51吃瓜app

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Dr Mounir Maafi

Job: Senior Lecturer

Faculty: Health and Life Sciences

School/department: Leicester School of Pharmacy

Address: De 51吃瓜app University, The Gateway, Leicester, LE1 9BH.

T: +44 (0)116 257 7704

E: mmaafi@dmu.ac.uk

W: /hls

 

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Personal profile

Mounir Maafi is a senior lecturer at the Leicester School of Pharmacy and he is an active researcher in drugs photostability and stabilisation. He holds an engineer degree from the National Institute of Industrial Chemistry (Algeria), a DEA in Spectrochemical Analysis of Organic and Biological Materials from Paris 6 - Paris 7 Universities, and a PhD in physical/analytical chemistry from Paris 7 University. Dr Maafi has held several Research Fellow/postdoctoral positions including at the Institute of Topology and System Dynamics (Paris, France), the Department of Analytical Chemistry (Badajoz, Spain), the Karolinska Institute at the Karolinska Hospital (Stockholm, Sweden), and at the University of Glamorgan (Cardiff, UK). He has also held university teaching positions as an Associate Professor at Marne La Vallée University, Paris 7 university and CPCM-Paris in France, and at University of Glamorgan at Cardiff. Dr Maafi is an editor for E-Journal of chemistry and a referee for several journals. He speaks five languages and hopes to learn a few more.

Research group affiliations

Chemistry for Health

Publications and outputs


  • dc.title: Editorial: Recent advances in photokinetics dc.contributor.author: Maafi, Mounir dc.description: open access article

  • dc.title: Excitation Wavelength-Dependent Photochemistry dc.contributor.author: Maafi, Mounir dc.description.abstract: The dependence of photochemistry on excitation wavelength is not a recently observed phenomenon; nonetheless, it has, surprisingly enough, been largely ignored in the field. The reasons for this situation are not fully understood but might be related to a provisional extension of Kasha鈥檚 rule to photochemistry, or perhaps to a difficulty to justify the kind of short time-scales implied in such photochemistry, that challenges the usually held view giving predominance to fast internal conversion and vibrational relaxation. Regardless of the reasons, it is still a matter of fact that a complete and satisfactory interpretation for experimentally proven wavelength-dependent photochemistry is not yet available and the community endeavor to build a holistic understanding and a comprehensive view of the phenomenon. The present review is a non-exhaustive overview of the published data in the field, reporting on some of the most prominent features, issues, and interpretations. dc.description: open access article

  • dc.title: On photokinetics under polychromatic light dc.contributor.author: Maafi, Mounir dc.description.abstract: Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should naturally play for such reactive photosystems, the literature lacks a comprehensive description of that area. Indeed, one fails to identify explicit model integrated rate laws for these reactions, a characteristic type for their kinetic behavior, or their kinetic order. In addition, there is no consensus in the community on standardized investigative tools to evaluate the reactivity of these photosystems, nor are there venues for the discussion of such photokinetic issues. The present work is a contribution addressing some of these knowledge gaps. It proposes an unprecedented general formula capable of mapping out the kinetic traces of photoreactions under polychromatic light irradiation. This article quantitatively discusses several reaction situations, including the effects of initial reactant concentration and the presence of spectator molecules. It also develops a methodology for standardizing actinometers and defines and describes both the spectral range of highest reactivity and the photonic yield. The validity of the model equation has been proven by comparing its results to both theoretical counterparts and those generated by fourth-order Runge鈥揔utta numerical calculations. For the first time, a confirmation of the 桅-order character of the kinetics under polychromatic light was established. dc.description: open access article

  • dc.title: On photokinetics under monochromatic light dc.contributor.author: Maafi, Mounir dc.description.abstract: The properties of photokinetics under monochromatic light have not yet been fully described in the literature. In addition, for the last 120 years or so, explicit, handy model equations that can map out the kinetic behaviour of photoreactions have been lacking. These gaps in the knowledge are addressed in the present paper. Several general features of such photokinetics were investigated, including the effects of initial reactant concentration, the presence of spectator molecules, and radiation intensity. A unique equation, standing for a pseudo-integrated rate law, capable of outlining the kinetic behaviour of any photoreaction is proposed. In addition, a method that solves for quantum yields and absorption coefficients of all species of a given photoreaction is detailed. A metric (the initial velocity) has been adopted, and its reliability for the quantification of several effects was proven by theoretical derivation, Runge鈥揔utta numerical integration calculations and through the model equation proposed. Overall, this study shows that, under monochromatic light, photoreaction kinetics is well described by 桅-order kinetics, which is embodied by a unifying model equation. This paper is aimed at contributing to rationalising photokinetics via reliable, easy-to-use mathematical tools. dc.description: open access article

  • dc.title: Photokinetics of Dacarbazine and Nifedipine under polychromatic light irradiation and their application as new reliable actinometers for the ultraviolet range dc.contributor.author: Maafi, Mounir; Al-Qarni, Mohammed Ahmed dc.description.abstract: The photokinetic behaviour of drugs driven by polychromatic light is an area of pharmaceutics that has not received a lot of attention. Most often, such photokinetic data is treated by thermal kinetic models (i.e., the classical 0th-, 1st- or 2nd-order equations). Such models were not analytically derived from the rate-laws of the photodegradation reactions. Polychromatic light kinetic modelling is hence of importance, as a means to providing adequate toolkits and metrics. This paper aims at proposing two reliable drug-actinometers useful for polychromatic UVA range. The general actinometric methodology offered here is also useful for any drugs/materials obeying a primary photoprocess where both reactant and photoproduct absorb the incident light, of the AB(1桅)蔚B鈮�0 type. The present method has been consolidated by the 畏-order kinetics. This framework further demonstrated the lamp-specificity of actinometers. Overall, Dacarbazine and Nifedipine photodegradations obeyed 畏-order kinetics, and stand as effective actinometers that can be recommended for the ICH Q1b photostability testing. dc.description: open access article

  • dc.title: Mono- and polychromatic light diarylethene-actinometer for the visible range dc.contributor.author: Maafi, Mounir; Al-Qarni, Mohammed Ahmed dc.description.abstract: Photochromes have proven to be attractive molecules for potential applications not necessary based on their spectacular colour change (such as biomimetic chemistry and photoswitchable nucleosides). Their development was incited by the versatility of compounds that could be prepared, but their applications also depended on their photobehaviour. The latter, conceptually requires a comprehensive description of their kinetics. A field which is somewhat still to be developed since, thus far, a single integrated rate-law (c = f (t), expressing the variation of the concentration with irradiation time) has been analytically established for samples exposed to monochromatic light. Similar integrated rate-law equations have yet to be analytically developed for polychromatic light irradiation. The present paper investigates the facets of photokinetics of a photochromic closed-form diarylethene de- rivative (c-DAE) and its variability with the light type impinging on the sample. An integrated rate-law equation has been derived, to describe kinetics under polychromatic light. The findings have then been applied to establish robust methodologies for both monochromatic and polychromatic light actinometries for the visible range. c- DAE is been shown to be a reliable, easily manipulated, actinometer for the 400鈥�600 nm range for both light types. It is an exemplar of a new generation of actinometers that are easy-to-handle, regenerated, reliable, do not require to have a wavelength-invariant quantum yield, useful for both monochromatic and polychromatic light set-ups, and their procedures are based on integrated rate-law equations. dc.description: The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.

  • dc.title: 桅-order spectrophotokinetic characterisation and quantification of trans-cis oxyresveratrol reactivity, photodegradation and actinometry. dc.contributor.author: Maafi, Mounir; Alqarni, M. dc.description.abstract: A new 桅-order kinetic method was proposed in this study for the investigation of trans-cis photoisomerization reaction of Oxyresveratol (ORVT) subjected to non-isosbestic irradiation. In ethanolic media, it has been proven that forward (桅_(A鈫払)^(l_irr )) and reverse (桅_(B鈫扐)^(l_irr )) reaction quantum yields were dependent on the monochromatic irradation wavelength according to a sigmoid pattern over the spectral ranges of their electronic absorption (260-360 nm). An 11.4鈥� and 6.6-fold increases were recorded for 桅_(B鈫扐)^(飦琠irr ) and 桅_(A鈫払)^(飦琠irr ), respectively. The efficiencies of the former (桅_(B鈫扐)^(飦琠irr ), ranging between 2.3 脳 10-2 and 26.3 脳 10-2) were 33 to 60 % smaller than those of the respective 桅_(A鈫払)^(l_irr ) measured at the irradiation wavelengths selected. Overall, between 57 and 97 % degradation of the initial trans-ORVT was observed under relatively weak light intensities, with the highest values recorded at the longest wavelengths. These findings strongly recommend protection from light in all situations of this biologically important phytomolecule that possesses therapeutic value of interest to pharmaceutical applications. The 桅-order kinetics also offered a simple way to develop a reliable actinometric method that proved ORVT to be an efficient actinometer for the dynamic range 295-360 nm. The usefulness of 桅鈥恛rder kinetics for the investigation and quantification of phytoproducts鈥� photodegradation was discussed. dc.description: The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.

  • dc.title: Montelukast photodegradation: Elucidation of 肖-order kinetics, determination of quantum yields and application to actinometry. dc.contributor.author: Maafi, W.; Maafi, Mounir dc.description.abstract: A recently developed F鈥搊rder semi鈥揺mperical integrated rate鈥搇aw for photoreversible AB(2F) photoreversible reactions has been successfully applied to investigate Montelukast sodium (Monte) photodegradation kinetics in ethanol. The model equations also served to propose a new stepwise kinetic elucidation method valid for any AB(2F) system and its application to the determination of Monte forward (桅A鈫払lirr) and reverse (桅B鈫扐lirr ) quantum yields at various irradiation wavelengths. It has been found that 桅A鈫払lirr undergoes a 15鈥揻old increase with wavelength between 220 and 360 nm, with the spectral section 250 鈥� 360 nm representing Monte effective photodegradation causative range. The reverse quantum yield values were generally between 12 and 54 % lower than those recorded for 桅A鈫払lirr, with the trans鈥搃somer (Monte) converts almost completely to its cis鈥揷ounterpart at high irradiation wavelengths. Furthermore, the potential use of Monte as an actinometer has been investigated and an actinometric method was proposed. This study demonstrated the usefulness of Monte for monochromatic light actinometry for the dynamic range 258 鈥� 380nm. dc.description: The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.

  • dc.title: Novel methods for the characterisation of nanosponges/drug complexes with fluorimetry. Detection and Quantification in human serum dc.contributor.author: Benson, G.; Maafi, Mounir; Grootveld, Martin dc.description.abstract: Cyclodextrins are oligosaccharides formed from a cyclic structure of 1,4-linked 伪-D-glucopyranose units, hydrophilic on the outside, and hydrophobic within they are able to form hydrogen bonds, van der Waals forces and hydrophobic interactions with non-polar guest molecules, including pharmaceuticals, altering their solubility and spectral properties, they are able to overcome biological barriers and be absorbed [1]. Cross-linking 尾-cyclodextrin with epichlorohydrin can create polymers, with modifiable properties, and greater solubility, which can form stronger inclusion complexes through both encapsulation, and adsorbing guest molecules to their exterior. Although this complexation has been investigated with some pharmaceuticals, enhancing their solubility [2], and yielding higher percentage recoveries than when monomeric 尾-cyclodextrin was used [3], it has also been found that an increase in the intensity of fluorimetric analytical signal also occurs as a result of this interaction, along with a shift in the maximum wavelength peak [4]. The inclusion complex doesn't appear to have been utilised for analytical chemistry purposes, therefore the drug-尾-cyclodextrin polymer-complex was explored through fluorimetry, as it is anticipated that this will allow for lower pharmaceutical detection limits; this technique was then applied for the determination of drugs in human serum and canal water. This poster will illustrate how 尾-cyclodextrin polymer can be utilised to enhance the fluorimetric signal of drugs, and be applied for the detection of pharmaceuticals in human serum and canal water.

  • dc.title: Usefulness of 桅-order kinetics for the investigation, characterisation and quantification of photodegradation processes dc.contributor.author: Maafi, Mounir; Alqarni, M. dc.description.abstract: 桅-order kinetics has been shown to be the best tool to study photokinetics [1 鈥� 6]. Various species have been studied using this approach including photochromes [1, 2] and drugs [3 鈥� 6]. The unimolecular photodegradation processes of the form AB (1桅) and photoreversible systems AB (2桅), where A, the initial species phototransforms into a product B (A鈫払) which itself can return to A (A鈫払) via two distinct photoprocesses, each characterized each by an individual efficiency (桅), have been mathematically described by integrated rate-law equations which express the so called '桅-order' kinetics [1 鈥� 6]. The application of this novel approach was found to be useful to determine a number of photoreaction attributes. The reaction's photochemical quantum yield(s), the effects of initial species concentration, or the impact of competitive absorbers on the rate-constant of the photoactive species were all made readily accessible by simple methods. More importantly, the 桅-order kinetics has proven to facilitate the development of a wide range of actinometers from AB (1桅) and AB (2桅) systems [2 鈥� 6]. This novel 桅-order kinetic method clearly has the potential for application in various fields including the photodegradation of natural products. The details of 桅-order elucidation kinetic methods will be discussed here and examples of application presented.

Key research outputs

The potential of AB(1) systems for direct actinometry. Diarylethenes as successful actimometers for the visible range. M Maafi, Phys Chem Chem Phys, 2010 12 (40), pp 13248-13254.

A mathematical analysis and elucidation of AB(2k,1φ) thermophotochromic kinetics. An analytical solution using pure kinetic data and considering as unknown The rate constants, quantum yield and both species’ spectra. M Maafi, R G Brown, Int J Chem Kinet, 41(4), pp 255 – 264 2009.

Kinetic analysis and kinetic elucidation options for AB(1k,2) systems. New Spectrokinetic methods for photochromes. M Maafi, R G Brown. Photochem Photobiol Sci, 7, pp 1360 – 1372 2008.

Spectrokinetic Methods for the Investigation of Photochromic and Thermo-Photochromic Spiropyrans. M Maafi, Molecules 13(9), pp 2260-2302 2008.

Comment on “Photokinetic methods: A mathematical analysis of the rate equations in photochromic systems; by G Ottavi, F Ortica, G Favaro, Int J Chem Kinet, 1999 31, 303-313.” M Maafi, Int J Chem Kinet, 40, pp 524-525 2008.

A Fundamental system of equation to describe ABC(3k,6 dynamics. Contribution to the elucdation of [2H]-naphthopyran kinetics. M Maafi, R G Brown, Int J Chem Kinet, 40, pp 268-281 2008.

The kinetic model for AB(1) systems. A Closed-form integration of the differential equation with a variable photokinetic factor. M Maafi, R G Brown, J Photochem Photobiol A:Chem, 187, pp.319-324 2007.

Research interests/expertise

  • Modelling photoreactions and spectrokinetics
  • Thermochromes and photochromic materials
  • Drug phodegradation and stabilisation
  • Drug specials
  • Anticancer, synthetic hormone and cardiovascular drugs
  • Cyclodextrin superamolecular systems
  • Drug delivery systems
  • Development of analytical methods for soil analysis.

Areas of teaching

  • Spectroscopy/spectrochmistry
  • Analytical chemistry
  • Physical chemistry and thermodynamics
  • Drug formulation and stability
  • Project supervision at undergraduate and postgraduate levels MPhil and PhD.

Qualifications

Engineer, DEA, PhD

Honours and awards

  • The Marquise index Who’s Who in the World, Editions 2008
  • The Dictionary of International Biography, 34th edition, Cambridge 2008
  • Nominated for a 51吃瓜app Vice Chancellors Distinguished Teaching Award.

Conference attendance

Kinetic tools for the investigation of unimolecular and bimolecular photoreactions of drugs. Potential for actinometry. 7th International Meeting on the Photostability of Drugs and Drug Products (1–3 October 2008). M Maafi, London.

A semi empirical kinetic law for AB(2φ) systems. usefulness for direct actinometry. XXII IUPAC Symposium on photochemistry (28 July–1 August 2008), M Maafi, Gothenburg, Sweden.

A complete elucidation of AB(2k,1φ) ThermoPhoto-Chromic Kinetics. A Mathematically Analytical method based on Pure Kinetic Data. XXII IUPAC Symposium on photochemistry (28 July–1 August 2008), M Maafi, R G Brown, Gothenburg, Sweden.

Current research students

First supervisor for the following PhD students: Damerdji Wassila, Lok Yan Lee, Leonie Hough.

Externally funded research grants information

In preparation: a research project on drugs stability.

Professional esteem indicators

E-Journal of chemistry and a referee for several journals.

Case studies

Citation in international journals in the year 2011.

Angewandte Chemie - International Edition : Imprinting chemical and responsive micropatterns into metal-organic frameworks, Han S, Wei Y, Valente C, Forgan R S, Gassensmith J J, Smaldone R A, Nakanishi H, (...), Grzybowski B A, 50 (1), pp 276-279 2011.

Journal of Photochemistry and Photobiology C: Photochemistry Reviews : Quantitative analysis of the dynamic behaviour of photochromic systems. Delbaere, S, Vermeersch,G, Micheau,J-C, 12(2), pp 74–105 2011.

Phys Chem Chem Phys: Tuning of switching properties and excited-state dynamics of fulgides by structural modifications, Ron Siewertsen, Frank Strübe, Jochen Mattay, Falk Renth and Friedrich Temps, 13, pp 3800-3808 2011.

European Journal of Organic Chemistry : Photochromism of Rotation-Hindered Furylfulgides Influenced by Steric Modifications, Frank Strübe, Ron Siewertsen, Frank D. Sönnichsen, Falk Renth, Friedrich Temps, Jochen Mattay, pp 1947–1955 2011.

Chemical Physics Letters : Deciphering the host–guest chemistry of Acridine Yellow and Cucurbit[7]uril: An integrated spectroscopic and calorimetric study, Brotati Chakraborty, Samita Basu, 507(1-3), pp 74-79 2011.

Photochemistry : Photochemistry of aromatic compounds. Mizuno,K, 38, pp 168-209 2011.

Journal of Molecular Liquids: Solvent effect on the spectroscopic properties of 6MAMC and 7MAMC, Melavanki,R M, Patil,N R, Kapatkar,S B, Ayachit,N H, Umapathy,S, Thipperudrappa,J, Nataraju,A R, 158 (2), pp 105-110 2011.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy : Comments on the determination of excited state dipole moment of molecules using the method of solvatochromism A Kawski, P Bojarski, 82 (1), pp 527-528 2011.

Photochemistry: Photochemistry of aromatic compounds. Mizuno,K, 38, pp 168-209 2011.

Photochemistry: Alkenes, alkynes, dienes, polyenes. Tsuno,T, 38, pp 110-142, 2011.

Book: Dey,D, Kumar Sarangi,M and Basu,S (2011) Chapter 9 : Hydrogen Bonding on Photoexcitation, in Hydrogen Bonding and Transfer in the Excited State, Volume I & II (eds K.-L. Han and G.-J. Zhao), John Wiley & Sons Ltd, Chichester, UK.

Book : Timcheva,I and Nikolov,P (2011) Chapter 12 : Intermolecular Hydrogen Bonding in the Fluorescence Excited State of Organic Luminophores Containing Both Carbonyl and Amino Groups, in Hydrogen Bonding and Transfer in the Excited State, Volume I & II (eds K.-L. Han and G.-J. Zhao), John Wiley & Sons Ltd, Chichester, UK.

Journal of Advanced Research in Physics: Solvent effects on the electronic absorption and fluorescence spectra, Mihaela Homocianu1, Anton Airinei and Dana Ortansa Dorohoi, 2(1), 011105, 2011.

Journal of Photochemistry and Photobiology A: Chemistry: Chemical reactions of benzophenone photoirradiated in 1,2-polybutadiene. Barboiu,V, Avadanei,M I, 222(1), pp 170-179 2011.

Journal of Molecular Liquids: On the ground and excited state dipole moments of dansylamide from solvatochromic shifts of absorption and fluorescence spectra. Tewari,N, Joshi,N K, Rautela,R, Gahlaut,R, Joshi,H C, Pant,S, 160(3), pp 150-153 2011.

Research Advance in the Effects of β-Cyclodextrin and Its Derivatives on Fluorescence Enhancement, Zhang Min, Zhang Yu-hao, Ma Liang , Vol 32, No 01 297 2011.