Graphene Oxide Membrane Reactor for Electrochemical Deuteration Reactions

The deuteration of organic molecules is considerably important in organic and medicinal chemistry. An electrochemical membrane reactor using proton-conducting graphene oxide (GO) nanosheets was developed to synthesize valuable deuterium-labeled products via an efficient hydrogen-to-deuterium (H/D) exchange under mild conditions at ambient temperature and atmospheric pressure. Deuterons (D+) formed by the anodic oxidation of heavy water (D2O) at the Pt/C anode permeate through the GO membrane to the Pt/C cathode, where organic molecules with functional groups (C≡C and C═O) are deuterated with adsorbed atomic D species. Deuteration occurs in outstanding yields with high levels of D incorporation. We also achieved the electrodeuteration of a drug molecule, ibuprofen, demonstrating the promising feasibility of the GO membrane reactor in the pharmaceutical industry.

Energy Application of Graphene Based Membrane: Hydrogen Separation

Hydrogen gas (H2 ) is a viable energy carrier that has the potential to replace the traditional fossil fuels and contribute to achieving zero net emissions, making it an attractive option for a hydrogen-based society. However, current H2 purification technologies are often limited by high energy consumption, and as a result, there is a growing demand for alternative techniques that offer higher H2 purity and energy efficiency. Membrane separation has emerged as a promising approach for obtaining high-purity H2 gas with low energy consumption. Nevertheless, despite years of development, commercial polymeric membranes have limited performance, prompting researchers to explore alternative materials. In this context, carbon-based membranes, specifically graphene-based nanomaterials, have gained significant attention as potential membrane materials due to their unique properties. In this review, we provide a comprehensive overview of carbon-based membranes for H2 gas separation, fabrication of the membrane, and its characterization, including their advantages and limitations. We also explore the current technological challenges and suggest insights into future research directions, highlighting potential ways to improve graphene-based membranes performance for H2 separations.

Selective Detection of CO Using Proton-Conducting Graphene Oxide Membranes with Pt-Doped SnO2 Electrocatalysts: Mechanistic Study by Operando DRIFTS

To reduce the risk of carbon monoxide (CO) poisoning, there is a strong need for small, compact gas sensors to detect and monitor CO at ppm concentrations. In this study, we focused on detecting CO with electrochemical sensors based on proton-conducting graphene oxide (GO) nanosheets at room temperature. We found that a Ce-doped GO nanosheet membrane fitted with the sensing electrode composed of Pt (10 wt %)-doped SnO2 nanocrystals exhibits an excellent sensor response to CO at 25 °C. Pt doping of SnO2 nanocrystals has made it possible to detect CO more selectively than H2 and ethanol. The CO detection mechanism is analyzed by operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Fourier transform infrared gas cell measurements, and comprehensive density functional theory-based calculations. The results revealed that adsorption of CO occurs predominantly on Pt sites, and the adsorbed CO is anodically oxidized at the interface between the sensing electrode and proton-conducting membrane, generating the selective sensor response. The strong adsorption of CO was realized with Pt (10 wt %)-doped SnO2 nanocrystals, as revealed by the DRIFTS analysis and temperature-programed desorption technique.

Bandgap Engineering of Melon using Highly Reduced Graphene Oxide for Enhanced Photoelectrochemical Hydrogen Evolution

The uncondensed form of polymeric carbon nitrides (PCN), generally known as melon, is a stacked 2D structure of poly(aminoimino)heptazine. Melon is used as a photocatalyst in solar energy conversion applications, but suffers from poor photoconversion efficiency due to weak optical absorption in the visible spectrum, high activation energy, and inefficient separation of photoexcited charge carriers. Experimental and theoretical studies are reported to engineer the bandgap of melon with highly reduced graphene oxide (HRG). Three HRG@melon nanocomposites with different HRG:melon ratios (0.5%, 1%, and 2%) are prepared. The 1% HRG@melon nanocomposite shows higher photocurrent density (71 µA cm-2 ) than melon (24 µA cm-2 ) in alkaline conditions. The addition of a hole scavenger further increases the photocurrent density to 630 µA cm-2 relative to the reversible hydrogen electrode (RHE). These experimental results are validated by calculations using density functional theory (DFT), which revealed that HRG results in a significant charge redistribution and an improved photocatalytic hydrogen evolution reaction (HER).

Single Crystallization of Cs4PbBr6 Perovskite from Supersaturated Organic Solutions Optimized Through Solubility Studies

We demonstrate the fabrication of millimeter-sized single crystals of 0D-Cs₄PbBr₆ grown in a supersaturated solution consisting of organic solvents without HBr (aq). One of the precursors, CsBr, was dissolved in ethylene glycol (EG) mixed with dimethyl sulfoxide, which is a good solvent for the other precursor, PbBr₂. At a solvent ratio of 20 vol % EG, the solubility of cesium bromide decreased and the title compound, Cs₄PbBr₆, was selectively formed, whereas, with an EG ratio of 80 vol %, 3D-CsPbBr₃ was formed. A phase diagram (solubility curve) of Cs₄PbBr₆ in the mixed solvent containing 20 vol % EG was obtained by visually observing dissolution and crystal precipitation while changing the temperature. Because the solubility was proportional to the temperature, the solubility curve demonstrated an upper critical solution phenomenon. The solubility near the boiling point of the solution (150 °C) was approximately 0.14 M. A single crystal of Cs₄PbBr₆ was formed by growing a seed crystal in a supersaturated solution on the low-temperature side of the solubility curve. X-ray analysis established the crystal structure; a fluorescence emission at 520 nm with a full width at half maximum of 20 nm confirms the composition of the single crystal to be Cs₄PbBr₆.

Light-Stimulated Luminescence Control of Lead Halide-Based Perovskite Nanocrystals Coupled with Photochromic Molecules via Electron and Energy Transfer

Photoswitchable nanomaterials are key materials in the development of advanced imaging techniques, such as super-resolution fluorescence microscopy. The combination of perovskite CsPbBr₃ nanocrystals (NCs) with bright photoluminescence (PL) emission and diarylethenes (DAEs) with structural changes in response to ultraviolet (UV) and visible light is a promising candidate system. Herein, CsPbBr₃ NCs are coupled with photochromic DAE molecules to control the PL emission from the NCs by light stimulation. The PL emission is successfully switched ON and OFF by alternating UV and visible light irradiation. Time-resolved PL emission studies suggest that Förster resonance energy transfer from CsPbBr₃ NCs to the closed-ring form of DAE occurs after UV irradiation, and the PL emission is quenched. Upon visible-light irradiation, DAE is converted to the open-ring isomer, and the PL emission is restored. Femtosecond pump-probe spectroscopy reveals that light stimulation induces not only energy transfer but also photoinduced electron transfer in the NC-DAE pair on the picosecond timescale to form DAE radicals. Thus, it is suggested that the holes residing in the NCs react with the NCs, degrading the PL emission. Stable PL switching is realized using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a hole scavenger to avoid the reaction between the holes and NCs.

Derivation and validation of a machine learning-based risk prediction model for in-hospital mortality in patients with acute heart failure

Background

Although risk stratification is important in patients with acute heart failure (AHF) to predict patient prognosis, pre-existing risk models have not often been used due to its complexity. Recently, machine learning methods have been presented as an alternative approach to analyzing the predictive probability of large clinical datasets.

Purpose

The aim of this study is to develop a user-friendly risk score developed by one of machine learning methods and compare the performance of the new risk score to the existing conventional risk models.

Methods

A machine-learning-based risk model was developed using least absolute shrinkage and selection operator (LASSO) regression by identifying predictors of in-hospital mortality in the derivation cohort (REALITY-AHF) and externally validating and comparing its performance with two pre-existing risk models: the Get With The Guidelines risk score incorporating brain natriuretic peptide and hypochloremia (GWTG-BNP-Cl-RS) and the acute decompensated heart failure national registry (ADHERE) risk model.

Results

In-hospital deaths in the derivation and validation (NARA-HF) cohorts were 76 (5.1%) and 61 (4.9%), respectively. The risk score comprised four variables (systolic blood pressure, blood urea nitrogen, serum chloride, and C-reactive protein) and was developed according to the results of the LASSO regression weighting the coefficient for selected variables using a logistic regression model (4V-RS). Even though 4V-RS comprised fewer variables, In the validation cohort, it showed a higher area under the receiver operating characteristic curve (AUC) than the ADHERE risk model (AUC, 0.783 vs. 0.740; P=0.059) and a significant improvement in net reclassification (0.359; 95% CI, 0.10–0.67; p=0.006). 4V-RS performed similarly to GWTG-BNP-Cl-RS in terms of discrimination (AUC, 0.783 vs. 0.759; p=0.426) and net reclassification (0.176; 95% CI, −0.08–0.43; p=0.178).

Conclusions

The 4V-RS model comprising only four readily available data points at the time of admission performed similarly to the more complex pre-existing risk model in patients with AHF.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Cardiovascular Research Fund

Study on Sensing Mechanism of Volatile Organic Compounds Using Pt-Loaded ZnO Nanocrystals

Understanding the surface chemistry of target gases on sensing materials is essential for designing high-performance gas sensors. Here, we report the effect of Pt-loading on the sensing of volatile organic compounds (VOCs) with ZnO gas sensors, demonstrated by diffuse reflection infrared Fourier transform (DRIFT) spectroscopy. Pt-loaded ZnO nanocrystals (NCs) of 13~22 nm are synthesized using the hot soap method. The synthesized powder is deposited on an alumina substrate by screen-printing to form a particulate gas sensing film. The 0.1 wt% Pt-loaded ZnO NC sensor shows the highest sensor response to acetone and ethanol at 350 °C, while the responses to CO and H₂ are small and exhibit good selectivity to VOCs. The gas sensing mechanism of ethanol with Pt-ZnO NCs was studied by in situ DRIFT spectroscopy combined with online FT-IR gas analysis. The results show that ethanol reacts with small Pt-loaded ZnO to produce intermediate species such as acetaldehyde, acetate, and carbonate, which generates a high sensor response to ethanol in air.

POS0822 HYPERTROPHIC PACHYMENINGITIS IN ANTINEUTROPHIL CYTOPLASMIC ANTIBODY-ASSOCIATED VASCULITIS: A MULTICENTER SURVEY IN JAPAN

Background

Hypertrophic pachymeningitis (HP), characterized by an inflammatory disorder indicating intracranial or spinal thickening of dura mater, is found to develop as a neurological involvement in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Meanwhile, the previous studies focusing on HP in AAV have been reported as a single-institution study, and the analyses were performed in a small number of patients because HP is a rare neurological disorder. Therefore, neither etiological nor clinical characteristics of HP in AAV have been adequately elucidated.

Objectives

This study clarified the characteristics of HP in AAV by analyzing the information of multicenter study in Japan (Japan collaborative registry of ANCA-associated vasculitis: J-CANVAS).

Methods

We analyzed the clinical information from 541 Asian patients with AAV enrolled in J-CANVAS. Of them, newly diagnosed and relapsed AAV were included in 448 and 93, respectively. The epidemiological and clinical findings were compared between patients with and without HP. Clinical manifestations related to AAV were evaluated based on the Birmingham Vasculitis Activity Score version 3. To elucidate independent factors in HP development, logistic regression analyses were additionally performed.

Results

Of the total 541 patients (mean age: 71±14 years, M:F = 1:1.2), HP was demonstrated in 28 (5.17%), including 17 (3.79%) in newly diagnosed AAV and 11 (11.8%) in relapsed AAV. The classification of granulomatosis with polyangiitis (GPA) was significantly higher in patients with HP than those without HP (50% vs. 21%, p = 0.0007). In newly diagnosed AAV, patients with HP significantly had higher GPA classification and higher positivity for PR3-ANCA than those without HP (53% vs. 17%, p = 0.001; 29% vs. 9%, p = 0.015, respectively). Conversely, positivity for MPO-ANCA was significantly higher in patients with HP than those without HP in relapsed AAV (91% vs. 55%, p = 0.025), despite not significantly different in the classification of AAV. Headache and cranial neuropathies were significant neurological symptoms in patients with HP compared to those without HP (82% vs. 6.6%, p < 0.0001; 32% vs. 2.9%, p < 0.0001, respectively). Besides, ear, nose and throat (ENT) and mucous membranes/eyes were significantly higher involvements in patients with HP than in those without HP (54% vs. 26%, p = 0.003; 29% vs. 9%, p = 0.003, respectively). Moreover, higher complications of “conjunctive hearing loss” and “sudden visual loss”, which are included in the categories of ENT and mucous membranes/eyes involvement, respectively, were significantly indicated in patients with HP than those without HP (39% vs. 7.2%, p < 0.0001; 21% vs. 1.2%, p < 0.0001, respectively). Multivariable logistic regression analysis identified that ENT (odds ratio [OR] 1.28, 95% confident interval [CI] 1.09 to 1.49, p = 0.002) and mucous membranes/eyes involvement (OR 1.37, CI 1.14 to 1.65, p = 0.0006), as well as conjunctive hearing loss (OR 4.52, CI 1.56 to 13.05, p = 0.005) and sudden visual loss (OR 1.84, CI 1.12 to 3.00, p = 0.015), were independent related factors in patients with HP.

Conclusion

GPA could be significantly classified in patients with HP. Notably, patients with HP significantly showed higher positivity for PR3-ANCA than those without HP in newly diagnosed AAV. Furthermore, sudden visual loss and conjunctive hearing loss might be implicated in HP development.

Disclosure of Interests

None declared

AB0625 Association between Cytomegalovirus Reactivation and Renal Prognosis during Remission Induction Therapy for ANCA-Associated Vasculitis

Background

Cytomegalovirus (CMV) has been associated with atherosclerosis in patients with chronic renal failure, and may cause secondary nephrotic syndrome. Therefore, we hypothesized that the reactivation of CMV by immunosuppressive therapy in patients with vasculitis may affect renal function.

Objectives

The purpose of this study was to investigate relationships between CMV infection and renal function during ANCA-associated vasculitis remission induction therapy.

Methods

This retrospective cohort study enrolled microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis patients at 25 sites in Japan who had a first or severe relapse between January 2017 and June 2020. Of these, patients with MPA or GPA who had a positive renal lesion score on BVAS (version 3) at baseline, or vasculitis findings on renal biopsy, CMV assayed by 48 weeks of treatment, were included. Patients were divided into two groups based on the presence or absence of a positive CMV antigen test during the remission induction phase (0–48 weeks of treatment). Outcomes were the rate of change in estimated glomerular filtration rate (eGFR) at 48 weeks after initiation of treatment in both groups, as determined by (eGFR at 48 weeks - eGFR at the initiation of treatment)/eGFR at the initiation of treatment; where lower values were associated with worse renal function. General linear models adjusted for age, gender, presence of diabetes or chronic kidney disease, and the use of rituximab or cyclophosphamide were generated.

Results

A total of 387 patients had CMV antigen measured during ANCA-associated vasculitis treatment, of which 164 had renal involvement and eGFR measured at 48 weeks. Seventy-seven (47.0%) were male and the median age was 75 years (range 69–80 years). CMV reactivation was observed in 44 patients (26.8%). The beta coefficient of multiple regression analysis with CMV positive as 1 and negative as 0 was 0.08 (95% confidence interval -0.13 to 0.29) (p = 0.47). The rate of change in eGFR was higher in the CMV positive group, but not statistically significantly.

Conclusion

Contrary to our hypothesis, renal prognoses tended to be better when CMV reactivation was observed. The patients in the CMV reactivation group may have been treated more aggressively, and some patients with a poor prognosis who were not followed up for 48 weeks dropped out. Further research investigating the adjustment of treatment methods is required.

Disclosure of Interests

None declared

POS0247 GLUCOCORTICOID TAPERING STRATEGY FOR ANCA-ASSOCIATED VASCULITIS: ADDRESSING THE GAP BETWEEN RECOMMENDATIONS AND REAL-WORLD PRACTICE

Background

Antineutrophil cytoplasmic antibody -associated vasculitis (AAV) is usually treated with combination of high-dose glucocorticoid (GC) and immunosuppressive agents, followed by tapering GC dose. Although the European League Against Rheumatism (EULAR) has specific recommendations for tapering the GC dose, clinicians often taper it slower than recommended due to concerns of potential disease relapse. However, such slower taper may prolong GC exposure for the patients, increasing the risk of adverse events, particularly infection.

Objectives

The aims of our study were (1) to clarify GC dose tapering in the treatment of AAV in a real-world setting, in contrast to the EULAR recommendation of 2015 and (2) to compare the incidence of AAV relapse and severe infection between patients underdoing EULAR-recommended tapering and those undergoing slower tapering than the recommendation.

Methods

In this multicenter (25 sites in Japan), observational, retrospective study of AAV, 541 patients who had initial or severe relapse were enrolled between January 2017 and June 2020. Of these, 349 patients with microscopic polyangiitis (MPA) or granulomatosis with polyangiitis (GPA) who entered in GC tapering phase after successful induction treatment were included. These patients were then grouped on the pace of GC tapering, defined as the GC dose at 12 weeks after treatment initiation: (1) EULAR group: 7.5-10 mg/day of GC, according to the EULAR recommendation of 2015, and (2) SLOWER group: >10 mg/day of GC. Their baseline characteristics and clinical outcomes were compared. Primary outcome was defined as relapse-free days from treatment initiation, whereas secondary outcome included the incidence of infectious events requiring hospitalization within 48 weeks from treatment initiation. Multivariable analysis was performed to assess the relationship between tapering pace and clinical outcomes.

Results

There were 44 patients (12.6%) in the EULAR group and 290 (83.2%) in the SLOWER group. Regarding baseline characteristics, compared with the EULAR group, the SLOWER group had significantly higher serum C-reactive protein level (EULAR, 5.89 ± 6.89 mg/dL vs SLOWER, 7.56 ± 6.01 mg/dL; p = 0.03), as well as a trend toward higher Birmingham Vasculitis Activity Score (version 3) (EULAR, 11.80 ± 7.01 SLOWER, 13.93 ± 7.06; p = 0.08) We did not observe any significant differences in the frequency of relapses between the two groups (EULAR, 8/44, 18.2% vs SLOWER, 55/290, 19.0%; p = 0.63). Multivariable Cox proportional hazard analysis revealed no relationship GC dose at 12 weeks from treatment initiation and incidence of relapse. However, upon logistic regression analysis, the SLOWER group was found to have significant higher risk of a severe infectious event within 48 weeks from treatment initiation (p = 0.046; hazard ratio, 1.27; 95% confidence interval, 1.004 – 1.601).

Conclusion

Our finding indicates that clinicians tended to taper GC slower for patients with higher disease activity. However, slower GC taper was not found to reduce the frequency of relapse. In addition, slower GC taper was found to increase the risk of a severe infection. Hence, clinicians should pay attention not only relapsing but also late GC taper resulting in the risk of serious infection, especially in patients with higher disease activity of AAV.

References

[1]Eur J Clin Invest 2015;45 (3): 346–368.

[2]Rheumatology (Oxford). 2021 Dec 24;61(1):205-212.

[3]Arthritis Res Ther. 2021 Mar 20;23(1):90.

[4]Scand J Rheumatol. 2022 Jan 20;1-13.

[5]J Rheumatol. 2018 Apr;45(4):521-528.

[6]Rheumatol Adv Pract. 2021 Mar 9;5(3):rkab018.

[7]Ann Rheum Dis. 2016 Sep;75(9):1583-94.

Figure 1.

Acknowledgements

We would like to thank Editage (www.editage.com) for English language editing.

Disclosure of Interests

None declared

POS0875 LATENT TRAJECTORY MODELING OF PULMONARY ARTERY PRESSURE IN SYSTEMIC SCLEROSIS: A RETROSPECTIVE COHORT STUDY

Background

Systemic sclerosis (SSc) is an autoimmune disease that is characterized by systemic vasculopathy and fibrosis. Pulmonary hypertension (PH), defined as elevated pulmonary arterial pressure (PAP), is one of the leading causes of death of SSc1. In recent years, various therapies have been developed to target each of the pathogenesis of SSc – autoimmunity, vasculopathy, and fibrosis. Accordingly, treatment strategies based on risk stratification for PH progression are aspired; however, prediction of changes in PAP in diverse patients with SSc has not been established2.

Objectives

To visualize the patterns of PAP elevation in SSc and to identify the clinical characteristics of each trajectory, by applying latent trajectory modeling for PAP measured repeatedly by echocardiography.

Methods

This was a multicenter, retrospective cohort study conducted at four referral hospitals in Kyoto, Japan. Patients with SSc who visited the study site between April 2008 and March 2021 and had at least three echocardiographic measurements of systolic pulmonary arterial pressure (sPAP) were included in this study. Follow-up concluded in March 2021. A group-based trajectory model3 was applied to the change in sPAP over time, and individual patients were classified into distinct subgroups that followed similar trajectories. The number and shape of the trajectories were estimated based on adequacy, goodness of fit, parsimony, and interpretability of the model. Clinical plausibility was assessed by comparing PH-free survival, i.e., time to either PH or death, for each trajectory. Multinomial logistic regression analysis was performed for baseline clinical characteristics associated with trajectory assignment.

Results

A total of 236 patients with a total of 1097 sPAP measurements were included. We identified five trajectories following the quadratic function as “rapid progression (n=9, 3.8%)”, “early elevation (n=30, 12.7%)”, “mid elevation (n=54, 22.9%)”, “late elevation (n=24, 10.2%)”, and “low stable (n=119, 50.4%)”. Each trajectory, in this order, showed earlier elevation of sPAP and shorter PH-free survival (Figure 1). In the multinomial logistic regression (with the “low stable” as reference), cardiac involvement was associated with the “rapid progression” (adjusted odds ratio [OR] 28.9, 95% confidence interval [CI] 3.21–259.5), diffuse cutaneous SSc was associated with the “early elevation” (OR 4.08, 95% CI 1.27–13.1), anti-centromere antibody positive was associated with the “mid elevation” (OR 4.50, 95% CI 1.11–18.2), and older age of onset was associated with the above three trajectories.

Conclusion

The pattern of changes in pulmonary artery pressure over time in SSc can be classified into five distinct trajectories. Each trajectory differed in baseline clinical characteristics and outcomes.

References

[1]Pokeerbux MR, et al. Survival and prognosis factors in systemic sclerosis: data of a French multicenter cohort, systematic review, and meta-analysis of the literature. Arthritis Res Ther. 2019;21(1):86.

[2]Denton CP, et al. Systemic sclerosis. Lancet. 2017;390(10103):1685-1699.

[3]Nagin DS, et al. Group-based trajectory modeling in clinical research. Annu Rev Clin Psychol. 2010;6:109-38.

Disclosure of Interests

None declared

Facile and Green Fabrication of Microwave-Assisted Reduced Graphene Oxide/Titanium Dioxide Nanocomposites as Photocatalysts for Rhodamine 6G Degradation

Organic pollutants, such as synthetic dyes, are treated to prevent them from contaminating natural water sources. One of the treatment methods is advanced oxidation process using a photocatalyst material as the active agent. However, many photocatalysts are hindered by their production cost and efficiency. In this study, nanocomposites consisting of reduced graphene oxide and titanium dioxide (rGO/TiO2) were prepared by a simple and green approach using the microwave-assisted method, and we utilized a graphene oxide (GO) precursor that was fabricated through the Tour method. The ratios of rGO/TiO2 in nanocomposites were varied (2:1, 1:1, and 1:2) to know the influence of rGO on the photocatalytic performance of the nanocomposites for rhodamine 6G degradation. Transmission electron microscopy (TEM) observation revealed that a transparent particle with a sheetlike morphology was detected in the rGO sample, suggesting that a very thin film of a few layers of GO or rGO was successfully formed. Based on scanning electron microscopy (SEM) observation, the rGO/TiO2 nanocomposites had a wrinkled and layered rGO structure decorated by TiO2 nanoparticles with average diameters of 125.9 ± 40.6 nm, implying that rGO layers are able to prevent TiO2 from agglomeration. The synthesized product contained only rGO and TiO2 in the anatase form without impurities that were proven by Raman spectra and X-ray diffraction (XRD). The nanocomposite with rGO/TiO2 ratio 1:2 (composite C) was found to be the best composition in this study, and it was able to degrade 82.9 ± 2.4% of the rhodamine 6G after UV irradiation for 4 h. Based on a time-resolved photoluminescence study at wavelength emission 500 nm, the average decay lifetime of R6G-rGO/TiO2 composites (2.91 ns) was found to be longer than that of the R6G-TiO2 sample (2.05 ns), implying that the presence of rGO in rGO/TiO2 composites successfully suppressed the electron-hole recombination process in TiO2 and significantly improved their photocatalytic performance. This study showed that the rGO/TiO2 nanocomposites synthesized through relatively simple and eco-friendly processes display promising prospects for photocatalytic degradation of dyes and other recalcitrant pollutants in a water stream.

Electrochemical hydrogen production from humid air using cation-modified graphene oxide membranes

Water electrolysis is an environment-friendly process of producing hydrogen with zero-carbon emission. Herein, we studied the water vapor electrolysis using a proton-conducting membrane composed of graphene oxide (GO) nanosheets intercalated with cations (Al3+ and Ce3+). We examined the effect of cation introduction on the physical and chemical structures, morphology, thermal and chemical stabilities, and the proton conductivity of stacked GO nanosheet membranes by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoemission spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), dynamic light scattering (DLS), thermogravimetric-differential thermal analysis (TG-DTA), and electrochemical impedance spectroscopy (EIS). Concentration cell measurements revealed that the cation-modified membranes are pure proton conductors at room temperature. The proton conductivity of a GO membrane was much improved by cation modification. The cation-modified GO membranes, sandwiched with Pt/C electrodes as the cathode and anode, electrolyzed humidified air to produce hydrogen at room temperature, indicating the feasibility of this carbon-based electrochemical device.

Synergizing Sulfonated Hydrothermal Carbon and Microwave Irradiation for Intensified Esterification Reaction

The synergy of sulfonated hydrothermal carbon and microwave (MW) irradiation was applied for the esterification of oleic acid with methanol (MeOH) to produce biodiesel. The effects of temperature, reaction time, ratio of oleic acid to methanol, and catalyst loading were investigated at a fixed MW power of 400 W. The addition of hexane, serving as a co-solvent and separator, was also investigated. The optimum conditions for the proposed process were oleic acid-to-methanol molar ratio of 1:5 and hexane-to-methanol ratio of 0.5 (v/v) in the presence of a 5 wt % catalyst, at 100 °C for 60 min, obtaining a 97% yield of oleic acid methyl ester. The addition of slight amounts of hexane resulted into an eightfold reduction in the amount of MeOH needed to obtain a yield above 90%, which normally required a MeOH-to-oil ratio of 40:1. This proposed novel approach could provide a more cost-effective method for the esterification of oil to produce biodiesel, that is, reactive separation utilizing carbon-based catalysts under MW irradiation.

Biogasoline production from linoleic acid via catalytic cracking over nickel and copper-doped ZSM-5 catalysts

Catalytic cracking of vegetable oil mainly processed over zeolites, and among all the zeolites particularly HZMS-5 has been investigated on wide range for renewable and clean gasoline production from various plant oils. Despite the fact that HZSM-5 offers a higher conversion degree and boost aromatics yield, the isomerate yield reduces due to high cracking activity and shape selectivity of HZSM-5. Hence, to overcome these problems, in this study the transition metals, such as nickel and copper doped over HZSM-5 were tested for its efficiencies to improve the isoparaffin compounds. The catalysts were screened with linoleic acid in a catalytic cracking reaction conducted at 450 ^ᵒC for 90 min in an atmospheric condition in batch reactor. Then, the gasoline composition of the organic liquid product (OLP) was analysed in terms of paraffin, isoparaffin, olefin, naphthenes and aromatics (PIONA). The results showed that Cu/ZSM-5 produced the highest liquid yield of 79.1%, at the same time reduced the production of gas and coke to 18.8% and 0.7%. Furthermore, the desired isoparaffin composition in biogasoline increased from 1.6% to 6.8% and at the same time reduced the oxygenated and aromatic compounds to 15.4% and 59.7%, respectively. The linoleic acid as model compound of rubber seed oil, in the catalytic cracking reaction provides a clearer understanding of the process. Besides, the water gas shift (WGS) reaction in catalytic cracking reaction provides insitu hydrogen production to saturate the branched olefin into the desired isoparaffin and the aromatics into naphthenes.

WO3-Based Gas Sensors: Identifying Inherent Qualities and Understanding the Sensing Mechanism

Semiconducting metal oxide-based gas sensors are an attractive option for a wide array of applications. In particular, sensors based on WO₃ are promising for applications varying from indoor air quality to breath analysis. There is a great breadth of literature which examines how the sensing characteristics of WO₃ can be tuned via changes in, for example, morphology or surface additives. Because of variations in measurement conditions, however, it is difficult to identify inherent qualities of WO₃ from these reports. Here, the sensing behavior of five different WO₃ samples is examined. The samples show good complementarity to SnO₂ (the most commonly used material)-based sensors. A surprising homogeneity, despite variation in morphology and preparation method, is found. Using operando diffuse reflectance infrared Fourier transform spectroscopy, it is found that the oxygen vacancies are the dominant reaction partner of WO₃ with the analyte gas. This surface chemistry is offered as an explanation for the homogeneity of WO₃-based sensors.

Role of alkan-1-ol solvents in the synthesis of yellow luminescent carbon quantum dots (CQDs): van der Waals force-caused aggregation and agglomeration

Carbon quantum dots (CQDs; luminescent carbon nanoparticles, size < 10 nm) have attracted much attention with respect to their eco-friendliness and multi-functionality. The solvent-dependent photoluminescence of CQDs has been well investigated to optimize the synthesis process and homogeneous dispersion. Although some alkan-1-ol solvents, such as ethanol, have been well utilized empirically as good solvents when synthesizing highly photoluminescent CQDs, the role of alkan-1-ol solvents, particularly long-chain alkan-1-ols (e.g., 1-nonanol, 1-decanol), has not yet been clarified. Herein, we demonstrate a method for the synthesis of strongly yellow emitting CQDs using solvothermal treatment and elucidate the role of alkan-1-ol solvents in the photoluminescence of CQDs. These CQDs have been characterized using theoretical calculations, ex situ morphological observations using transmission electron microscopy (TEM) and dynamic light scattering (DLS), and 500 MHz ¹H nuclear magnetic resonance (NMR) and ¹³C NMR spectroscopy. A comparative study of alkan-1-ol solvents suggests a mechanism for the agglomeration and aggregation of carbon precursors, intermediates, and CQDs, which is expected to lead to further synthesis studies on highly luminescent CQDs.

Carbon quantum dots (CQDs; luminescent carbon nanoparticles, size < 10 nm) have attracted much attention with respect to their eco-friendliness and multi-functionality.

Production of gasoline range hydrocarbons from catalytic cracking of linoleic acid over various acidic zeolite catalysts

Employment of edible oils as alternative green fuel for vehicles had raised debates on the sustainability of food supply especially in the third-world countries. The non-edible oil obtained from the abundantly available rubber seeds could mitigate this issue and at the same time reduce the environmental impact. Therefore, this paper investigates the catalytic cracking reaction of a model compound named linoleic acid that is enormously present in the rubber seed oil. Batch-scale experiments were conducted using 8.8 mL Inconel batch reactor having a cyclic horizontal swing span of 2 cm with a frequency of 60 cycles per minute at 450 °C under atmospheric condition for 90 min. The performance of HZSM-5, HBeta, HFerrierite, HMordenite and HY catalysts was tested for their efficiency in favouring gasoline range hydrocarbons. The compounds present in the organic liquid product were then analysed using GC-MS and classified based on PIONA which stands for paraffin, isoparaffin, olefin, naphthenes and aromatics respectively. The results obtained show that HZSM-5 catalyst favoured gasoline range hydrocarbons that were rich in aromatics compounds and promoted the production of desired isoparaffin. It also gave a higher cracking activity; however, large gaseous as by-products were produced at the same time.

Utilization of rice husk to enhance calcium oxide-based sorbent prepared from waste cockle shells for cyclic CO2 capture in high-temperature condition

The CO₂ capture capacity and cyclic stability of calcium oxide (CaO) prepared from cockle shells (CS) were enhanced by incorporating rice husk (RH) and binder through wet-mixing method. The cyclic reaction of calcination and carbonation was demonstrated using thermal gravimetric analyzer (TGA) which the calcination was performed in a pure N₂ environment at 850 °C for 20 min and carbonation at 650 °C for 30 min in 20 vol% of CO₂ in N₂. The analysis using x-ray fluorescence (XRF) identified silica (Si) as the major elements in the sorbents. The RH-added sorbents also contained several types of metal elements such as which was a key factor to minimize the sintering of the sorbent during the cyclic reaction and contributed to higher CO₂ capture capacity. The presence of various morphologies also associated with the improvement of the synthesized sorbents performance. The highest initial CO₂ capture capacity was exhibited by CS+10%RH sorbent, which was 12% higher than the RH-free sorbent (CS). However, sorbents with the higher RH loading amount such as 40 and 50 wt% were preferred to maintain high capture capacity when the sorbents were regenerated and extended to the cyclic reaction. The sorbents also demonstrated the lowest average sorption decay, which suggested the most stable sorbent for cyclic-reaction. Once regenerated, the capture capacity of the RH-added sorbent was further increased by 12% when clay was added into the sorbent. Overall, the metal elements in RH and clay were possibly the key factor that enhances the performance of CaO prepared from CS, particularly for cyclic CO₂ capture. Graphical abstract Cyclic calcination and carbonation reaction.

Carbocatalysed hydrolytic cleaving of the glycosidic bond in fucoidan under microwave irradiation

Biomass valorization involves breaking down naturally occurring long chain polysaccharides into their constituent monomers. The polysaccharide chain consists of monomers adjoined via C (carbon)–O (oxygen) glycosidic linkages that are typically cleaved via hydrolytic scission. In this study, we aimed to recover fucose from the polysaccharide fucoidan, which can be extracted from seaweed biomass. We investigated the depolymerisation behavior of fucoidan sourced from two different species of seaweeds, namely Undaria pinnatifida (F-UP) and Fucus vesiculosus (F-FV). Catalytic depolymerisation experiments were performed using four different carbon-based catalysts – graphene, multiwalled carbon nanotubes (MWCNT), graphene oxide (GO), and reduced graphene oxide (rGO) – under microwave (MW) irradiation. Our results showed that the depolymerisation of fucoidan was best achieved using GO, which was attributed to the abundance of oxygen functionalities on its surface. Furthermore, based on gel permeation chromatography analyses, the depolymerisation of fucoidan was found to follow a two-step process: (1) random scission leading to the production of short-chain oligosaccharides and (2) acid-catalysed hydrolysis of the oligosaccharides to fucose. Because of the longer chain length of F-UP (61 kDa), the highest fucose yield of 17.4% using this species was obtained at a higher temperature of 120 °C in a closed vessel. Meanwhile, in the case of F-FV (1.1 kDa), the highest yield of 54.0% was obtained under reflux conditions at a lower temperature of 104 °C. Our mechanistic study based on semi-empirical quantum calculations also revealed that the recovery of fucose from F-FV is more energetically favoured than from F-UP as a result of their structural differences.

Fucose recovery from Undaria pinnatifida (F-UP) and Fucus vesiculosus (F-FV) via microwave-carbocatalysis consist of random scission leading to the production of short-chain oligosaccharides followed by acid-catalysed hydrolysis.

Reversible ON/OFF switching of photoluminescence from CsPbX3 quantum dots coated with silica using photochromic diarylethene

Highly luminescent silica-coated CsPbX₃ quantum dots (QDs) with good photostability were synthesized and coupled with photochromic diarylethene to modulate the QDs’ photoluminescence (PL).

Sustainable green pretreatment approach to biomass-to-energy conversion using natural hydro-low-transition-temperature mixtures

Natural hydro-low-transition-temperature mixtures (NH-LTTMs) tend to be the most favorable next-generation green solvents for biomass pretreatment, as they are cheap and environmental friendly. The amount of water bound into the NH-LTTMs greatly affected their thermal stability, whereby the highest thermal stability was observed with the water content of 7.6 wt%. It is worth noting that, the highest molar transition energy of NH-LTTMs (47.57 kcal mol^-1), which indicated the highest solubility, was optimized with the molar ratio of hydrogen bond donor (HBD)-hydrogen bond acceptor (HBA)-water (2:4:3) at a temperature of 60 °C. Hydrogen bonding networks of the NH-LTTMs, which led to the dissolution of biomass, were confirmed by the alteration in the peaks of the involved bonds and resonance signal to lower field through FTIR and ¹H NMR spectra, respectively. The components evidenced in high-resolution mass spectra of extracted lignin showed its high potential to be valorized into useful fuels and chemicals.

Thermogravimetric analysis and kinetic modeling of low-transition-temperature mixtures pretreated oil palm empty fruit bunch for possible maximum yield of pyrolysis oil

The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment.

Integrating reduced graphene oxide with microwave-subcritical water for cellulose depolymerization

Subcritical water compensates for the loss of functionalities in reduced graphene oxide to facilitate high depolymerization rate of cellulose under microwave.

Choline chloride (ChCl) and monosodium glutamate (MSG)-based green solvents from optimized cactus malic acid for biomass delignification

This work aimed to develop an efficient microwave-hydrothermal (MH) extraction of malic acid from abundant natural cactus as hydrogen bond donor (HBD) whereby the concentration was optimized using response surface methodology. The ideal process conditions were found to be at a solvent-to-feed ratio of 0.008, 120°C and 20min with 1.0g of oxidant, H₂O₂. Next generation environment-friendly solvents, low transition temperature mixtures (LTTMs) were synthesized from cactus malic acid with choline chloride (ChCl) and monosodium glutamate (MSG) as hydrogen bond acceptors (HBAs). The hydrogen-bonding interactions between the starting materials were determined. The efficiency of the LTTMs in removing lignin from oil palm biomass residues, empty fruit bunch (EFB) was also evaluated. The removal of amorphous hemicellulose and lignin after the pretreatment process resulted in an enhanced digestibility and thermal degradability of biomass.

Selective depletion of cultured macrophages by magnetite nanoparticles modified with gelatin

Previous studies have indicated pro-tumor functions of macrophages in tumor progression in different types of malignant tumors. The detailed mechanisms of cell-cell interaction between macrophages and tumor cells have been investigated by means of in vitro co-culture experiments. The present study developed magnetite nanoparticles modified with gelatin that are specifically engulfed by macrophages and investigated methods to deplete these macrophages in co-culture experiments using a magnet. T98G glioma cell line and human monocyte-derived macrophages were mixed and co-cultured for 2 days. The T98G cells were isolated by depletion of the macrophages using the magnetite nanoparticles. mRNA expression of a number of pro-tumor molecules in the isolated T98G cells, with or without co-culture with macrophages, was then evaluated. The mRNA expression levels of chemokine (CC motif) ligand 2, interleukin-6 and macrophage-colony stimulating factor receptor (M-CSFR) were significantly upregulated in T98G cells by co-culture with macrophages (P<0.01). M-CSFR protein expression was also increased by co-culture with macrophages. The conditioned medium of co-cultured cells increased M-CSFR expression in T98G cells. Magnetite nanoparticles may be a novel tool not only for investigating the unique activation status of tumor cells in co-culture conditions, but also for targeting pro-tumor macrophages in tumor tissues.

Order by Quenched Disorder in the Model Triangular Antiferromagnet RbFe(MoO_{4})_{2}

We observe a disappearance of the 1/3 magnetization plateau and a striking change of the magnetic configuration under a moderate doping of the model triangular antiferromagnet RbFe(MoO_{4})_{2}. The reason is an effective lifting of degeneracy of mean-field ground states by a random potential of impurities, which compensates, in the low-temperature limit, the fluctuation contribution to free energy. These results provide a direct experimental confirmation of the fluctuation origin of the ground state in a real frustrated system. The change of the ground state to a least collinear configuration reveals an effective positive biquadratic exchange provided by the structural disorder. On heating, doped samples regain the structure of a pure compound, thus allowing for an investigation of the remarkable competition between thermal and structural disorder.

Solid Electrolyte Gas Sensor Based on a Proton-Conducting Graphene Oxide Membrane

Graphene oxide (GO) is an ultrathin carbon nanosheet with various oxygen-containing functional groups. The utilization of GO has attracted tremendous attention in a number of areas, such as electronics, optics, optoelectronics, catalysis, and bioengineering. Here, we report the development of GO-based solid electrolyte gas sensors that can continuously detect combustible gases at low concentrations. GO membranes were fabricated by filtration using a colloidal solution containing GO nanosheets synthesized by a modified Hummers' method. The GO membrane exposed to humid air showed good proton-conducting properties at room temperature, as confirmed by hydrogen concentration cell measurements and complex impedance analyses. Gas sensor devices were fabricated using the GO membrane fitted with a Pt/C sensing electrode. The gas-sensing properties were examined by potentiometric and amperometric techniques. The GO sensor showed high, stable, and reproducible responses to hydrogen at parts per million concentrations in humid air at room temperature. The sensing mechanism is explained in terms of the mixed-potential theory. Our results suggest the promising capability of GO for the electrochemical detection of combustible gases.

Correction: Synthesis and characterization of nitrogen-functionalized graphene oxide in high-temperature and high-pressure ammonia

Correction for ‘Synthesis and characterization of nitrogen-functionalized graphene oxide in high-temperature and high-pressure ammonia’ by F. H. Baldovino et al., RSC Adv., 2016, 6, 113924–113932.

Ultrasensitive Detection of Volatile Organic Compounds by a Pore Tuning Approach Using Anisotropically Shaped SnO2 Nanocrystals

Gas sensing with oxide nanostructures is increasingly important to detect gaseous compounds for safety monitoring, process controls, and medical diagnostics. For such applications, sensor sensitivity is one major criterion. In this study, to sensitively detect volatile organic compounds (VOCs) at very low concentrations, we fabricated porous films using SnO₂ nanocubes (13 nm) and nanorods with different rod lengths (50-500 nm) that were synthesized by a hydrothermal method. The sensor response to H₂ increased with decreasing crystal size; the film made of the smallest nanocubes showed the best sensitivity, which suggested that the H₂ sensing is controlled by crystal size. In contrast, the responses to ethanol and acetone increased with increasing crystal size and resultant pore size; the highest sensitivity was observed for a porous film using the longest nanorods. Using the Knudsen diffusion-surface reaction equation, the gas sensor responses to ethanol and acetone were simulated and compared with experimental data. The simulation results proved that the detection of ethanol and acetone was controlled by pore size. Finally, we achieved ultrahigh sensitivity to ethanol; the sensor response (S) exceeded S = 100 000, which corresponds to an electrical resistance change of 5 orders of magnitude in response to 100 ppm of ethanol at 250 °C. The present approach based on pore size control provides a basis for designing highly sensitive films to meet the criterion for practical sensors that can detect a wide variety of VOCs at ppb concentrations.

Role of vanadium oxide and palladium multiple loading on the sensitivity and recovery kinetics of tin dioxide based gas sensors

Improving the gas sensing properties by Pd and V₂O₅ co-loading on the SnO₂ attributed to the role of each additive.

Synthesis and characterization of nitrogen-functionalized graphene oxide in high-temperature and high-pressure ammonia

Successful N-functionalization of graphene oxide with high-temperature and high-pressure ammonia obtaining over 10% N-doping level.

Characterization of natural low transition temperature mixtures (LTTMs): Green solvents for biomass delignification

The aim of this work was to characterize the natural low transition temperature mixtures (LTTMs) as promising green solvents for biomass pretreatment with the critical characteristics of cheap, biodegradable and renewable, which overcome the limitations of ionic liquids (ILs). The LTTMs were derived from inexpensive commercially available hydrogen bond acceptor (HBA) and l-malic acid as the hydrogen bond donor (HBD) in distinct molar ratios of starting materials and water. The peaks involved in the H-bonding shifted and became broader for the OH groups. The thermal properties of the LTTMs were not affected by water while the biopolymers solubility capacity of LTTMs was improved with the increased molar ratio of water and treatment temperature. The pretreatment of oil palm biomass was consistence with the screening on solubility of biopolymers. This work provides a cost-effective alternative to utilize microwave hydrothermal extracted green solvents such as malic acid from natural fruits and plants.