Triisopropylsilylethynyl Pentacene Research Articles

Role of Singlet and Triplet Excited States in the Oxygen-Mediated Photophysics and Photodegradation of Polyacenes.

Polyacenes, such as tetracene and pentacene, are common model systems for the study of photophysical phenomena such as singlet fission (SF) and triplet fusion, processes which may lead to increased photovoltaic efficiencies. While they exhibit desirable photophysical properties, these materials are not photostable and convert to unwanted endoperoxides in the presence of oxygen and light, limiting their use in real-world applications. Not only does oxygen degrade polyacenes but also it can affect their photophysics, leading to both the sensitization and quenching of different excited states. In this study, we characterize the effect of oxygen on 5,12-bis(triisopropylsilylethynyl) tetracene (TIPS-Tn) and 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) using transient absorption spectroscopy, and show that oxygen can significantly influence the population of excited states, in particular enhancing the polyacene triplet population. We additionally combine the time-resolved excited-state dynamics with photodegradation studies to determine the predominant mechanism of photooxidation, which has previously been unclear. We find that both molecules photodegrade predominantly via singlet oxygen; however, for TIPS-Tn, this occurs through the triplet state, whereas for TIPS-Pn, degradation occurs through the excited singlet. The photodegradation of TIPS-Tn is thus enhanced by faster rates of SF, whereas SF in TIPS-Pn increases the molecule's photostability. This work has implications both for the design of new materials for next-generation photovoltaics that can avoid photooxidation and for the study of their photophysics in real-world environments.

Improving Ultraviolet Stability of Perovskite Solar Cells via Singlet Fission Down‐Conversion†

Comprehensive SummaryThe instability of perovskite materials under continuous ultraviolet (UV) light irradiation and high sensitivity in humid environments remain obstacles to future commercialization. Especially, the photovoltaic performance of perovskite solar cells (PVSCs) is prone to decline under UV light exposure for sustained periods of time. However, in conventional methods, preventing UV light from entering PVSCs usually comes at the expense of reducing short circuit photocurrent (Jsc). Herein, the UV stability of PVSCs is modified by introducing a singlet fission down‐conversion layer 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐PEN) via one‐step anti‐solvent method without sacrificing device efficiency. The introduction of down conversion layer can not only improve the Jsc by converting UV light into multiple excitons, but also enhance the open‐circuit voltage (Voc) owing to a better matched energy level alignment at the perovskite/spiro‐OMeTAD interface. Consequently, the TIPS‐PEN incorporated PVSCs attain the champion power conversion efficiency (PCE) up to 22.92% accompanied with dramatically increased UV photostability which can retain 80% of its primitive PCE under continuous UV light soaking for 150 h. Moreover, the unencapsulated PVSCs with TIPS‐PEN exhibit remarkable moisture stability which can sustain over 80% of the initial value under air conditions (50% relative humidity, 25 °C) after 1000 h.

Fully Atomistic Molecular Dynamics Simulation of a TIPS-Pentacene:Polystyrene Mixed Film Obtained via the Solution Process

Organic thin-film transistors using small-molecule semiconductor materials such as 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-P) have been recently studied for the production of flexible and printed electronic devices. Blending a semiconductor with an insulating polymer, such as polystyrene, is known to improve the device performance; however, its molecular-level structure remains unknown. In this study, we performed molecular dynamics (MD) simulations on a mixed system of TIPS-P and atactic polystyrene (aPS) with fully atomistic models to understand the structure of the mixed thin film at the molecular level and the influence on the device properties. To reproduce the deposition from the solution, we gradually reduced the number of toluene molecules in the simulation. The dynamic characteristics of the system, mean squared displacement, diffusion coefficient, density profile, and P2 order parameter were analyzed. Some of the simulated systems reached the equilibrium state. In these systems, the simulated structures suggested the presence of more TIPS-P molecules on the surface than inside the bulk, even at the low molecular weight of aPS, where phase separation was not observed experimentally. The results of the fully atomistic MD simulations are also a basis for the coarse-grained model to increase the speed of the MD simulation.

Effect of Nanoscale Confinement on Ultrafast Dynamics of Singlet Fission in TIPS-Pentacene.

Singlet fission (SF) is a phenomenon for the generation of a pair of triplet excitons from anexcited molecule in singlet electronic state interacting with another adjacent molecule in its ground electronic state. By increasing the effective number of charge carriers and reducing thermal dissipation of excess energy, SF is promised to enhance light-harvesting efficiency for photovoltaic applications. While SF has been extensively studied in thin films and crystals, the same has not been explored much within a confined medium. Here, we report the ultrafast SF dynamics of triisopropylsilylethynyl pentacene (TIPS-Pn) in micellar nanocavity of varying sizes (prepared from TX-100, CTAB, and SDS surfactants). The nanoparticles with a smaller size contain weakly coupled chromophores which are shown to be more efficient for SF followed by triplet generation as compared to the nanoparticles of larger size which contain strongly coupled chromophores which are less efficient due to the presence of singlet exciton traps. Through these studies, we delineate how a subtle interplay between short-range and long-range interaction among chromophores confined within nanoparticles, fine-tuned by the curvature of the micellar interface but irrespective of the nature of the micelle (cationic or anionic or neutral), play a crucial role in SF through and generation of triplets.

Time-Domain Photothermal AFM Spectroscopy via Femtosecond Pulse Shaping

A time-domain version of photothermal microscopy using an atomic force microscope (AFM) is reported, which we call Fourier transform photothermal (FTPT) spectroscopy, where the delay between two laser pulses is varied and the Fourier transform is computed. An acousto-optic modulator-based pulse shaper sets the delay and phases of the pulses shot-to-shot at 100 kHz, enabling background subtraction and data collection in the rotating frame. The pulse shaper is also used to flatten the pulse spectrum, thereby eliminating the need for normalization by the laser spectrum. We demonstrate the method on 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) microcrystals and Mn-phthalocyanine islands, confirming subdiffraction spatial resolution, and providing new spectroscopic insights likely linked to structural defects in the crystals.

Molecular Engineering of Printed Semiconducting Blends to Develop Organic Integrated Circuits: Crystallization, Charge Transport, and Device Application Analyses.

Solution-based printing has contributed to the facile deposition of various types of materials, including the building blocks of printed electronics. In particular, solution-processable organic semiconductors (OSCs) are regarded as one of the most fascinating candidates for the fabrication of printed electronics. Herein, we report electrohydrodynamic (EHD) jet-printed p- and n-type OSCs, namely 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) and 6,13-bis((triisopropylsilyl)ethynyl)-5,7,12,14-tetraazapentacene (TIPS-TAP), and their use as single-OSC layers and as OSC mixed p-n layers to fabricate solution-processed p-, n-, and ambipolar-type organic field-effect transistors (OFETs). Use of the dragging mode of EHD jet printing, a process driven under a low electrostatic field with a short nozzle-to-substrate distance, was found to provide favorable conditions for growth of TIPS-PEN and TIPS-TAP crystals. In this way, the similar molecular structures of TIPS-PEN and TIPS-TAP yielded a homogeneous solid solution and showed ambipolar transport properties in OFETs. Therefore, the combination of single- and mixed-OSC layers enabled the preparation of various charge-transported devices from unit to integrated devices (NOT, NAND, NOR, and multivalued logic). Therefore, this fabrication technology can be useful for assisting in the production of OSC layers for practical applications in the near future.

Electrohydrodynamic jet printing of small-molecule semiconductor crystals on chemically patterned surface for high-performance organic field-effect transistors

Direct writing of organic semiconducting crystals by electrohydrodynamic jet (EHD) printing has enabled the low-cost large-area fabrication of organic semiconducting crystal arrays without the need of complicated patterning procedures. However, morphological variations within a single printed pattern (e.g., variations in thickness, crystallinity, and local crystal orientation) caused by the “coffee-ring effect” can be an issue during their application in organic field-effect transistors (OFETs) since their charge-transport properties significantly affect the device characteristics. Herein, we report the EHD printing of small-molecule semiconducting crystals on a chemically patterned substrate to suppress the “coffee-ring effect” and produce uniform high-quality crystals oriented along the printing direction. The EHD printing of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) on hydrophobic polyurethane acrylate line patterns on a dielectric surface enables the selective and guided growth of the crystals. The OFETs with the TIPS-PEN crystals printed on the patterned surface exhibit an average field-effect mobility of 0.34 cm2/(V s), which is more than twice of that of the OFETs fabricated with crystals grown on unpatterned surfaces. Thus, the use of chemically patterned surface to improve the uniformity and crystallinity of organic semiconducting crystals is expected to promote the application of EHD printing for fabricating high-performance OFETs.

Crystallization from a Droplet: Single-Crystalline Arrays and Heterojunctions for Organic Electronics.

ConspectusSingle crystals of organic semiconductors (OSCs) are believed to have both high mobility and intrinsic flexibility, making them promising candidates for flexible electronic/optoelectronic applications and being consistently pursued by researchers. The van der Waals force in OSC enables low-temperature solution processing of single crystals, but the relatively weak binding energy brings challenges in forming large, uniform, and defect-free single crystals. To promote the study on OSC single crystals, a generalized method that grows high-quality crystals in an easy-to-handle, time/resource-saving, and repeatable manner is apparently necessary. In 2012, Li et al. developed a droplet-pinned crystallization (DPC) method that uses a rather simple strategy to create a steadily receding contact line for the growth of OSC single crystals. Instead of setting up expensive equipment, controlling strict deposition parameters, or waiting for days or weeks for countable crystal seeds, the DPC method offers a time- and cost-effective way to obtain OSC single crystals for further study of the tendency of crystallization, single-crystal mobility, and molecular packing information. The DPC method is primarily a powerful tool for studying the charge-transport mechanisms in OSC single crystals. In pioneering work, high-mobility single crystals of both p-type 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and n-type C60 materials were obtained. Driven by the demands from practical applications, we then focused on the general lagging of electron mobility in OSC materials. The ambipolar property of TIPS-PEN was studied, and a strong correlation between electron mobility and polar species (polar solvent residuals and surface hydroxyl groups) was observed. The latter further guided the harvest of electron mobility in a series of OSC materials. Undoubtfully, the facile DPC method accelerated these studies by providing a time-efficient, reliable, and repeatable testing platform. Additionally, flexibility on OSC materials and solvents, where not only one-component but also binary systems were allowed, is another critical integrity of the DPC method. The m-xylene/carbon tetrachloride binary solvent was proven to be efficient for growing ribbon-like C60 single crystals rather than needle-like crystals from typical one-component solvents. Afterward, a variety of OSC materials (including p-type, n-type, and ambipolar ones) and a series of solvents (including aromatic, aliphatic, and polar ones) were studied. The crystallization of OSC single crystals was primarily found at either the top liquid-air interface or the bottom solid-liquid interface. The interactions between OSC molecules and substrate surfaces were deduced as the qualitative determining factor. By utilizing the top interface crystallization, the two-step sequential deposition of single-crystalline OSC heterojunctions was enabled. Moreover, by selecting appropriate pairs of OSC materials that crystallize at separate interfaces, the facile one-step formation of single-crystalline OSC heterojunctions was achieved. The OSC single crystals and heterojunctions (including horizontal, vertical, and bulk heterojunctions) thereof exhibit promising potentials in circuits, photovoltaics, and photodiodes and would probably provide new insights for the future development of organic electronics.

Solution-processed flexible nonvolatile organic field-effect transistor memory using polymer electret

Flexible organic field-effect-transistor (OFET) memory is one of the promising candidates for next-generation wearable nonvolatile data storage due to its low price, solution-processability, light-weight, mechanically flexibility, and tunable energy level via molecular tailoring. In this paper, we report flexible nonvolatile OFET memory devices fabricated with solution-processed polystyrene-brush electret and organic semiconductor blends of p-channel 6, 13-bis-(triisopropylsilylethynyl)pentacene (TIPS-PEN) and n-channel poly-{[N,N′-bis(2- octyldodecyl)-naphthalene-1,4,5,8-bis-(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P-(NDI2OD-2T); N2200). Fabricated flexible OFET memory devices exhibited high memory window (30 V) and ON/OFF current ratio (memory ratio) over 103. Furthermore, we obtained reliable memory ratio (~103) over retention time of 108 s, 100 times of repeated programming/erasing cycles, and 1000 times of bending tests at a radius of 3 mm.

Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

Aqueous nanoparticle (NP) dispersions are commonly used as model systems for spectro- scopic study of singlet exciton fission (SF) in acenes such as 6,13-(triisopropylsilylethynyl) pentacene (TIPS-Pn). However, the potential for particle size effects to complicate interpretation of results in such model systems is generally ignored. In this work, we study amorphous TIPS-Pn NP dispersions prepared by the re-precipitation method over a range of particle sizes. Time-resolved fluorescence and femtosecond transient absorption spectroscopy show that exciton dynamics in these systems depend significantly upon particle size. Kinetic analysis reveals that SF becomes slower at smaller NP sizes, while triplet exciton decay (through both correlated triplet pair relaxation and geminate triplet-triplet annihilation) accelerates. These significant size-dependent effects are ascribed to increased morphological disorder within smaller NPs, weakening the intermolecular couplings which control SF and triplet migration. A non-radiative singlet quenching channel separate from SF is also identified, which has not been previously reported for NPs of SF-capable chromophores. This non-radiative singlet decay becomes a significant relaxation pathway at small particle sizes, substantially reducing SF yields. Interestingly, exciton kinetics in 81-nm NPs approach those of bulk amorphous TIPS-Pn, suggesting that NPs of this size or larger are likely good models for bulk TIPS-Pn. This work demonstrates that particle-size effects are significant for small NPs of SF chromophores, and must be accounted for in order to accurately model bulk materials with such NP dispersions.

Organic Semiconductors with Benzoic Acid Based Additives for Solution- Processed Thin Film Transistors

Background: although solution-processed small molecular organic semiconductors have attracted great attention for organic electronic applications, the intrinsic crystal misorientation of the organic semiconductors still remains a challenging issue. Objective: two benzoic acid-based additives, i.e. 4-propylbenzoic acid (RBA) and 4-octylbenzoic acid (OBA), were employed to regulate the crystal growth and charge transport of organic semiconductors. Methods: RBA and OBA were mixed with a π-conjugated organic semiconductor 6,13- bis(triisopropylsilylethynyl) pentacene (TIPS pentacene), respectively. Organic thin-film transistors (OTFTs) with different bottom-gate, top-contact and bottom-gate, bottom-contact configurations were fabricated to investigate charge transport. Results: RBA and OBA share a similar benzoic acid structure with the same hydrophilic head but differ in the length of the hydrophobic tail. The benzoic acid-based additive forms a stratified selfassembled interfacial layer and maneuvers nucleation seed distribution via synergetic interactions with the silanol groups on silicon dioxide and with the bulky side chains of the semiconductor. The TIPS pentacene film with OBA additive exhibited a 10-fold reduction in misorientation angle as compared to the counterpart with RBA. Conclusion: Distinct thin film morphology in terms of crystal alignment and grain width was observed and correlated to the hydrophobic tail length. In particular, OTFTs incorporating the TIPS pentacene/benzoic acid mixture as the active layer showed a mobility of up to 0.15 cm2/Vs.

Morphological and structural comparison of TIPS-PEN:PS and neat TIPS-PEN films grown onto cPVP-patterned plastic substrates

In the present study, spray-coated blends of 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) with Polystyrene (PS) insulating polymer were employed to improve the performance of spray-coated neat TIPS-PEN Organic Field-Effect Transistors (OFETs) on plastic substrates. By combining TIPS-PEN with PS insulating polymer, control over the TIPS-PEN crystallization behavior can be achieved. A surface morphology study on the TIPS-PEN blended with PS films at an optimized weight ratio of 0.8:0.2 was carried out, in order to investigate the phase separation phenomena between the two components within the blend. The crystallinity and the crystalline characteristics of the sprayed TIPS-PEN:PS blend films were also investigated and compared to those of the sprayed neat TIPS-PEN films. Finally, these improved characteristics of the blend-based films are correlated with the extracted electrical parameters (mobility value, on/off current ratio, threshold voltage value) of the sprayed TIPS-PEN:PS blend OFETs and are compared with those of the sprayed neat TIPS-PEN OFETs, both in terms of values and inter-device uniformity.

Photogenerated carrier dynamics of TIPS-pentacene films as studied by photocurrent and electrically detected magnetic resonance.

The carrier generation process and spin dynamics through photoexcitation in the vacuum vapour deposition film of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) were investigated by temperature dependence measurements of photocurrent and electrically detected magnetic resonance (EDMR). The EDMR signal was constructed from two components and showed a maximum at approximately 200 K. The temperature dependence was analysed using quantum mechanical simulation, assuming the carrier dynamics of the weakly coupled electron-hole pair (e-h pair). In addition, the analytical formula of photocurrent generation and EDMR signal intensity were also derived based on classical rate equations and used to understand the carrier dynamics. Through phase-shift analysis in quadrature detection of the EDMR signals, one of the two components was well analysed by using a narrow Lorentzian shape, and the other was by using a broad Gaussian.

Anisotropic Triplet Exciton Diffusion in Crystalline Functionalized Pentacene

Exciton multiplication through singlet fission (SF) offers scope for next-generation photovoltaic devices to exceed the Shockley–Queisser limit. Organic SF chromophores typically exhibit significant structural anisotropy in their crystal packing, which can impact exciton transport and influence the design of SF-enhanced devices. An improved understanding of the link between structural anisotropy and exciton diffusion is therefore crucial for developing SF-based photovoltaics. Here, we use femtosecond transient absorption spectroscopy to quantify the anisotropic triplet mobility in 6,13-(triisopropylsilylethynyl)pentacene (TIPS-Pn), a prototypical SF chromophore. Bimolecular triplet–triplet annihilation (TTA) in crystalline TIPS-Pn is well-described by a kinetic model that assumes isotropic, three-dimensional triplet exciton diffusion, but with best-fit parameters that do not correspond to any physical parameters of the material. Kinetic models that assume either one-dimensional or anisotropic three-dimensional exciton diffusion describe the annihilation equally well but yield more physically realistic fit parameters, suggesting that triplet diffusion on the subnanosecond time scale occurs mostly along a single axis of the material. These findings highlight the need to treat parameters obtained from fits of experimental data with models of isotropic diffusion with caution for systems with anisotropic packing such as TIPS-Pn. Diffusion coefficients calculated by density functional theory predict that triplet exciton diffusion occurs predominantly along the crystallographic a-axis, with migration in any other direction through the crystal slower by over an order of magnitude. This anisotropic diffusion suggests that fast, directional exciton transport in layers or films of TIPS-Pn may be achieved by control of the chromophore morphology.

Poly(4-vinylphenol-co-methyl methacrylate)/Hafnium Oxide Nanocomposite Gate Insulators for Organic Thin-Film Transistors.

We fabricate 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) thin-film transistors (TFTs) with nanocomposite insulators. The insulator layers consist of both poly(4-vinylphenol-co-methyl methacrylate) and high-dielectric constant hafnium oxide (HfO₂) nanoparticles. The HfO₂ nanoparticles are ball-milled for sufficient dispersion in a nanocomposite solution to enable solution process methods to be used in preparing the insulator layers. The nanocomposite insulators demonstrate high capacitances and improve the performance of TIPS-Pn TFTs. Nonetheless, particle aggregates are produced in the nanocomposites solution with high HfO₂ concentrations, generating detrimental effects on the dielectric properties and the TFT performance. Our experimental result implies that the optimum concentration of HfO₂ nanoparticles in a mixed solution will find to be ~11.5 wt%.

Super‐ and Ferroelastic Organic Semiconductors for Ultraflexible Single‐Crystal Electronics

AbstractLike silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS‐P) crystals can undergo mechanically induced structural transitions to exhibit superelasticity and ferroelasticity. These properties arise from cooperative and correlated molecular displacements and rotations in response to mechanical stress. By utilizing a bending‐induced ferroelastic transition of TIPS‐P, flexible single‐crystal electronic devices were obtained that can tolerate strains (ϵ) of more than 13 % while maintaining the charge carrier mobility of unstrained crystals (μ>0.7 μ0). Our work will pave the way for high‐performance ultraflexible single‐crystal organic electronics for sensors, memories, and robotic applications.

Super- and Ferroelastic Organic Semiconductors for Ultraflexible Single-Crystal Electronics.

Like silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS-P) crystals can undergo mechanically induced structural transitions to exhibit superelasticity and ferroelasticity. These properties arise from cooperative and correlated molecular displacements and rotations in response to mechanical stress. By utilizing a bending-induced ferroelastic transition of TIPS-P, flexible single-crystal electronic devices were obtained that can tolerate strains (ϵ) of more than 13 % while maintaining the charge carrier mobility of unstrained crystals (μ>0.7 μ0 ). Our work will pave the way for high-performance ultraflexible single-crystal organic electronics for sensors, memories, and robotic applications.

(Invited) Electron Spin Polarization Generated by Transport of Spin-Entanglements in Singlet Fissions

Applications of singlet fission (SF)1 are expected to exceed the Shockley–Queisser theoretical limit because two separated triplet excitons (T+T) can be produced from one excited singlet state (S1S0) sharing its excitation energy with a neighboring ground-state chromophore. Subsequent two charge-separations (CS) at the D:A domain interfaces after individual triplet-exciton diffusions may cause the boost of the photocurrent density of the OSCs. Applications of the SF-induced triplet generations are also promising for boosting the organic light emitting diode (OLED) efficiency. Several studies clarified the initial multiexciton (TT) generation mechanisms from the S1S0 states. More importantly, elucidation of TT T+T dissociation mechanism is highly desired. The dissociation time constants ranging from sub-picosecond to microsecond regions are reported. However little is known how the T+T dissociation or the decoupling2 occurs from the strongly coupled TT states.The strongly coupled singlet TT states are known to be initially generated from the S1S0 states. Generations of the quintet state in the triplet–triplet pair3-7 have been reported and are thought to be essential for preventing the loss of the SF-born multiexciton through the singlet channels. Using the time-resolved electron paramagnetic resonance (TREPR) method for TIPS-tetracene thin films, Weiss et al. 8 characterized the SF-induced strongly-coupled quintet of 5(TT). The quintet electron spin polarization (ESP) was detected as the microwave absorption (A) and emission (E) in 5(TT) for frozen aggregates of the SF-materials. The ESPs were interpreted using the sublevel-selective quintet conversions by the zero-field splitting (ZFS) interaction at the singlet-quintet level-crossings in the presence of the negative exchange coupling (J) during triplet exciton-diffusion and subsequent re-encounter in the highly disordered region, causing modulation of the J-coupling to result in spontaneous 5(TT) generations.4 Interestingly, transport of spin-entangled multiexcitons by the dissociative exciton diffusion have been observed using an ultrafast transient absorption imaging of pentacene crystals and by the magnetic field effect on the fluorescence time-profiles. Although such transportation of spin-entanglements is key to elucidate the dissociation mechanism and to apply in quantum information science, no direct evidence for the transportation of the spin-entanglements has been examined in the separated T+T states with the singlet and quintet characters.The present study thus focuses on how the spin-entanglements develop and affect the direct TREPR detection of the T+T state. The transport of the quantum entanglements was demonstrated in thin films. When the triplet excitons are separated from each other to result in a negligible magnitude of the exchange coupling (J 0), spin correlations in the triplet-triplet pair may occur to induce diagonalized nine spin-states as the quantum superpositions of the singlet-triplet-quintet character through the spin-spin dipolar couplings of the individual triplet species. This is quite similar to the spin-correlated radical pair (SCRP) model9, 10 in the photoinduced long-range charge-separation system generated by singlet or triplet precursors, causing the superpositions of the singlet-triplet characters when the J-coupling is small in the radical pairs. We herein demonstrate that the transportations of the SF-induced 5(TT) and 1(TT) characters can be distinguished on the T+T dissociations using the ESPs of correlated T-T states by applying TREPR spectroscopy to thin films of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn).REFERENCES 1. M. B. Smith and J. Michl, Chem. Rev., 2010, 110, 6891-6936.2. K. Miyata, F. S. Conrad-Burton, F. L. Geyer and X. Y. Zhu, Chem. Rev., 2019, 119, 4261-4292.3. D. Lubert-Perquel, E. Salvadori, M. Dyson, P. N. Stavrinou, R. Montis, H. Nagashima, Y. Kobori, S. Heutz and C. W. M. Kay, Nat. Commun., 2018, 9, 4222.4. H. Nagashima, S. Kawaoka, S. Akimoto, T. Tachikawa, Y. Matsui, H. Ikeda and Y. Kobori, J. Phys. Chem. Lett., 2018, 9, 5855-5861.5. Y. Matsui, S. Kawaoka, H. Nagashima, T. Nakagawa, N. Okamura, T. Ogaki, E. Ohta, S. Akimoto, A. Sato-Tomita, S. Yagi, Y. Kobori and H. Ikeda, J. Phys. Chem. C, 2019, 123, 18813-18823.6. T. Saegusa, H. Sakai, H. Nagashima, Y. Kobori, N. V. Tkachenko and T. Hasobe, J. Am. Chem. Soc., 2019, 141, 14720-14727.7. H. Sakai, R. Inaya, H. Nagashima, S. Nakamura, Y. Kobori, N. V. Tkachenko and T. Hasobe, J. Phys. Chem. Lett., 2018, 9, 3354-3360.8. L. R. Weiss, S. L. Bayliss, F. Kraffert, K. J. Thorley, J. E. Anthony, R. Bittl, R. H. Friend, A. Rao, N. C. Greenham and J. Behrends, Nat. Phys., 2017, 13, 176-181.9. Y. Kobori, T. Ako, S. Oyama, T. Tachikawa and K. Marumoto, J. Phys. Chem. C, 2019, 123, 13472-13481.10. J. H. Olshansky, M. D. Krzyaniak, R. M. Young and M. R. Wasielewski, J. Am. Chem. Soc., 2019, 141, 2152-2160.

Fabrication and characterization of PLGA nanoparticles encapsulating large CRISPR\u2013Cas9 plasmid

BackgroundThe clustered regularly interspaced short palindromic repeats (CRISPR) and Cas9 protein system is a revolutionary tool for gene therapy. Despite promising reports of the utility of CRISPR–Cas9 for in vivo gene editing, a principal problem in implementing this new process is delivery of high molecular weight DNA into cells.ResultsUsing poly(lactic-co-glycolic acid) (PLGA), a nanoparticle carrier was designed to deliver a model CRISPR–Cas9 plasmid into primary bone marrow derived macrophages. The engineered PLGA-based carriers were approximately 160 nm and fluorescently labeled by encapsulation of the fluorophore 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene). An amine-end capped PLGA encapsulated 1.6 wt% DNA, with an encapsulation efficiency of 80%. Release studies revealed that most of the DNA was released within the first 24 h and corresponded to ~ 2–3 plasmid copies released per nanoparticle. In vitro experiments conducted with murine bone marrow derived macrophages demonstrated that after 24 h of treatment with the PLGA-encapsulated CRISPR plasmids, the majority of cells were positive for TIPS pentacene and the protein Cas9 was detectable within the cells.ConclusionsIn this work, plasmids for the CRISPR–Cas9 system were encapsulated in nanoparticles comprised of PLGA and were shown to induce expression of bacterial Cas9 in murine bone marrow derived macrophages in vitro. These results suggest that this nanoparticle-based plasmid delivery method can be effective for future in vivo applications of the CRISPR–Cas9 system.

Organizing Crystalline Functionalized Pentacene Using Periodicity of Poly(Vinyl Alcohol).

Nanoparticles of acenes exhibit highly efficient intermolecular singlet fission (SF). Recent reports indicate that altering the morphology of 6,13-bis-(triisopropylsilylethynyl)pentacene (TIPS-Pn) nanoparticles has a profound influence on their SF dynamics. Here, we show that poly(vinyl alcohol) (PVA) induces a phase transition in preformed TIPS-Pn nanoparticles. These nanoparticles are amorphous when initially formed but crystalline after addition of PVA. Surface characterization indicates that a diffuse PVA layer surrounds the nanoparticles. We propose that a periodic interaction between the hydroxyl groups of PVA and TIPS groups of TIPS-Pn on the nanoparticle surface induces a large-scale structural rearrangement to yield crystalline TIPS-Pn. Such reorganization in preformed organic nanoparticles is unprecedented, and we believe that this is the first report of such an effect induced by polymer adsorption. Transient absorption spectroscopic results reveal that SF within these nanoparticles is accelerated by an order of magnitude upon structural rearrangement.