Class Of Polycyclic Aromatic Hydrocarbons Research Articles

Recent Advances in the Cascade Cyclization of Alkyne Units for the Construction of Benzofluorenes

AbstractBenzofluorenes are an important class of polycyclic aromatic hydrocarbons (PAHs), which are widely used in materials science for light‐sensitive electronic components. In addition, the benzofluorene skeleton also serves as a key structural unit in various natural products. Therefore, the development of synthetic strategies for the construction of benzofluorenes has been a prominent research topic in synthetic chemistry. Over the past few decades, numerous efforts have been made for the construction of benzofluorenes via cascade cyclization of alkyne units. This review aims to summarize recent advances in the cascade cyclization of alkyne units for the construction of Based on the different reaction mechanisms underlying these transformations, this review can be divided into four categories: (1) thermal‐induced cascade cyclization of alkyne units for the construction of benzofluorenes, (2) metal‐catalyzed cascade cyclization of alkyne units for the construction of benzofluorenes, (3) acid‐promoted/catalyzed cyclization of alkyne units for the construction of benzofluorenes, and (4) base‐promoted cascade cyclization of alkyne units for the construction of benzofluorenes.

Unveiling Structural Variations in Armchair-Edge Coronoids by Spectroscopies.

This study explores the electronic and vibrational properties of armchair coronoids (ACs), a unique class of polycyclic aromatic hydrocarbons with varying molecular and cavity sizes. Through density functional theory simulations, we investigated the X-ray photoelectron spectroscopy (XPS) and Raman spectra of C222, C114, C42, and their derivatives with different cavity sizes. The results reveal that band gaps and electronic properties of ACs can be precisely tuned by adjusting the molecular and cavity dimensions. XPS spectra demonstrated shifts in binding energy correlating with bandgap variations, while Raman spectra exhibited distinct C-C stretching and breathing modes. Notably, the introduction of cavities led to shifts in the breathing mode band, providing insights into the structural identification of ACs through Raman spectroscopy. The findings suggest that combining XPS and Raman spectroscopy can effectively characterize ACs, offering a comprehensive understanding of their structure-property relationships. This research lays the groundwork for future experimental and theoretical studies on the potential applications of ACs in electronic materials.

The Magnetic Properties of Fluorenyl and tert-Butyl-nitroxyl Acene-Based Derivatives: A Quantum Chemical Insight

Acenes, as a class of polycyclic aromatic hydrocarbons, attract considerable attention due to their remarkable nonlinear optical and magnetic properties. The aim of this work was the elucidation of the capability of radical-substituted acene derivatives to undergo spin-state-switching rearrangements. For this purpose, a series of acene-based (anthracene, pentacene, heptacene) molecules bearing fluorenyl and tert-butyl-nitroxyl radicals were investigated through comprehensive quantum chemical modeling of their electronic structures, isomerization and magnetic properties. A possible mechanism of the transformation of the closed-shell folded isomer into the biradical twisted structure of the bis-fluorenyl anthracene has been ascertained by applying the procedure of searching for the Minimum Energy Crossing Point. The conditions favoring the occurrence of spin-state-switching in such classes of polycyclic aromatic hydrocarbon derivatives have been formulated. By varying the size of an acene core and the type of radical substituent, the compounds capable of changing their magnetic properties have been revealed. Considering the unique features of radical-bearing acene-based derivatives, the proposed molecules can be used as functional materials in photonics and electronics.

Pollution Characteristics and Ecological Impact of Screening Analysis of Fishing Port Sediments from Dalian, North China.

Environmental pollution from synthetic chemical mixtures has significant adverse impacts on marine ecosystems. However, identifying the main constituents of chemical mixtures that pose ecological threats is challenging due to the necessity of an integrated workflow for comprehensive identification and toxicological prioritization of pollutants. Here, an all-in-one mass spectrometric strategy integrating target, suspect, and nontarget analysis was used to investigate organic pollutants of concern in fishing port sediments, with 355 pollutants (32 from target analysis, 118 from suspect screening and 205 from nontarget analysis) identified in 11 categories. The chemical classes of polycyclic aromatic hydrocarbons (PAHs), pesticides, and intermediates were the extensively detected chemical classes. The ecological risks of absolutely quantified pollutants (i.e., 16 parent PAHs, 7 organophosphate esters (OPEs), 10 pesticides and 4 benzotriazole ultraviolet absorbers) were assessed using toxicity-weighted concentration ranking, with o,p'-DDT being the major contributor. Under the toxicological priority index (ToxPi) framework, an extended ranking of all identified pollutants was achieved by combining instrument response and detection frequency, with a priority control list of 15 pollutants obtained, of which benzo[ghi]perylene (BghiP) and p,p'-DDE had the highest risk priority. Due to frequent detection rates and significant environmental risks, routine monitoring of petroleum pollutants is considered essential. This study presents a general workflow that includes comprehensive identification and prioritization of pollutants, facilitating chemical management and ecological risk assessment.

Dissecting the long-term neurobehavioral impact of embryonic benz[a]anthracene exposure on zebrafish: Social dysfunction and molecular pathway activation

Benz[a]anthracene (BaA), a prevalent environmental contaminant within the polycyclic aromatic hydrocarbon class, poses risks to both human health and aquatic ecosystems. The impact of BaA on neural development and subsequent social behavior patterns remains inadequately explored. In this investigation, we employed the zebrafish as a model to examine the persisting effects of BaA exposure on social behaviors across various developmental stages, from larvae, juveniles to adults, following embryonic exposure. Our findings indicate that BaA exposure during embryogenesis yields lasting neurobehavioral deficits into adulthood. Proteomic analysis highlights that BaA may impair neuro-immune crosstalk in zebrafish larvae. Remarkably, our proteomic data also hint at the activation of the aryl hydrocarbon receptor (AHR) and cytochrome P450 1A (CYP1A) pathway by BaA, leading to the hypothesis that this pathway may be implicated in the disruption of neuro-immune interactions, contributing to observable behavioral disruptions. In summary, our findings suggest that early exposure to BaA disrupts social behaviors, such as social ability and shoaling behaviors, from the larval stage through to maturity in zebrafish, potentially through the detrimental effects on neuro-immune processes mediated by the AHR-CYP1A pathway.

Synthesis of Tridecacene by Multistep Single-Molecule Manipulation.

Acenes represent a unique class of polycyclic aromatic hydrocarbons that have fascinated chemists and physicists due to their exceptional potential for use in organic electronics. While recent advances in on-surface synthesis have resulted in higher acenes up to dodecacene, a comprehensive understanding of their fundamental properties necessitates their expansion toward even longer homologues. Here, we demonstrate the on-surface synthesis of tridecacene via atom-manipulation-induced conformational preparation and dissociation of a trietheno-bridged precursor on a Au(111) surface. The generated tridecacene has been investigated by scanning tunneling microscopy and spectroscopy (STM/STS), combined with first-principles calculations. We observe that the STS transport gap (1.09 eV) shrinks again following the gap reopening of dodecacene (1.4 eV). Spin-polarized density functional theory calculations confirm an antiferromagnetic open-shell ground-state electronic configuration for tridecacene in the gas phase. Interestingly, tridecacene's open-shell character is significantly reduced upon interaction with the Au(111) surface despite being only physisorbed. The interaction with the surface leads to a lowering of the magnetization of tridecacene, a reduced gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), compared to the gas phase, and a reduced relative energy to the nonmagnetic state, making it nearly isoenergetic. These observations show qualitatively that the influence of the Au(111) substrate on the properties of long acenes is significant, which is important for interpreting the measured STS transport gaps. Our work contributes to a fundamental understanding of the electronic properties of long acenes, confirming a nonmonotonous length-dependent HOMO-LUMO gap, and to the development of multistep tip-assisted synthesis of elusive compounds.

Generalized kekulenes and clarenes as novel families of cycloarenes: structures, stability, and spectroscopic properties.

Cycloarenes constitute a captivating class of polycyclic aromatic hydrocarbons with unique structures and properties, but their synthesis represents a challenging task in organic chemistry. Kekulenes and edge-extended kekulenes as classic types of cycloarenes play an important role in the comprehension of π electron distribution, but their sparse molecular diversity considerably limits their further development and application. In this work, we propose two novel classes of cycloarenes, the generalized kekulenes and the clarenes. Using density functional theory, we carry out a comprehensive study of all possible isomers of the generalized kekulenes and clarenes with different sizes. By applying a simple Hückel model, we show that π delocalization plays a crucial role in determining the relative stability of isomers. We also discover that π-π stacking is commonly present in certain larger clarenes and provides a considerable additional stabilization effect, making the corresponding isomers the lowest-energy ones. Among all considered typical looped polyarenes, generalized kekulenes and/or clarenes are revealed to be the energetically most stable forms, suggesting that these novel cycloarenes proposed here would be viable targets for future synthetic work. The simulated 1H NMR spectra and UV-vis absorption spectra provide valuable information about the electronic and optoelectronic properties for the most stable generalized kekulene and clarene species and may support their identification in future synthesis and experimental characterization.

Polycyclic aromatic hydrocarbons and petroleum products in soil samples of urban areas in Eastern Siberia

Introduction. In industrial cities, the problem of environmental pollution by supertoxicants, which include the class of polycyclic aromatic hydrocarbons (PAHs), is especially acute. Since among PAHs there are substances that have a carcinogenic effect, their quantitative identification in environmental objects is an urgent task.
 Materials and methods. The content of PAHs and petroleum products (PP) in the soil of an industrial city, taken in various functional zones, was studied. Determination of sixteen PAHs was carried out by gas chromatography-mass spectrometry (GC-MS) with optimized sample preparation. It is proposed to determine PAHs by GC-MS using dispersive liquid-liquid microextraction (DLLME). Petroleum products (PP) were determined by the fluorimetric method.
 Results. Total PAHs content (ΣPAH) varied from 7.50 to 319.11 µg/kg. ΣPAH-carcinogens in the residential and sanitary protection zones was on average 25.1–31.2 times higher than in the background site. PP content levels in urban soils ranged from 3.0 to 62.4 mg/kg.
 Limitations. The study is limited to the study of the upper layers of soil up to 5 cm. The possibility of PAH migration into groundwater has not been studied.
 Conclusion. The structure of PAHs was dominated by 4-6-nuclear structures: dibenz(a,h)anthracene, benzo(g,h,i)perylene, fluoranthene, benzo(b)fluoranthene, etc., making up > 87% of the total amount of PAHs. The proportion of these polyarenes in the total ΣPAH in the residential area increases by 1.3 times compared to the background, which indicates the possibility of their technogenic origin. The PAH and PP indicators are characterized by a scatter of data and, as a result, 
 a large influence of the local factor on the formation of soil cover pollution.

Insight into personal exposure characteristics and health effects of PM2.5 and PM0.25-bound PAHs and their derivatives with different heating ways in the Fenwei Plain, China

Personal exposure (PE) to polycyclic aromatic hydrocarbons (PAHs) and their derivatives in particulate matter with two aerodynamic sizes of 2.5 and 0.25 μm (PM2.5 and PM0.25) from rural housewives was studied in the Fenwei Plain, China. A total of 15 households were divided into five different groups based on the type of solid fuel and heating device used, including biomass briquette-furnace (BBF), biomass-elevated Kang (BEK), outdoor lump coal-boiler (OLC), indoor briquette coal-stove (IBC), and electricity (ELE). The PE concentrations of the PAHs and biomarkers in urine collected from the participants were determined. The results showed that the PE concentrations of total quantified PAHs in the biomass group (i.e., BBF and BEK) were 2.2 and 2.0 times higher than those in the coal groups (i.e., OLC and IBC) in PM2.5 and PM0.25, respectively. The housewives who used biomass as fuel suffered from higher potential health impacts than the coal fuel users. The incremental lifetime cancer risk for the PAHs in PM2.5 in the BBF and BEK groups exceeded the international safety threshold. Furthermore, the PE concentrations of oxygenated PAH (o-PAHs) in PM2.5 and PM0.25 in the biomass groups and the nitrated PAHs (n-PAHs) in PM0.25 in the coal groups showed strong correlations with the biomarkers. The results of this study proved the associations between exposure to the different classes of PAHs and health hazards. The findings could also serve as a guideline in establishing efficient measures for using solid fuels for cooking and household warming in northern China.

Environmental and health impacts of household energy conversion on PAHs and their derivatives in PM2.5 in typical areas of northern China

Heavy use of solid fuels in rural households of northern China emits huge amounts of fine particulate matter (i.e., PM2.5) that pose notable indoor air pollution and severe inhalation health risks. In this study, the environmental and health benefits of clean energy substitution were accessed by monitoring indoor and personal exposure to polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and pulmonary function and biological parameters. After substitutions of traditional lump coal and biomass fuels by clean coal, indoor concentrations of parent PAHs (p-PAHs), alkylated PAHs (a-PAHs), oxygenated PAHs (o-PAHs), and nitro PAHs (n-PAHs) reduced by 71 %, 32 %, 70 %, and 76 %, while personal exposure concentrations decreased by 82 %, 87 %, 93 %, and 86 %, respectively. However, the proportion of low molecular weight PAHs increases, especially for 2-ring a-PAHs and 3-ring n-PAHs. Domestic solid fuel burning induces greater damage to the small airway than the large airway. Pulmonary function parameter reductions in the clean coal group are much less than those in the other two fuel groups. Salivary interleukin-6 (IL-6) and 8-hydroxy-2′-deoxyguanosine (8-OHdG) significantly correlated with PAH species, among which p-PAHs and PAHs derivatives strongly with IL-6 and 8-OHdG, respectively. The correlation between PAHs and biomarkers in urine is insignificant. In addition, the use of clean coal can reduce the cancer risk for the four classes of PAHs by 60 %–97 %, mainly owing to the lower contributions from p-PAHs and o-PAHs. The result of the study provides scientific support for clean energy retrofit and an understanding of health benefits from solid fuel substitutions.

Palladium‐Catalyzed Cyclization of a Pyryne Precursor to Higher Pyrenylenes

AbstractThe palladium catalyzed cyclotrimerization of ortho‐silylaryl triflates as aryne precursors is meanwhile an established method to synthesize polycyclic aromatic hydrocarbons (PAHs) with triphenylene cores. During the palladium‐catalyzed reaction of a pyrene with an o‐silylaryl triflate moiety in the K‐region higher homologues with central eight‐ and ten‐membered rings (the pyrenylenes) were found, besides the expected trimer and a protocol was developed to isolate all members of this series. This unprecedented new class of PAHs was fully investigated by all means, including X‐ray diffraction of single‐crystals, UV/Vis and fluorescence spectroscopy and theoretical calculations. Supported by density‐functional theory (DFT) calculations, a mechanism of all higher cyclooligomers is proposed.

Palladium-Catalyzed Cyclization of a Pyryne Precursor to Higher Pyrenylenes.

The palladium catalyzed cyclotrimerization of ortho-silylaryl triflates as aryne precursors is meanwhile an established method to synthesize polycyclic aromatic hydrocarbons (PAHs) with triphenylene cores. During the palladium-catalyzed reaction of a pyrene with an o-silylaryl triflate moiety in the K-region, besides the expected trimer higher homologues with central eight- and ten-membered rings (the pyrenylenes) were found and a protocol developed to isolate all members of this series. This unprecedented new class of PAHs was fully investigated by all means, including X-ray diffraction of single-crystals, UV/vis and fluorescence spectroscopy and theoretical calculations. Furthermore, supported by density-functional theory (DFT) calculations, a mechanism of all higher cyclooligomers is proposed.

Aryne Atropisomers: Chiral Arynes for the Enantiospecific Synthesis of Atropisomers and Nanographene Atropisomers

The basics about arynes and their applications in synthetic organic chemistry are briefly presented, and the concept of atropisomerism is defined, highlighting that it is a time-dependent form of isomerism and chirality. It is remembered that racemization is a macroscopic and statistical irreversible process, while enantiomerization is a nanoscopic reversible process that occurs at the molecular scale, with racemization being twice as fast as enantiomerization. The concept of aryne atropisomers is introduced with a naive question: Can synthetically useful nonracemic aryne atropisomers having a triple bond ortho to the stereogenic single bond exist in solution? It was found that such aryne atropisomers can be generated in solution from easily available ortho-iodoaryl triflate precursors and excess trimethylsilylmethylmagnesium chloride. Analysis of the barriers to enantiomerization of some aryne atropisomers by computational modeling revealed the key contribution to the configurational stability of the H atom in tris-ortho-substituted biphenyl-based atropisomers. Using a specially designed prototype of aryne atropisomer, for which the barrier to enantiomerization was accurately evaluated by advanced computational modeling, the kinetic parameters of its reaction with furan were experimentally determined. From these measurements, it was concluded that any aryne atropisomer with a barrier to enantiomerization ΔGenant⧧ equal to or higher than 50 kJ mol-1 would lead to fully enantiospecific reactions. The synthetic applications of two structurally distinct aryne atropisomers built on a 1-phenylnaphthalene platform are described: one has the aryne triple bond embedded in the naphthyl moiety, and the other has the aryne triple bond embedded in the phenyl moiety. Both aryne atropisomers allowed for the fully enantiospecific, and possibly overall enantioselective, syntheses of original atropisomers based on standard aryne chemistry. For instance, reactions with anthracene and perylene afforded triptycene and nanographene atropisomers, respectively, in high enantiomeric excesses. A bis(aryne) atropisomer synthetic equivalent prepared from either enantiomer of BINOL is described for 3D bidirectional reactions with a single handedness. Its 2-fold reactions with anthracene and perylene afforded the corresponding severely congested bis(benzotriptycene) (99% ee) nanocarbon atropisomer and bis(anthra[1,2,3,4-ghi]perylene) (98% ee) nanographene atropisomer, respectively. This allowed the discovery of bis(twistacene) atropisomers as a new class of polycyclic aromatic hydrocarbons (PAH) with multiple stereogenicities. Cross reactions with the bis(aryne) atropisomer synthetic equivalent and two different arynophiles proved feasible, providing a nanographene atropisomer with a benzotriptycene unit and an anthra[1,2,3,4-ghi]perylene unit assembled around a stereogenic axis as a unique chiral PAH (99% ee). Overall, because the concept is simple and its implementation is easy, aryne atropisomers is an attractive approach to the synthesis of atropisomers in a broad meaning. Applications to the synthesis of large PAH atropisomers with single handedness are particularly promising.

Polyradical character assessment using multireference calculations and comparison with density-functional derived fractional occupation number weighted density analysis.

The biradicaloid character of different types of polycyclic aromatic hydrocarbons (PAHs) based on small band gaps is an important descriptor to assess their opto-electronic properties. In this work, the unpaired electron densities and numbers of unpaired electrons (NU values) calculated at the high-level multireference averaged quadratic coupled-cluster (MR-AQCC) method are used to develop a test set to assess the capabilities of different biradical descriptors based on density functional theory. A benchmark collection of 29 different compounds has been selected. The DFT descriptors contain primarily the fractional occupation number weighted electron density (FOD) based on simplified thermally-assisted-occupation density functional theory (TAO-DFT) calculations, but the singlet-triplet energy difference and other descriptors denoted as y0 and nLUNO have been considered as well. After adjustment of the literature-recommended finite temperatures, a very good, detailed agreement between unpaired density and FOD analysis is observed which is also manifested in excellent statistical correlations. The other two descriptors also show good correlations even though the absolute scaling is not satisfactory. A new linear fit of FOD data to the MR-AQCC reference values leads to an improved regression relation for determining the recommended finite temperature value in dependence of the Hartree-Fock exchange. This provides the basis for fast and reliable assessment of the biradical character of many classes of PAHs without the need for performing computationally extended MR calculations.

Identification and classification of PAH in asphalt binders with FTIR spectroscopy and multivariate analysis methods

Reclaimed asphalt pavements (RAP) with increased contents of polycyclic aromatic hydrocarbons (PAH) are restricted for reuse due to their harmful effects on humans and the environment. This work investigated whether Fourier transform infrared (FTIR) spectroscopy is suitable for a fast and simple identification and quantification of PAH in binders recovered from reclaimed asphalts. For this, the binders from 34 RAP samples were recovered using a rapid procedure developed at the Universität Kassel and were examined with infrared spectroscopy. The obtained spectra were pre-processed (Standard Normal Variate transformation, 1st derivative) and evaluated using a combination of factor analysis and linear discriminant analysis. The results showed that various PAH groups with differently pronounced aromatic structures are present in the binders. However, with FTIR spectroscopy combined with the multivariate methods, a statistical model was developed allowing for the differentiation between the PAH groups and also for the distinction between PAH contents below or above the threshold of 25mg/kg valid in Germany.

Computation of Neighborhood M-Polynomial of Three Classes of Polycyclic Aromatic Hydrocarbons

Chemical graph theory is a branch of mathematical chemistry that significantly affects the development of the chemical sciences. The neighborhood M-polynomial approach is an extraordinary process for determining neighborhood degree sum-based topological indices to estimate materials’ various physical, chemical, and biological characteristics. The present work deals with obtaining the NM-polynomial of three types of polycyclic aromatic hydrocarbons (PAHs). Using NM-polynomials as tools, specific degree-based topological indices are retrieved. The applications of these PAHs are pharmaceuticals, lubricating materials, photographic products, agricultural products and other chemical industries. The graphical representations of the outcomes are displayed. These results are compared to several well-known degree-based indices.

(Invited, Digital Presentation) Synthesis, Aromaticity and Application to OFET and OLED of Peri-Pentacenopentacene

Recently, there has been increasing interest in a class of polycyclic aromatic hydrocarbons (PAHs) with peri-extension of acenes. These peri-fused systems, referred to as peri-acenes and acenoacenes, are considered to be nanographenes.[1–3] Thus, the compounds based on tetracene and larger acenes show singlet biradical nature at the zigzag edge, offering unique and interesting properties.However, the synthesis schemes for these compounds are generally complicated, which hinder the extensive development of these derivatives and application to organic optoelectronics such as organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). A pentacene derivative with two triisopropylsilylethynyl groups at the central ring (TIPS-PEN) was developed in 2001. It shows good solubility, stability, and semiconducting property, resulting in being one of the most studied organic semiconductors. In contrast, the peri-extended compound of TIPS-PEN has not been developed because of the difficulty in synthesis using the same method as TIPS-PEN.[4] Here, we found the synthetic conditions to avoid the competition between 1,2- and 1,4-addition of lithium acetylide on large aromatic dione and succeeded in synthesizing TIPS-ethynyl-substituted peri-pentacenopentacene (TIPS-PPP).[5]The stability of TIPS-PPP was 16 times superior to that of TIPS-PEN, which is attributed to higher aromaticity as shown in an electronic structure of two-fused anthracene. TIPS-PPP shows the crystal packing of the 2D-brickwall motif like TIPS-PEN. The high mobility of up to 1 cm2 V−1 s−1 was obtained in OFET fabricated by wet process owing to large transfer integrals and low reorganization energies. In addition, TIPS-PPP showed high quantum yield in near-infrared (NIR) region. Thus, it was used as an emitter for NIR-OLED devices, resulting in high external quantum efficiency at 800 nm. These results suggest that acene-like materials are very promising for developing NIR emitters.

On counting polynomials of certain classes of polycyclic aromatic hydrocarbons

Polya was the first to establish the concept of a counting polynomial in chemistry. Despite the fact that the spectra of the characteristic polynomial of graphs were exhaustively researched by quantitative means in order to ascertain the molecular orbitals of unsaturated hydrocarbons, the field garnered little attention from chemists for several decades. Polynomials can be used to produce a variety of significant topological indices, either explicitly or after calculating derivatives or numerical methods. Certain firmly related polynomials, namely Theta, Omega, PI, and Sadhana polynomials, subordinate the equidistant edges and non-equidistant edges of structural graphs, which have a rich application in computing the corresponding topological indices. A topological index is a numerical value associated with a network that predicts chemical, physical, and biological activities. This article investigates these polynomials for three classes of polycyclic aromatic hydrocarbons as hexa-peri-hexabenzocoronene, hexa-cata-hexabenzocoronene, and dodeca-benzo-circumcoronene. In addition, closed formulas for these polynomials’ corresponding indices are proposed.

Assessment of the treatment efficiency of some polycyclic aromatic hydrocarbon (PAHs) in the water by doped TiO2

Treatment of persistent organic pollutants by advanced oxidation processes is a trend nowadays because of its efficiency. Through studies, it has been found that enhanced oxidation processes can treat organic pollutants that are difficult to decompose due to OH radicals and can convert those substances into nontoxic substances which areH2O và CO2. TiO2is a strong oxidizing agent; especially with the addition of catalysts, it is highly likely to be able to to treat persistent pollutants. PAHs are a class of polycyclic aromatic hydrocarbons that are highly toxic and persistent in the environment. The treatment of PAHs with 1% Fe-doped TiO2 coated on silica gel combined with using a 365nm UV lamp model initially produced certain results. Treatment efficiency is up to over 90% after 48 hours. On that basis, the article proposes a feasible solution for the treatment of PAHs in particular and toxic organic substances in general.

Laser-induced fluorescence for studying the influence of potassium and sodium salts on PAH formation in sooting premixed flames

Previous studies have shown that alkali salts influence combustion processes and soot formation, although the effects seem to vary across systems. Moreover, fundamental studies on the effect of potassium and sodium salts on formation of polycyclic aromatic hydrocarbons (PAH), which are precursors in soot formation, are scarce. Here, we report a study in which the effects on PAH formation due to the addition of alkali metal salts (KCl, KOH, K2CO3, NaCl and NaOH) to premixed ethylene–air flames were investigated. Different size classes of PAHs were probed using both spectral and 2D measurements of laser-induced fluorescence (PAH-LIF) using the excitation wavelengths 266 nm and 532 nm, while detecting the fluorescence emission at selected wavelength ranges. Elastic light scattering (ELS) measurements were also used to complement the fluorescence data. It was found that potassium and sodium salts do not significantly influence the formation of small PAHs (2–3 rings), while decreasing the concentration of larger PAHs at higher heights above burner (HAB). Another important result was that the anion in the salt (Cl−, OH−, CO32−) negligibly influences the PAH and soot formation processes after dissociation of the salts.