Broad Signal Research Articles

Single‐Step Acer pentapomicum‐Mediated Green Synthesis of Silver Nanoparticles and Their Potential Antimicrobial and Antioxidant Activities

The current investigation is aimed at synthesizing nonhazardous, ecofriendly silver nanoparticles (AgNPs) from aqueous leaf extract of Acer pentapomicum and at evaluating its antibacterial, antifungal, and antioxidant activities. In the present study, AgNPs were synthesized at room temperature by mixing 7 mL of 1 mM AgNO3 with 1 mL of A. pentapomicum leaf extract. The synthesized AgNPs were then characterized via various techniques, including UV/visible spectrophotometry showing maximum absorbance at 450 nm. Scanning electron microscopy (SEM) reveals a spherical shape of AgNPs with a size range of 19‐25 nm, while the average crystalline nanosize of 9.5 nm and crystalline nature were confirmed by XRD. FTIR showing a broad signal of 3394.71 which confirmed the coating of phenolic and alcoholic compounds on AgNPs, indicating their possible role in the capping and stabilization of silver nanoparticles. EDX showed the elemental composition of the synthesized nanoparticles. Our AgNPs were also found stable at a temperature of 55°C and pH range of 6‐7 and in the presence of a salt solution. Furthermore, the green synthesized AgNPs were found to exhibit potent antibacterial activity against various bacterial species, with a maximum of 66% inhibition against Pseudomonas aeruginosa and 50.5% against E. coli and Xanthomonas campestris. These nanoparticles also possess good antifungal activity against various fungal species. Regarding the antioxidant activity, the AgNPs were found to possess a maximum of 93% antioxidant activity against DPPH at a concentration of 250 μg/mL and a minimum of 74% scavenging activity at 5 μg/mL.

Multi-channel optical hybrid filter controlled by extrinsic parameters in various phases of Eu3+:BiPO4

We propose a multi-channel optical hybrid filter which can regulate into a single-channel narrowband filter (SCNBF), hybrid band filter (HBF), and the dual-channel narrow band filter (DCNBF) when the input is a broad signal. The multi-channel optical hybrid filter results from the multiple evolutions of the spectral linewidth of fluorescence (FL) signal and Stokes signal generated by the spontaneous four-wave mixing. These evolutions can be controlled by changing the extrinsic parameters (i.e., gate position, gate width, laser power, and detuning) in various phases of europium-doped BPO (Eu3+:BiPO4) as the extrinsic parameters manipulate the ratio of FL and Stokes in the composite signal (FL + Stokes) and select the energy levels. The composite signal contents vary as per the linewidth through the out-of-phase and in-phase k-vectors due to destructive and constructive interferences. The maximum bandwidth contrast we attained was 91% for SCNBF, 49% and 85% for HBF, and 90% and 88% for DCNBF.

Solvent-Dependent Excited-State Evolution of Prodan Dyes.

Excited-state character and dynamics of two 6-(dimethylamino)-2-acylnaphthalene dyes (Prodan and Badan-SCH2CH2OH) were studied by picosecond time-resolved IR spectroscopy (TRIR) in solvents of different polarity and relaxation times: hexane, CD3OD, and glycerol-d8. In all these solvents, near-UV excitation initially produced the same S1(ππ*) excited state characterized by a broad TRIR signal. A very fast decay (3, ∼100 ps) followed in hexane, whereas conversion to a distinct IR spectrum with a ν(C═O) band downshifted by 76 cm-1 occurred in polar/H-bonding solvents, slowing down on going from CD3OD (1, 23 ps) to glycerol-d8 (5.5, 51, 330 ps). The final relaxed excited state was assigned as planar Me2N → C═O intramolecular charge transfer S1(ICT) by comparing experimental and TDDFT-calculated spectra. TRIR conversion kinetics are comparable to those of early stages of multiexponential fluorescence decay and dynamic fluorescence red-shift. This work presents a strong evidence that Prodan-type dyes undergo solvation-driven charge separation in their S1 state, which is responsible for the dynamic fluorescence Stokes shift observed in polar/H-bonding solvents. The time evolution of the optically prepared S1(ππ*) state to the S1(ICT) final state reflects environment relaxation and solvation dynamics. This finding rationalizes the widespread use of Prodan-type dyes as probes of environment dynamics and polarity.

Synthesis and Properties of the Octaboron Cluster Series hypercloso‐B8Cl8, the Radical Anion hypercloso‐[B8Cl8].− and the Dianion closo‐[B8Cl8]2−

AbstractThe synthesis, spectroscopic data, redox properties of B8Cl8, [B8Cl8].−, and [B8Cl8]2−, and the single‐crystal X‐ray structure analysis of [Ph4P]+2 [B8Cl8]2− ⋅ CH3CN are described. Temperature‐dependent 11B NMR measurements and theoretical studies (DFT) concerning the fluxional behavior of [B8Cl8]2− will be discussed. – B8Cl8 reacts with reductants like iodide to the intense purple colored radical anion [B8Cl8].− which is formed as well from B8Cl8 by traces of water. The colorless dianion closo‐[B8Cl8]2− is obtained by the reaction of B8Cl8 or [B8Cl8].− with iodide. The single‐crystal X‐ray structure analysis of [Ph4P]+2[B8Cl8]2− confirms the dodecahedral D2d structure of [B8Cl8]2−. The 11B NMR spectra of [B8Cl8]2− solutions show only one broad signal even at low temperatures due to the fast fluctuation of the [B8Cl8]2− polyhedron. The energy of the C2v structure isomer of [B8Cl8]2− was calculated by DFT methods to be only 0.6 kcal/mol higher in energy than the D2d form, and the activation barrier for the D2d to C2v transformation is predicted to be about 0.9 kcal/mol.

Siglecs as Therapeutic Targets in Cancer.

Simple SummaryHyperglycosylated cancer cells are often decorated with abundant sialic acids, which are recognized by Sialic acid binding immunoglobulin type lectins (Siglecs) expressed on immune cells. As sialic acids are normally expressed on almost all cell types, Siglecs can function as receptors for “self”. Presently, 15 human Siglecs (including non-sialic acid binding Siglec XII) are known, of which most are immunoinhibitory receptors that induce strong inhibitory signaling when Siglecs bind sialic acids. Hence, tumor cells use hyper sialic acid expression in their favor to modify the immune system that can lead to immune suppression. Such engagement along the Siglec-sialic acid axis can dampen major killing modes of effector immune cells and suppress the activation of immune responses, which can lead to immune tolerance and tumor growth. In this review, we emphasized recent studies on all 15 Siglecs found in humans, many of which still remain understudied. In addition, we highlighted different strategies in disrupting the surface Siglec-sialic acid interactions, including antibodies and glycan moieties, which can steer back antitumor immune responses to reduce tumor size and improve overall survival of cancer patients.Hypersialylation is a common post-translational modification of protein and lipids found on cancer cell surfaces, which participate in cell-cell interactions and in the regulation of immune responses. Sialic acids are a family of nine-carbon α-keto acids found at the outermost ends of glycans attached to cell surfaces. Given their locations on cell surfaces, tumor cells aberrantly overexpress sialic acids, which are recognized by Siglec receptors found on immune cells to mediate broad immunomodulatory signaling. Enhanced sialylation exposed on cancer cell surfaces is exemplified as “self-associated molecular pattern” (SAMP), which tricks Siglec receptors found on leukocytes to greatly down-regulate immune responsiveness, leading to tumor growth. In this review, we focused on all 15 human Siglecs (including Siglec XII), many of which still remain understudied. We also highlighted strategies that disrupt the course of Siglec-sialic acid interactions, such as antibody-based therapies and sialic acid mimetics leading to tumor cell depletion. Herein, we introduced the central roles of Siglecs in mediating pro-tumor immunity and discussed strategies that target these receptors, which could benefit improved cancer immunotherapy.

Unveiling an NMR-Invisible Fraction of Polymers in Solution by Saturation Transfer Difference.

The observation of signals in solution NMR requires nuclei with sufficiently large transverse relaxation times (T2). Otherwise, broad signals embedded in the baseline afford an invisible fraction of nuclei (IF). Based on the STD (saturation transfer difference) sequence, IF-STD is presented as a quick tool to unveil IF in the 1H NMR spectra of polymers. The saturation of a polymer in a region of the NMR spectrum with IF (very short 1H T2) results in an efficient propagation of the magnetization by spin diffusion through the network of protons to a visible–invisible interphase with larger 1H T2 (STDon). Subtracting this spectrum from one recorded without saturation (STDoff) produces a difference spectrum (STDoff-on), with the nuclei at the visible–invisible interphase, that confirms the presence of an IF. Analysis of a wide collection of polymers by IF-STD reveals IF more common than previously thought, with relevant IF figures when STD > 0.4% at 750 MHz. A fundamental property of the IF-STD experiment is that the signal is generated within a single state comprising polymer domains with different dynamics, as opposed to several states in exchange with different degrees of aggregation. Contrary to a reductionist visible–invisible dichotomy, our results confirm a continuous distribution of nuclei with diverse dynamics. Since nuclei observed (edited) by IF-STD at the visible–invisible interphase are in close spatial proximity to the IF (tunable with the saturation time), they emerge as a privileged platform from which gaining an insight into the IF itself.

Maintaining chromatic dispersion and signal gain performances in a chalcogenide buffer step-index optical fiber.

Aiming at maintaining the chromatic dispersion properties and fiber optical parametric amplification (FOPA) performance when fiber core fluctuation occurs, we propose a buffer step-index optical fiber. The AsSe2 chalcogenide glass is employed as the core material due to its high nonlinearity and broad transmission spectrum. The calculated results in this study show that the chromatic dispersion variation due to the change of core diameter can be greatly suppressed and a continuous and very broad FOPA signal gain spectrum can be obtained and maintained by carefully controlling the core, buffer and cladding properties such as refractive index and diameters. The calculated results in this study showed that by using the proposed 3-cm-long fiber pumped at 5.02 µm, a broad signal gain bandwidth from 3 to 14 µm at about 15 dB is attainable although the fiber core diameter Dc drastically fluctuated from 2 to 5 µm and the buffer diameter Db varies from 8.9 to 9.3 µm. Moreover, when Dc varies in smaller range from 3 to 4 µm, the FOPA signal gain spectra calculated at different fixed values of Db in the range from 8.9 to 9.3 µm are highly maintained. When Db is kept at 9.0 µm and Dc varies from 3 to 4 µm, the calculated FOPA signal gain spectra at different pump wavelengths from 4.98 to 5.02 µm are also nearly identical in the wavelength range from 3 up to 13 µm.

Superimposed contributions to two-terminal and nonlocal spin signals in lateral spin-transport devices

The spin voltages produced by spin accumulation and Hanle spin precession in a lateral spin-transport device with a silicon channel and ferromagnetic tunnel contacts (Fe/MgO) are probed for a wide range of magnetic fields. Signal analysis reveals that for the interpretation of the two-terminal magnetoresistance and the nonlocal spin signals, one needs to consider various superimposed contributions, namely, (i) spin signals arising from spin transport of mobile carriers through the Si channel from one ferromagnetic contact to the other, thus depending on the relative magnetization of the two contacts, (ii) spin signals also arising from the spin accumulation of mobile carriers in the Si channel but generated at each of the ferromagnetic contacts separately, and (iii) spin signals originating from spin accumulation of carriers that are confined at or near the Si/MgO interface of the magnetic tunnel contacts, with rather different spin precession characteristics. Perhaps surprisingly, in the nonlocal spin signal a clear broad Hanle signal from confined electrons is also observed, and argued to be mediated by heat flow from the injector to the nonlocal detector.

CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b

Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 Å and the He I triplet at 10 830 Å. We present the discovery of the Ca II IRT at 7σ in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, Hα, and K I. The upper limits reported here for these lines are consistent with previous studies.

Exploration of Graphene Layers in Various Carbon Materials by Raman Spectroscopic Techniques

Structural figure prints for identifying the molecules in graphene layers of various carbon materials can be obtained from Raman spectroscopy. In this review we have discussed the Microraman analysis of few- layer graphenes from different carbon samples originating from hydrocarbon and agricultural derivatives. This review also shows the crystallite size dependence of the D-band in the Raman spectrum. Deconvolution of broad signal peaks is done to get multiple overlapping bands giving information about various aspects of defects and structure of graphitic materials. This review also contains information regarding different types of defects that can be analyzed using Raman spectroscopy.

Complexes of 1,3-Diisobutyl Thiourea with Copper(I), Zinc(II) and Mercury(II): Their Antioxidant and Antibacterial Evaluation

The reaction of 1,3-Diisobutyl thiourea (Tu) with metal salts, {[CuX (X = Cl, I)], [ZnCl2] and [HgI2] in an appropriate stoichiometric ratio afforded the corresponding metal complexes [Tu2CuCl] (1), [Tu3CuI] (2), [Tu2ZnCl2] (3) and [Tu2HgI2] (4) in good yields. The FT-IR data show typically broad signals (3278–3288 cm−1) attributed to the involvement of NH bonds in extensive hydrogen bonding. The structures of complexes were proposed based on a spectroscopic data set. Compounds 1 and 2 were additionally characterized by single-crystal X-ray analysis. Complexes 1–4 were tested for their free radical scavenging efficiency using 2,2-diphenyl-1-picrylhydrazyl free radical (hereafter abbreviated as DPPH). The free radical scavenging activity was a function of decrease in the resultant absorption of DPPH solution after the mixing of an appropriate concentration of the respective complex. The activity of complexes was determined to be dose dependent and increased concentration of the complex resulted in improved antioxidant activity. Compound 1 was found to be the most efficient, with 79.9% free radical scavenging activity. Complexes were also tested for their efficiency against selected strains of bacteria (E. coli, S. flexneri, S. typhi, and P. aeruginosa) and the activities were compared to commercially available standard drug cephradine. Compound 1 was more active against P.aeruginosa (ZI 13.25), while compound 4 was found to be more active against E. coli (ZI 11.0), S. flexneri (ZI 11.2), and S. typhi (ZI 10.5).

Loudspeaker configuration in reverberation rooms for sound absorption measurement using room mode determination

For Sabine absorption coefficient measurements in reverberation rooms, it is preferable to excite as many room modes as possible. But the number of excited room modes is significantly affected by many factors, among which one dominating factor is the loudspeaker location particularly at frequencies below the Schroeder frequency. In turn, this could significantly influence the statistical absorption coefficient obtained according to ISO 354. Therefore, this study aims to investigate the impact of loudspeaker configurations on the excitation of room modes. Frequency response functions are measured using a broad band steady state noise signal using four sound sources at various locations, and the numbers of excited room modes in the one-third octave bands are quantified and compared against those by Green's function simulations. A procedure for determining favorable loudspeaker positions based on the excited room modes is proposed, which can be a useful input to the working group of the ISO 354 standard.

Abstract 1789: Triggering anti-tumor immunity by overexpressing of MAVS in combination with PD-L1 ICB in immune insensitive colorectal cancers

Abstract While the use of immune checkpoint blockade (ICB) has gained significant traction as a viable therapy for cancers, many more cancers remain refractory to these immunotherapies due to their highly immunosuppressive tumor microenvironment (TME). From both the earlier published report and our analysis of clinical cohorts of colorectal cancer, we found that the expression of MAVS (Mitochondrial Antiviral Signaling Protein) was significantly reduced. Because MAVS are known to play a key role in the initiation of anti-viral innate immunity, we hypothesized that MAVS may be critical in anti-tumor immune response and tumor cells are under evolutionary pressure to reduce MAVS expression. As such, the stimulation of the MAVS pathway in tumor cells may be a necessary precursor to trigger anti-tumor immune response and reverse local immunosuppressive TME. To circumvent issues associated with intracellular double stranded RNA ligand stimulation, we exploited the ability of MAVS to constitutively polymerize and elicit broad downstream interferon signaling through an overexpression strategy. This approach provided a novel genetic mean to elicit ligand free innate immune signaling in the TME, which we found to elicit robust stimulation of multiple interferon genes. Overexpression of MAVS in colorectal cell lines stimulated significant anti-tumors responses in vivo, which we found to be primarily mediated through the induction of tumor antigen-specific adaptive immunity. Utilizing viral vectors overexpressing MAVS, we demonstrate significant induction of interferon responses among different types of tumor cells and different types of cells in the tumor microenvironment. Intra-lesional injection of tumors using these vectors elicited profound anti-tumor responses against primary tumors, as well as, an abscopal effect against syngeneic implanted tumors. Overexpression of MAVS also stimulated the expression of PD-L1 as an immunosuppressive feedback mechanism due to stimulation of the MAVS pathway. As such, we tested the combination of MAVS overexpression and PD-L1 ICB in colorectal cancers and found that this combination allowed for significantly improved anti-tumor immunity. In conclusion, our findings suggest that a combination of MAVS cancer gene therapy and ICB may offer an alternative approach to activate immunity in "immunologically cold" tumors. Citation Format: Bin-Jin Hwang. Triggering anti-tumor immunity by overexpressing of MAVS in combination with PD-L1 ICB in immune insensitive colorectal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1789.

The leucine-NH4+ uptake regulator Any1 limits growth as part of a general amino acid control response to loss of La protein by fission yeast.

The sla1+ gene of Schizosachharoymces pombe encodes La protein which promotes proper processing of precursor-tRNAs. Deletion of sla1 (sla1Δ) leads to disrupted tRNA processing and sensitivity to target of rapamycin (TOR) inhibition. Consistent with this, media containing NH4+ inhibits leucine uptake and growth of sla1Δ cells. Here, transcriptome analysis reveals that genes upregulated in sla1Δ cells exhibit highly significant overalp with general amino acid control (GAAC) genes in relevant transcriptomes from other studies. Growth in NH4+ media leads to additional induced genes that are part of a core environmental stress response (CESR). The sla1Δ GAAC response adds to evidence linking tRNA homeostasis and broad signaling in S. pombe. We provide evidence that deletion of the Rrp6 subunit of the nuclear exosome selectively dampens a subset of GAAC genes in sla1Δ cells suggesting that nuclear surveillance-mediated signaling occurs in S. pombe. To study the NH4+-effects, we isolated sla1Δ spontaneous revertants (SSR) of the slow growth phenotype and found that GAAC gene expression and rapamycin hypersensitivity were also reversed. Genome sequencing identified a F32V substitution in Any1, a known negative regulator of NH4+-sensitive leucine uptake linked to TOR. We show that 3H-leucine uptake by SSR-any1-F32V cells in NH4+-media is more robust than by sla1Δ cells. Moreover, F32V may alter any1+ function in sla1Δ vs. sla1+ cells in a distinctive way. Thus deletion of La, a tRNA processing factor leads to a GAAC response involving reprogramming of amino acid metabolism, and isolation of the any1-F32V rescuing mutant provides an additional specific link.

Evaluation of the Rotating-Frame Relaxation (T1ρ) Filter and Its Application in Metabolomics as an Alternative to the Transverse Relaxation (T2) Filter.

Nuclear magnetic resonance (NMR)-based metabolomic studies commonly involve the use of T2 filter pulse sequences to eliminate or attenuate the broad signals from large molecules and improve spectral resolution. In this paper, we demonstrate that the T1ρ filter-based pulse sequence represents an interesting alternative because it allows the stability and the reproducibility needed for statistical analysis. The integrity of the samples and the stability of the instruments were assessed for different filter durations and amplitudes. We showed that the T1ρ filter pulse sequence did not induce sample overheating for a filter duration of up to 500 ms. The reproducibility was evaluated and compared with the T2 filter in serum and liver samples. The implementation is relatively simple and provides the same statistical and analytical results as those obtained with the standard filters. Regarding tissues analysis, because the duration of the filter is the same as that of the spin-lock, the synchronization of the echo delays with the magic angle spinning (MAS) rate is no longer necessary as for T2 filter-based sequences. The results presented in this article aim at establishing a new protocol to improve metabolomic studies and pave the way for future developments on T1ρ alternative filters, in liquid and HR-MAS NMR experiments.

Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear MII3O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet-Quartet Transitions in the Dianions.

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain MII3O clusters inside a π-extended trianionic (Hhp3-) macrocycle have been prepared. Studies of the magnetic properties of NiII3O(Hhp) and CuII3O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp3-) macrocycle and diamagnetic NiII3(O2-) or paramagnetic CuII3(O2-) tetracations. The positive charge of MII3O(Hhp) is compensated by one acetate anion {MII3O(Hhp)}+(CH3CO2-). The three-electron reduction of {MII3O(Hhp)}+ yields {cryptand(Cs+)}2{NiII2NiIO(Hhp5-)}2-·2C7H8 (1) and {cryptand(Cs+)}2{CuII3O(Hhp•6-)}2-·C7H8 (2) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp5- and the reduction of nickel(II) to the paramagnetic NiI ion (S = 1/2), which is accompanied by the formation of the {NiII2NiIO(Hhp5-)}2- dianion. As a result, the magnetic moment of 1 is 1.68 μB in the 20-220 K range, and a broad EPR signal of NiI was observed. The Hhp5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp5-. The {NiII2NiIO(Hhp5-)}2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2, a highly reduced Hhp•6- radical hexaanion (S = 1/2) coexists with a CuII3(O2-) cluster (S = 1/2) in the {CuII3O(Hhp•6-)}2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm-1. The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.

Twist and Stretch: Assignment and Surface Charge Sensitivity of a Water Combination Band and Its Implications for Vibrational Sum Frequency Spectra Interpretations.

The vibrational spectrum of water at hydrophobic/hydrophilic interfaces is crucial to understanding complex surface chemistry phenomena. Vibrational sum frequency (VSF) spectroscopy is a valuable nonlinear spectroscopic technique for exploring the details of vibrational spectra of molecules at surfaces. However, spectral assignments and analysis of VSF spectra are often more nuanced than in linear spectroscopy. This study is aimed at understanding the source of the broad VSF signal in the oil-water surface water spectrum at energies slightly higher than traditionally examined, beyond the unbound free OH oscillator of surface water molecules. Analyzing isotopic dilutions of the aqueous solvent with VSF spectroscopy, we demonstrate that this signal is due to a combination band of water stretch and libration motions. The spectral characteristics of this band are found to be highly sensitive to the sign and magnitude of the surface charge induced by adsorption of both anionic and cationic surfactants. The results have implications for VSF measurements of the C-H stretching vibrations of various adsorbates when studied with D2O as the aqueous solvent. Because the vibrational signal from the water combination band is dependent on surface charge, it is imperative to include the presence of the combination band when fitting surface spectra.

Trocylation of 3-quinuclidinol, a key marker for the chemical warfare agent 3-quinuclidinyl benzilate, for its enhanced detection at low levels in complex soil matrices by electron ionization gas chromatography-mass spectrometry.

Detection of 3-quinuclidinol (3Q), a marker for the chemical warfare agent 3-quinuclidinyl benzilate, is very difficult by gas chromatography-mass spectrometry (GC/MS), providing low, broad signals even when analyzed in isolated form. Therefore, a method that can convert 3Q into a substrate with enhanced detectability by GC/MS would be an important tool for its analysis. 2,2,2-Trichloroethoxycarbonyl chloride (TrocCl) was used in the derivatization of 3Q in three different soils of varying composition and total organic content (Virginia type A soil, Nebraska EPA standard soil and Ottawa sand) when present at a 10μg g-1 concentration in each. A direct derivatization protocol and one involving the pre-extraction of the analyte were evaluated for their individual efficiencies and subsequent analysis using electron ionization GC/MS. The practical derivatization of 3Q, when present at low levels (10μg g-1 ) in three different soil matrices, was found to be rapid (1h) and to take place smoothly at ambient temperature (and as low as 4°C). The method detection limit was determined to be 30 ng mL-1 for the Virginia type A soil, 49 ng mL-1 for the Nebraska EPA standard soil and 72 ng mL-1 for the Ottawa sand sample. An expedient and practical derivatization method for 3Q, a chemical warfare degradation product difficult to detect by GC/MS, has been realized using trichloroethyl chloroformate. The reaction provides 3Q-Troc, a derivative with better detectability than 3Q by electron ionization GC/MS such as peak sharpness and a unique mass spectrum for its unambiguous identification.

NMR Study of LiCo0.96Al0.04O2 As a Positive Electrode Material for Li-Ion Batteries: Homogeneity and Role of Doping on Mechanisms

LiCoO2 (LCO) is one of the most widely used positive electrode materials in lithium-ion batteries due to its high volumetric energy density which can be further improved by charging at high voltages. However, working at high potential (above 4.3 V vs. Li+/Li) causes a deterioration in cycling performance induced by structural instabilities, electrolyte oxidation and Co dissolution. Extensive studies have been devoted to increasing energy density by increasing the cutoff voltage. The substitution of cobalt with various metals is one of the classic methods, the choice of aluminum as dopant for example is based on several criteria: low cost and non-toxicity, a similar radius for Al3+ compared to Co3+ (0.535 Å vs. 0.545 Å) facilitates the replacement of the latter and maintains the structure leading to the complete solid solution LiCo1-yAlyO2.We will focus here on LiCo0.96Al0.04O2, synthesized by the solid route and characterized by 7Li, 27Al and 59Co Nuclear Magnetic Resonance (NMR) and synchrotron X-Ray Diffraction (XRD). In addition to the characterization of the mean structure by XRD, the NMR allows us to study the local environments of the different nuclei. 27Al MAS NMR and synchrotron XRD studies revealed that the Al-doping in this material is homogeneous. 7Li MAS NMR indicates that its stoichiometry (Li/M=1.00) is ideal. The electrochemical study has shown that the phase transitions occurring during delithiation of LiCoO2, were partially eliminated by aluminum doping even with a low doping amount and the high potential mechanisms appear to be different. In order to better understand the role of Al-doping on the mechanisms involved during cycling, several phases LixCo0.96Al0.04O2 were prepared by electrochemical deintercalation and studied by 7Li, 59Co, and 27Al NMR and by XRD.During lithium deintercalation, Co3+ is oxidized to Co4+ then one unpaired electron is generated in the t2g band of Co atoms (t2g 5eg 0). For 0.8 ≤ x ˂ 1.00 the 7Li MAS NMR shows that the system behaves locally as two phase domain: domain with localized electrons and domain with delocalized ones on Con+ ions (Knight shift), even for very low amount of deintercalation (x=0.98), thus the XRD results confirm the existence of the biphasic domain. Whereas, a single phase domain is observed for the deintercalated materials with 0.4 ≤ x ≤ 0.8 and also at the NMR time of scale a single signal (Knight shift) is observed. This signal increases in intensity at the expense of 0 ppm and shifts to the higher isotropic displacement values up to x=0.5 then decreases, thus the evolution of the chex lattice parameter is correlated with the signal shift. For x = 0.3 and x = 0.2: a new broad signal appears probably due to formation of new Li environment in stacking faulted layers (O1 type). These different contributions will be more detailed on the presentation.

A simple method for the preparation of 2,4,6-trichloroborazine and evaluation of 1H-NMR spectra

ABSTRACT: The compound 2,4,6-trichloroborazine (TCB) is known as a valuable precursor to prepare boron nitride and various derivatives of borazine. Difficulties in the preparation of TCB via conventional methods on the one hand, and its importance for the material science, on the other hand, were our motivation to modify the Brown’s method for TCB synthesis. So far, all reports on the synthesis procedure of TCB are based on the use of gaseous BCl3 with NH4Cl powder at 110-130 °C in chlorobenzene requiring complicated low-temperature equipment such as a cold finger condenser, and dry ice-acetone reflux condenser to retain BCl3 gas in the reaction flask. According to our study, using BCl3 solution in n-hexane was more convenient than using gaseous BCl3. The reaction of BCl3 solution with NH4Cl was carried out without loss of BCl3. Furthermore, the reduction in the reflux temperature from 130 °C in some previous studies to 86 °C in our study, was a valuable advantage, leading to the release of the coordinated BCl3 from the adduct complex [CH3CN·BCl3] gradually and the prevention of thermal decomposition of TCB, unwanted polymerization reactions and the formation of undesirable products, resulting in the increased reaction yield. TCB was fully characterized by ATR-FTIR, 11B-, 14N- and 1H-NMR spectroscopic methods. 1H-NMR spectra of TCB were performed for the first time at various temperatures to elucidate the quadrupolar effect of nitrogen, which led to evaluate the splitting of the proton resonance of the 14N-H bond by coupling with the 14N quadrupole nucleus. The broad peak observed at room temperature was clearly split into a triplet at 100 °C due to the long TqN and fast molecular motion of TCB molecules. The 14N-NMR spectrum was also shown for the first time as a broad signal at δ = –271.3 ppm (h1/2 = 186 Hz).