Increasing Alkyl Chain Length Research Articles

Tuning Sensing Efficacy of Oligo(phenylenevinylene) Based Chromogenic Probes: Effect of Alkyl Substituents on Metal Ion Detection at Micelle-Water Interface.

In this work, we conducted a comparative analysis of the metal ion sensing capabilities of two pyridine-end oligo p-phenylenevinylene compounds featuring different alkyl substituents (-C4H9 and -C16H33) within a micelle medium. Our findings revealed a correlation between the positioning of the probe molecules within the micelle and the length of the alkyl chains, impacting their self-assembly tendencies and optical characteristics. The compound with shorter alkyl chains demonstrated a superior affinity towards Hg2+ ions, whereas exposure to the compound with longer alkyl substituent resulted in a color-changing response with both Cu2+and Hg2+ ions. Intriguingly, the sensitivity towards Hg2+ ions heightened with increasing alkyl chain length. This trend persisted in non-polar solvents like THF. The capacity to modulate sensing efficacy solely by adjusting the length of the alkyl chains represents a relatively uncommon occurrence in the existing literature. This discovery suggests promising prospects for engineering sensory devices equipped with adaptable sensitivity.

Evolution of Surface Tension and Hansen Parameters of a Homologous Series of Imidazolium-Based Ionic Liquids.

In this study, we systematically analyze the surface tension and Hansen solubility parameters (HSPs) of imidazolium-based ionic liquids (ILs) with different anions ([NTf2]-, [PF6]-, [I]-, and [Br]-). These anions are combined with the classical 1-alkyl-3-methyl-substituted imidazolium cations ([CnC1Im]+) and a group of oligoether-functionalized imidazolium cations ([(mPEGn)2Im]+) based on methylated polyethylene glycol (mPEGn). In detail, the influences of the length of the alkyl- and the mPEGn-chain, the anion size, and the water content are investigated experimentally. For [CnC1Im]+-based ILs, the surface tension decreases with increasing alkyl chain length in all cases, but the magnitude of this decrease depends on the size of the anion ([NTf2]- < [PF6]- < [Br]- ≤ [I]-). Molecular dynamics (MD) simulations on [CnC1Im]+-based ILs indicate that these differences are caused by the interplay of charged and uncharged domains, in particular in the different anions, which affects the ability of the alkyl chains of the cation to orient toward the liquid-gas interface. An increase in the mPEGn-chain length of the [(mPEGn)2Im][A] ILs does not significantly influence the surface tension. These changes upon variation of the cation/anion combination do not correlate with the evolution of the HSPs for the two sets of ILs. Finally, our data suggest that significant water contents up to water mole fractions of x(H2O) = 0.25 do not significantly affect the surface tension of the studied binary IL-water mixtures.

Effect of Alkyl Chain Length on the Corrosion Inhibition Performance of Imidazolium-Based Ionic Liquids for Carbon Steel in 1 M HCl Solution: Experimental Evaluation and Theoretical Analysis.

In this study, five kinds of 1-alkyl-3-methylimidazolium bromide ([CXami]Br) ionic liquids with different alkyl chain lengths (8, 10, 12, 14, and 16) were selected as inhibitors. Then, their corrosion inhibition performances for Q235 steel in 1.0 mol L-1 HCl solution were investigated via a weight loss test, polarization curve method, and surface analysis techniques. The results show that these five imidazolium-based ionic liquids are all mixed-type inhibitors, and they can be spontaneously adsorbed onto the Q235 steel surface. The adsorption process follows the Langmuir model and involves mixed physical-chemical adsorption. Theoretical calculations confirm that the increase in alkyl chain length is conducive to the imidazolium-based ionic liquids exhibiting stronger chemical bonding abilities and forming denser adsorption films. The inhibition efficiency significantly increases below the critical micelle concentration (CMC) with an increase in alkyl chain length, and the highest inhibition efficiency is 95.17% for the [C16ami]Br inhibitor at the concentration of 0.005 mM. However, above the CMC, the inhibition efficiency is minimally affected by the alkyl chain length since all ionic liquid inhibitors have reached adsorption saturation on the steel surface.

Reversing the Trend: Deciphering Self-Assembly of Unconventional Amphiphiles having both Alkyl-chain and PEG.

In the field of molecular self-assembly, the core of an assembly is always made up of hydrophobic moiety like a long alkyl chain, whereas the outer part has always been a hydrophilic moiety such as poly(ethylene glycol) (PEG), or charged species. Hence, reversing the trend to manifest self-assembled structures with a PEG core and a surface consisting of alkyl chains in aqueous system is incredibly challenging. Herein, we architected a unique class of cationic bolaamphiphiles containing low molecular weight PEG and alkyl chains of different lengths. The bolaamphiphiles spontaneously form vesicles without external stimuli. These vesicles are unprecedented because PEG makes up the vesicle core, while the alkyl chains appear on the vesicles' exterior. Hence, this is the first report on an assembly that reverses the usual trend. The vesicle size increases with the increase in alkyl chain-length. To our great surprise, we obtained large micelles for longest alkyl-chain amphiphile, which in turn act as a gemini amphiphile. The shift from a particular bolaamphiphile to gemini amphiphile with the variation of alkyl chain is also unexplored. Therefore, this specific class of self-assembled structure would compound a new paradigm in the fields of molecular self-assembly and supramolecular chemistry.

Structural Analysis of Aggregates Formed by Linear- and Star-type Quaternary Ammonium Salt-Based Trimeric Surfactants Using Rheology and Small-Angle X-ray Scattering.

We performed a structural analysis of aggregates formed by two types of trimeric surfactants based on quaternary ammonium salts─linear-type 3Cnlin-s-Q and star-type 3Cntris-s-Q─featuring varying alkyl chain lengths (n) and spacer chain lengths (s) in aqueous solutions. We performed rheology, dynamic light scattering, and small-angle X-ray scattering measurements on the trimeric surfactants and investigated the effects of the alkyl chain length, spacer chain length, spacer skeleton structure, and surfactant concentration on their aggregation behavior. Linear-type 3C12lin-3-Q transitioned from gel solutions to worm-like micelles at high concentrations, and 3C14lin-3-Q became gel solutions over a wide range of concentrations. In contrast, all other studied surfactants formed ellipsoidal micelles. The minor and major axes of the ellipsoidal micelles formed by liner-type 3Cnlin-3-Q increased with the increasing alkyl chain length. As the spacer chain length of 3Cnlin-s-Q increased from 3 to 6, and as the spacer skeleton expanded from linear-type 3Cnlin-s-Q to star-type 3Cntris-s-Q, the surfactants formed ellipsoidal micelles without the formation of aggregates with a high-order structure, demonstrating this behavior over a broad concentration range.

Simulation of adsorption behavior for various functionalized graphene nanosheets containing alkyl chain/polymer nanocomposites using ReaxFF

The non-covalent interactions in polymer/functionalized graphene nanosheet (FGN) nanocomposites containing the alkyl chain were investigated in this study. For this purpose, the non-covalent interactions at the interfaces of the mentioned polymer nanocomposites were accurately assessed using reactive molecular dynamics (RMD) simulation. The considered structures included poly(3-(4-n-octyl)-phenylthiophene) (POPT) and poly(3-phenylhydrazone thiophene) (PPHT) with FGNs featuring primary amine (PA), secondary amine (SA), alkanolamine (AA), and diamine (D) functional groups in alkyl chain. The functional groups varied in alkyl chain lengths via n (n equal to carbon atoms). Results from RMD simulations highlighted that the minimum interaction energy occurred between polymers and G-SA 1 %. PPHT exhibited strong interactions with G-D-4 1 % and G-PA-16 1 %. Contrary to other FGN, especially G-PA 1 %, increasing alkyl chain length in G-SA 1 % negatively affected polymers/G-SA 1 % interaction energy. Moreover, Hydrogen bonding (H-bonding) was examined in all different nanocomposites of PPHT/FGN. Also, the effect of an increase in coverage percentage and temperature was evaluated. These findings offer valuable insights into interactions of polymer-FGN with different alkyl chain lengths, aiding in the design of tailored nanocomposites.

Short-chain fatty acids of various lengths differentially inhibit Klebsiella pneumoniae and Enterobacteriaceae species.

The gut microbiota is inextricably linked to human health and disease. It can confer colonization resistance against invading pathogens either through niche occupation and nutrient competition or via its secreted metabolites. Short-chain fatty acids (SCFA) are the primary metabolites in the gut as a result of dietary fiber fermentation by the gut microbiota. In this work, we demonstrate that the interaction of single-species gut commensals on solid media is insufficient for pathogen inhibition, but supernatants from monocultures of these commensal bacteria enriched in acetate confer inhibition against anaerobic growth of the enteric pathogen Klebsiella pneumoniae. The three primary SCFAs (acetate, propionate, and butyrate) strongly inhibit the intestinal commensal Escherichia coli Nissle as well as a panel of enteric pathogens besides K. pneumoniae at physiological pH of the cecum and ascending colon. This inhibition was significantly milder on anaerobic gut commensals Bacteroides thetaiotaomicron and Bifidobacterium adolescentis previously demonstrated to be associated with microbiota recovery after antibiotic-induced dysbiosis. We describe a general suppression of bacterial membrane potential by these SCFAs at physiological cecum and ascending colonic pH. Furthermore, the strength of bacterial inhibition increases with increasing alkyl chain length. Overall, the insights gained in this study shed light on the potential therapeutic use of SCFAs for conferring colonization resistance against invading pathogens in a dysbiotic gut.IMPORTANCERising antimicrobial resistance has made treatment of bacterial infections increasingly difficult. According to the World Health Organization, it has become a burgeoning threat to hospital and public health systems worldwide. This threat is largely attributed to the global rise of carbapenem-resistant Enterobacteriaceae in recent years, with common hospital-acquired pathogens growing increasingly resistant to last-line antibiotics. Antibiotics disrupt the homeostatic balance of the gut microbiota, resulting in the loss of colonization resistance against enteric pathogens. This work describes the ability of short-chain fatty acids (SCFAs) produced by gut microbiota to be effective against a wide panel of enteric pathogens without major impact on common gut commensal species. We also demonstrate a previously undescribed link between alkyl chain length and antibacterial effects of SCFAs. SCFAs, thus, hold promise as an alternative therapeutic option leveraging on the antimicrobial activity of these endogenously produced gut metabolites without disrupting gut microbiota homeostasis.

Role of Alkyl Chain Length in Surfactant-Induced Precipitation of Reactive Brilliant Blue KN-R

To develop a cost-effective method for the effective removal of reactive brilliant blue KN-R (RBB KN-R) from wastewater, we investigated the interactions between RBB KN-R and three cationic surfactants with different alkyl chain lengths, namely dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyltrimethylammonium bromide (CTAB). Employing a conductivity analysis, surface tension analysis, ultraviolet-visible spectrophotometry, and molecular dynamics simulation, we ascertained that RBB KN-R formed a 1:1 molar ratio dye–surfactant complex with each surfactant through electrostatic attraction. Notably, an augmentation in alkyl chain length correlated with increased binding strength between RBB KN-R and the surfactant. The resulting dye–surfactant complex exhibited heightened surface activity, enabling interactions through hydrophobic forces to generate dye–surfactant aggregates when the molar ratio was below 1:1. Within these mixed aggregates, self-assembly of RBB KN-R molecules occurred, leading to the formation of dye aggregates. Due to the improved hydrophobicity with increased alkyl chain length, TTAB and CTAB could encapsulate dye aggregates within the mixed aggregates, but DTAB could not. The RBB KN-R aggregates tended to distribute on the surface of the RBB KN-R-DTAB mixed aggregates, resulting in low stability. Thus, at a DTAB concentration lower than CMC, insoluble particles readily formed and separated from surfactant aggregates at an RBB KN-R and DTAB molar ratio of 1:4. Analyzing the RBB KN-R precipitate through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) and measuring the DTAB concentration in the supernate revealed that, at this molar ratio, all RBB KN-R precipitated from the dye–surfactant mixed solution, with only 7.5 ± 0.5% of DTAB present in the precipitate. Furthermore, the removal ratio of RBB KN-R reached nearly 100% within a pH range of 1.0 to 9.0 and standing time of 6 h. The salt type and concentration did not significantly affect the precipitation process. Therefore, this simultaneous achievement of successful RBB KN-R removal and effective separation from DTAB underscores the efficacy of the proposed approach.

Computational insight into the effect of alkyl chain length in tetraalkylammonium-based deep eutectic solvents

The effect of the increase in the alkyl chain length of cation on the properties of deep eutectic solvents based on ethylene glycol has been investigated employing classical molecular dynamics simulations. The change in the structural and dynamic properties in both the bulk and liquid–vapor interface is explored through various analyses. The interaction between the anion and the ethylene glycol increases with an increase in the alkyl chain length of the cation, as observed in the increase of the lifetime of the hydrogen bond formed between the two. The terminal carbon atoms are found to be closer to each other when the cation changes from tetraethylammonium to tetrabutylammonium. The cations are located closer to the interface, and the association of the alkyl chains becomes more significant with increased alkyl chain length, decreasing the surface tension values.

Synthesis of Boron-Containing Nucleoside Analogs.

Over the last century, nucleoside-based therapeutics have demonstrated remarkable effectiveness in the treatment of a wide variety of diseases from cancer to HIV. In addition, boron-containing drugs have recently emerged as an exciting and fruitful avenue for medicinal therapies. However, borononucleosides have largely been unexplored in the context of medicinal applications. Herein, we report the synthesis, isolation, and characterization of two novel boron-containing nucleoside compound libraries which may find utility as therapeutic agents. Our synthetic strategy employs efficient one-step substitution reactions between a diverse variety of nucleoside scaffolds and an assortment of n-alkyl potassium trifluoroborate-containing electrophiles. We demonstrated that these alkylation reactions are compatible with cyclic and acyclic nucleoside substrates, as well as increasing alkyl chain lengths. Furthermore, regioselective control of product formation can be readily achieved through manipulation of base identity and reaction temperature conditions.

Unveiling the role of linear alkyl organic cations in 2D layered tin halide perovskite field-effect transistors.

Two-dimensional (2D) tin halide perovskites are promising semiconductors for field-effect transistors (FETs) owing to their fascinating electronic properties. However, the correlation between the chemical nature of organic cations and charge carrier transport is still far from understanding. In this study, the influence of chain length of linear alkyl ammonium cations on film morphology, crystallinity, and charge transport in 2D tin halide perovskites is investigated. The carbon chain lengths of the organic spacers vary from propylammonium to heptanammonium. The increase of alkyl chain length leads to enhanced local charge carrier transport in the perovskite film with mobilities of up to 8 cm2 V-1 s-1, as confirmed by optical-pump terahertz spectroscopy. A similar improved macroscopic charge transport is also observed in FETs, only to the chain length of HA, due to the synergistic enhancement of film morphology and molecular organization. While the mobility increases with the temperature rise from 100 K to 200 K due to the thermally activated transport mechanism, the device performance decreases in the temperature range of 200 K to 295 K because of ion migration. These results provide guidelines on rational design principles of organic spacer cations for 2D tin halide perovskites and contribute to other optoelectronic applications.

Alkyl chain length influence of the functionalized diethanolamine ligand on the slow relaxation of the magnetization in {CoIII3DyIII3} complexes.

We report the synthesis, structural characterization and magnetic properties of a series of Co(III)/Dy(III) complexes built up from an N-alkyl derivatized amino-alcohol ligand diethanolamine, functionalized with CnH2n+1 alkyl chains (n = 3, 4, 6, 8 and 10). While n = 3 afforded a butterfly {CoIII2DyIII2} core, the other alkyl chains (n = 4, 6, 8) afforded hexanuclear triangle-in-triangle {CoIII3DyIII3} complexes as shown by single-crystal X-ray determinations. Infrared spectroscopy allows us to characterize the C10 derivative complex, which did not crystallize. Magnetic ac susceptibility data collected below 10 K at driving frequencies up to 10 kHz under zero-dc field and up to 1 T provide insight into the SMM behaviour of the studied complexes. The characteristic time of the magnetization dynamics can be understood in terms of the competing Raman, Direct and Orbach-like mechanisms. A relationship between the magnetization dynamics within the family of complexes and the increasing alkyl chain length is discussed.

Symmetry versus asymmetry game in vaporization enthalpies of imidazolium-based ionic liquids

The vaporization enthalpy as a function of alkyl chain length was studied using both experimental techniques and molecular dynamics simulations for imidazolium based ionic liquids (ILs) with symmetric and asymmetric imidazolium substitution. It was found that the vaporization enthalpy increases with increasing alkyl chain length due to the increased van der Waals (vdW) interaction. In addition, the vaporization enthalpies of the symmetric ILs ([CnCnIm][X], X = NTf2-, Cl-, Br-, I-) series were found to be systematically lower (by 5–10 kJ mol−1) in comparison with the corresponding asymmetric imidazolium-based ILs ([CmC1Im][X]). This energetic difference was attributed to the intramolecular dispersion interactions between the two alkyl side chains existing in the symmetric cation series.

Regulation of Hydrophobic Structures of Antibacterial Guanidinium-Based Amphiphilic Polymers for Subcutaneous Implant Applications.

Antimicrobial peptide mimics have been used to kill bacteria and construct antibacterial materials. Precise design and construction of chemical structure are essential for easy access to highly effective antimicrobial peptide mimics. Herein, cationic guanidinium-based polymers (PGXs) with varying hydrophobic structures were synthesized to explore the structure and antibacterial activity relationship of antimicrobial peptide mimics and to construct antibacterial implants. The effect of the hydrophobic chemical structure, including carbon chain length and configuration, on the antimicrobial activities against both Escherichia coli and Staphylococcus aureus was investigated. The antibacterial activities of PGXs improved with increasing alkyl chain length, and PGXs with a straight-chain hydrophobic structure exhibited better bactericidal activities than those with cyclic alkane and aromatic hydrocarbon. Furthermore, PGXs grafted with poly(dimethylsiloxane) (PDMS-PGXs) showed a similar bactericidal change tendency of PGXs in solution. Additionally, the PDMS-PGXs showed potent antibiofilm performance in vitro, which can inhibit bacterial infection in vivo as subcutaneous implants. This study may propose a basis for the precise design and construction of antibacterial materials and provide a promising way of designing biomedical devices and implants with bacterial infection-combating activities.

Efficient and selective adsorption of TcO4−/ReO4− by n-alkyl-imidazolium ionic liquids functionalized cellulose microspheres and their application in simulated Beishan groundwater

Removal of technetium from radioactive waste has become attractive due to its huge environmental hazard. Herein, a series of n-alkyl-imidazolium ionic liquids functionalized cellulose microspheres (MCC-[CnVIm]Br, n = 2, 4, 6, 8, 10) were synthesized by radiation method, and their grafting regularity were investigated. In order to explore the effect of alkyl chain length on adsorption performance, the adsorption behaviors of MCC-[CnVIm]Br for TcO4−/ ReO4− were researched in detail via batch and column experiments. MCC-[CnVIm]Br exhibited high ReO4− adsorption efficiency over a wide pH range from 4 to 9, and the maximum adsorption capacity was 230.41 mg/g. The adsorption efficiency of MCC-[CnVIm]Br barely changed after 5 times reused. Remarkably, the selectivity of ReO4− enhanced with the increase of alkyl chain length, while the adsorption capacity and rate were hardly affected by it. The column experiment showed that MCC-[C10VIm]Br can selectively capture ReO4− from simulated Beishan groundwater. The adsorption performance suggested that MCC-[C10VIm]Br is promising for high-efficiency uptake of ReO4− from Beishan groundwater and other radioactive wastes.

Role of conformational entropy in low melting point of ionic liquids: a molecular dynamics simulation study

Abstract Ionic liquids (ILs) are liquid salts which have very low melting points among the salts. To understand the contribution of conformational entropy (Sconf) to the low melting points of ILs, molecular dynamics (MD) simulations of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([Cnmim][NTf2] where n = 2, 4, 6, 8, and 10) were performed in liquid and gas states. The increase in Sconf with increasing alkyl chain length corresponded to an increase in fusion entropy (ΔfusS), suggesting that the other entropic contributions such as kinetic and configurational entropies depend negligibly on the alkyl chain length. Comparing the same cation, Sconf in the liquid state with a long alkyl chain was slightly smaller than that in the gas state because the trans conformers of the cation were favored in the liquid state. The trans conformers of the cations in the liquid state were stabilized by the van der Waals and Coulomb interactions. Meanwhile, populations of the trans conformer for the anion in the gas and liquid state were almost the same.

Re-evaluation of solution enthalpies of aliphatic hydrocarbons functional derivatives and terpenes in n-heptane and their validation by thermochemical consistency

The aim of this study was to investigate the influence of the position of the functional group and the choice of solvent on the relationships between the enthalpies of solution and the alkyl chain length of aliphatic hydrocarbons functional derivatives. The results show that the selection of an appropriate solvent for functional derivatives, such as methanol for alcohols and acetonitrile for alkyl nitriles, is not a viable option because the enthalpies of solution increase non-linearly with increasing alkyl chain length, leading to significant errors in the prediction of enthalpies of solution.On the other hand, the enthalpies of solution of aliphatic hydrocarbons functional derivatives in n-heptane decrease non-linearly with increasing number of methylene fragments in the chain. In this work, complementary measurements of the enthalpies of solution of homologous series of dialkyl ethers, alkyl-amines and nitroalkanes in n-heptane were carried out. These new data were used to develop an approach to estimate the enthalpies of solution of dialkyl ethers, alkyl-nitriles and alkyl-amines in n-heptane. The absolute deviations between predicted and experimental solution enthalpies for most of the investigated compounds do not exceed 0.5 kJ mol−1. The proposed approach to predict the solution enthalpies of aliphatic hydrocarbon derivatives in n-heptane was applied to estimate the enthalpies of fusion of 11 aliphatic hydrocarbon derivatives, which agreed well with the values obtained by differential scanning calorimetry. Complementary vapour pressure measurements were carried out on cyclic aliphatic hydrocarbons from the terpene family using a transpiration method to derive their enthalpies of vaporisation. The latter were used for independent validation of the re-evaluated solution enthalpies.

Molecular design and experimental study on the alkylation of benzene with C6 olefin dimer with Lewis acidic monoamine ionic liquids and its sulfonate surfactant properties

Long-chain alkyl benzene (LAB), conventionally manufactured by petrochemical routes, is an important intermediate for the synthesis of high-value chemicals, especially detergents and oil displacement agents. The preparation of LAB from coal-based olefins has attracted extensive research interest. In this work, the alkylation activity of four Lewis acidic monoamine chloroaluminate ionic liquids (LAMCILs), designed by AlCl3 and monoamine hydrochloride with alkyl chains of different lengths, was predicted by quantum chemical calculations using the synthesis of 1-methyl-1-butylheptylbenzene (MBHB) with benzene and C6 olefin dimer as a model reaction. The HOMO*-LUMO* gap indicated that the alkylation activity was enhanced with increasing alkyl chain length of the organic amine molecules in the LAMCILs, in the following order: [n-C6H13NH3]Cl-AlCl3 > [n-C4H9NH3]Cl-AlCl3 > [n-C3H7NH3]Cl-AlCl3 > [C2H5NH3]Cl-AlCl3. These four LAMCILs were successfully synthesized and used to catalyze the alkylation of benzene with the C6 olefin dimer. The experimental results are consistent with the calculated results. The UV/VIS characterization showed that their Hammett acidity function (H0) increased as the alkyl chain of organic monoamine molecules in the LAMCILs extended. Therefore, a two-way correlation between the HOMO*-LUMO* gap, MBHB yield and Hammett acidity function can be established. Furthermore, the effect on the yield of MBHB was investigated by the method of metal chloride modified [n-C4H9NH3]Cl-AlCl3 ionic liquids. The results showed that the CuCl2-modified [n-C4H9NH3]Cl-AlCl3 ionic liquid had better catalytic activity in this study. Under optimal reaction conditions, the conversion of the C6 olefin dimer and selectivity toward MBHB reached 100 % and 91.34 %, respectively. Finally, the surfactant properties of sodium 1-methyl-1-butylheptylbenzene sulfonate (SMBHBS) were examined, and the results indicated that its surfactant properties were basically comparable to those of commercial LAS.

Side-chain engineering of benzotriazole-based polymers as hole transport material enables high-efficiency CsPbI2Br single-junction and tandem perovskite solar cells

Rational design and synthesis of high-performance doping-free hole transport polymers is critical to achieve high-efficiency and stable perovskite solar cells (PSCs). Side chain engineering is a widely employed strategy for modulating the photoelectronic properties of polymers. In this study, based on dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophenes (DTBDT) as D unit, benzo[d][1,2,3]triazole (BTA) as A segment, and thiophene as a π bridge, three D-π-A type polymeric materials with different length of alkyl side chain (PE51, PE52, and PE53) were utilized as hole transport materials in CsPbI2Br-based PSCs and perovskite/organic tandem solar cells (TSCs). With the increase of alkyl chain length from 2-butyloctyl (PE51) to 2-hexyldecyl (PE52) and to 2-octyldodecyl (PE53), the highest occupied molecular orbital energy level of the polymer gradually decreases, and the molecular stacking of the material gradually shifts from edge-on stacking to face-on stacking. Moreover, among three polymers, the PE53 exhibits the most efficient hole extraction at the CsPbI2Br/hole transport layer (HTL) interface. Hence, the CsPbI2Br-based PSCs and perovskite/organic TSCs employing PE53 as HTL realize the highest power conversion efficiency (PCE) of 17.65% and 23.07%, respectively. Our results indicate that side chain engineering of HTM is an effective strategy to modulate their molecular orientation and improve the photovoltaic performance of PSCs.

Ion Mobility in Hydroxy-Functionalized Ionic Liquids Depends on Cationic Clustering: Tracking the Alkyl Chain Length Behavior with Deuteron NMR Relaxation.

Observing and quantifying the like-charge attraction in liquids and solutions is still challenging. However, we showed that elusive cation-cation hydrogen bonding may govern the structure and interaction in hydroxyl-functionalized ionic liquids. Therefore, cationic cluster formation depends on the shape, charge distribution, and functionality of the ions. We demonstrated by means of solid-state 2H NMR spectroscopy that cationic clusters change the structure and dynamics of ionic liquids. With increasing alkyl chain length, we observed two deuteron quadrupole coupling constants for the OD groups, differing by about 30 kHz. The lower value was assigned to the cation-cation interaction, indicating that the average (c-c) hydrogen bonds are stronger than the (c-a) hydrogen bonds between the cation and the anion despite the repulsive and attractive Coulomb interaction in the first and latter cases. Ion mobility could be studied by 2H NMR spectroscopy, although the deuterons in the hydrogen-bonded clusters underwent fast exchange. Our results also showed that simple relaxation models are not applicable anymore and that anisotropic motion must be considered.