parameters used were a d.c. target voltage of -2.5 kV, a total sputtering pressure P of 30–70 m Torr (4–9.3 Pa), N₂ mol.% C_N2 values of 0–100 and a target-to-substrate separation d of 3–6 cm. Under these conditions no indication of complete nitride formation at the target surface or of sputter ejection of InN molecular species was obtained. Increasing C_N2 at a constant value of P caused a decrease of the target sputtering rate R. This decrease was due primarily to a decrease in the ion current i_T, which was caused by thermalization of low energy electrons in the plasma through excitation of vibrational modes in molecular N₂. Atomic absorption provided a real-time monitor of R over the entire range of sputtering parameters. The optical emission intensity from sputtered indium atoms in the cathode glow was found to increase with C_N2 (even though R decreased) because of enhanced excitation through collisions with N₂ metastable species.The nitrogen concentration in the deposited films, as determined by X-ray photoelectron spectroscopy and X-ray diffraction, was found to depend strongly on C_N2, P_N2 and d. The dependence on d was caused by the position of the growing film surface with respect to the negative glow region where most of the atomic nitrogen was formed through the reaction N₂⁺ + N₂ → N₂ + N⁺ + N In discharges with short mean free paths this is the primary mechanism of nitrogen incorporation since indium does not chemisorb N₂, only atomic nitrogen. InN films grown on glass substrates at about 80°C were found to be polycrystalline n-type semiconductors with a room temperature resistivity of 40 mΩ cm, a carrier concentration of about 5×10¹⁸ cm^-3 and an electron mobility of approximately 20 cm² V^-1 s^-1. The refractive index at a wavelength of 1 μm and the room temperature direct band gap were found to be 2.85 and 1.7 eV respectively.     

Application of fullerene C60 nano-oil for performance enhancement of domestic refrigerator compressors

In this work, the fullerene C₆₀ nano-oil is proposed as a promising lubricant to enhance the performance of domestic refrigerator compressors. The stability of fullerene C₆₀ nanoparticles dispersed in a mineral oil and the lubrication properties of the nano-oil were investigated experimentally. It was confirmed that the nanoparticles steadily suspend in the mineral oil at stationary conditions for a long period of time. The friction coefficients of the nano-oil significantly decrease with increasing the concentration of nanoparticles in the mineral oil, especially at the lower applied loads. The friction coefficients of the nano-oil with the concentration of 1–3 g L⁻¹ are 12.9–19.6% lower than that of pure mineral oil. The applications of the nano-oil with the specific concentration of 3 g L⁻¹ to two domestic refrigerator compressors were examined by compressor calorimeter experiments. The results shows the COPs of two compressors were improved by 5.6% and 5.3%, respectively, when the nano-oil was used instead of pure mineral oil.     

Design of non-flammable mixed refrigerant Joule-Thomson refrigerator for precooling stage of high temperature superconducting power cable

A cryogenic Joule-Thomson (JT) refrigerator has many advantages for large industrial applications, including easy cooling power adjustability and high reliability because there are no moving parts at low temperature. In this paper, a single stage and a cascade type of non-flammable (NF) mixed refrigerant (MR) JT refrigerators have been proposed for the precooling process of a neon/nitrogen mixed refrigerant JT refrigerator. The neon/nitrogen MR JT refrigerator is used to maintain a subcooled state of liquid nitrogen coolant for an HTS (high temperature superconductor) cable.Both selected MRs for the 1st stage (low temperature cycle) of the cascade MR JT refrigerator and the single MR JT refrigerator are composed of Nitrogen (N₂), Argon (Ar), Tetrafluoromethane (CF₄, R14) and Octafluoropropane (C₃F₈, R218). R410A is selected as the refrigerant for the 2nd stage (high temperature cycle) of the cascade MR JT refrigerator, of which the cooling temperature is approximately 240 K. A commercial software with Peng-Robinson equation of state (EOS) is utilized to design the non-flammable MR JT refrigerator. The optimal design is discussed with consideration for various parameters such as the temperature staging, the operating pressure of the compressor and the mass flow rate of the working fluid. The maximum coefficient of performance (COP) and Carnot efficiency of the cascade MR JT refrigerator are obtained as 0.216 and 40%, respectively at 105 K. Exergy analysis is also carried out in this paper to reveal the irreversibility of the refrigeration cycle.     

Synthesis and characterization of lanthanide(III) complexes with a mesogenic Schiff-base,N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine

A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine, H₂ddsdp (abbreviated as H₂L³) that exhibits nematic mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H₂L³, upon condensation with hydrated lanthanide(III) nitrates, yields Ln^III complexes of the general composition [Ln₂(L³H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. Among the metal complexes, only that of Ho^III is found to be mesogenic with smectic-X and nematic phases. The IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L³H₂) to the Ln^III ions through two phenolate oxygens, rendering the overall geometry of the complexes to seven-coordinated polyhedron, possibly distorted mono-capped octahedron.     

Is the Roton in Superfluid 4He the Ghost of a Bragg Spot?

It has always been assumed that the roton in ⁴He had to do with local vorticity—hence the name! We present here an alternate view: the roton is viewed as a “soft mode”, precursor of a crystallization instability. In such a picture the liquid is “nearly solid”, and the long observed similarities of heat propagation in liquid and solid phases are naturally explained. In this qualitative paper we consider three models successively. A lattice gas with one atom per site displays a Mott localization transition, as shown by the Bangalore group. The important result is the vanishing of the superfluid order parameter (condensate fraction N _o) at the transition. There is no breakdown of translational symmetry and consequently no soft mode. Another lattice model with half filling, with an added nearest neighbour repulsion, was studied by Matsubara and Matsuda in the early 1950s it displays a first order transition between a superfluid and a localized charge density wave state. The excitation spectrum has a soft mode at zone edge near the transition, signalling the proximity of the CDW instability. Finally, we consider the realistic situation of a continuous system with no preexisting lattice. We approach the problem from the limit N _o = 0 instead of the ideal gas N _o = N. When N _o = 0 the quasiparticle spectrum and the charge density spectrum are decoupled. The latter should have a soft mode ω=ω_m if crystallization is close. That soft mode is a normal state property that has nothing to do with superfluidity. A small N _o acts to hybridize quasiparticles and density fluctuations: the resulting anticrossing lowers ω_m ² as well as the ground state energy. We show that N _o is bounded for two reasons: (i) if ω _m ² turns negative, the liquid is unstable towards freezing (ii) depletion due to quantum fluctuation exceeds N _o if the latter is too large. The resulting upper bound noindent for N/N _{o is} ? 1, a consequence of the deep roton minimum. The whole paper is qualitative, based on outrageous simplifications in order to make algebra tractable.     

Textural features of highly ordered Al-MCM-41 molecular sieve studied by X-ray diffraction,nitrogen adsorption and transmission electron microscopy

The preparation of a Al-MCM-41 mesoporous materials has been carried out using silica-gel and pseudoboehmite as silica and aluminum sources, respectively, and surfactant cetyltrimethylammonium bromide as structure template. The textural properties of the calcined Al-MCM-41 were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ isothermal adsorption measurements. The hexagonal structure parameter a_o was calculated based on d₍₁₀₀₎ XRD reflection as 4.75 nm. TEM images revealed the formation of a well-ordered Al-MCM-41. Accordingly, nitrogen adsorption measurements (BJH) showed a material with very narrow distribution and medium pore diameter of 3.14 nm. Mesopore volume based on adsorbed nitrogen was 0.51 cm³ g^− 1. Through a combination of XRD and N₂ adsorption data, the thickness of the channel walls of 1.61 nm could be calculated.     

2D Electrocatalysts for Converting Earth-Abundant Simple Molecules into Value-Added Commodity Chemicals: Recent Progress and Perspectives

The electrocatalytic conversion of earth-abundant simple molecules into value-added commodity chemicals can transform current chemical production regimes with enormous socioeconomic and environmental benefits. For these applications, 2D electrocatalysts have emerged as a new class of high-performance electrocatalyst with massive forward-looking potential. Recent advances in 2D electrocatalysts are reviewed for emerging applications that utilize naturally existing H₂O, N₂, O₂, Cl⁻ (seawater) and CH₄ (natural gas) as reactants for nitrogen reduction (N₂ → NH₃), two-electron oxygen reduction (O₂ → H₂O₂), chlorine evolution (Cl⁻ → Cl₂), and methane partial oxidation (CH₄ → CH₃OH) reactions to generate NH₃, H₂O₂, Cl₂, and CH₃OH. The unique 2D features and effective approaches that take advantage of such features to create high-performance 2D electrocatalysts are articulated with emphasis. To benefit the readers and expedite future progress, the challenges facing the future development of 2D electrocatalysts for each of the above reactions and the related perspectives are provided.     

Preparation of Nanoporous Carbonaceous Promoters for Enhanced CO2 Absorption in Tertiary Amines

Aqueous solutions of tertiary amines are promising absorbents for CO₂ capture, as they are typically characterized by a high absorption capacity, low heat of reaction, and low corrosivity. However, tertiary amines also exhibit very low kinetics of CO₂ absorption, which has made them unattractive options for large-scale utilization. Here, a series of novel nanoporous carbonaceous promoters (NCPs) with different properties were synthesized, characterized, and used as rate promoters for CO₂ absorption in aqueous N, N-diethylethanolamine (DEEA) solutions. To prepare a DEEA–NCP nanofluid, NCPs were dispersed into aqueous 3 mol·L⁻¹ DEEA solution using ultrasonication. The results revealed that among microporous (GC) and mesoporous (GS) carbonaceous structures functionalized with ethylenediamine (EDA) and polyethyleneimine (PEI) molecules, the GC–EDA promoter exhibited the best performance. A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO₂ absorption at 40 °C by 38.6% (36.8–50.7 kPa·min⁻¹) and improves the equilibrium CO₂ absorption capacity (15 kPa; 40 °C) by 13.2% (0.69–0.78 mol of CO₂ per mole of DEEA). Moreover, the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is suggested. The outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO₂ absorption and facilitate their large-scale deployment.     

Complexes of some rare earth metal ions of the mesogenic Schiff-base,N,N′-di-(4′-octyloxybenzoatesalicylidene)-l″,8″-diamino-3″,6″-dioxaoctane: Synthesis and spectral studies

A mesogenic Schiff-base, N,N′-di-(4′-octyloxybenzoatesalicylidene)-l″,8″-diamino-3″,6″-dioxaoctane; H₂dobsdd (H₂L³), that nematogenic mesophase was synthesized and its structure studied by elemental analysis and FAB mass, NMR and IR spectra. The Schiff-base, H₂L³, upon condensation with hydrated lanthanide(III) nitrates, yields Ln^III complexes of the general composition [Ln₂(L³H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. The IR and NMR spectral data imply a bi-dentate of the Schiff-base through two phenolate oxygens in its zwitterionic form (as L³H₂) to the Ln^III ions, rendering the overall geometry of the complexes to seven-coordinated polyhedron — possibly distorted mono-capped octahedron. Among the metal complexes, only that of La^III and Gd^III are found to be mesogenic.     

Review of the Current Synthesis and Properties of Energetic Pentazolate and Derivatives Thereof

The latest member of the azole family, the pentazolate or cyclo-N₅⁻, has received increased attention since its first mass-spectral detection by Christe et al. in 2002. As it is carbon- and hydrogen-free, the pentazolate anion can release large amounts of energy while simultaneously decomposing to environmentally friendly nitrogen gas. Due to these attractive qualities, cyclo-N₅⁻ and related compounds are essential in the advancement of high-energy-density materials (HEDMs) research. This review aims to provide a consolidated report on all research done on cyclo-N₅⁻, with a focus on pentazoles as energetic materials and on their experimental synthesis. Included in this review are the following: ① the historical significance of cyclo-N₅⁻; ② precursors of cyclo-N₅⁻; ③ synthesis routes of cyclo-N₅⁻ with a focus on arylpentazole precursors; ④ factors affecting the stability of cyclo-N₅⁻; ⑤ energetic performances of current energetic cyclo-N₅⁻-containing compounds; and ⑥ future possible experimental research. This review is a comprehensive summary of the current understanding of cyclo-N₅⁻, in an effort to further understand the potential of this anion for adoption as a powerful and environmentally friendly next-generation explosive.     

Double-Shelled Porous g-C3N4 Nanotubes Modified with Amorphous Cu-Doped FeOOH Nanoclusters as 0D/3D Non-Homogeneous Photo-Fenton Catalysts for Effective Removal of Organic Dyes

Graphite phased carbon nitride (g-C₃N₄) has attracted extensive attention attributed to its non-toxic nature, remarkable physical–chemical stability, and visible light response properties. Nevertheless, the pristine g-C₃N₄ suffers from the rapid photogenerated carrier recombination and unfavorable specific surface area, which greatly limit its catalytic performance. Herein, 0D/3D Cu-FeOOH/TCN composites are constructed as photo-Fenton catalysts by assembling amorphous Cu-FeOOH clusters on 3D double-shelled porous tubular g-C₃N₄ (TCN) fabricated through one-step calcination. Combined density functional theory (DFT) calculations, the synergistic effect between Cu and Fe species could facilitate the adsorption and activation of H₂O₂, and the separation and transfer of photogenerated charges effectively. Thus, Cu-FeOOH/TCN composites acquire a high removal efficiency of 97.8%, the mineralization rate of 85.5% and a first-order rate constant k = 0.0507 min⁻¹ for methyl orange (MO) (40 mg L⁻¹) in photo-Fenton reaction system, which is nearly 10 times and 21 times higher than those of FeOOH/TCN (k = 0.0047 min⁻¹) and TCN (k = 0.0024 min⁻¹), respectively, indicating its universal applicability and desirable cyclic stability. Overall, this work furnishes a novel strategy for developing heterogeneous photo-Fenton catalysts based on g-C₃N₄ nanotubes for practical wastewater treatment.     

Study on nonlinear optical,dielectric and pyroelectric properties of novel organic–inorganic hybrid material

A novel organic and inorganic hybrid material was prepared from a nonlinear, optically active imidazole derivative, 4-(nitrophenyl)-2,4-bis-(4,4′-[N,N-bis-(2-hydroxyethyl)aminophen-yl])imidazole (NPAH4), and metal alkoxide of Ta(V) via sol–gel process. The second-order nonlinear and pyroelectric properties of the hybrid film were investigated in terms of the second harmonic generation (SHG) and pyroelectric coefficient measurement. The SHG coefficient d₃₃ was found to be 28.6 pm/V at the fundamental wavelength of 1064 nm and the pyroelectric coefficient P was found to be 1.6×10⁻⁶ C/cm² K.     

Volatility of mercury in water

The rate of volatilization of mercury and oxygen from the aqueous phase to the gas phase was studied by bubbling with nitrogen. The ratio, K_L^Hg/K_L^O₂, of the mass transfer coefficient of mercury to that of oxygen was determined in the temperature range 278–308 K. The ratio of 0.94 ± 0.08 which was obtained was found to be higher than that for 19 other substances, such as krypton, radon, ethylene, methylene chloride and benzene, quoted in the literature. Thus, mercury was found to be readily volatilized from the aqueous to the gas phase, despite having a much lower vapor pressure and a higher molecular weight than the other substances.