Nuclear Magnetic Field Research Articles

JADES – the Rosetta stone of JWST-discovered AGN: deciphering the intriguing nature of early AGN

ABSTRACT JWST has discovered a large population of active galactic nuclei (AGN) at high redshift, which are weak in the X-rays. Here we present the NIRSpec spectrum of the most extreme of these objects, GN-28074, an AGN at $z=2.26$ with prominent hydrogen and He i broad lines, and with the highest limit on the bolometric to X-ray luminosity ratio among all spectroscopically confirmed AGN in GOODS. This source is also characterized by a mid-IR excess, likely associated with the AGN torus’ hot dust. The high bolometric luminosity and moderate redshift of this AGN allow us to explore its properties more in depth relative to other JWST-discovered AGN. The NIRSpec spectrum reveals prominent, slightly blueshifted absorption of H$\alpha$, H$\beta$, and He i $\lambda$10830. The Balmer absorption lines require gas with densities of $n_{\rm H}\gt 10^8~{\rm cm}^{-3}$, consistent with clouds in the broad-line region (BLR). This finding suggests that part of the X-ray weakness is due to high (Compton-thick) X-ray absorption by clouds in the BLR, or in its outer regions. GN-28074 is also extremely radio-weak. The radio weakness can also be explained in terms of absorption, as the inferred density of the BLR clouds makes them attenuate the radio emission through free–free absorption. Alternatively, the nuclear magnetic field may be underdeveloped, resulting both in intrinsically weak radio emission and lack of hot corona, hence intrinsic X-ray weakness. Finally, we show that recently proposed scenarios, invoking hyper-dense outflows or Raman scattering to explain the broad H$\alpha$, are ruled out.

Structure, Surface Topography, and Glass Transition Temperature of Dental Poly (Methyl Methacrylate) Resin Conjugated with 3,9-bisethenyl-2,4,8,10-tetraoxaspiro [5,5] Undecane as Cross-linker: An In Vitro Research.

To characterize and analyze the structural presentation of a new denture base copolymer with a spiro-acetal cross-linker at 10 and 20 wt.% concentrations by nuclear magnetic resonance (NMR) and field emission scanning electron microscopy-energy-dispersive X-ray (FESEM-EDX) spectroscopies. Also, to evaluate the glass transition temperature (TG) of the new copolymer. The investigational groups G10 and G20 were heat-cured with the new spiro-acetal cross-linker at the above-mentioned concentrations, respectively. The control group G0 was heat-cured without the new cross-linker. Nuclear magnetic resonance and EDX spectroscopies determined the copolymerization along with elemental composition. The surface characteristics were discerned by FESEM. Differential scanning calorimetry was employed to evaluate the TG of the resultant copolymer. Appropriate statistical operations were performed to compare the mean TG of the groups. The new copolymer's structure with the spiro-acetal cross-linker was configured with protons, carbons, aluminum, zirconium, yttrium, and silicon atoms. The TG of the resultant copolymer was high when compared with the G0. The 20 wt.% spiro-acetal cross-linker in the copolymer exhibited the highest TG. The spiro-acetal cross-linking comonomer incorporated in the heat-cure denture polymer produced a new denture base copolymer with elevated TG. The resultant configuration of the new copolymer was characterized, structurally presented, and confirmed. The new copolymer might exhibit augmented strength due to the copolymerized spiro-acetal cross-linker. Moreover, the smooth and regular surface of the copolymer would have minimum or negligible microbial adhesion due to the hydrophobicity of the spiro-acetal comonomer incorporated in the denture base composition. How to cite this article: Ravivarman C, Ajay R, Saatwika L, et al. Structure, Surface Topography, and Glass Transition Temperature of Dental Poly (Methyl Methacrylate) Resin Conjugated with 3,9-bisethenyl-2,4,8,10-tetraoxaspiro [5,5] Undecane as Cross-linker: An In Vitro Research. J Contemp Dent Pract 2024;25(5):486-493.

Porosity and pore structure evolution during the weathering of black shale

Pore type and pore structure evolves systematically across continuous black shale weathering profile. However, the extend and process of pore structure change is still an enigma. In this study, we try to unveil the pore structure evolution during weathering process through studying Cambrian Hetang shales in southern China. Fourteen shale samples, from protolith zone (PZ), fractured and weathered shale zone (FWZ), and saprolite zone (SZ), were collected to elucidate how porosity and pore structure develop during black shale weathering under subtropical condition. Through low pressure argon (Ar) gas adsorption (LP-ArGA), high pressure mercury intrusion (HPMI), nuclear magnetic resonance(NMR) and field emission scanning electron microscope (FESEM) observation, the results reveal significant differences in physical properties and pore structures among the PZ, FWZ, and SZ samples. Specifically, compared to PZ, FWZ and SZ samples are characterized by higher clay mineral content, lower organic matter (OM), and the absence of carbonates and pyrite. Total porosity, determined through HPMI and NMR, exhibits a gradual increase from PZ (6.70 % and 6.41 %) to FWZ (20.47 % and 13.45 %) and SZ (23.22 % and 12.48 %). Ar adsorption isotherms indicate a change in pore type from predominantly ink-bottle and slit-shaped in the PZ to mainly slit-shaped in FWZ and SZ. Integrated analysis of LP-ArGA, HPMI, NMR and SEM observation suggests a substantial decrease in the contribution of micropores to total pore volume (PV) and a concurrent increase in larger pores (meso-macropores) with the increase of weathering intensity. This results in smoother surfaces of micro-transition pores but rougher surfaces of macropores. Changes in mineralogy composition during weathering play a crucial role in influencing pore structure of shales and further accelerating the release and migration of toxic elements in black shale. Our study provides the essential theoretical foundation for the remediation of soil and water environmental pollution caused by black shale weathering.

Regulating sulfur migration and transformation in low water-binder ratio cementitious system incorporating phosphogypsum aggregate: Environmentally friendly clean materials

The paper aims to clarify the regulation mechanism of sulfur migration and transformation in a low water-binder ratio system incorporating phosphogypsum aggregate (LWC-PG). Firstly, the combination of S-containing adhesive material and phosphate gypsum aggregate can reduce the migration of sulfate ions (SO42−) in the phosphate gypsum aggregate. The reaction mechanism and macro and micro properties of LWC-PG are characterized by universal testing machine, low field nuclear magnetic field, isothermal calorimeter, XRD diffractometer, scanning electron microscope and nano-indentation. The results show that the calcium sulfoaluminate cementitious system (CSA) is compatible with PG. The results show that CSA is compatible with PG, and the 28d strength of 80 % phosphogypsum is 83.4 MPa, which can maintain the required strength for high-performance concrete. Secondly, the sulfides in PG react with C4A6S in CSA, resulting in the formation of ettringite that coats the surface of the C–S–H gel, thereby retarding the hydration rate of the slurry. However, due to the presence of phosphate gypsum aggregate, the reaction continues, enhancing the hydration of sulfate cement. Moreover, the interfacial transition zone between the PG and matrix exhibits a strong bond and shows no significant signs of deterioration. Lastly, when using 80 % phosphogypsum aggregate instead of natural sand and gravel to produce 100 m3 of concrete, 42 t of phosphogypsum aggregate can be used, which reduces the consumption of natural sand and gravel by 61.4 t, decreases energy consumption by 3070 MJ, reduces CO2 emissions by 178.06 kg, SO2 emissions by 0.37 kg, NOX emissions by 0.25 kg, and dust emissions by 0.087 kg. Life cycle evaluation demonstrates that the production of LWC-PG is associated with low carbon emissions and environmental friendliness, which significantly reduces environmental burden. This is of significant research importance for solid waste management and energy-saving and carbon reduction efforts.

Understanding Ion Dynamics in Closoborate-Type Lithium-Ion Conductors on Different Time-Scales.

The lithium-ion transport mechanism in 0.7Li(CB9H10)-0.3Li(CB11H12) complex hydride solid electrolyte was studied over a wide time-scale (ns-ms) by choosing appropriate techniques for assessing ionic motion on the desired time-scale using nuclear magnetic resonance (NMR) relaxation, AC impedance, and pulsed field gradient-NMR (PFG-NMR) measurements. The 7Li NMR line width decreased with increasing temperature, and the spin-lattice relaxation time T1 for the cation and anions showed a minimum near 303 K, indicating that the lithium ions and the anions were highly mobile. The activation energy estimated from the analysis of the NMR relaxation time matched well with the values estimated from the AC impedance and PFG-NMR. This confirms that the lithium-ion motion in 0.7Li(CB9H10)-0.3Li(CB11H12) is the same over a wide time-scale, suggesting steady Li-ion motion over a wide transport range. This understanding offers insights into strategies for designing complex hydride lithium superionic conductors.

Investigation of cross-scale characterization of porous structure and fluid index in bituminous coal via microwave-LN2 freeze-thaw cycles

Microwave-LN2 cyclic processing (MLCP) is a clean and high-efficiency anhydrous fracturing technology. The change in the porous structure of coal after freeze-thaw cycles significantly affects development efficiency of coalbed methane (CBM) in low porosity and permeability reservoirs, while there is a lack of in-depth macro-meso-micro studies. The damage mechanism of coal under microwave-LN2 cold and thermal shock and the evolution of pore fluid reservoir space is based on cross-scale pore characterisation. This paper evaluates the multi-scale porous structure variations of coal before and after MLCP was assessed by hydrogen nuclear magnetic resonance (1H NNR) and field emission scanning electron microscopy (FE-SEM). The evolutionary trends in coal pore fluid fugacity space under freeze-thaw cycles was indirectly characterised by T1-T2 spectra. Additionally, utilizing T2 distribution, peak area and pore throat changes reflect the evolution trend of coal pore space. The results indicate that as the cycles increased, the coal free water and total fluid reservoir space gradually expanded beyond the cycle threshold (n > 10), the free-fluid index rose to 25.68 %, and the free fluid saturation increased by 20.39 %. Additionally, the NMR permeability of the coal increased by 98.37–1471.65 %, and the pore throat distribution increased by 28.05 %. Comprehensive analysis showed that as the cycles progressed, the free water space in the pore space increased significantly, the proportion of bound water gradually decreased, and the internal pores and fluid space of the coal were improved. This study provides fundamental support for multidimensional evaluation of the porous structure of microwave-LN2 freeze-thaw cycles.

Self-Standing Thin Films of Cellulose Nanocrystals and Graphene Quantum Dots for Detection of Trace Iron(III)

Cellulose nanocrystal (CNC) thin films have gained attention for application in green optoelectronics devices. However, the dependence on plasticizers, external cross-linkers, or auxiliary polymers can impair the full exploration of the nanomaterials’ properties. Herein, we report on the evaluation of a surface-oxidized CNCs ultrathin film, made from a formulation that excludes the use of auxiliary compounds, to be used as a sensing platform. The physicochemical characterizations using UV–vis, Fourier transform infrared , and Raman spectroscopies, nuclear magnetic resonance, zeta potential, transmission electron and field emission scanning electron microscopies, X-ray diffraction, thermogravimetric analysis, and contact angle measurement showed that the adopted procedure led to (i) the modification of the CNC surface and (ii) the formation of smaller CNCs. The production of casting films from highly diluted CNC-modified aqueous suspensions showed that a very thin, transparent, self-supporting, and manipulable film could be obtained, which was not the case for diluted unmodified CNC suspension. Additionally, the CNC thin film has been demonstrated to be a suitable platform for hosting graphene quantum dots, based on which an optochemical sensor was successfully employed to detect iron(III) in a dynamic range from 1 fM to 2 pM, yielding a limit of detection of 0.8 fM.

Cations impact radical reaction dynamics in concentrated multicomponent aqueous solutions.

Ultraviolet (UV) photolysis of nitrite ions (NO2-) in aqueous solutions produces a suite of radicals, viz., NO·, O-, ·OH, and ·NO2. The O- and NO· radicals are initially formed from the dissociation of photoexcited NO2-. The O- radical undergoes reversible proton transfer with water to generate ·OH. Both ·OH and O- oxidize the NO2- to ·NO2 radicals. The reactions of ·OH occur at solution diffusion limits, which are influenced by the nature of the dissolved cations and anions. Here, we systematically varied the alkali metal cation, spanning the range from strongly to weakly hydrating ions, and measured the production of NO·, ·OH, and ·NO2 radicals during UV photolysis of alkaline nitrite solutions using electron paramagnetic resonance spectroscopy with nitromethane spin trapping. Comparing the data for the different alkali cations revealed that the nature of the cation had a significant effect on production of all three radical species. Radical production was inhibited in solutions with high charge density cations, e.g., lithium, and promoted in solutions containing low charge density cations, e.g., cesium. Through complementary investigations with multinuclear single pulse direct excitation nuclear magnetic resonance (NMR) spectroscopy and pulsed field gradient NMR diffusometry, cation-controlled solution structures and extent of NO2- solvation were determined to alter the initial yields of ·NO and ·OH radicals as well as alter the reactivity of NO2- toward ·OH, impacting the production of ·NO2. The implications of these results for the retrieval and processing of low-water, highly alkaline solutions that comprise legacy radioactive waste are discussed.

Structure Regulation of Sodium Ion on Nanosilica Growth Visualized Using 29Si Nuclear Magnetic Resonance Spectroscopy

Understanding the action mechanism of sodium ions in sodium silicate solutions is necessary for the synthesis of nanosilica. The microstructure of sodium silicate solutions with SiO2:Na2O ratios ranging from 2 to 4 was characterized by 29Si nuclear magnetic resonance spectroscopy, and the magnetic shielding tensor of the nuclear magnetic field was calculated using the density functional theory. Sodium ions contribute significantly to the magnetic shielding tensor, thereby playing a key role in the structural evolution of sodium silicate solution species. Wave function analysis was used to further study the mechanism of action of sodium ions. Theoretical calculation results show that Na not only affects the magnetic shielding and regulates the splitting and change of NMR peaks but also regulates the aggregation-free energy and growth morphology of silica nanoparticles. Thus, the structural regulation of sodium ions on nanosilica growth and aggregation was proposed. Magnetic shielding caused by partial symmetry disappears with the reduction of sodium ions in the system, resulting in uniform magnetic shielding. Meanwhile, the anisotropic aggregation free energy of microscopic particles tends to be isotropically distributed, resulting in the spherical growth tendency of the nanosilica particles. Small-angle X-ray scattering and transmission electron microscopy were used to verify these conclusions. In this work, we adopted the leading quantum chemical computational methods with advanced computer technology and quantum chemical methods to research the microscopic effect of sodium ions during nanosilica growth, thereby overcoming the limitations of the analytical experience and paradigm established with traditional organic chemistry and providing important theoretical reference value for the field of spectral systems and characterization measurement methods. At the same time, the reasonable mechanism of action is proposed, which greatly expands the product application field of nanosilica.

Electromagnetic and thermal characteristics of supplementary-conductor-based no-insulation REBCO pancake coils with comparison to conventional-based ones

A no-insulation (NI) winding technique was originally developed in 2011 to enhance the thermal stability of Rare-Earth Barium Copper Oxide (REBCO) pancake coils. Thereafter, several similar techniques of controlling turn-to-turn contact resistance have been proposed, and they can be categorized as the conventional NI winding technique, named a conventional-based NI (CNI) technique in this paper. Recently, a few novel winding techniques different from the CNI winding technique but similar have been proposed: an intra-layer no-insulation technique and a conductive-epoxy-resin-coating technique. These techniques utilize supplementary conductors attached or embedded on REBCO coils as bypassing current paths, which is, in this paper, categorized as supplementary-conductor-based no-insulation (SNI) techniques. These conventional-based and supplementary-conductor-based NI techniques have high a potential for high-field applications. As of today, the applications of these NI techniques are nuclear magnet resonance and magnetic field imaging, and compact nuclear reactors. Those applications require a high performance; however, it is still uncertain which NI technique is suitable for which application since the differences in the characteristics are not clarified well. Therefore, we have systematically investigated the thermal stability of SNI REBCO pancake coils with different circuit parameters in this paper. The thermal stability simulation results of SNI REBCO coils were compared with those of CNI REBCO coils. As a result, the SNI REBCO pancake coils are able to be operated with high thermal stability without deteriorating charging performance as long as the turn-to-turn contact resistances between REBCO tapes and supplementary conductors are low.

Search for a space charge layer in thin film battery materials with low-energy muons

In an all solid state Li-ion battery, it is crucial to reduce ionic resistivity at the interface between the electrode and the electrolyte in order to enhance Li+ mobility across the interface. Recent first principles calculations predict the presence of a space-charge layer (SCL) at the interface due to the difference in the Li+ chemical potential at the interface between two different materials, as in the metal-semiconductor junction in electronic devices. However, the presence of SCL has never been experimentally observed. Our first attempt in a fresh multilayer sample, Cu(10 nm)/Li3PO4(50 nm)/LiCoO2(100 nm) on a sapphire substrate, with low-energy µ +SR (LE µ +SR) revealed a gradual change in the nuclear magnetic field distribution width as a function of implantation depth even across the interface between Li3PO4 and LiCoO2. This implies that the change in the field distribution width at SCL of the sample is too small to be detected by LE µ +SR.

Negative muon spin rotation and relaxation on superconducting MgB2

The internal nuclear magnetic field in a superconducting MgB2 powder sample was studied with a µ− SR technique. Although the past µ +SR study on MgB2 reported the appearance of a dynamic behavior even below Tc due to µ + diffusion, µ− SR shows a static behavior in the whole temperature range measured, as expected. The ZF-µ− SR spectra do not suggest any appearance of additional magnetic field below Tc within the experimental accuracy. Considering the small asymmetry of the µ− SR signal, it is a challenge to detect the appearance of an internal magnetic field below Tc caused by the time reversal symmetry breaking.

Study of the effect of magnetic field characteristics on Rayleigh-Taylor instability with density gradient layers

Inertial confinement fusion (ICF) is a possible path of fusion technology for fusion ignition, but during the implosion of a magnetized plasma target by compression, the magnetic Rayleigh-Taylor (R-T) instability similar to that at the interface of the denser and less dense phases can arise when the plasma is subjected to gravitational and magnetic forces, which in turn affect the confinement characteristic and the process of fusion burn. In this study, the R-T instability of two phases in the presence/ absence of a magnetic field in a two-dimensional rectangular duct is simulated based on the MHD model adopted in ANSYS FLUENT. The simulation results show that the R-T instability is substantially weakened for the case with an Atwood number of 0.29 where a constant (DC) magnetic field is imposed in the opposite direction to the gravitational acceleration, meanwhile, a strong countercurrent flow, which occurs near the side walls, enhances the heat and mass transport process, which is related to the M-shape velocity profile formed in the flow channel. Besides, when a DC magnetic field perpendicular to the direction of the gravitational acceleration is introduced, the R-T instability vanishes from the initial moment to the end. When a sinusoidal wave form of varying (AC) magnetic field is introduced, the R-T instability is substantially facilitated. The evolutions of the interface and pressure field distribution are significantly correlated with the change in intensity and direction of the AC magnetic field. After about one cycle of the magnetic field's variation, the density gradient layers in the vertical direction are entirely converted to a density stratification in the horizontal direction with the denser phase occupying the region near the sidewalls of the duct, and ever since then, the R-T instability disappears completely. These findings can provide supports for the design of nuclear fusion devices and magnetic fields.

Spin exchange optically pumped nuclear spin self compensation system for moving magnetoencephalography measurement.

Recording moving magnetoencephalograms (MEGs ), in which a person's head can move freely as the brain's magnetic field is recorded, has been a key subject in recent years. Here, we describe a method based on an optically pumped atomic co-magnetometer (OPACM) for recording moving MEGs. In the OPACM, hyper-polarized nuclear spins produce a magnetic field that blocks the background fluctuation low-frequency magnetic field noise while the rapidly changing MEG signal is recorded. In this study, the magnetic field compensation was studied theoretically, and we found that the compensation is closely related to several parameters such as the electron spin magnetic field, nuclear spin magnetic field, and holding magnetic field. Furthermore, the magnetic field compensation was optimized based on a theoretical model . We also experimentally studied the magnetic field compensation and measured the responses of the OPACM to different magnetic field frequencies. We show that the OPACM clearly suppresses low-frequency (under 1 Hz) magnetic fields. However, the OPACM responses to magnetic field frequencies around the band of the MEG. A magnetic field sensitivity of 3 fT/Hz1/2 was achieved. Finally, we performed a simulation of the OPACM during utilization for moving MEG recording. For comparison, the traditional compensation system for moving MEG recording is based on a coil that is around 2 m in dimension , while our compensation system is only 2 mm in dimension .

A dual-axis high-order harmonic and single-axis phase-insensitive demodulation atomic magnetometer for in situ NMR detection of Xe

Based on the parametric oscillation process, we demonstrate the dual-axis phase-sensitive demodulation (PSD) and single-axis phase-insensitive demodulation (PISD) for the atomic magnetometer in an in situ nuclear magnetic resonance (NMR) detection system, which can separate the precession signals of NMR from the oscillating magnetic fields. The two orthogonal magnetic fields can be detected simultaneously and independently by selecting the optimal demodulation phases with the traditional PSD method. The response signals of the parametric modulation magnetometer demodulated with high order harmonic signals are evaluated, which is a new exploration. The first order harmonic demodulation can present the best sensitivity about 250 fT/Hz1/2. The high order harmonic demodulation technology supplies a twofold 3 dB bandwidth. With the PISD method, a single-axis demodulation technique is proposed. The transverse nuclear spin precession magnetic fields can be extracted effectively with the demodulation R signal outputs by setting a specific longitudinal modulation magnetic field amplitude, which is a new demodulation strategy compared with the traditional demodulation method for the NMR system.

Operando Muon Spin Rotation and Relaxation Measurement on LiCoO2 Half-Cell

The self-diffusion coefficient of Li+ ions (DLiJ) in LixCoO2 has been determined during charge and discharge reactions of a LiCoO2 half-cell using a positive muon spin rotation and relaxation (μ+SR) technique through the observation of the fluctuating nuclear magnetic field at room temperature: specifically, with an operando μ+SR technique in the half-cell potential range between 3.0 and 4.7 V. The estimated DLiJ was found to range between 10–12 and 10–11 cm2/s and increase as Li content (x) decreased. Although the slope (dDLiJ/dx) was relatively steep below the vicinity of x = 1, DLiJ slowly increases with decreasing x at x < 0.8 with two small minima at x ∼ 2/3 and x ∼ 1/2. The obtained result in the initial charging process agreed with that obtained in the second charging process. Furthermore, it was discovered that the change in DLiJ with x is similar to that of the reported self-diffusion coefficient estimated using an electrochemical technique for a film sample. By combining with the electrochemical measurement, the x dependence of the reactive surface area of the LixCoO2 electrode was first determined, while it was assumed to be independent of x.

Hybrid perylene-cored poly(amidoamine) dendrimer with coumarin and calcozine red 6G end groups: From photophysical properties to cell imaging

In this article, we looked at how to make fluorescence hybrid dendrimers using perylenediimide (PTCDI) cores and calcozine red 6 G and coumarin end groups. Perylenetetracarboxylic dianhydride (PTCDA) is used as core, and 4th generation poly(amidoamine) dendrimer (PAMAM) is synthesized to produce PG4.0. Then, PG4.0 is reacted with calcozine red 6 G and 7-methacryloyloxy-4-methylcoumarin (MCMC). Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) are used to characterize the structure of synthesized fluorescent hybrid dendrimers. Optical properties are demonstrated using fluorescence microscopy, a fluorescence spectrophotometer, and UV–vis–NIR reflectance spectra. Hybrid dendrimers were transparent in the NIR range, according to UV-Vis-NIR reflectance spectra. Moreover, quantum yield (Φs) of hybrid dendrimers was calculated in dimethylformamide (DMF), ethanol, and distilled water (H2O). PG4R32 and PG4M16R16 showed the maximum quantum yield in ethanol due to great interaction of structure with ethanol and the arrangement of ring-opened amide shape of calcozine red 6 G gather in compound. At long last, SH-SY5Y cells were utilized to measure cell uptake and fluorescence imaging exhibitions of PG4.0 (perylene-3,4,9,10-tetracarboxylic diimide (PTCDI)-based generation 4 amino terminated poly(amidoamine)dendrimers), PG4M32 (perylene-3,4,9,10-tetracarboxylic diimide (PTCDI)-based generation 4 amino terminated poly(amidoamine)dendrimers in which 32 amine groups of PAMAM are conjugated with coumarin derivatives), PG4R32 (perylene-3,4,9,10-tetracarboxylic diimide (PTCDI)-based generation 4 amino terminated poly(amidoamine)dendrimers in which 32 amine groups of PAMAM are conjugated with rhodamine derivatives), and PG4M16R16 (perylene-3,4,9,10-tetracarboxylic diimide (PTCDI)-based generation 4 amino terminated poly(amidoamine)dendrimers in which 16 amine groups of PAMAM are conjugated with rhodamine and coumarin derivatives) pigments, and as a result, pigments had a great capacity for live-cell fluorescence imaging.

3D food printing curing technology based on gellan gum

The fluid state of 3D food printing products greatly limits the customization of the shape. To improve the molding quality, a 3D food printing curing technology based on the temperature-sensitive phase-change characteristics of gellan gum was developed. Corn starch was used as the printing substrate to produce a gel that solidifies during printing. The pre-gelatinized starch slurry containing gellan gum was placed in a barrel with a heating function and extruded onto the printing platform at room temperature. Rheological tests, printing quality evaluations, and low-field nuclear magnetic fields proved that the slurry with gellan gum had good extrusion and printing feasibility. The product supplemented with 4% or 6% gellan gum exhibited significant plastic deformation, which indicated formation of a solid gel. Temperature sweep rheology analyses revealed that gellan gum guided the curing performance by affecting the curing temperature and curing speed of the slurry. Gellan gum improved hardness of the product and destroyed the network structure by self-cooling cross-linking and inhibiting starch gelatinization, which changed product adhesion.

Nanoscale solid-state nuclear quadrupole resonance spectroscopy using depth-optimized nitrogen-vacancy ensembles in diamond

Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) spectroscopy of bulk quantum materials have provided insight into phenomena, such as quantum phase criticality, magnetism, and superconductivity. With the emergence of nanoscale 2D materials with magnetic phenomena, inductively detected NMR and NQR spectroscopy are not sensitive enough to detect the smaller number of spins in nanomaterials. The nitrogen-vacancy (NV) center in diamond has shown promise in bringing the analytic power of NMR and NQR spectroscopy to the nanoscale. However, due to depth-dependent formation efficiency of the defect centers, noise from surface spins, band bending effects, and the depth dependence of the nuclear magnetic field, there is ambiguity regarding the ideal NV depth for surface NMR of statistically polarized spins. In this work, we prepared a range of shallow NV ensemble layer depths and determined the ideal NV depth by performing NMR spectroscopy on statistically polarized 19F in Fomblin oil on the diamond surface. We found that the measurement time needed to achieve a signal-to-noise ratio of 3 using XY8-N noise spectroscopy has a minimum at an NV ensemble depth of 5.5 ± 1.5 nm for ensembles activated from 100 ppm nitrogen concentration. To demonstrate the sensing capabilities of NV ensembles, we perform NQR spectroscopy on the 11B of hexagonal boron nitride flakes. We compare our best diamond to previous work with a single NV and find that this ensemble provides a shorter measurement time with excitation diameters as small as 4 μm. This analysis provides ideal conditions for further experiments involving NMR/NQR spectroscopy of 2D materials with magnetic properties.

Reflectance and photophysical properties of rhodamine 6G/2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid as cold hybrid colorant

Rhodamine 6G (Rh6G) is modified by ethylenediamine to obtain rhodamine with amine functional groups (Rh6G-NH2). Rh6G-NH2 as an initial core is used to bond coumarin derivatives. Synthesized fluorescent colorants are specified using Fourier transform infrared spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) to analyze the structure of the fluorescent pigments. Fluorescence microscopy, fluorescence spectrophotometer, and UV–visible–NIR reflectance spectra are used to demonstrate the optical properties. UV–Vis–NIR reflectance spectra showed that synthesized colorants were transparent in NIR region. Also, photophysical properties of 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid (MOHCYAA), Rh6G-NH2, and hybrid 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid/rhodamine 6G (HMR) were investigated. Type of solvent had a strong effect on quantum yield. Rh6G-NH2 (ϕs = 0.66) and HMR (ϕs = 0.72) displayed the maximum quantum yield in ethanol due to good interaction with ethanol and the formation of ring-opened amide form of rhodamine group. Finally, Rh6G-NH2 and HMR displayed the maximum quantum yield in ethanol due to good interaction of structure with ethanol and the formation of ring-opened amide form of rhodamine group in compound.