Fused Ring Structures Research Articles

Fused-Ring Pyrrole-Based Near-Infrared Emissive Organic RTP Material for Persistent Afterglow Bioimaging.

Organic near-infrared room temperature phosphorescence (RTP) materials offer remarkable advantages in bioimaging due to their characteristic time scales and background noise elimination. However, developing near-infrared RTP materials for deep tissue imaging still faces challenges since the small band gap may increase the non-radiative decay, resulting in weak emission and short phosphorescence lifetime. In this study, fused-ring pyrrole-based structures were employed as the guest molecules for the construction of long wavelength emissive RTP materials. Compared to the decrease of the singlet energy level, the triplet energy level showed a more effectively decrease with the increase of the conjugation of the substituent groups. Moreover, the sufficient conjugation of fused ring structures in the guest molecule suppresses the non-radiative decay of triplet excitons. Therefore, a near-infrared RTP material (764 nm) was achieved for deep penetration bioimaging. Tumor cell membrane is used to coat RTP nanoparticles (NPs) to avoid decreasing the RTP performance compared to traditional coating by amphiphilic surfactants. RTP NPs with tumor-targeting properties show favorable phosphorescent properties, superior stability, and excellent biocompatibility. These NPs are applied for time-resolved luminescence imaging to eliminate background interference with excellent tissue penetration. This study provides a practical solution to prepare long-wavelength and long-lifetime organic RTP materials and their applications in bioimaging.

Fused‐Ring Pyrrole‐Based Near‐Infrared Emissive Organic RTP Material for Persistent Afterglow Bioimaging

AbstractOrganic near‐infrared room temperature phosphorescence (RTP) materials offer remarkable advantages in bioimaging due to their characteristic time scales and background noise elimination. However, developing near‐infrared RTP materials for deep tissue imaging still faces challenges since the small band gap may increase the non‐radiative decay, resulting in weak emission and short phosphorescence lifetime. In this study, fused‐ring pyrrole‐based structures were employed as the guest molecules for the construction of long wavelength emissive RTP materials. Compared to the decrease of the singlet energy level, the triplet energy level showed a more effectively decrease with the increase of the conjugation of the substituent groups. Moreover, the sufficient conjugation of fused ring structures in the guest molecule suppresses the non‐radiative decay of triplet excitons. Therefore, a near‐infrared RTP material (764 nm) was achieved for deep penetration bioimaging. Tumor cell membrane is used to coat RTP nanoparticles (NPs) to avoid decreasing the RTP performance compared to traditional coating by amphiphilic surfactants. RTP NPs with tumor‐targeting properties show favorable phosphorescent properties, superior stability, and excellent biocompatibility. These NPs are applied for time‐resolved luminescence imaging to eliminate background interference with excellent tissue penetration. This study provides a practical solution to prepare long‐wavelength and long‐lifetime organic RTP materials and their applications in bioimaging.

Distinct property of biochar from pyrolysis of poplar wood, bark, and leaves of the same origin

The biochemical composition of wood, bark, and leaves is different, and this difference will inevitably project to products from the pyrolysis of different parts of a tree. In this study, different tissues of the same poplar tree (wood, bark, and leaves) were pyrolyzed to probe the characteristics of pyrolysis products of varied feedstock. The results indicated that wood tended to be pyrolyzed to form bio-oil with the highest yield (57.7% at 600 °C) while gases with the lowest yield (12.2% at 400 °C) among the three feedstocks. The high content of inorganic species in bark (5.8%) and especially leaves (10.3%) promoted the gasification of the aliphatic structures to produce a high yield of gases (18.9% of gas yield in leaves pyrolysis at 600 °C). In addition, unlike that in pyrolysis of wood, the pyrolysis of leaves produced little sugar derivatives like ketones (0%) /aldehydes (0%), but more hydrocarbons, N-containing organics, and phenolics with large fused ring structures. The organic components in leaves and bark were highly unstable, and their decomposition was further enhanced with the abundant inorganic species. This hindered the aromatization of the leaves/bark-derived biochar, resulting in their lower heating value, energy density, thermal stability, and their lower comprehensive combustion index than the biochar derived from wood. Additionally, as the pyrolysis temperature increases, the varied composition of feedstock also led to distinct patterns for the evolution of functionalities of biochar.

Pyrolysis of sawdust impregnated with xylose: Tailoring property of biochar with sugar-derived intermediates

Cellulose and hemicellulose are major components of woody biomass, pyrolysis of which would inevitably produce anhydrate sugars or sugar-like organics. These sugars might tailor property of biochar via interactions when they pass through inner and outer surface of biochar, which were investigated herein in pyrolysis of poplar sawdust impregnated with various loading of xylose, a model sugar from hemicellulose, at 600 °C. The results suggested that the addition of xylose enhanced the cracking reactions to form more gaseous products but less biochar and bio-oil. Nevertheless, the intermediates from xylose enhanced aromatization of volatiles to form more light phenolics while aided precipitation of heavy organics on surface of biochar. The accelerated carbonization, deoxygenation and dehydrogenation reactions with presence of xylose enhanced aromatization reactions, making the biochar carbon-rich with increased heating value, crystallinity and hydrophobicity. Additionally, xylose addition could substantially enhance thermal stability of the biochar, even with loading of only 5 wt%. The DRIFTS characterization showed that the degradation of xylose produced abundant carbonyls-containing species that react with organics on surface of biochar, forming large aromatics of fused ring structures.

Universally Exhaustive Generation of Molecular Structures and Prediction of Their Electronic States Using Machine Learning for N-type Organic Transistor Materials.

We have proposed a new method for the exploration of organic functional molecules, using an exhaustive molecular generator combined without combinatorial explosion and electronic state predicted by machine learning and adapted for developing n-type organic semiconductor molecules for field-effect transistors. Our method first enumerates skeletal structures as much as possible and next generates fused ring structures using substitution operations for atomic nodes and bond edges. We have succeeded in generating more than 4.8 million molecules. We calculated the electron affinity (EA) of about 51 thousand molecules with DFT calculation and trained the graph neural networks to estimate EA values of generated molecules. Finally, we obtained the 727 thousand molecules as candidates that satisfy EA values over 3 eV. The number of these possible candidate molecules is far beyond what we have been able to propose based on our knowledge and experience in synthetic chemistry, indicating a wide diversity of organic molecules.

Multicolor fluorescent probes for volatile organic vapors based on poly(tetraphenylethylene-co-phenylene)s prepared via solid-state oxidative coupling polymerization

The development of effective detectors for volatile organic vapor detection has attracted extensive attention. Through solid-state oxidative coupling polymerization, poly(tetraphenylethylene-co-phenylene)s were prepared by mechanical grinding of tetraphenylethylene and 1,4-dipentoxybenzene with FeCl3 as the oxidative catalyzer. The FT-IR and NMR spectra confirmed the main chain to be composed of segments of dipentoxybenzenes, segments of tetraphenylethylenes, and segments of fused ring structures, which were formed via the intermolecular coupling reaction and intramolecular coupling reaction. With the increased ratios of TPE monomers, the copolymers displayed a concentration-induced discoloration behavior from blue-emitting red-shifting to green-emitting. Although the formation of planar fused rings led to an ACQ phenomenon of the copolymers, the polymer conformations, and the polymer stacking could be adjusted by solvent molecules absorbed by the TLC plates, thereby the copolymers could be used as fluorescent probes for various violate organic vapors. The multicolor fluorescent could be observed by the naked eye to distinguish a variety of organic molecules with similar structures, for example, methanol and other alcohols, pentane and other alkanes, the dimethyl benzenes with different substitution positions, and so on. Therefore, multicolor fluorescent probes have a potential application in the detection of volatile organic vapors.

Molecular Insights of Non-fused Ring Acceptors for High-Performance Non-fullerene Organic Solar Cells.

Non-fullerene acceptors with fused-ring structures have rapidly improved the performance of organic solar cells over the past five years, but they still suffer from synthetic complexity and thus high material costs, one of the major obstacles of hindering their commercialization process. The construction of non-fused ring acceptors (NFRAs) has recently been regarded as a feasible solution due to their facile synthesis and satisfactory device performances. Thus in this concept, we highlight the important progress of NFRAs in recent years, and discuss the key relationship between molecular design strategies and device performance. Finally, we provide some potential molecular insights for the future design of high-performance NFRAs.

Pyrolysis of sawdust coupled with steam reforming for simultaneously production of heavy organics and hydrogen

In hydrotreatment of bio-oil, it is difficult to convert the aliphatic compounds with the carbon number less than four into liquid fuel via hydrodeoxygenation. Thus, ideally, the very light organics of bio-oil could be reformed to generate hydrogen for further upgrading the heavier organics in bio-oil to biofuel or fine chemicals. In this study, the pyrolysis of poplar sawdust coupled with the simultaneously steam reforming of the bio-oil (pyro-reforming) were studied over Ni/SBA-15 catalyst at the medium temperature range from 450 to 650 °C for transforming mainly the light aliphatic compounds into H2. The results showed that the effective steam reforming of the aliphatic compounds like carboxylic acid and small aldehydes/ketones took place to remarkable extent from 550 °C, while the furans, anhydrate sugars, light phenols and heavy phenolics of fused ring structures could be largely retained in the resulting bio-oil. Coking reached the maximum with increasing temperature to 500 °C from cracking/polymerization of the volatiles. Further increase of temperature to 650 °C accelerated steam reforming and gasification of precursors of coke, shifting the morphology of coke from amorphous form to unregular carbon nanotube structures (stringed beads-like) and making the coke more aromatic and more resistant to oxidation. Nevertheless, in overall, the coke produced from 450 to 650 °C was aliphatic with low C/H ratio, low thermal stability and low crystallinity, originating from the significant contribution from the aliphatic compounds in the bio-oil for coking.

Rational Design of Dyes and Donor-Acceptor Type Molecules for Organic Solar Cells

Organic solar cells (OSCs) have received considerable attention as clean energy conversion devices because of their lightweightness, cost effectiveness, flexibility, and suitability for roll-to-roll printing. In dye-sensitized solar cells the core structure has included a dye-anchored TiO2 electrode for photoinduced charge separation, while in bulk heterojunction OSCs, the active layer of OSC devices has usually consisted of a mixture of conjugated polymers as donors and fullerene derivatives as acceptors.1,2 In particular, the power conversion efficiency (PCE) of OSCs based on fullerene derivative acceptors has reached over 10%. However, it is difficult to further increase the PCE of fullerene-based OSCs due to their inherent limitations including arduous energy-level tunability and low absorption profile. To enhance the photovoltaic performance of OSCs, nonfullerene acceptors (NFAs) with aromatic fused-ring structures have emerged rapidly in recent years to fabricate high-efficiency OPVs. Compared to traditional fullerene acceptors, NFAs possess several advantages, such as facile synthesis and high absorption profile. Most high-performance NFAs possess acceptor-donor-acceptor (A-D-A) type structures, in which fused multi-ring ladder structures are used as the D unit and 1,1-dicyanomethylene-3-indanone (IC) derivatives as the A unit.In this talk I will give an overview of our recent studies on rational design and synthesis of novel dyes and nonfullerene acceptors. In paticular, several nonfullerene acceptors possessing different D units have been designed and synthesized to address the relationship between the structure and the photophysical and photovoltaic properties of the A-D-A type nonfullerene acceptors.3-6 [1] T. Umeyama and H. Imahori, J. Mater. Chem. A (Feature Article), 2, 11545-11560 (2014).[2] T. Umeyama and H. Imahori, Acc. Chem. Res. 52, 2046-2055 (2019).[3] T. Umeyama, K. Igarashi, D. Sasada, Y. Tamai, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Chem. Sci., 11, 3250-3257 (2020).[4] T. Umeyama, K. Igarashi, D. Sasada, K. Ishida,T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Appl. Mater. Interfaces, 12, 39236-39244 (2020).[5] T. Umeyama, K. Igarashi, Y. Tamai, T. Wada, T. Takeyama, D. Sasada, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Sus. Energy Fuels, 5, 2028-2035 (2021).[6] T. Umeyama, T. Wada, K. Igarashi, K. Kato, A. Yamakata, T. Takeyama, Y. Sakamoto, Y. Tamai, H. Ohkita, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Adv. Energy Mater., in press.

Pyrolysis of furfural residues: Property and applications of the biochar

Furfural residue (FR) is a solid waste generated during the production of furfural from corn cobs. The chemical energy and material potential of FR can be potentially recovered via pyrolysis. In this study, the pyrolysis of FR at the temperature ranging from 350 to 650 °C at the varied heating rate was investigated, aiming to understand the characteristics of the pyrolysis products. The results indicate that the organic components of FR tend to be cracked to form biochar and gases as the dominate products, due to the high ash content of FR. The FR-derived bio-oil also contained abundant organics derived from cellulose and lignin. Increasing pyrolysis temperature favored formation of the organics with fused ring structures. Lower heating rate in pyrolysis also formed biochar with higher thermal stability and higher fixed carbon content by enhancing the extent of deoxygenation. Additionally, the transformation of –OH via dehydration, -C-H into = C–H via dehydrogenation, and the cracking of CO during carbonization of biochar in the pyrolysis were also observed during pyrolysis of FR. Activation of the FR-derived biochar generated abundant micropores and mesopores, rendering the activated carbon with superior specific capacitance as electrodes of electrocapacitors (329 Fg-1) and the excellent adsorption efficiency of phosphate (up to 98.81%).

Insight into the fast pyrolysis of lignin: Unraveling the role of volatile evolving and char structural evolution

Unraveling the role of volatile evolving and char structural evolution, as well as the pyrolysis reaction pathway, is crucial for lignin effective valorization by a pyrolysis-based biorefinery approach. The fast pyrolysis of lignin at 200–800 °C was conducted to explore volatile release characteristics and their link with char structure evolution. The release of simple substituted aryl compounds below 350 °C was aided by the cleavage of β-O-4 and α-O-4. The C-O, C–C, and carboxyl groups of the depolymerized free radical fragments were cleaved further, providing stable mono-phenol (350 °C → 500 °C). Secondary reactions and pyrolytic macromolecular compounds resulted in the synthesis of polycyclic aromatic hydrocarbons (>700 °C). A cubic polynomial was developed to correlate the aromaticity with the atom ratio of H/C. The ring condensation degree and H/C demonstrated an excellent positive linear correlation. Additionally, the aromatization started at 350 °C, and small aromatic rings were changed into more ordered rings (≥6 rings). The fused-ring structures of char had progressed in the following order: 1 × 2, 2 × 3, 4 × 4, and 4 × 5, corresponding to 350 °C, 500 °C, 600 °C, and 800 °C, respectively. High temperatures contributed to the formation of aromatic monomers. Lignin pyrolysis pathway was established based on the correlation between volatile release characteristics and char structural evolution.

Non-fused ring acceptors for organic solar cells

Organic solar cells (OSCs) have experienced rapid development and achieved significant breakthroughs in power conversion efficiencies owing to the emergence of non-fullerene acceptors (NFAs) with ladder-type multiple fused ring structures. However, the high synthetic complexity and production cost of multiple fused ring NFAs hinder the commercial prospects of OSCs. In this context, the development of non-fused ring acceptors (NFRAs) with simple structures and facile synthesis has been proposed. In this mini review, we summarize the important progress in this field spanning from molecular design strategies to structure-performance relationships. Ultimately, with the aim of realizing the practical application of NFRAs in OSCs, we discuss the current challenges and future directions in terms of achieving high performance and low synthetic complexity simultaneously. These discussions provide valuable insights into the development of new NFRAs.

A High-Performance Nonfused Wide-Bandgap Acceptor for Versatile Photovoltaic Applications.

Wide-bandgap (WBG) nonfullerene acceptors (NFAs) with nonfused conjugated structures play a critical role in organic photovoltaic (OPV) cells. Here, NFAs named GS-OEH, GS-OC6, and GS-ISO, with optical bandgaps larger than 1.70eV, are synthesized without using the fused ring structures. Compared with GS-OEH and GS-OC6, GS-ISO exhibits much stronger crystallinity, leading to a smaller energetic disorder and a larger exciton diffusion coefficient. GS-ISO also possesses a higher electroluminescence external quantum efficiency of 1.0×10-2 . The OPV cell based on PBDB-TF:GS-ISO demonstrates a power conversion efficiency (PCE) of 11.62% under the standard one sun illumination. Besides, the PBDB-TF:GS-ISO-based cell with effective area of 1.0cm2 exhibits a PCE of 28.37% under 2700K illumination of 500lux. A tandem OPV cell using PBDB-TF:GS-ISO as the front subcell shows an outstanding efficiency of 19.10%. Importantly, the GS-ISO-based OPV cell exhibits promising stability under the continuous illumination of simulated sunlight. This study indicates that the molecular design strategy demonstrated in this work has great superiority in developing nonfused NFAs and also that GS-ISO is a promising WBG acceptor for versatile photovoltaic applications.

Steam reforming of n-hexane and toluene: Understanding impacts of structural difference of aliphatic and aromatic hydrocarbons on their coking behaviours

Plastic wastes are potential feedstock for the production of hydrogen via gasification. Aliphatic hydrocarbons and aromatic hydrocarbons are important fractions from pyrolysis of plastic wastes, which might show the different reaction behaviors in steam reforming reactions due to their distinct molecular structures. To explore this, in this study, steam reforming of n-hexane and toluene, two model compounds representing respective aliphatic hydrocarbons and aromatic hydrocarbons, over Ni/SBA-15 catalyst were carried out. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization of the steam reforming indicated that the dissociative absorption of n-hexane on nickel took place even at 100 °C, form abundant CHx species and consequently more CH4 in gaseous products. Nevertheless, the reaction intermediates from n-hexane could be gasified by the OH from adsorbed water rapidly. In comparison, the fragments from dissociative adsorption of toluene reacted with hydroxyl group of water, forming the stable intermediates bearing OH, CO, COC and CC functionalities, which were the precursors of coke and resulted in more serious coking. The coke from steam reforming of toluene showed a higher thermal stability, higher resistivity to oxidation as it was more aromatic and contained more defective with big fused ring structures. In addition, the majority carbon nanotubes generated during steam reforming of toluene had an inner diameter of 3–6 nm and outer diameter of 10–20 nm. Nickel species on tip of the nanotubes were wrapped with a carbon layer, which contributed to the deactivation of the catalyst in steam reforming of toluene.

Rational Molecular Design of Nonfullerene Acceptors for Bulk Heterojunction Solar Cells

Organic photovoltaics (OPVs) have received considerable attention as clean energy conversion devices because of their lightweightness, cost effectiveness, flexibility, and suitability for roll-to-roll printing. In the past few decades, the active layer of OPV devices has usually consisted of conjugated polymers as donors and fullerene derivatives as acceptors, which typically form a bulk heterojunction (BHJ) structure.1,2 The power conversion efficiency (PCE) of OPVs based on fullerene derivative acceptors has reached over 10%. However, it is difficult to further increase the PCE of fullerene-based OPVs due to their inherent limitations including arduous energy-level tunability and low absorption profile. To enhance the photovoltaic performance of OPVs, nonfullerene acceptors (NFAs) with aromatic fused-ring structures have been extensively developed in recent years to fabricate high-efficiency OPVs. Compared to traditional fullerene acceptors, NFAs possess several advantages, such as facile synthesis and high absorption profile. Most high-performance NFAs possess acceptor-donor-acceptor (A-D-A) type structures, in which fused multi-ring ladder structures are used as the D unit and 1,1-dicyanomethylene-3-indanone (IC) derivatives as the A unit.In this talk I will give an overview of our recent studies on novel nonfullerene acceptors. In paticular, several nonfullerene acceptors possessing different D units have been designed and synthesized to address the relationship between the structure and the photophysical and photovoltaic properties of the A-D-A type nonfullerene acceptors.3,4 [1] T. Umeyama and H. Imahori, J. Mater. Chem. A (Feature Article), 2, 11545-11560 (2014).[2] T. Umeyama and H. Imahori, Acc. Chem. Res. 52, 2046-2055 (2019).[3] T. Umeyama, K. Igarashi, D. Sasada, Y. Tamai, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Chem. Sci., 11, 3250-3257 (2020).[4] T. Umeyama, K. Igarashi, D. Sasada, K. Ishida,T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Appl. Mater. Interfaces, 12, 39236-39244 (2020).

Co-hydrothermal carbonization of swine and chicken manure: Influence of cross-interaction on hydrochar and liquid characteristics

Swine and chicken manures are abundant solid wastes that can be converted into carbonaceous materials through hydrothermal carbonization (HTC). Owing to their unique biochemical compositions, co-HTC of these two types of manures may have significant implications for the generated products. We investigated the co-HTC of swine manure and chicken manure to understand the influence of the interaction between contrasting manures on the properties of the derived products. The results indicated that co-HTC treatment enhanced the formation of solid product and improved the C and N contents, heating value, and energy yield of the resulting hydrochar. Regarding the ignition temperature and comprehensive combustion index, the combustion properties of the hydrochar were enhanced owing to the mutual effect of the HTC intermediates. Additionally, the interaction of the intermediates significantly impacted the transfer of nitrogenous species and generation of organic acids and organic polymers with fused-ring structures. Therefore, co-HTC processing of animal manures could potentially provide a sustainable pathway for the conversion of animal waste into solid products with improved characteristics compared to those produced by treating the two feedstocks separately.

Biochar catalyzing polymerization of the volatiles from pyrolysis of poplar wood

In this study, the pyrolysis of poplar wood chips with biochar catalyst produced from gasification of the same poplar wood chips was conducted, aiming to probe its influence on the evolution of the pyrolysis products. From the results, it was concluded that the biochar catalyst enhanced the polymerization of the volatiles produced from the pyrolysis, and thus reduced the yields of the gaseous compounds while increased the yield of char. The carbonaceous deposit on surface of the char was oxygen-rich and more aliphatic, which decreased the thermal stability and crystallinity of the char, while made the char prone to oxidation. The biochar catalyst also promoted the formation of methoxy phenols at the expense of alkyl phenols, and the formation of the phenolics with bigger π-conjugated structures. In addition, the volatile-biochar interaction removed the defective structures in the large aromatic structures in the biochar catalyst. Highlights Biochar catalyzed polymerization, but not cracking, of volatiles in pyrolysis. Biochar catalyst enhances char formation while reduces gas formation in pyrolysis. Char in catalytic pyrolysis is more O-rich and aliphatic and low thermal stability. Biochar catalyzed condensation of volatiles to form bigger fused ring structures. Biochar-volatiles interaction removes defective structure in fused ring of biochar.

Pyrolysis of herb waste: Effects of extraction pretreatment on characteristics of bio-oil and biochar

The extracted herbal residue, an agricultural waste, was pyrolyzed to produce value-added products by exploring the impact of extraction pretreatment on the pyrolysis performance of herbal feedstock. The Artemisia capillaris thumb, a kind of Chinese herbal medicine, was extracted with ethanol to get the herbal waste. The herbal residue and herbal feedstock were pyrolyzed at different pyrolysis temperature. The results showed the extraction of the herb with ethanol affected both the yields and composition/properties of bio-oil/biochar. Extraction of the herb also affected the pyrolysis of cellulose, hemicellulose or lignin in distinct ways. Compared with the extracted herbs, the yield of ketones, acids and furans in bio-oils produced by herb pyrolysis at 300 °C was higher than 11, 14 and 41%, respectively, which belonged to the derivates from the cellulose component or hemicellulose component. However, when the herb was pyrolyzed at 500 °C, it was compared with when the extract herb was pyrolyzed at 500 °C that the yield of the phenolics with monocyclic ring or fused ring structures in the bio-oil was lower than 3%. According to the DRIFTS analysis, the evolution of the carbonyl-containing organics during the pyrolysis was also affected by the extraction of the herb. As for the char, more carbonyl group was retained in the char from the extracted herb. Nevertheless, the results from thermal analysis showed that thermal stability of the char from extracted herb was remarkably lower than that from herb feedstock.

Phytogenic Products and Phytochemicals as a Candidate Strategy to Improve Tolerance to Coronavirus.

Coronaviruses are the causative agents of many infectious diseases in human and animals. These included severe acute respiratory syndrome (SARS), avian infectious bronchitis (IBV) in poultry, Middle East respiratory syndrome (MERS), and coronavirus disease 2019 (COVID-19) in humans. These results had considerable death burdens and negative influences on social–economic life. Since the appearance of the outbreak of the COVID-19 pandemic, continuous investigations have been carried out by researchers to find active compounds, mainly from plants, as natural sources, that could inhibit or stop the proliferation of the causative agent of COVID-19 (SARS-CoV-2). The most common symptoms caused by infections with COVID-19 can include cough, fever, and sore throat. Nevertheless, there is a shortage of active antiviral compounds for treating different strains of coronavirus. Herbal medicine is a class of medication that originates from nature and is aimed at decreasing the use of preservatives, excipients, or other additives and, consequently, lesser side effects. The rapid spread of COVID-19 infection besides the lack of knowledge about any treatments and the growing concern of the public from the virus directed us toward writing this review article in an aim to provide alternatives to the allopathic medicine use. There is a wealth of chemical diversity in the naturally existing compounds, including their antiviral activities, which may encourage their utilization as therapeutics against viral infections, including coronaviruses. The majority of publications on the herbal remedies of coronavirus, MERS, or SARS focused primarily on the use of polar compounds. These substances displayed encouraging inhibitory influences on coronavirus in humans. These include psoralidin, scutellarein, silvestrol, tryptanthrin, caffeic acid, quercetin, myricetin, saikosaponin B2, griffithsin (lectins), and isobavachalcone. Some other agents like lycorine may be useful, if the antiviral activity is obtained by concentrations below the toxic plasma levels. According to the available literatures, the most promising inhibitors of coronaviruses are polyphenolic compounds, which are small molecules with conjugated fused ring structures.

Impacts of co-feeding alcohols on pyrolysis of cellulose

Reactive atmosphere significantly affects pyrolysis of biomass, as the gases such as NH3 involves in the reaction network in pyrolysis. In this study, instead of feeding reactive gas, the impacts of co-feeding ethanol or glycol on the pyrolysis of cellulose were investigated at varied pyrolysis temperatures (400 and 600 °C). The results showed that the co-feeding of the alcohols affected yields of bio-char and tar, evolution of light organics and heavy organics, elemental composition, formation of fused ring structures, crystallinity, thermal stability, distribution of functionalities in the bio-char. The co-feeding of both glycol and ethanol enhanced the formation of the heavy components with the π-conjugated ring structures and affected the production of the light organics such as furfural and glycolaldehyde. Glycol or its derivatives cross-polymerized with the organics in bio-char, increasing bio-char yield and made the bio-char more oxygen-rich. Ethanol, however, showed the converse effects. Co-feeding of the alcohols promoted crystallinity but showed distinct effects on thermal stability of the bio-char at the varied pyrolysis temperatures. Both pyrolysis temperature and structures of the alcohols determined their extents of involvement in the pyrolysis of cellulose.