Kowalik P., Penkala M., Bujak P., Kmita A., Gajewska M., Ostrowski A., Slodek A., Pron A. From Ag2S to luminescent Ag-In-S nanocrystals: Via an ultrasonic method-an in situ synthesis study in an NMR tube
Journal of Materials Chemistry C 2020, 8, 26, 8942-4952
DOI: 10.1039/d0tc01880e

Abstract: Starting from simple metal precursors (AgNO₃ and InCl₃), ligands (oleylamine (OLA) and 1-dodecanethiol (DDT)) and popular sulfur precursor S/OLA, we have developed a new method for the preparation of colloidal Ag₂S nanocrystals and highly luminescent ternary AgInS₂ nanocrystals. The significant advantage of this method is that the nanocrystals can be prepared at room temperature in an ultrasonic bath, without the need for an inert gas atmosphere. In particular, using this method, it was possible to perform the synthesis of the studied nanocrystals in an NMR tube providing direct analytical access to chemical transformations occurring in the reaction mixture during the nanocrystal synthesis. Detailed analysis of the evolution of NMR signals originating from ligands (OLA and DDT) enabled us to identify the nucleation and growth stages as well as the stabilization stage of the nanocrystal formation i.e. the stage in which the ligands were permanently attached to the nanocrystal surface. We also demonstrated that under the analyzed conditions, the reactivities of silver and indium precursors resulting in appropriate cation-to-ligand connections (Ag⁺–DDT and In³⁺–OLA) were crucial for the nucleation of ternary AgInS₂ nanocrystals exhibiting intense red luminescence.

Maranda-Niedbała A., Krzyżewska K., Kotwica K., Skórka L., Drapała J., Jarzembska K.N., Zagórska M., Proń A., Nowakowski R. 9,10-Anthraquinones Disubstituted with Linear Alkoxy Groups: Spectroscopy, Electrochemistry, and Peculiarities of Their 2D and 3D Supramolecular Organizations
Langmuir 2020, 36, 49, 15048-15063
DOI: 10.1021/acs.langmuir.0c02586

Abstract:Spectroscopic, electrochemical, and structural properties of 2,6-dialkoxy-9,10-anthraquinones (Anth-OCn, n = 4, 6, 8, 10, and 12) of increasing alkoxy substituents length were investigated. UV–vis spectroscopy showed a substitution-induced bathochromic shift of the least energetic band from 325 nm in the case of unsubstituted anthraquinone to ca. 350 nm for the studied derivatives. Similarly as unsubstituted anthraquinone, the studied compound showed two reversible one electron reductions to a radical anion and spinless anions, respectively. The first reduction was affected by electron-donating properties of the substituents, its potential being shifted to ca. −1.5 V (vs Fc/Fc⁺), i.e., by 80 to 95 mV as compared to the case of unsubstituted anthraquinone. This corresponded to a decrease of |EA| from 3.27 to 3.19–3.17 eV. The experimental spectroscopic and electrochemical data were in full agreement with the DFT calculations. The introduction of the alkoxy substituent improved solution processibility of the studied compounds and facilitated the formation of their ordered supramolecular 2D aggregation on HOPG as well as single crystal growth from solutions. Comparative structural investigations carried out on single crystals and monolayers deposited on HOPG revealed two, mutually related, effects of the substituent length on the resulting supramolecular organization. The first one concerns both the 2D organization in the monolayers and 3D molecular arrangement in crystals: increasing substituent length evolution of the structure occurs from herringbone-type to lamellar. The second effect, observed in monolayers of the derivatives with longer substituents, concerns gradual evolution of their lamellar structures with increasing substituent length. This evolution is induced by the structure of the graphite substrate and involves increasing correlation of the molecules orientation (anthraquinone cores as well as alkoxy substituents) with the symmetry of the graphite substrate. As a result, their 2D and 3D structures become dissimilar.

Kowalik P., Bujak P., Penkala M., Pron A. Organic-to-aqueous phase transfer of alloyed AgInS2-ZnS nanocrystals using simple hydrophilic ligands: Comparison of 11-mercaptoundecanoic acid, dihydrolipoic acid and cysteine
Nanomaterials 2021, 11, 4, Art. No. 843
DOI: 10.3390/nano11040843

Abstract: The exchange of primary hydrophobic ligands for hydrophilic ones was studied for two types of alloyed AgInS2-ZnS nanocrystals differing in composition and by consequence exhibiting two different emission colors: red (R) and green (G). Three simple hydrophilic ligands were tested, namely, 11-mercaptoundecanoic acid, dihydrolipoic acid and cysteine. In all cases, stable aqueous colloidal dispersions were obtained. Detailed characterization of the nanocrystal surface before and after the ligand exchange by NMR spectroscopy unequivocally showed that the exchange process was the most efficient in the case of dihydrolipoic acid, leading to the complete removal of the primary ligands with a relatively small photoluminescence quantum yield drop from 68% to 40% for nanocrystals of the R type and from 48% to 28% for the G ones.

Kowalik P., Mucha S.G., Matczyszyn K., Bujak P., Mazur L.M., Ostrowski A., Kmita A., Gajewska M., Pron A. Heterogeneity induced dual luminescence properties of AgInS2and AgInS2-ZnS alloyed nanocrystals
Inorganic Chemistry Frontiers 2021, 8, 14, 3450-3462
DOI: 10.1039/d1qi00566a

Abstract: We have elaborated a new preparation method of ternary AgInS₂ and alloyed quaternary AgInS₂–ZnS nanocrystals which consisted of two consecutive injections of sulfur (S dissolved in oleylamine, OLA) and silver (AgNO₃ or Ag₂CO₃ dissolved in dichlorobenzene, DCB) precursors into a mixture of indium(III) chloride, zinc stearate and 1-dodecanethiol (DDT) dissolved in 1-octadecene (ODE). Under these conditions, nucleation of cubic In₂S₃ seeds took place followed by the growth of orthorhombic AgInS₂ or alloyed AgInS₂–ZnS cubic phases to yield heterodimer type nanocrystals. In both types of nanocrystals clearly separated photoluminescence peaks could be observed, confirming their heterogenic nature. The first one at 430 nm originated from the luminescence of the In₂S₃ phase. The second one was ascribed to the presence of a ternary Ag–In–S or quaternary Ag–In–Zn–S phase and its position, within the spectroscopic range from 515 nm to 710 nm, strongly dependent on the nanocrystal composition. The registered two-dimensional excitation–emission topographical maps clearly indicated that the observed emissions in two different spectral regions were related to the excitation in the same spectral range (300–400 nm); however their photoluminescence mechanisms were distinctly different. The photoluminescence lifetime of ∼3 ns measured for the emission at shorter wavelengths was typical of the simple mechanism of exciton radiative recombination in the In₂S₃ phase. The significantly longer lifetime of the longer wavelength emission (∼26 μs) seemed to clearly indicate that in this case the photoluminescence mechanism was more complex, involving exciton trap states whose positions depended on the composition of the ternary (or quaternary) phase.

Jung J., Selerowicz A., Maczugowska P., Halagan K., Rybakiewicz-Sekita R., Zagorska M., Stefaniuk-Grams A. Electron transport in naphthalene diimide derivatives
Materials 2021, 14, 14, Art. No. 4026
DOI: 10.3390/ma14144026

Abstract: Two naphthalene diimides derivatives containing two different (alkyl and alkoxyphenyl) N-substituents were studied, namely, N,N′-bis(sec-butyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-s-Bu) and N,N′-bis(4-n-hexyloxyphenyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-4-n-OHePh). These compounds are known to exhibit electron transport due to their electron-deficient character evidenced by high electron affinity (EA) values, determined by electrochemical methods and a low-lying lowest unoccupied molecular orbital (LUMO) level, predicted by density functional theory (DFT) calculations. These parameters make the studied organic semiconductors stable in operating conditions and resistant to electron trapping, facilitating, in this manner, electron transport in thin solid layers. Current–voltage characteristics, obtained for the manufactured electron-only devices operating in the low voltage range, yielded mobilities of 4.3 × 10⁻⁴ cm²V⁻¹s⁻¹ and 4.6 × 10⁻⁶ cm²V⁻¹s⁻¹ for (NDI-s-Bu) and (NDI-4-n-OHePh), respectively. Their electron transport characteristics were described using the drift–diffusion model. The studied organic semiconductors can be considered as excellent candidates for the electron transporting layers in organic photovoltaic cells and light-emitting diodes

Kotwica K., Wielgus I., Proń A. Azaacenes based electroactive materials: Preparation, structure, electrochemistry, spectroscopy and applications-a critical review
Materials 2021, 14, 18, Art. No. 5155
DOI: 10.3390/ma14185155

Abstract:This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc⁺. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300–310) to yield, for the first time, a set of normalized data, which could be directly compared.

Kowalik P., Bujak P., Penkala M., Maroń A.M., Ostrowski A., Kmita A., Gajewska M., Lisowski W., Sobczak J.W., Pron A. Indium(II) Chloride as a Precursor in the Synthesis of Ternary (Ag-In-S) and Quaternary (Ag-In-Zn-S) Nanocrystals
Chemistry of Materials 2022, 34, 2, 809-825
DOI: 10.1021/acs.chemmater.1c03800

Abstract:A new indium precursor, namely, indium(II) chloride, was tested as a precursor in the synthesis of ternary Ag–In–S and quaternary Ag–In–Zn–S nanocrystals. This new precursor, being in fact a dimer of Cl₂In–InCl₂ chemical structure, is significantly more reactive than InCl₃, typically used in the preparation of these types of nanocrystals. This was evidenced by carrying out comparative syntheses under the same reaction conditions using these two indium precursors in combination with the same silver (AgNO₃) and zinc (zinc stearate) precursors. In particular, the use of indium(II) chloride in combination with low concentrations of the zinc precursor yielded spherical-shaped (D = 3.7–6.2 nm) Ag–In–Zn–S nanocrystals, whereas for higher concentrations of this precursor, rodlike nanoparticles (L = 9–10 nm) were obtained. In all cases, the resulting nanocrystals were enriched in indium (In/Ag = 1.5–10.3). Enhanced indium precursor conversion and formation of anisotropic, longitudinal nanoparticles were closely related to the presence of thiocarboxylic acid type of ligands in the reaction mixture. These ligands were generated in situ and subsequently bound to surfacial In(III) cations in the growing nanocrystals. The use of the new precursor of enhanced reactivity facilitated precise tuning of the photoluminescence color of the resulting nanocrystals in the spectral range from ca. 730 to 530 nm with photoluminescence quantum yield (PLQY) varying from 20 to 40%. The fabricated Ag–In–S and Ag–In–Zn–S nanocrystals exhibited the longest, reported to date, photoluminescence lifetimes of ∼9.4 and ∼1.4 μs, respectively. It was also demonstrated for the first time that ternary (Ag–In–S) and quaternary (Ag–In–Zn–S) nanocrystals could be applied as efficient photocatalysts, active under visible light (green) illumination, in the reaction of aldehydes reduction to alcohols.

Kulszewicz-Bajer I., Nowakowski R., Zagórska M., Maranda-Niedbała A., Mech W., Wróbel Z., Drapała J., Wielgus I., Korona K.P. Copolymers Containing 1-Methyl-2-phenyl-imidazole Moieties as Permanent Dipole Generating Units: Synthesis, Spectroscopic, Electrochemical, and Photovoltaic Properties
Molecules 2022, 27, 3, Art. No. 915
DOI: 10.3390/molecules27030915

Abstract:New donor–acceptor conjugated alternating or random copolymers containing 1-methyl-2-phenylbenzimidazole and benzothiadiazole (P1), diketopyrrolopyrrole (P4), or both acceptors (P2) are reported. The specific feature of these copolymers is the presence of a permanent dipole-bearing moiety (1-methyl-2-phenyl imidazole (MPI)) fused with the 1,4-phenylene ring of the polymer main chain. For comparative reasons, polymers of the same main chain but deprived of the MPI group were prepared, namely, P5 with diketopyrrolopyrrole and P3 with both acceptors. The presence of the permanent dipole results in an increase of the optical band gap from 1.51 eV in P3 to 1.57 eV in P2 and from 1.49 eV in P5 to 1.55 eV in P4. It also has a measurable effect on the ionization potential (IP) and electrochemical band gap (E_g^CV), leading to their decrease from 5.00 and 1.83 eV in P3 to 4.92 and 1.79 eV in P2 as well as from 5.09 and 1.87 eV in P5 to 4.94 and 1.81 eV in P4. Moreover, the presence of permanent dipole lowers the exciton binding energy (E_b) from 0.32 eV in P3 to 0.22 eV in P2 and from 0.38 eV in P5 to 0.26 eV in P4. These dipole-induced changes in the polymer properties should be beneficial for photovoltaic applications. Bulk heterojunction solar cells fabricated from these polymers (with PC₇₁BM acceptor) show low series resistance (r_s), indicating good electrical transport properties. The measured power conversion efficiency (PCE) of 0.54% is limited by the unfavorable morphology of the active layer.

Rybakiewicz-Sekita R., Toman P., Ganczarczyk R., Drapala J., Ledwon P., Banasiewicz M., Skorka L., Matyjasiak A., Zagorska M., Pron A. D-A-D Compounds Combining Dithienopyrrole Donors and Acceptors of Increasing Electron-Withdrawing Capability: Synthesis, Spectroscopy, Electropolymerization, and Electrochromism
Journal of Physical Chemistry B 2022, 126, 22, 4089-4105

Abstract: Five D-π-A-π-D compounds consisting of the same donor unit (dithieno[3,2-b:2′,3′-d]pyrrole, DTP), the same π-linker (2,5-thienylene), and different acceptors of increasing electron-withdrawing ability (1,3,4-thiadiazole (TD), benzo[c][1,2,5]thiadiazole (BTD), 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP), 1,2,4,5-tetrazine (TZ), and benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NDI)) were synthesized. DTP-TD, DTP-BTD, and DTP-DPP turned out to be interesting luminophores emitting either yellow (DTP-TD) or near-infrared (DTP-BTD and DTP-DPP) radiation in dichloromethane solutions. The emission bands were increasingly bathochromically shifted with increasing solvent polarity. Electrochemically determined electron affinities (|EA|s) were found to be strongly dependent on the nature of the acceptor changing from 2.86 to 3.84 eV for DTP-TD and DTP-NDI, respectively, while the ionization potential (IP) values varied only weakly. Experimental findings were strongly supported by theoretical calculations, which correctly predicted the observed solvent dependence of the emission spectra. Similarly, the calculated IP and EA values were in excellent agreement with the experiment. DTP-TD, DTP-BTD, DTP-TZ, and DTP-NDI could be electropolymerized to yield polymers of very narrow electrochemical band gap and characterized by redox states differing in color coordinates and lightness. Poly(DTP-NDI) and poly(DTP-TD) showed promising electrochromic behavior, not only providing a rich color palette in the visible but also exhibiting near-infrared (NIR) electrochromism.

Kulszewicz-Bajer I., Guzauskas M., Makowska-Janusik M., Zagórska M., Mahmoudi M., Grazulevicius J.V., Proń A., Volyniuk D. Acridone and quinacridone derivatives with carbazole or phenoxazine substituents: synthesis, electrochemistry, photophysics and application as TADF electroluminophores
Journal of Materials Chemistry C 2022, 10, 34,  12377-12391
DOI: 10.1039/d2tc02270b

Abstract:Six acridone (quinacridone) derivatives containing either carbazole or phenoxazine substituents were designed and synthesized with the aim of elucidating the effect of the donor (D) and acceptor (A) linking pattern (D–A, D–A–D or D–π–A–π–D) on their photophysical and electrochemical properties. These new electroactive compounds combine reversible electrochemical oxidation with excellent luminescent properties. Their electrochemically determined ionization potentials (IPs) are in the range from 5.09 eV to 5.45 eV, higher for derivatives with carbazole donors as compared to phenoxazine ones. The measured electron affinities (EAs) are in the range from −2.53 eV to −2.64 eV with the exception of the quinacridone derivative showing EA of −3.03 eV. Their vacuum-deposited films emit radiation in a wide spectral range from sky-blue to red. Compounds with carbazole moieties (compounds 1, 2 and 6 in the subsequent text) showed prompt fluorescence and aggregation-caused quenching. Photoluminescent quantum yields (PLQYs) of their toluene solutions reached values up to 69%. Compounds containing phenoxazine moieties (compounds marked as 3–5) demonstrated thermally activated delayed fluorescence (TADF) and aggregation-induced emission enhancement (AIEE). Their neat films showed PLQYs of 35%. Quinacridone disubstituted with carbazole (compound 6) showed the highest hole mobility reaching 2.53 × 10⁻³ cm² V⁻¹ s⁻¹ at electric field of 3.6 × 10⁵ V cm⁻¹. Carbazolyl disubstituted acridone (compound 2) and phenoxazinyl monosubstituted acridone (compound 3) turned out to be ambipolar compounds showing reasonably balanced electron and hole mobilities. The appropriate combination of redox, transport and luminescent properties makes the studied compounds suitable candidates for optoelectronic applications. Test OLEDs fabricated from 3 exhibited maximum external quantum efficiencies reaching 16.7%. Finally, an excellent agreement between the experimental results and those obtained by DFT calculations should be stressed. The basics for selection according to the user needs of either D–A, D–A–D or D–π–A–π–D types of molecular structures of TADF/AIEE luminophores are provided in this study.