Abstract:A new DπAπD compound consisting of naphthalene diimide core-functionalized with 1,4-phenylene-functionalized carbazole, namely 2,6-bis[4-(9H-carbazol-9-yl)phenyl]-N,N’-bis(2-ethylhexyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (CNDI) was synthesized. Its redox properties (reduction and oxidation potentials, electron affinities (EA) and ionization potentials (IP)) were compared with those of 4,7-bis(4-(9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD) – a specially synthesized reference compound containing identical Dπ- units and significantly weaker acceptor (benzothiadiazole). It was demonstrated that the acceptor strength, determined as the index of the spatial extent of the charge transfer, D_CT^P, only weakly influenced the molecule oxidation potential and by consequence its ionization potential. To the contrary, strong effect of charge transfer, expressed by D_CT^P, was found for the reduction potential of CNDI and CBTD, showing significantly higher reduction potential of the former leading to much higher |EA|. CNDI could be electrochemically polymerized yielding a low band gap polymer (E_g = 1.63 eV) of ambipolar character, exhibiting low ionization potential (IP = 5.48 eV) and high electron affinity (|EA| = 3.85 eV). In its cyclic voltammograms polyCNDI shows five redox states, namely neutral, first and second reduction and first and second oxidation ones. As revealed by detailed studies of electrochromic parameters only three redox states (neutral, first reduction and first oxidation) demonstrate good electrochromic performance. © 2020

Abstract: A semiconducting molecule containing a thiol anchor group, namely 2-(5-mercaptothien-2-yl)-8-(thien-2-yl)-5-hexylthieno[3,4-c]pyrrole-4,6-dione (abbreviated as D-A-D-SH), was designed, synthesized, and used as a ligand in nonstoichiometric quaternary nanocrystals of composition Ag1.0In3.1Zn1.0S4.0(S6.1) to give an inorganic/organic hybrid. Detailed NMR studies indicate that D-A-D-SH ligands are present in two coordination spheres in the organic part of the hybrid: (i) inner in which the ligand molecules form direct bonds with the nanocrystal surface and (ii) outer in which the ligand molecules do not form direct bonds with the inorganic core. Exchange of the initial ligands (stearic acid and 1-aminooctadecane) for D-A-D-SH induces a distinct change of the photoluminescence. Efficient red luminescence of nanocrystals capped with initial ligands (λmax = 720 nm, quantum yield = 67%) is totally quenched and green luminescence characteristic of the ligand appears (λmax = 508 nm, quantum yield = 10%). This change of the photoluminescence mechanism can be clarified by a combination of electrochemical and spectroscopic investigations. It can be demonstrated by cyclic voltammetry that new states appear in the hybrid as a consequence of D-A-D-SH binding to the nanocrystals surface. These states are located below the nanocrystal LUMO and above its HOMO, respectively. They are concurrent to deeper donor and acceptor states governing the red luminescence. As a result, energy transfer from the nanocrystal HOMO and LUMO levels to the ligand states takes place, leading to effective quenching of the red luminescence and appearance of the green one. © 2020 American Chemical Society.

Abstract:Three D-π-Α-π-D organic luminophores of tunable donor-acceptor interactions were synthesized by combining carbazole D-units with two different A units, namely 2,5-dithiophen-2-yl-[1,3,4]-thiadiazole and benzo[c][1,2,5]thiadiazole. In the third compound tert-butyl groups were introduced to the carbazole ring to increase its electron-donating properties. This compound, namely 4,7-bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD2) turned out to be a very good photoluminophore showing the photoluminescence quantum yield (φ) of 62% in toluene solution and 45% when dispersed in a solid blend consisting of poly(vinylcarbazole) (PVK) and 2-([1,1′-biphenyl]-4-yl)-5-(4′-(tert-butyl)-[1,1′-phenyl]-4-yl)-1,3,4-oxadiazole (PBD). Moreover, its electrochemically determined ionization potential (IP = 5.55 eV) and electron affinity (EA = −2.73 eV) made it a very promising candidate for application as an active component in light emitting diodes of guest/host configuration with PVK-PBD matrix. The fabricated diodes of the following structure ITO/PEDOT:PSS/PVK-PBD + CBTD2/Ca/Ag showed the luminance reaching 6000 cd/m² with luminous efficiency of 1 cd/A. © 2020 Elsevier B.V.

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. This journal is © The Royal Society of Chemistry.

Abstract: Self-organization in mono- and bilayers on HOPG of two groups of benz[5,6]acridino[2,1,9,8-klmna]acridine derivatives, namely, 8,16-dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines with an increasing alkoxy substituent length and 8,16-bis(3- or 4- or 5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines, i.e., three positional isomers of the same benzoacridine, is investigated by scanning tunneling microscopy. The layers were deposited from a solution of the adsorbate (in hexane or dichloromethane) and imaged ex situ at molecular resolution. In all cases, the resulting two-dimensional (2D) supramolecular organization is governed by the interactions between large, fused heteroaromatic cores that form densely packed rows separated by areas covered by substituents. In 8,16-dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines, the alkoxy substituents, separating the rows of densely packed cores, are interdigitated. An increasing substituent length leads to an intuitively expected increase in this 2D unit cell parameter that corresponds to the orientation of the substituent in the monolayer. In the case of 8,16-bis(3- or 4- or 5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine positional isomers, the self-assembly processes are more complex. Although the determined 2D unit cell is in all cases essentially the same, the role of alkylthienylene substituents in layer formation is distinctly different. Thus, the formation of monolayers and bilayers is very sensitive to isomerism. 8,16-Bis(5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine is capable of forming the most stable monolayer and the most labile bilayer. In the case of 8,16-bis(3-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine, an inverse phenomenon is observed leading to the most labile monolayer and the most stable bilayer. These differences are rationalized in terms of dissimilar molecular geometries of the studied isomers and different interdigitation patterns in their 2D supramolecular structures. Copyright © 2020 American Chemical Society.

Abstract:  Three new donor-acceptor (D-A) compounds, positional isomers of phenoxazine-substituted acridone, namely 1-phenoxazine-N-hexylacridone ( o-A ), 2-phenoxazine-N-hexylacridone ( m-A ) and 3-phenoxazine-N-hexylacridone ( p-A ), were synthesized. The synthesized compounds showed interesting, isomerism-dependent electrochemistry. Their oxidation was reversible and their potential (givenvs.Fc/Fc⁺) changed from 0.21 V for o-A to 0.36 V for p-A . In contrast, their reduction was irreversible, isomerism-independent and occurred at rather low potentials (ca.−2.25 to −2.28 V). The electrochemical results led to the following values of the ionization potentials (IPs) and electron affinities (EAs): 5.03 eV and −2.14 eV, 5.15 eV and −2.20 eV, and 5.20 eV and −2.28 eV for o-A m-A and p-A , respectively. The experimentally obtained values were in very good agreement with those predicted by DFT calculations. All three isomers readily formed single crystals suitable for their structure determination. o-A and p-A crystallized inP1̄ andP2₁/nspace groups, respectively, with one molecule per asymmetric unit, while m-A crystallized in theP2₁/cspace group with two molecules in the asymmetric unit accompanied by disordered solvent molecules. The UV-vis spectra of the studied compounds were isomerism and solvent independent, yielding absorption maxima in the vicinity of 400 nm. Their photoluminescence spectra, in turn, strongly depended on isomerism and the used solvent showing smaller Stokes shifts for the emission bands registered in toluene as compared to the corresponding bands measured in dichloromethane. The photoluminescence quantum yields (ϕ) were systematically higher for toluene solutions reaching the highest value of 20% for p-A . For all three isomers studied, stationary and time-resolved spectroscopic investigations carried out in toluene at different temperatures revealed spectral features indicating a contribution of thermally activated delayed fluorescence (TADF) to the observed spectroscopic behaviour. The measured photoluminescence quantum yields (ϕ) were higher for solid state films of pure compounds and for their dispersions in solid matrices (zeonex) than those recorded for toluene and dichloromethane solutions of the studied phenoxazine-N-hexylacridone isomers. The obtained experimental spectroscopic and structural data were confronted with theoretical predictions based on DFT calculations. © the Owner Societies 2020.

Abstract:  1,3,4-Thiadiazole, 2,2′-bi(1,3,4-thiadiazole), 2,2′:5′,2″-ter(1,3,4-thiadiazole), and 2,2′:5′,2″:5″,2′-quater(1,3,4-thiadiazole) symmetrically disubstituted with 3-alkyl-(2,2′-bithiophen)-5-yl were synthesized by new procedures using readily available ethyl 3-alkyl-(2,2′-bithiophene)-5-carboxylate as a convenient substrate. These new compounds with a fixed number of donor rings and increasing number of acceptor rings showed very interesting, tunable redox properties. In particular, they exhibited electron affinities (EAs) ranging from -3.06 to -3.83 eV, reaching EA values desired for air-operating n-type organic semiconductors. Their electrochemically determined ionization potentials were only moderately dependent on the number of thiadiazole rings, varying from 5.83 to 6.01 eV. Emission spectra of these compounds could also be tuned in a wide range (from 470 to 600 nm). Spectroscopic and electrochemical data were confirmed by density functional theory calculations demonstrating full consistency. © 2019 American Chemical Society.

Abstract:  Quantum dots (QDs) are attractive semiconductor fluorescent nanomaterials with remarkable optical and electrical properties. The broad absorption spectra and high stability of QD transducers are advantageous for sensing and bioimaging. Molecular imprinting is a technique for manufacturing synthetic polymeric materials with a high recognition ability towards a target analyte. The high selectivity of the molecularly imprinted polymers (MIPs) is a result of the fabrication process based on the template-tailored polymerization of functional monomers. The three-dimensional cavities formed in the polymer network can serve as the recognition elements of sensors because of their specificity and stability. Appending specific molecularly imprinted layers to QDs is a promising strategy to enhance the stability, sensitivity, and selective fluorescence response of the resulting sensors. By merging the benefits of MIPs and QDs, inventive optical sensors are constructed. In this review, the recent synthetic strategies used for the fabrication of QD nanocrystals emphasizing various approaches to effective functionalization in aqueous environments are discussed followed by a detailed presentation of current advances in QD conjugated MIPs (MIP-QDs). Frontiers in manufacturing of specific imprinted layers of these nanomaterials are presented and factors affecting the specific behaviour of an MIP shell are identified. Finally, current limitations of MIP-QDs are defined and prospects are outlined to amplify the capability of MIP-QDs in future sensing. © 2019 The Royal Society of Chemistry.

Abstract:  Colloidal semiconductor nanocrystals consist of an inorganic core determining their physical properties and a shell of organic ligands that induce their colloidal stability in a wide range of solvents, both nonpolar and polar. They are considered as extremely promising nanomaterials for modern electronics. The band gaps of these nanocrystalline semiconductors can be conveniently tuned by their composition, type of crystal structure, and size (via quantum confinement), yielding nanomaterials whose physical and photophysical properties are unmatched by conventional materials. In the first part of the chapter, binary chalcogenide-type nanocrystals are described (CdS, CdSe, and CdTe) with special emphasis on their synthesis, photoluminescence quantum yield (PLQY) improvement through the preparation of core/shell systems, and/or alloying. The effect of organic ligands binding to the nanocrystal surface is described in detail because they not only assure the colloidal stability of these nano-objects but also influence to a certain extent their physicochemical properties. Ligand exchange procedures are discussed, which render the nanocrystals hydrophilic. The role of linker ligands is described, which assures further surface functionalization through grafting molecules (or macromolecules) of interest to the nanocrystal surface. The synthesis and functionalization of nanocrystals that do not contain toxic elements are illustrated in the subsequent part of the chapter, among them ternary Cu(Ag)-In-S(Se) and quaternary Cu(Ag)-In-Zn-S(Se), Cu-Zn-Sn-S(Se) nanocrystals, which can be considered not only as alternatives to binary nanocrystals but also significantly broaden their application spectrum. In addition to these indepth study of nanocrystals chemistry, we introduced the possible application of photopatternable nanocrystals in the microfabrication of 2D/3D functional structures. Energy and charge transfer in the semiconducting nanocrystal based organic-inorganic hybrid materials are also described. Lastly, we discussed recent development of metal halide perovskite materials and their applications in the field of optoelectronics. Recently developed low-dimensional perovskite materials are introduced with their light emitting device applications. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA.

Abstract: Two new electropolymerizable monomers were synthesized, namely dithieno[3,2-b:2′,3′-d]pyrrole N-functionalized with 4-(2-heptylthiazol-4-yl)phenyl (DTP1) and 4-(5-octylthiophen-2-yl)phenyl (DTP2) groups. Both monomers readily electropolymerize to yield the corresponding polyDTP1 and polyDTP2. Electrochemically determined ionization potential (IP) of both polymers (about 4.75 eV) are higher than IPs of poly(dithieno[3,2-b:2′,3′-d]pyrrole) N-substituted with alkyl or alkylphenyl groups. This finding, corroborated by DFT calculations, suggests that electron accepting nature of (thiazol-4-yl)phenyl and (thiophen-2-yl)phenyl substituents lowers the π-electron density in the dithienopyrrole moiety making the polymers oxidation more difficult. Optical band gaps of polyDTP1 (E_{g opt} = 1.76 eV) and polyDTP2 (E_{g opt} = 1.78 eV) are lower than the gaps of poly(dithieno[3,2-b:2′,3′-d]pyrrole) N-substituted with alkyl or alkylphenyl groups. This combined with higher IP value yield higher electron affinity (ǀEAǀ) value. Thus, the obtained new polymers are more difficult to oxidize but easier to reduce as compared to poly(dithieno[3,2-b:2′,3′-d]pyrrole)s studied to date. Again, these findings are in a very good agreement with DFT calculations. As evidenced by UV–vis–NIR spectroelectrochemistry, both polymers undergo classical (for conjugated polymers) oxidation, involving the formation of polarons in the first step and bipolarons in the second one. An interesting feature of the oxidation of polyDTP2 is the highly delocalized nature of bipolarons, indicative of the metallic state (featureless absorption tails extending towards NIR part of the spectrum). In order to elucidate the exact nature of the electrochemical oxidation process detailed Raman spectroelectrochemical investigations of polyDTP2 were carried out supported by the vibrational model calculations using two methods: DFT and General Valence Force Field (GVFF). This combined experimental and theoretical study leads to a conclusion that radical cations (polarons) formed at the first stage of oxidation are formed in the pyrrole ring whereas dications formed in the second stage show classical bipolaron configuration with positive charges located on the thiophene rings. © 2018

Abstract: Quinacridone, an industrial pigment, has recently shown a high charge carriers mobility in field-effect transistors. In search for new cheap organic semiconductors of improved vacuum processability we have synthesized three dialkyl derivatives of quinacridone, namely N,N′-dialkylquinacridones (alkyl = butyl, octyl, dodecyl), abbreviated as QA-C4, QA-C8 and QA-C12. The alkylation of quinacridone results in a significant decrease of its melting temperature which drops from 390 °C for quinacridone to 261 °C, 177 °C and 134 °C for QA-C4, QA-C8 and QA-C12, respectively, while retaining the onset of thermal decomposition above 390 °C. The elimination of the hydrogen bonding network between the carbonyl groups and amine hydrogens through alkylation not only lowers the melting temperature, but also induces supramolecular ordering in contrast to unsubstituted quinacridone. Detailed morphological and structural investigations of the vacuum deposited thin films have revealed that the length of the alkyl substituent is crucial for the molecular self-organization. Compound QA-C4 forms poorly ordered films, whereas QA-C8 and QA-C12 grow into a spherulitic dense morphology with increasing domain size at higher deposition temperatures. The more pronounced morphology is related to the lower melting point of the compounds and strong molecular diffusion during deposition. The poorly ordered films of QA-C4 do not show any field-effect response, what is consistent with previous reports. In contrast, transistors with QA-C8 or QA-C12 as active layers exhibit hole transport. Optimization of the deposition temperature, in which nucleation and crystal growth are properly balanced, resulted in OA-C8-based transistors with a hole mobility of 0.3 cm²/V, i.e. higher than in devices with unsubstituted quinacridone. © 2018 Elsevier B.V.

Abstract: The presented research is focused on the synthesis of alloyed Ag-In-Zn-S colloidal nanocrystals from a mixture of simple metal precursors such as AgNO ₃ , InCl ₃ , zinc stearate combined with 1-dodecanethiol (DDT), 1-octadecene (ODE), and sulfur dissolved in oleylamine (OLA). In particular, the focus is on the effect of the solvent (ODE vs 1,2-dichlorobenzene (DCB)) and the type of sulfur precursor (S/OLA vs S/n-octylamine (OCA)) on the metal precursors reactivates and on the chemical composition, crystal structure, and luminescent properties of the resulting nanocrystals. The replacement of ODE by DCB as a solvent lowers the reactivity of metal precursors and results in a 3-fold decrease of the photoluminescence quantum yields (Q.Y.) values (from 67% to 21%). This negative effect can be fully compensated by the use of S/OCA as a source of sulfur instead of S/OLA (Q.Y. increases from 21% to 64%). NMR studies of the isolated organic phase indicate that the S/OLA precursor generates two types of ligands being products of (Z)-1-amino-9-octadecene (OLA) hydrogenation. These are „surface bound” 1-aminooctadecane (C ₁₈ H ₃₇ NH ₂ ) and crystal bound, i.e., alkyl chain covalently bound to the nanocrystal surface via surfacial sulfur (C ₁₈ H ₃₇ -NH-S crystal). Highly luminescent Ag-In-Zn-S nanocrystals exhibit a cation-enriched (predominantly indium) surface and are stabilized by a 1-aminooctadecane ligand, which shows more flexibility than OLA. These investigations were completed by hydrophilization of nanocrystals obtained via exchange of the primary ligands for 11-mercaptoundecanoic acid, (MUA) with only a 2-fold decrease of photoluminescence Q.Y. in the most successful case (from 67% to 31%). Finally, through ligand exchange, an electroactive inorganic/organic hybrid was obtained, namely, Ag-In-Zn-S/7-octyloxyphenazine-2-thiol, in which its organic part fully retained its electrochemical activity. © 2019 American Chemical Society.

Abstract: Ternary and quaternary chalcopyrite-type nanocrystals of M^IM^IIIE₂ and M^IM^IIIZnE₂ type (M^I = Ag, Cu; M^III = In, Fe; E = S, Se) and their core/shell structures have attracted a huge interest in the past decade because they combine size- and composition-tunable optical and electronic properties without relying on toxic elements such as Cd and Pb. These materials had been primarily studied as light harvesters in solar cell applications. However, in the form of colloidal nanocrystals, they exhibit remarkable photoluminescence properties in the visible and near infrared range. At the same time, the underlying emission mechanisms are distinctly different from those occurring in binary semiconductor quantum dots. Several models have been developed to explain the origin of the observed phenomena, in particular the line width broadening, large Stokes shifts and long photoluminescence lifetimes. This review first focusses on the current understanding of the optical properties of the title compounds. Next, an overview of the main synthesis methods is given, both in organic solvents and in the aqueous phase. In the second part, the surface chemistry and ligand exchange procedures are discussed. Finally, organic/inorganic hybrids of chalcopyrite nanocrystals with electroactive molecules are presented as well as their use in photovoltaics. © 2019 The Royal Society of Chemistry.

Abstract: Alloying of CuFeS₂ and CuFeSe₂ nanocrystals leads to a new plasmonic nanomaterial in which the plasmon resonance is hypsochromically shifted by ca. 80 nm as compared to the case of CuFeS₂, i.e. from 486 nm to 408 nm. Preparation of CuFeS_2-xSe_x facilitates, in addition, the exchange of the hydrophobic ligands for hydrophilic ones, rendering the nanocrystals dispersible in nonpolar and polar (aqueous) media. © 2019 The Royal Society of Chemistry.