Amine Ions Research Articles

Insights into the catalytic effect of atmospheric organic trace species on the hydration of Criegee intermediates

The bimolecular reactions between Criegee intermediates (CIs) and atmospheric trace species have been extensively investigated, with a particular focus on the reaction with water, while the catalytic role of atmospheric organic compounds in hydration reactions was often neglected. In this study, we employed quantum chemical calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations to investigate the catalytic effects of atmospheric organic amines, organic acids, and alcohols on the hydration reactions of CIs in the gas phase and at the gas-liquid interface. The catalytic reactions were found to follow a cyclic catalytic structure and a stepwise reaction mechanism. Gas-phase studies revealed that organic acids exhibited stronger catalytic effects compared to amines and alcohols, and the catalytic efficiency of amines and alcohols was similar to those of single water molecule. In addition, the catalytic reaction barriers of organic acids and alcohols were positively correlated with their gas-phase acidity (R2 = 0.94 to 0.97). A negative correlation was observed between the catalytic reaction barrier of amines and their gas-phase basicity (R2 = 0.84 to 0.90) and proton affinity (R2 = 0.84 to 0.92). At the gas-liquid interface, organic acids promoted the formation of hydroxyethyl hydroperoxide (HEHP, CH3CH(OH)(OOH)), organic acid ions, and H3O+, whereas the catalytic hydration of CIs by organic amines resulted in the formation of CH3CH(OH)OO and amine ions. Both HEHP and CH3CH(OH)OO can be further decomposed to form OH and HO2, or participate in new particles formation as precursors. This study complements the research gap on the reaction of CIs with water, providing valuable insights into the atmospheric sources of HEHP and HOx as well as the formation of secondary organic aerosols (SOAs).

Extended Quinolizinium-Fused Corannulene Derivatives: Synthesis and Properties.

Reported here is the design and synthesis of a novel class of extended quinolizinium-fused corannulene derivatives with curved geometry. These intriguing molecules were synthesized through a rationally designed synthetic strategy, utilizing double Skraup-Doebner-Von Miller quinoline synthesis and a rhodium-catalyzed C-H activation/annulation (CHAA) as the key steps. Single-crystal X-ray analysis revealed a bowl depth of 1.28-1.50 Å and a unique "windmill-like" shape packing of 12a(2PF6-) due to the curvature and incorporation of two aminium ions. All of the newly reported curved salts exhibit green to orange fluorescence with enhanced quantum yields (Φf = 9-13%) and improved dispersibility compared to the pristine corannulene (Φf = 1%). The reduced optical energy gap and lower energy frontier orbital found by doping extended corannulene systems with nitrogen cations was investigated by UV-vis, fluorescence, and theoretical calculations. Electrochemical measurements reveal a greater electron-accepting behavior compared with that of their pyridine analogues. The successful synthesis, isolation, and evaluation of these curved salts provide a fresh perspective and opportunity for the design of cationic nitrogen-doped curved aromatic hydrocarbon-based materials.

Characteristics of aerosol aminiums over a coastal city in North China: Insights from the divergent impacts of marine and terrestrial influences

Aminium ions, as crucial alkaline components within fine atmospheric particles, have a notable influence on new particle formation and haze occurrence. Their concentrations within coastal atmosphere depict considerable variation due to the interplay of distinctive marine and terrestrial sources, further complicated by dynamic meteorological conditions. This study conducted a comprehensive examination of aminiums ions concentrations, with a particular focus on methylaminium (MMAH+), dimethylaminium (DMAH+), trimethylaminium (TMAH+), and triethylaminium (TEAH+) within PM2.5, over varying seasons (summer, autumn, and winter of 2019 and summer of 2021), at an urban site in the coastal megacity of Qingdao, Northern China. The investigations revealed that the total concentration of particulate aminium ions (∑Aminium) was 21.6 ± 23.6 ng/m3, exhibiting higher values in the autumn and winter compared to the two summer periods. Considering diurnal variations during autumn and winter, concentrations of particulate aminium ions (excluding TEAH+) exhibited a slight increase during the day compared to night, with a notable peak during the morning hours. However, it was not the case for TEAH+, which was argued to be readily oxidized by ambient oxidants in the afternoon. Additionally, the ∑Aminium within the summer demonstrated markedly elevated levels during the day compared to night, potentially attributed to daytime sea fog associated with sea-land breeze interactions. Positive matrix factorization results indicate terrestrial anthropogenic emissions, including vehicle emission mixed with road dust and primary pollution, as the primary sources of MMAH+ and DMAH+. Conversely, TMAH+ was predominantly emitted from agricultural and marine sources. With the dominance of sea breeze in summer, TMAH+ was identified as a primary marine emission correlated with sea salt, while MMAH+, DMAH+, and TEAH+ were postulated to undergo secondary formation. Furthermore, a notable inverse correlation was observed between TMAH+ and methanesulfonate in PM2.5, consistent with dynamic emissions of sulfur-content and nitrogen-content gases reported in the literature.

Mn-Doped M2CdCl4 (M = CH3NH3+, C2H8N+, and C3H10N+) Layered Hybrid Perovskite and Its Flexible Film Based on Simple Mechanochemical Synthesis.

Layered hybrid perovskites show significant advantages in the field of optoelectronics. However, the low quantum efficiency and complex preparation methods limit their applications. In this work, we developed a series of perovskite powders with a two-dimensional (2D) layered structure of organic-inorganic hybrid metal halides M2CdCl4:x%Mn (M = CH3NH3+, C2H8N+, C3H10N+) via facile mechanochemical methods. The prepared manganese Mn-doped MA2CdCl4 produces orange emission at 605 nm under both 254 and 420 nm excitation, which originates from a dual excitation channel competition mechanism, and its excitation channel could be changed with the increase of Mn2+ ion concentration. Typically, MA2CdCl4:20%Mn powder exhibits high photoluminescence quantum yield (PLQY) close to 90% at 605 nm due to the organic amine ions enlarging the Mn-Mn interlayer distances. In addition, we prepared MA2CdCl4:x%Mn@PVA flexible films, which also exhibit good luminescence at 254 nm excitation and were unexpectedly found to have a better response to Cs+, which could be a candidate for anticounterfeiting applications.

Modulating Skeletons of Covalent Organic Framework for High-Efficiency Gold Recovery.

Covalent organic frameworks (COFs) have attracted considerable attention as adsorbents for capturing and separating gold from electronic wastes. To enhance the binding capture efficiency, constructing hydrogen-bond nanotraps along the pore walls was one of the most widely adopted approaches. However, the development of absorbing skeletons was ignored due to the weak binding ability of the gold salts (Au). Herein, we demonstrated skeleton engineering to construct highly efficiently absorbs for Au capture. The strong electronic donating feature of diarylamine units enhanced the electronic density of binding sites (imine-linkage) and thus resulted in high capacities over 1750 mg g-1 for all three COFs. Moreover, the absorbing performance was further improved via the ionization of diarylamine units. The ionic COF achieved 90 % of the maximal adsorption capacity, 1.63 times of that from the charge-neutral COF within ten minutes, and showed remarkable uptakes of 1834 mg g-1 , exceptional selectivity (97.45 %) and cycling stability. The theoretical calculation revealed the binding sites altering from imine bonds to ionic amine sites after ionization of the frameworks, which enabled to bind the AuCl4 - via coulomb force and contributed to enhanced absorbing kinetics. This work inspires us to design molecular/ionic capture based on COFs.

Modulating Skeletons of Covalent Organic Framework for High‐Efficiency Gold Recovery

AbstractCovalent organic frameworks (COFs) have attracted considerable attention as adsorbents for capturing and separating gold from electronic wastes. To enhance the binding capture efficiency, constructing hydrogen‐bond nanotraps along the pore walls was one of the most widely adopted approaches. However, the development of absorbing skeletons was ignored due to the weak binding ability of the gold salts (Au). Herein, we demonstrated skeleton engineering to construct highly efficiently absorbs for Au capture. The strong electronic donating feature of diarylamine units enhanced the electronic density of binding sites (imine‐linkage) and thus resulted in high capacities over 1750 mg g−1 for all three COFs. Moreover, the absorbing performance was further improved via the ionization of diarylamine units. The ionic COF achieved 90 % of the maximal adsorption capacity, 1.63 times of that from the charge‐neutral COF within ten minutes, and showed remarkable uptakes of 1834 mg g−1, exceptional selectivity (97.45 %) and cycling stability. The theoretical calculation revealed the binding sites altering from imine bonds to ionic amine sites after ionization of the frameworks, which enabled to bind the AuCl4− via coulomb force and contributed to enhanced absorbing kinetics. This work inspires us to design molecular/ionic capture based on COFs.

Melt Castable Derivatives of Pentaerythritol Tetranitrate.

In the search for high-performance and environmentally friendly energetic materials, the derivatization of known materials is an often-applied concept to fulfill modern-day demands. Surprisingly, the long know pentaerythritol tetranitrate (PETN) has only been derivatized to a limited extent. PETN shows a brought application in energetic materials or pharmaceutics. In this work, the PETN backbone is modified by introducing nitramine, ionic nitramine, amine, ionic amine and tetrazole functionalities. The obtained and structurally similar compounds allow good comparability and insights into functional group effects on sensitivity, thermal behavior and performance. The functionalizations result in melting points in the range of 64 to 126 °C. Some compounds are therefore potential candidates to replace toxic TNT.

Non-volatile marine and non-refractory continental sources of particle-phase amine during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES)

Abstract. Amines were measured by aerosol mass spectrometry (AMS) and Fourier transform infrared (FTIR) spectroscopy during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) cruises. Both AMS non-refractory (NR) amine ion fragments comprising the AMS CxHyNz family and FTIR non-volatile (NV) primary (C–NH2) amine groups typically had greater concentrations in continental air masses than in marine air masses. Secondary continental sources of AMS NR amine fragments were identified by consistent correlations with AMS NR nitrate, AMS NR f44 (the contribution of AMS ion signal at m/z 44 (CO2+) to the total AMS NR organic mass (OM) signal), ion chromatography (IC) non-sea-salt potassium (nssK+), and radon for most air masses. FTIR NV amine group mass concentrations for particles with diameters <1µm showed large contributions from a primary marine source that was identified by significant correlations with measurements of wind speed, chlorophyll a (chl a), seawater dimethylsulfide (DMS), AMS NR chloride, and IC sea salt as well as FTIR NV alcohol groups in both marine and continental air masses. FTIR NV amine group mass concentrations in <0.18 and <0.5 µm particle samples in marine air masses likely have a biogenic secondary source associated with strong correlations with FTIR NV acid groups, which are not present for <1 µm particle samples. The average seasonal contribution of AMS NR amine fragments and FTIR NV amine groups ranged from 27±57 % amine from primary marine sources and 73±152 % secondary continental amine during early spring to 53±76 % amine from primary marine sources and 47±68 % secondary continental amine during winter. These results demonstrate that AMS NR and FTIR NV amine measurements are complementary and can be used together to investigate the variety and sources of amines in the marine environment.

Nitrate adsorption towards ultrasound-assisted modified oil palm frond: Characterization and performance investigation using response surface methodology

Nitrate is known as one of the nutrients contributing towards eutrophication condition, when its concentration exceeds threshold. Adsorption of nitrate had been studied extensively, and lignocellulosic adsorbent has been favourable of many researchers. In Malaysia, oil palm biomass is a readily available lignocellulosic material in high volume, specifically oil palm frond (OPF). However, the potential of OPF for nitrate adsorption is still not vastly explored. Hence, this study aims to determine the structural properties of ultrasound-assisted modified OPF and to investigate the performance as an adsorbent for the adsorption of nitrate via response surface methodology (RSM). Batch adsorption experiment was carried out according to the parameters set by central composite design (CCD) under RSM via Design Expert software. A steady state nitrate recovery of 65.0 % and adsorption capacity of 1.65 mg/g were achieved at pH 7.0, initial concentration of 15 mg/L, adsorbent dosage of 5.5 g/L, contact time of 12 hours and temperature of 32.5℃ Meanwhile, optimization condition was conducted with at pH 5.12, initial concentration of 25.0 mg/L, adsorbent dosage of 1.0 g/L, and contact time of 5 hours at 25℃ resulted to an average of 65.28 % nitrate removal percentage and 16.25 mg/g of adsorption capacity. FESEM, BET and FTIR showed successful grafting of quaternary amine ions on ultrasound-assisted modified OPF. This shows that the modified OPF is a potential adsorbent for nitrate.

Synchronous regulation of bulk and interfacial defects by an ionic liquid for efficient and stable perovskite solar cells

Charge recombination at grain-boundary interfaces and charge extraction loss at perovskite-carrier transport layer interfaces are the two main causes for the performance deficiency in perovskite solar cells. Herein we reported the synthesis of an ionic liquid compound 9-bromo-6,7-diphenylpyrido[2,1-a]isoquinolin-5-ium hexafluorophosphate (DPPIQ+PF6−), which can synchronously react with perovskites at these two essential interfaces. Specifically, the PF6− anions are incorporated into the perovskite film bulk, immobilizing organic amine ions via hydrogen bonding, while the DPPIQ+ cations are mainly accumulated at the top film surface, binding the [PbI3]− through anion-π interactions. Reduced defect density and improved energy level alignment are achieved in the resultant perovskite solar cells. The best-performing DPPIQ+PF6− incorporated device shows a high power conversion efficiency of 23.41% and demonstrates 90% efficiency retention upon maximum-power-point tracking for 1260 h under continuous one-sun-intensity illumination.

In Situ Turn-On Room Temperature Phosphorescence and Vapor Ultra-sensitivity at Lifetime Mode

Organic room temperature phosphorescence (RTP) systems are rarely reported for vapor phase sensing due to the contradiction between vapor permeability and phosphorescence ability. Till now, almost all reported works are based on ″turn-off″ mode RTP detection by destroying the compact-packaging oxygen-free environment. ″Turn-on″ mode RTP detection owns additional anti-interference capability due to a lower initial RTP background signal, while its realization is even harder. In this research, in situ phosphorescence ″turn-on″ sensing was realized for methamphetamine (MPEA) vapor detection. Based on the formation of aromatic phenolic aldehyde-secondary amine ion pairs with air-stable RTP performance, the fluorescent tri-formyl phenol (TFP) film was converted into a stable RTP state after being exposed to the MPEA vapor, as supported by nuclear magnetic resonance (NMR) and mass spectrometry together with theoretical calculations. The red-shifted absorption and emission, enhanced emission intensity, and 49.7 μs phosphorescence lifetime allowed multiple mode MPEA vapor sensing from chromaticity to fluorescence to phosphorescence. The lifetime mode detection limit reached 0.4 ppt, 5 orders of magnitude lower than the intensity mode detection limit of 20.3 ppb.

Preparation and performance of sulfonated poly(ether ether ketone) membranes enhanced with ammonium ionic liquid and graphene oxide

The exploration of proton exchange membranes with excellent performance has always been under focus for improving the performance of proton exchange membrane fuel cells. In this study, novel ternary composite proton exchange membranes based on sulfonated poly(ether ether ketone) (SPEEK), triethylamine phosphate (TEAP) as the ammonium ionic liquid (AIL), and graphene oxide (GO) were prepared. The prepared membranes were characterized for their physical, physico-chemical, structural, morphological, thermal, mechanical, and electrical characteristics. The thermal stability of the SPEEK membrane was improved by the addition of GO and TEAP. GO was inserted into the composite membrane to form proton transfer channels. The amine ions in AIL formed acid–base pairs with the sulfonic acid group, whereas the oxygen-containing group on GO formed hydrogen bonds with the phosphate group. These groups interacted with each other to form a honeycomb-like structure, which anchored the AIL in the membrane and reduced its loss, providing additional sites for proton transport at higher temperatures. The proton conductivity of the SPEEK/AIL/GO-2 membrane reached 17.345 mS/cm at 120°C, which was 2.09 times higher than that of the pristine SPEEK membrane. This study provides the possibility for better preparation of proton exchange membranes used for high-temperature proton exchange membrane fuel cells.

Assembling covalent organic framework membranes with superior ion exchange capacity

Ionic covalent organic framework membranes (iCOFMs) hold great promise in ion conduction-relevant applications because the high content and monodispersed ionic groups could afford superior ion conduction. The key to push the upper limit of ion conductivity is to maximize the ion exchange capacity (IEC). Here, we explore iCOFMs with a superhigh ion exchange capacity of 4.6 mmol g−1, using a dual-activation interfacial polymerization strategy. Fukui function is employed as a descriptor of monomer reactivity. We use Brønsted acid to activate aldehyde monomers in organic phase and Brønsted base to activate ionic amine monomers in water phase. After the dual-activation, the reaction between aldehyde monomer and amine monomer at the water-organic interface is significantly accelerated, leading to iCOFMs with high crystallinity. The resultant iCOFMs display a prominent proton conductivity up to 0.66 S cm−1, holding great promise in ion transport and ionic separation applications.

Mapping gaseous dimethylamine, trimethylamine, ammonia, and their particulate counterparts in marine atmospheres of China’s marginal seas – Part 2: Spatiotemporal heterogeneity, causes, and hypothesis

Abstract. Spatiotemporal heterogeneities in the concentrations of alkaline gases and their particulate counterparts in the marine atmosphere over China's marginal seas were investigated in terms of causes and chemical conversion during two winter cruise campaigns, using semi-continuous measurements made by an onboard URG-9000D Ambient Ion Monitor-Ion Chromatograph (AIM-IC, Thermo Fisher). During the cruise campaign over the East China Sea from 27 December 2019 to 6 January 2020, the concentrations of gas-phase atmospheric trimethylamine (TMAgas) varied by approximately 1 order of magnitude, with an average (± standard deviation) of 0.10±0.04 µg m−3 corresponding to a mixing ratio of 26±17 pptv. Corresponding mean values were 0.037±0.011 µg m−3 (14±5 pptv in mixing ratio) over the Yellow Sea during the period from 7 to 16 January 2020 and 0.031±0.009 µg m−3 (12±4 pptv in mixing ratio) over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. By contrast, the simultaneously observed concentrations of TMA in PM2.5, detected as TMAH+, over the East China Sea were 0.098±0.069 µg m−3 and substantially smaller than the 0.28±0.18 µg m−3 observed over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. A significant correlation between TMAgas and particulate TMAH+ was observed over the East China Sea, but no correlation was found over the Yellow Sea and Bohai Sea. Proportional or disproportional variations in concentrations of TMAgas with particulate TMAH+ over the sea zones were probably attributed to the difference in the enrichment of TMAH+ in the sea surface microlayer. In addition, spatiotemporal heterogeneities in concentrations of atmospheric ammonia (NH3gas), atmospheric dimethylamine (DMAgas), and DMA in PM2.5, detected as DMAH+, were investigated. Case analyses were performed to illustrate the formation and chemical conversion of particulate aminium ions in marine aerosols. Finally, we hypothesized the release of basic gases and particulate counterparts from the ocean to the atmosphere, together with the secondary formation of DMAH+ and chemical conversion of TMAH+, in the marine atmosphere.

Anharmonic IR spectra of solvated ammonium and aminium ions: resemblance between water and bisulfate solvations.

In this work, we analyze the vibrational spectra of ammonium, methylammonium, and dimethylammonium ions solvated by either water molecules or bisulfate anions using anharmonic vibrational algorithms. Rich and complicated spectral features in the 2700-3200 cm-1 region of the experimental spectra of these clusters are attributed to originate from strong Fermi resonance between hydrogen-bonded NH stretching fundamentals and NH bending overtones. Additional weaker bands around 2500-2600 cm-1 in solvated aminium ions are assigned to the combination tones involving the CH-NH (methyl-amino) rocking modes. Furthermore, the qualitative resemblance in band positions and spectral patterns between two-water-solvated and two-bisulfate-solvated cations suggest a common vibrational coupling scheme beneath the two seemingly different micro-solvation environments.

Mapping gaseous dimethylamine, trimethylamine, ammonia, and their particulate counterparts in marine atmospheres of China's marginal seas – Part 1: Differentiating marine emission from continental transport

Abstract. To study sea-derived gaseous amines, ammonia, and primary particulate aminium ions in the marine atmosphere of China's marginal seas, an onboard URG-9000D Ambient Ion Monitor-Ion Chromatograph (AIM-IC, Thermo Fisher) was set up on the front deck of the R/V Dongfanghong-3 to semi-continuously measure the spatiotemporal variations in the concentrations of atmospheric trimethylamine (TMAgas), dimethylamine (DMAgas), and ammonia (NH3gas) along with their particulate matter (PM2.5) counterparts. In this study, we differentiated marine emissions of the gas species from continental transport using data obtained from 9 to 22 December 2019 during the cruise over the Yellow and Bohai seas, facilitated by additional short-term measurements collected at a coastal site near the Yellow Sea during the summer, fall, and winter of 2019. The data obtained from the cruise and coastal sites demonstrated that the observed TMAgas and protonated trimethylamine (TMAH+) in PM2.5 over the Yellow and Bohai seas overwhelmingly originated from marine sources. During the cruise, no significant correlation (P>0.05) was observed between the simultaneously measured TMAH+ and TMAgas concentrations. Additionally, the concentrations of TMAH+ in the marine atmosphere varied around 0.28±0.18 µg m−3 (average ± standard deviation), with several episodic hourly average values exceeding 1 µg m−3, which were approximately 1 order of magnitude larger than those of TMAgas (approximately 0.031±0.009 µg m−3). Moreover, there was a significant negative correlation (P<0.01) between the concentrations of TMAH+ and NH4+ in PM2.5. Therefore, the observed TMAH+ in PM2.5 was overwhelmingly derived from primary sea-spray aerosols. Using TMAgas and TMAH+ in PM2.5 as tracers for sea-derived basic gases and sea-spray particulate aminium ions, the values of non-sea-derived DMAgas, NH3gas, and non-sea-spray particulate DMAH+ in PM2.5 were estimated. The estimated average values of each species contributed 16 %, 34 %, and 65 % of the observed average concentrations for non-sea-derived DMAgas, NH3gas, and non-sea-spray particulate DMAH+ in PM2.5, respectively. Uncertainties remained in the estimations, as TMAH+ may decompose into smaller molecules in seawater to varying extents. The non-sea-derived gases and non-sea-spray particulate DMAH+ likely originated from long-range transport from the upwind continents based on the recorded offshore winds and increased concentrations of non-sea-salt SO42- (nss-SO42-) and NH4+ in PM2.5. The lack of a detectable increase in particulate DMAH+, NH4+, and nss-SO42- concentrations in several SO2 plumes did not support the secondary formation of particulate DMAH+ in the marine atmosphere.

Determination of individual oligonucleotide impurities by small amine ion pair-RP HPLC MS and MS/MS: n − 1 impurities

Ion pair-reversed phase (IP-RP) HPLC is one of the most widely used methods for the analysis of oligonucleotide impurities. The method is compatible with mass spectrometry and has been used to guide the development of improved synthesis and purification approaches. The ability to detect and characterize impurities depends on the reagents and the IP buffer system employed, as each can directly affect the degree of chromatographic separation and the sensitivity of detection by MS. Previous work in our laboratory has shown that small alkyl amines are suitable IP reagents for the analysis of impurities in phosphate diester oligonucleotides and can be used to differentiate among individual members of composite impurity families. The addition of an alkyl acid often further enhances peak separation, but at the detriment of ion signal. An improved method with increased chromatographic performance and sensitivity of detection is presented here. Improvements were mainly realized through the use of lower concentrations of small alkyl amine (i.e., 5 mM) and acid (0.5 mM) IP reagents, and ammonium bicarbonate (20 mM) as a buffer. The improved capabilities of the new method are demonstrated by separation of the individual components of the composite n − 1 impurity in a set of four production-scale batches of a single oligonucleotide. Addition of the alkyl acid resulted in resolution of most individual n − 1 impurities. The observed enhanced sensitivity of detection allowed multiple reaction monitoring (MRM) experiments, which were used to differentiate among unresolved impurities.

A general method for the synthesis of covalent and ionic amine borane complexes containing trinitromethyl fragments.

A general approach for the synthesis of covalent and ionic amine borane complexes containing trinitromethyl fragments has been developed through metathesis reactions between amine chloroborane complexes and potassium salt of trinitromethyl (K[C(NO2)3]). Five covalent and ionic trinitromethyl amine borane complexes have been synthesized in good yields with high purity and it is found that the ionic complex, [H2B(NH3)2][C(NO2)3], might be a promising energetic material on the basis of the investigation of its thermal decomposition behaviour.

Switchable solvent N, N, N′, N′-tetraethyl-1, 3-propanediamine was dissociated into cationic surfactant to promote cell disruption and lipid extraction from wet microalgae for biodiesel production

Switchable solvent N, N, N', N'-tetraethyl-1,3-propanediamine (TEPDA) was proposed to extract lipids from wet Nannochloropsis oceanica with a 5% higher extraction efficiency than chloroform–methanol. It was found that TEPDA acted mainly as an organic solvent to soften and dissolve lipids, while a small amount of TEPDA was dissociated into tertiary amine ion, i.e.,(C2H5)2N-(CH2)3-NH+(C2H5)2. This cation acted as a surfactant to promote cell disruption and lipid separation. With moisture increasing from 0 to 84 wt%, more TEPDA was dissociated into cationic surfactant to induce local rearrangement of phospholipid bilayers in cell membranes through electrostatic interaction, resulting in the fractal dimension of disrupted cells increased from 1.49 to 1.66. Accordingly, the yield of fatty acid methyl ester (FAME) through transesterification of lipids extracted with TEPDA increased by 9%, while FAME yield from lipids extracted with chloroform and n-hexane decreased by 41% and 65%, respectively.

Effects of pretreatment temperature on the analysis of size‐fractionated aerosol particles using ToF‐SIMS

Size‐fractionated aerosol particles were collected with a MOUDI 10‐stage cascade impactor from an urban roadside place in a downtown area of Hong Kong. Fine aerosol particulate samples from stage 6 (aerodynamic particle diameter between 0.56 and 1 μm) and stage 9 (aerodynamic particle diameter between 0.10 and 0.18 μm) were pretreated at a chosen temperature, including −100°C, −50°C, 25°C, and 60°C, in a load lock chamber and then analyzed using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) at the same temperature (−100°C). Principal component analysis (PCA) was applied to further analyze ToF‐SIMS spectra of aerosol particles with different pretreatment temperatures from two selected stages. ToF‐SIMS results showed that the intensities of aliphatic hydrocarbon ions such as C4H7+ and C4H9+ and amine ions such as C2H8N+ and C4H12N+ decreased with an increase of the pretreatment temperature under ultrahigh vacuum conditions. We have shown that analyses of this type of aerosol particles using ToF‐SIMS should not be conducted at ambient temperature but at low temperature (eg, −50°C). In addition, we also developed a procedure that can be used to analyze aerosol particle samples under ultrahigh vacuum environment.