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25th Anniversary of Molecules—Recent Advances in Green Chemistry

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 45345

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Special Issue Editors

Prof. Dr. Gonzalo de Gonzalo

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Guest Editor

Departamento de Química Orgánica, Universidad de Sevilla, 41014 Sevilla, Spain
Interests: biocatalysis; catalytic reactions; sustainable chemistry; pharmaceutical synthesis
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Mara G. Freire

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Guest Editor

CICECO - Aveiro Institute of Materials, Chemistry Department, University of Aveiro, Aveiro, Portugal
Interests: separation processes; ionic liquids; deep eutectic solvents; (bio)pharmaceuticals; biomarkers; purification; stability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In 2020 we are celebrating the 25th anniversary of our journal Molecules. Over the years, Molecules has been increasing its visibility and scientific standards, with more than 20,000 papers published to date. The journal’s website currently attracts 115,000 monthly visits and more than 395,000 monthly page views. We acknowledge all readers, authors, reviewers, editors, and all people working in the journal who have contributed to these achievements.

To mark the anniversary of Molecules, an important milestone in a current era of sustainability and circular economy, a Special Issue entitled “25th Anniversary of Molecules—Recent Advances in Green Chemistry” will be launched. In 2015, seventeen Sustainable Development Goals (SDGs) were defined by the UN (“Transforming Our World: The 2030 Agenda for Sustainable Development”), expressing a plan of action for people, the planet, and prosperity. Some of these goals reinforce the demand for green/sustainable chemistry and engineering, in which green solvents and processes play a key role. Neoteric solvents and sustainable processes have been a hot research topic in the past years, resulting in the implementation of some innovative and sustainable processes at the industrial level. However, there are still some gaps to fill in this research arena involving green solvents and processes, namely, the analysis of cost, availability, purity, safety regulations, disposal procedures, and recycling procedures, among others. Furthermore, the entire life cycle of the solvents and processes used is a critical issue to consider. Given the critical need of improving the green metrics of both solvents and processes, this Special Issue will publish original research and review manuscripts. We encourage and acknowledge all research groups working in the fields of Green Chemistry, Sustainability, and Circular Economy to contribute to this Special Issue of Molecules.

Prof. Gonzalo de Gonzalo
Dr. Mara G. Freire
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Green Chemistry
Neoteric solvents
Sustainable processes
(Bio)catalysis
Biorefinery
Circular economy
Sustainable goals

Published Papers (13 papers)

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Editorial

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2 pages, 172 KiB

Open AccessEditorial

25th Anniversary of Molecules—Recent Advances in Green Chemistry

by Gonzalo de Gonzalo and Mara G. Freire

Molecules 2021, 26(12), 3768; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26123768 - 21 Jun 2021

Viewed by 1485

Abstract

Green Chemistry has been defined by the EPA as the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances [...] Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

Research

Jump to: Editorial, Review

20 pages, 9749 KiB

Open AccessArticle

Functional Modification of Cellulose Acetate Microfiltration Membranes by Supercritical Solvent Impregnation

by Irena Zizovic, Marcin Tyrka, Konrad Matyja, Ivana Moric, Lidija Senerovic and Anna Trusek

Molecules 2021, 26(2), 411; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020411 - 14 Jan 2021

Cited by 7 | Viewed by 2295

Abstract

This study investigates the modification of commercial cellulose acetate microfiltration membranes by supercritical solvent impregnation with thymol to provide them with antibacterial properties. The impregnation process was conducted in a batch mode, and the effect of pressure and processing time on thymol loading was followed. The impact of the modification on the membrane’s microstructure was analyzed using scanning electron and ion-beam microscopy, and membranes’ functionality was tested in a cross-flow filtration system. The antibiofilm properties of the obtained materials were studied against Staphyloccocus aureus and Pseudomonas aeruginosa, while membranes’ blocking in contact with bacteria was examined for S. aureus and Escherichia coli. The results revealed a fast impregnation process with high thymol loadings achievable after just 0.5 h at 15 MPa and 20 MPa. The presence of 20% of thymol provided strong antibiofilm properties against the tested strains without affecting the membrane’s functionality. The study showed that these strong antibacterial properties could be implemented to the commercial membranes’ defined polymeric structure in a short and environmentally friendly process. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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18 pages, 1830 KiB

Open AccessArticle

Amorphous Polymers’ Foaming and Blends with Organic Foaming-Aid Structured Additives in Supercritical CO₂, a Way to Fabricate Porous Polymers from Macro to Nano Porosities in Batch or Continuous Processes

by Margaux Haurat and Michel Dumon

Molecules 2020, 25(22), 5320; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25225320 - 14 Nov 2020

Cited by 15 | Viewed by 2685

Abstract

Organic polymers can be made porous via continuous or discontinuous expansion processes in scCO₂. The resulting foams properties are controlled by the interplay of three groups of parameters: (i) Chemical, (ii) physico-chemical, and (iii) technological/process that are explained in this paper. The advantages and drawbacks of continuous (extrusion, injection foaming) or discontinuous (batch foaming) foaming processes in scCO₂, will be discussed in this article; especially for micro or nano cellular polymers. Indeed, a challenge is to reduce both specific mass (e.g., ρ < 100 kg·m⁻³) and cell size (e.g., average pore diameter ϕ_average^pores < 100 nm). Then a particular system where small “objects” (coreshells CS, block copolymer MAM) are perfectly dispersed at a micrometric to nanometric scale in poly(methyl methacrylate) (PMMA) will be presented. Such “additives”, considered as foaming aids, are aimed at “regulating” the foaming and lowering the pore size and/or density of PMMA based foams. Differences between these additives will be shown. Finally, in a PMMA/20 wt% MAM blend, via a quasi one-step batch foaming, a “porous to nonporous” transition is observed in thick samples. A lower limit of pore size (around 50 nm) seems to arise. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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24 pages, 2208 KiB

Open AccessArticle

Recovery and Stabilization of Anthocyanins and Phenolic Antioxidants of Roselle (Hibiscus sabdariffa L.) with Hydrophilic Deep Eutectic Solvents

by Oscar Zannou, Ilkay Koca, Turki M. S. Aldawoud and Charis M. Galanakis

Molecules 2020, 25(16), 3715; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25163715 - 14 Aug 2020

Cited by 51 | Viewed by 4252

Abstract

Deep eutectic solvents (DESs) have got huge interest as new green and sustainable solvents for the extraction of bioactive compounds from plants in recent decades. In the present study, we aimed to investigate the effectiveness of hydrophilic DES for the extraction of anthocyanin and polyphenol antioxidants from Roselle. A natural hydrophilic DES constituted of sodium acetate (hydrogen bond acceptor) and formic acid (hydrogen bond donor) designed to evaluate the total phenolic compound (TPC), total flavonoid (TFC), total anthocyanin (TACN), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) values of Roselle. Distilled water, 70% ethanol, and 80% methanol used as conventional solvents for comparison. The results indicated that the DES prepared in molarity ratio (SAFA_m) was the most efficient. Subsequently, this prominent DES selected for the optimization and the optimum extraction conditions were 1:3.6 molarity ratio, 0% additional water, and 10 mL solvent. TPC, TFC, TACN, FRAP, and DPPH radical scavenging at the optimum point were 233.26 mg GAE/g, 10.14 mg ECE/g, 10.62 mg D3S/g, 493.45 mmol ISE/g, and 343.41 mmol TE/g, respectively. The stability tests showed that anthocyanins were more stable in SAFA_m. These findings revealed that SAFA_m is an effective green solvent for the extraction of polyphenols from various plants. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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17 pages, 1643 KiB

Open AccessArticle

An Eco-Friendly Hydrophobic Deep Eutectic Solvent-Based Dispersive Liquid–Liquid Microextraction for the Determination of Neonicotinoid Insecticide Residues in Water, Soil and Egg Yolk Samples

by Rawikan Kachangoon, Jitlada Vichapong, Yanawath Santaladchaiyakit, Rodjana Burakham and Supalax Srijaranai

Molecules 2020, 25(12), 2785; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25122785 - 16 Jun 2020

Cited by 32 | Viewed by 3537

Abstract

A green, simple and sensitive hydrophobic DES-based dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of neonicotinoid insecticide residues in various samples. A hydrophobic deep eutectic solvent (DES) was synthesized using decanoic acid as a hydrogen bond donor and tetrabutylammonium bromide (TBABr) as a hydrogen bond-acceptor. DESs were synthesized and characterized by Fourier transform-infrared (FTIR) spectroscopy. Two disperser solvents were substituted with surfactants and acetonitrile, which could afford more effective emulsification and make the extraction relatively greener. The hydrophobic DES extraction phase occurred 10 min after centrifugation, being easy to be collected for analysis. Several parameters were investigated and optimized. Under the optimum condition, the calibration curve of this method was linear in the range of 0.003–1.0-µg·mL⁻¹, with a correlation coefficient (R²) higher than 0.99 and a good repeatability, with the relative standard deviations (RSDs) were less than 5.00%. The limits of detection were in the range of 0.001–0.003 µg·mL⁻¹; the limits of quantitation were in the range of 0.003–0.009 µg·mL·mL⁻¹. Finally, the presented method was implemented to determine the neonicotinoid insecticide residues in water, soil, egg yolk samples and acceptable recoveries were obtained. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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9 pages, 792 KiB

Open AccessArticle

Chemical and Electrochemical Recycling of End-Use Poly(ethylene terephthalate) (PET) Plastics in Batch, Microwave and Electrochemical Reactors

by Tessa H. T. Myren, Taylor A. Stinson, Zachary J. Mast, Chloe G. Huntzinger and Oana R. Luca

Molecules 2020, 25(12), 2742; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25122742 - 13 Jun 2020

Cited by 34 | Viewed by 5291

Abstract

This work describes new methods for the chemical recycling of end-use poly(ethylene terephthalate) (PET) in batch, microwave and electrochemical reactors. The reactions are based on basic hydrolysis of the ester moieties in the polymer framework and occur under mild reaction conditions with low-cost reagents. We report end-use PET depolymerization in refluxing methanol with added NaOH with 75% yield of terephthalic acid in batch after 12 h, while yields up to 65% can be observed after only 40 min under microwave irradiation at 85 °C. Using basic conditions produced in the electrochemical reduction of protic solvents, electrolytic experiments have been shown to produce 17% terephthalic acid after 1 h of electrolysis at −2.2 V vs. Ag/AgCl in 50% water/methanol mixtures with NaCl as a supporting electrolyte. The latter method avoids the use of caustic solutions containing high-concentration NaOH at the outset, thus proving the concept for a novel, environmentally benign method for the electrochemical recycling of end-use PET based on low-cost solvents (water and methanol) and reagents (NaCl and electricity). Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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15 pages, 1188 KiB

Open AccessArticle

The Impact of Organic Matter on Polycyclic Aromatic Hydrocarbon (PAH) Availability and Persistence in Soils

by Aleksandra Ukalska-Jaruga and Bożena Smreczak

Molecules 2020, 25(11), 2470; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25112470 - 26 May 2020

Cited by 42 | Viewed by 3605

Abstract

Polycyclic aromatic hydrocarbons (PAHs) exhibit persistence in soils, and most of them are potentially mutagenic/carcinogenic and teratogenic for human beings but also influence the growth and development of soil organisms. The PAHs emitted into the atmosphere are ultimately deposited (by dry or wet deposition processes) onto the soil surface where they tend to accumulate. Soil organic matter (SOM) plays an important role in the fate and transformation processes of PAHs, affecting their mobility, availability, and persistence. Therefore, the aim of this research was to investigate the influence of SOM fractional diversification (fulvic acids—FA, humic acids—HA, and humins—HN) on PAH availability and persistence in soils. Twenty soil samples (n = 20) were collected from upper horizons (0–30 cm) of agricultural soils exposed to anthropogenic emissions from industrial and domestic sources. The assessment of PAH concentrations included the determination of medium-molecular-weight compounds from the US EPA list: fluoranthene—FLA, pyrene—PYR, benz(a)anthracene—BaA, and chrysene—CHR. The assessment was conducted using the GC-MS/MS technique. Three operationally defined fractions were investigated: total extractable PAHs (TE-PAHs) fraction, available/bioavailable PAHs (PB-PAHs) fraction, and nonavailable/residual PAHs (RE-PAHs) fraction, which was calculated as the difference between total and available PAHs. TE-PAHs were analyzed by dichloromethane extraction, while PB-PAHs were analyzed with a hydrophobic β-cyclodextrin solution. SOM was characterized by total organic carbon content (Turin method) and organic carbon of humic substances including FA, HA, HN (IHSS method). Concentrations of PAHs differed between soils from 193.5 to 3169.5 µg kg⁻¹, 4.3 to 226.4 µg kg⁻¹, and 148.6 to 3164.7 µg kg⁻¹ for ∑4 TE-PAHs, ∑4 PB-PAHs, and ∑4 RE-PAHs, respectively. The ∑4 PB-PAHs fraction did not exceed 30% of ∑4 TE-PAHs. FLA was the most strongly bound in soil (highest content of RE-FLA), whereas PYR was the most available (highest content of PB-PYR). The soils were characterized by diversified total organic carbon (TOC) concentration (8.0–130.0 g kg⁻¹) and individual SOM fractions (FA = 0.4–7.5 g kg⁻¹, HA = 0.6–13.0 g kg⁻¹, HN = 0.9–122.9 g kg⁻¹). FA and HA as the labile fraction of SOM with short turnover time strongly positively influenced the potential ∑4 PAH availability (r = 0.56 and r = 0.52 for FA and HA, respectively). HN, which constitutes a stable fraction of organic matter with high hydrophobicity and poor degradability, was strongly correlated with ∑4 RE-PAHs (r = 0.75), affecting their persistence in soil. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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17 pages, 3486 KiB

Open AccessArticle

Chemical Kinetic Model of Multicomponent Gasoline Surrogate Fuel with Nitric Oxide in HCCI Combustion

by Chao Yang and Zhaolei Zheng

Molecules 2020, 25(10), 2273; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25102273 - 12 May 2020

Cited by 4 | Viewed by 2468

Abstract

This study presents a simplified mechanism of a five-component gasoline surrogate fuel (TDRF–NO) that includes n-heptane, isooctane, toluene, diisobutylene (DIB) and nitric oxide (NO). The mechanism consists of 119 species and 266 reactions and involves TDRF and NO submechanisms. Satisfactory results were obtained in simulating HCCI combustion in engines. The TDRF submechanism is based on the simplified mechanism of toluene reference fuel (TRF) and adds DIB to form quaternary surrogate fuel for gasoline. A simplified NO submechanism containing 33 reactions was added to the simplified mechanism of TDRF, considering the effect of active molecular NO on the combustion of gasoline fuel. The ignition delay data of the shock tube under different pressure and temperature conditions verified the validity of the model. Model verification results showed that the ignition delay time predicted by the simplified mechanism and its submechanics were consistent with the experimental data. The addition of NO caused the ignition delay time of the mechanism simulation to advance with increasing concentration of NO added. The established simplified mechanism effectively predicted the actual combustion and ignition of gasoline. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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17 pages, 2388 KiB

Open AccessArticle

Tricyclic Derivative of Acyclovir and Its Esters in Relation to the Esters of Acyclovir Enzymatic Stability: Enzymatic Stability Study

by Izabela Muszalska-Kolos, Monika A. Lesniewska-Kowiel, Szymon Plewa and Agnieszka Klupczyńska

Molecules 2020, 25(9), 2156; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25092156 - 05 May 2020

Cited by 4 | Viewed by 2588

Abstract

The 3,9-dihydro-3-[(2-hydroxyethoxy)methyl]-6-(4-methoxyphenyl)-9-oxo-5H-imidazo[1,2-a]–purine (6-(4-MeOPh)-TACV) was selected to assess the enzymatic stability of the tricyclic acyclovir derivatives from the imidazo[1,2-a]-purine group. The parent compound and its esters (acetyl, isobutyryl, pivaloyl, nicotinic, ethoxycarbonyl) were subjected to kinetic studies and compared with the stability of analogous acyclovir (ACV) esters. The enzymatic hydrolysis was observed in vitro in a medium of 80% human plasma in the absence and presence of porcine liver esterase (PLE). The tests were carried out at 37 °C. To determine the kinetic parameters (k_obs., t_0.5) of the observed reaction, the validated HPLC-UV method in the reversed phase was used. The HPLC-MS/MS method was used to identify the degradation products under the tested conditions. In summary, it was found that 6-(4-MeOPh)-TACV esters are more susceptible to esterase metabolism than ACV esters. It was confirmed by HPLC-MS/MS that in the plasma, the main product of their hydrolysis is 6-(4-MeOPh)-TACV and not ACV, which confirms that their antiviral activity observed in vitro does not result from ring degradation. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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15 pages, 872 KiB

Open AccessArticle

Residues of Persistent Organic Pollutants (POPs) in Agricultural Soils Adjacent to Historical Sources of Their Storage and Distribution—The Case Study of Azerbaijan

by Aleksandra Ukalska-Jaruga, Karolina Lewińska, Elton Mammadov, Anna Karczewska, Bożena Smreczak and Agnieszka Medyńska-Juraszek

Molecules 2020, 25(8), 1815; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25081815 - 15 Apr 2020

Cited by 17 | Viewed by 3775

Abstract

The aim of this study was to identify and examine the levels of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in soil collected from the surroundings of historical pesticide storage facilities on former agricultural aerodromes, warehouses, and pesticide distribution sites located in the most important agricultural regions in Azerbaijan. The conducted research included determination of three groups of POPs (occurring together), in the natural soil environment influenced for many years by abiotic and biotic factors that could have caused their transformations or decomposition. In this study, soil samples were collected in 21 georeferenced points located in the administrative area of Bilasuvar, Saatly, Sabirabad, Salyan and Jalilabad districts of Azerbaijan. Soil chemical analysis involved determination of organochlorine compounds (OCP): hexachlorocyclohexanes (HCHs) (three isomers α-HCH, β-HCH and γ-HCH) and dichlorodiphenyltrichloroethanes (DDTs) (six congeners 2,4′DDT; 4,4′DDT; 2,4′DDE; 4,4′DDE; 2,4′DDE; and 4,4′DDE); polycyclic aromatic hydrocarbons (PAHs): 16 compounds from the United States Environmental Protection Agency US EPA list and, PCBs (seven congeners identified with the following IUPAC numbers: 28, 52, 101, 118, 138, 153, and 180). Our research showed that OCPs reached the highest concentration in the studied areas. The total concentrations of OCPs ranged from 0.01 to 21,888 mg∙kg⁻¹ with significantly higher concentrations of Σ6DDTs (0.01 μg kg⁻¹ to 21880 mg kg⁻¹) compared to ΣHCH (0.14 ng kg⁻¹ to 166.72 µg kg⁻¹). The total concentrations of PCBs in the studied soils was varied from 0.02 to 147.30 μg·kg⁻¹ but only PCB138 and PCB180 were detected in all analyzed samples. The concentrations of Σ16 PAHs were also strongly diversified throughout the sampling areas and ranged from 0.15 to 16,026 mg kg⁻¹. The obtained results confirmed that the agricultural soils of Azerbaijan contained much lower (up to by three orders of magnitude) concentrations of PCBs and PAHs than DDT. It is supported by the fact that PCBs and PAHs were not directly used by agriculture sector and their content results from secondary sources, such as combustion and various industrial processes. Moreover, the high concentrations of PAHs in studied soils were associated with their location in direct neighborhood of the airport, as well as with accumulation of contaminants from dispersed sources and long range transport. The high concentrations of pesticides confirm that deposition of parent OCPs have occurred from obsolete pesticide landfills. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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Review

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13 pages, 2624 KiB

Open AccessReview

Production of Bulk Chemicals with Biocatalysis: Drivers and Challenges Reflected in Recent Industrial Granted Patents (2015–2020)

by Nadia Guajardo and Pablo Domínguez de María

Molecules 2021, 26(3), 736; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26030736 - 31 Jan 2021

Cited by 13 | Viewed by 3507

Abstract

The application of biocatalysis and White Biotechnology tools in chemical areas concerning the production of bulk compounds and other related low-added value products (with high volumes) has been gaining importance in recent years. The expected drivers of biocatalysis for these sectors are energy savings, regioselectivity (leading to cleaner products), the possibility of using thermolabile substrates, as well as the generation of less by-products and manageable wastes. This paper explores some recent industrial granted patents related to biocatalysis and bulk chemicals. Several patents have been identified in fields such as biodiesel and esterification reactions, and sugar or furan chemistry. Overall, innovative strategies involve the identification of novel enzymes, the set-up of improved immobilization methods, as well as novel reactor designs that can offer improved performances and economics. The reported examples indicate that biocatalysis can certainly offer opportunities for these areas as well, far from the typical pharmaceutical and fine chemical applications often reported in the literature. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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26 pages, 2490 KiB

Open AccessFeature PaperReview

Biocatalyzed Redox Processes Employing Green Reaction Media

by Carmen Aranda and Gonzalo de Gonzalo

Molecules 2020, 25(13), 3016; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25133016 - 01 Jul 2020

Cited by 17 | Viewed by 3850

Abstract

The application of biocatalysts to perform reductive/oxidative chemical processes has attracted great interest in recent years, due to their environmentally friendly conditions combined with high selectivities. In some circumstances, the aqueous buffer medium normally employed in biocatalytic procedures is not the best option to develop these processes, due to solubility and/or inhibition issues, requiring biocatalyzed redox procedures to circumvent these drawbacks, by developing novel green non-conventional media, including the use of biobased solvents, reactions conducted in neat conditions and the application of neoteric solvents such as deep eutectic solvents. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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26 pages, 2174 KiB

Open AccessReview

Development of Biopolymer and Conducting Polymer-Based Optical Sensors for Heavy Metal Ion Detection

by Nur Syahira Md Ramdzan, Yap Wing Fen, Nur Ain Asyiqin Anas, Nur Alia Sheh Omar and Silvan Saleviter

Molecules 2020, 25(11), 2548; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25112548 - 30 May 2020

Cited by 45 | Viewed by 5020

Abstract

Great efforts have been devoted to the invention of environmental sensors as the amount of water pollution has increased in recent decades. Chitosan, cellulose and nanocrystalline cellulose are examples of biopolymers that have been intensively studied due to their potential applications, particularly as sensors. Furthermore, the rapid use of conducting polymer materials as a sensing layer in environmental monitoring has also been developed. Thus, the incorporation of biopolymer and conducting polymer materials with various methods has shown promising potential with sensitively and selectively toward heavy metal ions. In this feature paper, selected recent and updated investigations are reviewed on biopolymer and conducting polymer-based materials in sensors aimed at the detection of heavy metal ions by optical methods. This review intends to provide sufficient evidence of the potential of polymer-based materials as sensing layers, and future outlooks are considered in developing surface plasmon resonance as an excellent and valid sensor for heavy metal ion detection. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Green Chemistry)

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