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Dr Mounir Maafi

Job: Senior Lecturer

Faculty: Health and Life Sciences

School/department: Leicester School of Pharmacy

Address: ÐßÐßÊÓƵ, The Gateway, Leicester, LE1 9BH.

T: +44 (0)116 257 7704

E: mmaafi@dmu.ac.uk

W: /hls

 

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Personal profile

Dr.Eng. Mounir Maafi is the author of Photokinetics: a new perspective and inventor of the Φ-order kinetics. He is also a registered UN consultant/UNIDO international expert, and an active peer-reviewer for more than 30 national and international scientific journals. He has a versatile research experience that was facilitated by his chemical engineering background and a postgraduate diploma in spectroscopic methods for analysis of materials. His PhD (in Paris 7 University), which focused on storage of sunlight energy in electro-polymers, preluded four postdoctoral positions (France, Spain, Sweden and UK), that were held in international institutions including the Karolinska institute. He has also been an academic in four European universities, where he mainly taught chemistry, math, pharmacy, pharmaceutical and forensic students. Since he joined ÐßÐßÊÓƵ, he successfully supervised to completion (as first supervisor), several national and an externally funded international Ph.D., and Masters by research students. He contributed oral and poster presentations in numerous conferences (where he was invited to plenary presentations in two conferences).  

The research programmes he was involved in, required versatile skills in physical and analytical chemistry, mathematics and mathematical modelling of chemical systems, coding and simulation, numerical integration methods, predictive modelling and experimental design. The gathered expertise was pivotal to his research on photokinetics (i.e., kinetics of photoreactions) and actinometry (i.e., determination of the photon flux of a light source).

His work was devoted to rationalising photokinetics along the standards of kinetics. He has published in this area more than 46 papers in reputable (refereed) scientific journals. Almost each of these papers brought a new idea or conceptualisation to the field. Some of the important outcomes of his research included the discovery of the -order kinetics, unprecedented general explicit integrated rate-law equations to fit any trace of photo- and photothermal reactions, an explanation and solutions for the identifiability issues, mathematical procedures for kinetic elucidation (unravelling all reaction parameters), easy means to prove the variability of the quantum yield with irradiation wavelength, and handy actinometric methods (where he proposed a series of new actinometers for the 220-580 nm domain). The predictive potential of the new equations for many reaction situations has been proven experimentally and/or on numerically generated data.             

The research was based on detailed mathematical framework combining the theoretical equations of photokinetics with mathematical simulations and experimental data. The rational being that any new concept, formula or procedure must be tested by computer-generated data and as much possible be confronted to experiment.   

The shift of paradigm introduced by his research work in the subject of photokinetics contributes to a rationalisation of the subject and opens alternative avenues for further developments.

Research group affiliations

Chemistry for Health

Publications and outputs


  • dc.title: Photokinetics of Bimolecular Reactions: Analytically Solvable Rate Laws dc.contributor.author: Maafi, Mounir dc.description.abstract: Light-induced bimolecular reactions occur in many naturally and artificially (laboratory or industrial) designed processes. The quantification of these reactions is generally performed by kinetics. In particular, the kinetic data of bimolecular photoreactions are often treated by second-order kinetic models. If this situation is effectively ubiquitous in practice, it remains that the underlying hypothesis, assuming that photoreactions obey the same kinetics as thermal transformations, is not consistent with the physical photosystem considered. In fact, it has been proven that unimolecular (mono-reactant) photoreactions are effectively modelled by Φ-order kinetics. The latter model is formalised by a logarithmic function bearing an exponential in its argument. Hence, Φ-order kinetics is mathematically different from the thermal reaction models. In the case of the bimolecular photoreactions that are described by different rate laws than those used for the thermal reactions, i.e., involving both radiation intensity and light absorption, there have been no reported solutions in the literature that were based on analytical integration. So much so, no kinetic order has ever been assigned to any bimolecular photoreaction. In the current situation, it is perhaps sensible to proceed, in a first step, by defining among the bimolecular photoreactions those whose rate laws can be solved analytically and establish the corresponding solutions by closed-form integration. Following such a strategy, the present paper unravels the first model equations for the kinetics of bimolecular photoreactions. The findings are part of an effort to standardise photokinetics along the same principles used in thermal kinetics. dc.description: open access article The paper presents the first ever published rate laws of bimolecular reactions and proves that these reactions obey Φ-order kinetics, demonstrating that the ubiquitous use of thermal second order kinetics is obsolete.

  • dc.title: Photokinetics : A new perspective dc.contributor.author: Maafi, Mounir dc.description.abstract: This monograph explores photokinetics, the study of reaction kinetics under light exposure, addressing its longstanding underdevelopment compared to thermal reaction kinetics. It systematically reviews fundamental concepts, introduces new methods and equations to quantify and predict photochemical and photothermal reaction rates, and provides a standardized framework for laboratory investigations. Covering both monochromatic and polychromatic light effects, the book presents a paradigm shift in the field, making it a valuable reference for students, researchers, and industry professionals. It lays the foundation for the advancement of photokinetics, bridging critical knowledge gaps and setting the stage for future developments. This volume serves as a valuable resource for students, researchers, and academics working with photoreactive systems.

  • dc.title: Photokinetics of Mixtures of Independent Photoreactions dc.contributor.author: Maafi, Mounir dc.description.abstract: The photokinetic behavior of concomitant and independent photo- and photothermal reac tions exposed to monochromatic or polychromatic irradiation, has not yet been described in photochemistry literature. The occurrence of such mixtures is reported in a wide range of fields, from living species to technologically designed devices. To address the lack of investigative tools that facilitate better understanding, quantification, and control of such parallel-reaction systems, a new holistic approach is proposed in the present study. It contributes to an effort dedicated to rationalizing photokinetics along the same criteria required for thermal kinetics. The methodology builds on a previously introduced general explicit integrated rate-law formula for single-reaction systems (whose integro-differential rate-equation is not solvable). The extension of its field of applicability to multi-component photoreactive mixtures is demonstrated in the present paper. For this purpose, a large number of combinations of both photo- and photothermal individual reactions, possessing distinctly different features, were studied in binary and ternary mixtures. The data of reactions/mixtures were generated by a fourth-order Runge–Kutta numerical integration. An excellent fitting of the species’ kinetic traces by the adapted explicit formula was ob tained for all mixtures. Also, the quantification of the effects of the variation in the initial concentration of one component of the mixture, and/or the presence of inert spectator molecules in the reactor, was successfully performed. The investigative photokinetic tools proposed here are shown to be handy, efficient, and useful. The findings of the present study are also thought to expand the application possibilities of reactive photothermal systems in mixtures. dc.description: open access article

  • dc.title: Photokinetics of Photothermal Reactions dc.contributor.author: Maafi, Mounir dc.description.abstract: Photothermal reactions, involving both photochemical and thermal reaction steps, are the most abundant sequences in photochemistry. The derivation of their rate laws is standardized, but the integration of these rate laws has not yet been achieved. Indeed, the field still lacks integrated rate laws for the description of these reactions’ behavior and/or identification of their reaction order. This made difficult a comprehensive account of the photokinetics of photothermal reactions, which created a gap in knowledge. This gap is addressed in the present paper by introducing an unprecedented general model equation capable of mapping out the kinetic traces of such reactions when exposed to light or in the dark. The integrated rate law model equation also applies when the reactive medium is exposed to either monochromatic or polychromatic light irradiation. The validity of the model equation was established against simulated data obtained by a fourth-order Runge–Kutta method. It was then used to describe and quantify several situations of photothermal reactions, such as the effects of initial concentration, spectator molecules, and incident radiation intensity, and the impact of the latter on the photonic yield. The model equation facilitated a general elucidation method to determine the intrinsic reaction parameters (quantum yields and absorptivities of the reactive species) for any photothermal mechanism whose number of species is known. This paper contributes to rationalizing photokinetics along the same general guidelines adopted in chemical kinetics. dc.description: open access article

  • 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’s 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–Kutta numerical calculations. For the first time, a confirmation of the Φ-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–Kutta numerical integration calculations and through the model equation proposed. Overall, this study shows that, under monochromatic light, photoreaction kinetics is well described by Φ-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(1Φ)εB≠0 type. The present method has been consolidated by the η-order kinetics. This framework further demonstrated the lamp-specificity of actinometers. Overall, Dacarbazine and Nifedipine photodegradations obeyed η-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 400–600 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.

Key research outputs

Maafi, M. Photokinetics: A New Perspective, Springer: Berlin/Heidelberg, Germany, 2025; ISBN 978-3-031-98984-1 ()

Maafi, M. Photokinetics of Bimolecular reactions:  Analytically solvable rate-laws. Molecules 31, 84, 2026. DOI: 10.3390/molecules31010084

Maafi, M. Photokinetics of mixtures of independent reactions. Molecules 30, 4122, 2025. DOI: 10.3390/molecules30204122

Maafi, M. Photokinetics of photothermal reactions. Molecules 30, 330, 2025. DOI: 10.3390/molecules30020330

Maafi, M. Excitation Wavelength-Dependent Photochemistry. Photochem 4, 233-270, 2024 . DOI: 10.3390/ photochem4020015

Maafi, M. Photokinetics under polychromatic light. Frontiers in Chemistry  12, 1367276, 2024. DOI: 10.3389/fchem.2024.1367276

Maafi, M. Photokinetics under monochromatic light. Frontiers in Chemistry 11, 1233151, 2023. DOI: 10.3389/fchem.2023.1233151   

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

M Maafi and RG Brown. 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. Int J Chem Kinet, 41(4), pp 255 – 264 2009.

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

M Maafi.  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.” Int J Chem Kinet, 40, pp 524-525 2008.

M Maafi and RG Brown. The kinetic model for AB(1) systems. A Closed-form integration of the differential equation with a variable photokinetic factor.
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

    • ÐßÐßÊÓƵ Vice Chancellors Distinguished Teaching Award.
  • The Marquise index Who’s Who in the World, Editions 2008
  • The Dictionary of International Biography, 34th edition, Cambridge 2008

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.