Atomistic Band Gap Engineering in Donor–Acceptor Polymers

Enhanced water decontamination via photogenerated electron delocalization of π → π* and D-π-A synergistically

Mixed-dimensional van der Waals heterojunctions (MD-vdWhs), known for exceptional electron transfer and charge separation capabilities, remain underexplored in photocatalysis. In this study, we leveraged the synergistic effect of intermolecular π → π* and D-π-A dual channels to fabricate novel MD-vdWhs. Owing to the synergistic effect, it exhibits superior electron transfer and delocalization ability, thereby enhancing its photocatalytic performance. The Optimal photocatalyst can degrade 98.78 % of 20 mg/L tetracycline (TC) within 15 min. Additionally, we introduced a novel proof strategy for investigating the photoelectron transfer path, creatively demonstrating the synergistic dual channels effect, which can be attributed to the carbonyl density and light-excitation degree. Notably, even under low-power light sources, it achieved complete inactivation of Escherichia coli within just 7 mins, far surpassing current cutting-edge research. This theoretical framework holds promise for broader applications within related studies.

Innovative Fluorescent Polymers in Niosomal Carriers: A Novel Approach to Enhancing Cancer Therapy and Imaging

Cancer is anticipated to become the pioneer reason of disease-related deaths worldwide in the next two decades, underscoring the urgent need for personalized and adaptive treatment strategies. These strategies are crucial due to the high variability in drug efficacy and the tendency of cancer cells to develop resistance. This study investigates the potential of theranostic nanotechnology using three innovative fluorescent polymers (FP-1, FP-2, and FP-3) encapsulated in niosomal carriers, combining therapy (chemotherapy and radiotherapy) with fluorescence imaging. These cargoes are assessed for their cytotoxic effects across three cancer cell lines (A549, MCF-7, and HOb), with further analysis to determine their capacity to augment the effects of radiotherapy using a Linear Accelerator (LINAC) at specific doses. Fluorescence microscopy is utilized to verify their uptake and localization in cancerous versus healthy cell lines. The results confirmed that these niosomal cargoes not only improved the antiproliferative effects of radiotherapy but also demonstrate the practical application of fluorescent polymers in in vitro imaging. This dual function underscores the importance of dose optimization to maximize therapeutic benefits while minimizing adverse effects, thereby enhancing the overall efficacy of cancer treatments.

Heterogenization of Homogeneous Donor-Acceptor Conjugated Polymers for Efficient Photooxidation: An Approach Toward Sustainable and Recyclable Photocatalysis

Recovery of homogeneous photocatalysts from reaction mixture is challenging, affecting the cost-effectiveness, and masks their advantages, including 4-8 fold higher catalytic activity than corresponding heterogeneous counterparts. Incorporation of long alkyl chains within the rigid π-conjugated backbone of conjugated polymers can augment their solubility in particular organic solvents; accordingly, they can function as homogeneous photocatalysts. Consequently, these polymers facilitate the recovery of catalysts through the reverse dissolution process, thus creating a well-suited platform to meet certain advantages of both homo- and heterogeneous photocatalysts. This work exemplifies the unprecedented perks of donor-acceptor conjugated polymers from benzodithiophene and substituted dibenzothiophene sulfone moieties for their homogeneous phase photoredox activities along with their heterogeneous recovery and reuse up to five runs. The potential intermediate singlet oxygen (1O2) and superoxide (O2•-) as reactive oxygen species generated by these photostable conjugated polymers efficiently catalyze the visible-light-driven oxidation of aryl sulfides (up to 92% yield) and oxidative hydroxylation of phenylboronic acids (up to 93% yield), respectively. Therefore, to actualize the heightened catalytic performance and formulate a design strategy for polymeric photoredox catalyst, our work introduces an alternative approach to the advancement of photocatalysis with diverse catalytic activities.

Regioisomerism in Thienothiophene-Based Covalent Organic Frameworks─A Tool for Band-Gap Engineering

The craft of tuning optical properties is well-established for crystalline inorganic and hybrid solids. However, a far greater challenge is to tune the optical properties of organic materials systematically by design. We now introduce a synthesis concept that enables us to alter the optical properties of crystalline covalent organic frameworks (COFs) systematically using isomeric structures of thienothiophene-based building blocks (T23/32T) combined with a variety of tetratopic aromatic amines, e.g., the Wurster moiety (W-NH2). This concept is demonstrated for the synthesis of COFs in bulk and film forms and provides highly crystalline and porous isomeric COFs featuring predesigned photophysical properties. The band gap of the framework can be tuned continuously and precisely by chemically doping the pristine W23TT COF with its related constitutional isomer building block. Density-functional theory investigations of COF model compounds indicate that the extent of π-conjugation is among the key characteristics enabling the band-gap engineering.

Effect of chalcogen atoms on the electronic band gaps of the quinoxaline containing donor-acceptor-donor type semiconducting polymers: a systematic DFT investigation

CONTEXT

Due to the widely known positive contributions of the quinoxaline group in organic semiconductors, we conducted a fully computational study using quantum mechanical methods to investigate the effect of quinoxaline in the electron acceptor unit with the combination of different chalcogen atoms on the band gap of a series of donor-acceptor-donor type conjugated polymers. Using density functional theory, we mainly calculated the electronic band gap values of the structures containing four different chalcogen atoms (O, S, Se, and Te) in the electron donor and acceptor units. While chalcogendiazoloquinoxaline groups were used as the electron acceptor units, furan, thiophene, selenophene, and tellurophene were used as the donor units. Our theoretical results showed that the use of heavy chalcogen atoms in both donor and acceptor units resulted in a low band gap. Besides this, the effect of heavy chalcogen atoms used in the electron donor units is much more pronounced compared to the ones used in the acceptor units. More importantly, our findings proved that the inclusion of the chalcogendiazoloquinoxaline group instead of benzochalcogenadiazole as the acceptor unit significantly decreases the electronic band gap of the conjugated polymer. The lowest band gap was found to be 0.10 eV for the 4,9-di(tellurophen-2-yl)-[1,2,5]telluradiazolo[3,4-g]quinoxaline polymer.

METHODS

Conformational analysis of the monomers and their corresponding oligomers was performed at the B3LYP/LANL2DZ level of theory. Then, long-range corrected hybrid functional LC-BLYP in a combination with the LANL2DZ basis set was utilized for the calculation of electronic properties and HOMO and LUMO energy gaps of monomers and oligomers through the reoptimization of the lowest energy conformers obtained from the B3LYP/LANL2DZ calculations in the previous step. All energy minimum structures were confirmed through vibrational frequency analysis at both calculation levels. The Gaussian 09 rev. D.01 software was used for all calculations, and GaussView 5.0.9 for visualizations.

General room-temperature Suzuki-Miyaura polymerization for organic electronics

π-Conjugated polymers (CPs) have broad applications in high-performance optoelectronics, energy storage, sensors and biomedicine. However, developing green and efficient methods to precisely synthesize alternating CP structures on a large scale remains challenging and critical for their industrialization. Here a room-temperature, scalable and homogeneous Suzuki-Miyaura-type polymerization reaction is developed with broad generality validated for 24 CPs including donor-donor, donor-acceptor and acceptor-acceptor connectivities, yielding device-quality polymers with high molecular masses. Furthermore, the polymerization protocol significantly reduces homocoupling structural defects, yielding more structurally regular and higher-performance electronic materials and optoelectronic devices than conventional thermally activated polymerizations. Experimental and theoretical studies reveal that a borate transmetalation process plays a key role in suppressing protodeboronation, which is critical for large-scale structural regularity. Thus, these results provide a general polymerization tool for the scalable production of device-quality CPs with alternating structural regularity.

Role of the Benzothiadiazole Unit in Organic Polymers on Photocatalytic Hydrogen Production

Organic polymers based on the donor-acceptor structure are a promising class of efficient photocatalysts for solar fuel production. Among these polymers, poly(9,9-dioctylfluorene-alt-1,2,3-benzothiadiazole) (PFBT) consisting of fluorene donor and benzothiadiazole acceptor units has shown good photocatalytic activity when it is prepared into polymer dots (Pdots) in water. In this work, we investigate the effect of the chemical environment on the activity of photocatalysis from PFBT Pdots for hydrogen production. This is carried out by comparing the samples with various concentrations of palladium under different pH conditions and with different sacrificial electron donors (SDs). Moreover, a model compound 1,2,3-benzothiadiazole di-9,9-dioctylfluorene (BTDF) is synthesized to investigate the mechanism for protonation of benzothiadiazole and its kinetics in the presence of an organic acid-salicylic acid by cyclic voltammetry. We experimentally show that benzothiadiazole in BTDF can rapidly react with protons with a fitted value of 0.1-5 × 1010 M-1 s-1 which should play a crucial role in the photocatalytic reaction with a polymer photocatalyst containing benzothiadiazole such as PFBT Pdots for hydrogen production in acidic conditions. This work gives insights into why organic polymers with benzothiadiazole work efficiently for photocatalytic hydrogen production.

Two Birds One Stone: Graphene Assisted Reaction Kinetics and Ionic Conductivity in Phthalocyanine-Based Covalent Organic Framework Anodes for Lithium-ion Batteries

This work reports a covalent organic framework composite structure (PMDA-NiPc-G), incorporating multiple-active carbonyls and graphene on the basis of the combination of phthalocyanine (NiPc(NH2 )4 ) containing a large π-conjugated system and pyromellitic dianhydride (PMDA) as the anode of lithium-ion batteries. Meanwhile, graphene is used as a dispersion medium to reduce the accumulation of bulk covalent organic frameworks (COFs) to obtain COFs with small-volume and few-layers, shortening the ion migration path and improving the diffusion rate of lithium ions in the two dimensional (2D) grid layered structure. PMDA-NiPc-G showed a lithium-ion diffusion coefficient (DLi + ) of 3.04 × 10-10 cm2 s-1 which is 3.6 times to that of its bulk form (0.84 × 10-10 cm2 s-1 ). Remarkably, this enables a large reversible capacity of 1290 mAh g-1 can be achieved after 300 cycles and almost no capacity fading in the next 300 cycles at 100 mA g-1 . At a high areal capacity loading of ≈3 mAh cm-2 , full batteries assembled with LiNi0.8 Co0.1 Mn0.1 O2 (NCM-811) and LiFePO4 (LFP) cathodes showed 60.2% and 74.7% capacity retention at 1 C for 200 cycles. Astonishingly, the PMDA-NiPc-G/NCM-811 full battery exhibits ≈100% capacity retention after cycling at 0.2 C. Aided by the analysis of kinetic behavior of lithium storage and theoretical calculations, the capacity-enhancing mechanism and lithium storage mechanism of covalent organic frameworks are revealed. This work may lead to more research on designable, multifunctional COFs for electrochemical energy storage.

Synthesis and Photocatalytic Activity of Novel Polycyclopentadithiophene

A novel π-conjugated polymer based on cyclopentadithiophene (CPDT) and poly(4,4']-(((4Hcyclopenta[2,1-b:3,4-b']dithiophene-4,4-diyl)bis(ethane-2,1-diyl))bis(oxy))bis(4-oxobutanoic acid)) (PCPDT-CO2H) was prepared as a sparingly soluble material. The generation of hydroxyl radicals from PCPDT-CO2H in water was confirmed by using coumarin as a hydroxyl radical indicator. Furthermore, PCPDT-CO2H was found to catalyze the oxidative hydroxylation of arylboronic acid and the oxidation of benzaldehyde, indicating that PCPDT-CO2H can be a promising candidate for metal-free and 100% organic heterogeneous photocatalysts.

Room Temperature Anhydrous Suzuki-Miyaura Polymerization Enabled by C-S Bond Activation

The Suzuki-Miyaura cross-coupling is one of the most important and powerful methods for constructing C-C bonds. However, the protodeboronation of arylboronic acids hinder the development of Suzuki-Miyaura coupling in the precise synthesis of conjugated polymers (CPs). Here, an anhydrous room temperature Suzuki-Miyaura cross-coupling reaction between (hetero)aryl boronic esters and aryl sulfides was explored, of which universality was exemplified by thirty small molecules and twelve CPs. Meanwhile, the mechanistic studies involving with capturing four coordinated borate intermediate revealed the direct transmetalation of boronic esters in the absence of H2 O suppressing the protodeboronation. Additionally, the room temperature reaction significantly reduced the homocoupling defects and enhanced the optoelectronic properties of the CPs. In all, this work provides a green protocol to synthesize alternating CPs.

Molecular Structure and Conformational Design of Donor-Acceptor Conjugated Polymers to Enable Predictable Optoelectronic Property

Tuning the optoelectronic properties of donor-acceptor conjugated polymers (D-A CPs) is of great importance in designing various organic optoelectronic devices. However, there remains a critical challenge in precise control of bandgap through synthetic approach, since the chain conformation also affects molecular orbital energy levels. Here, D-A CPs with different acceptor units are explored that show an opposite trend in energy band gaps with the increasing length of oligothiophene donor units. By investigating their chain conformation and molecular orbital energy, it is found that the molecular orbital energy alignment between donor and acceptor units plays a crucial role in dictating the final optical bandgap of D-A CPs. For polymers with staggered orbital energy alignment, the higher HOMO with increasing oligothiophene length leads to a narrowing of the optical bandgap despite decreased chain rigidity. On the other hand, for polymers with sandwiched orbital energy alignment, the increased band gap with increasing oligothiophene length originates from the reduction of bandwidth due to more localized charge density distribution. Thus, this work provides a molecular understanding of the role of backbone building blocks on the chain conformation and bandgaps of D-A CPs for organic optoelectronic devices through the conformation design and segment orbital energy alignment.

Acceptor-Induced Fluorescence of Phenolic Polymers Based on Triphenylamine Derivatives

Conductive polymers facilitate the electrical current flow through the transfer of electrons and holes. They show promise for novel photo-functional materials in photovoltaics. However, substantial electrostatic interactions between electron donors and acceptors induce polymer aggregation, limiting moldability and conductivity. In this study, robust donor polymers with high heat resistance were synthesized by bonding triphenylamine (TPA) derivatives and formaldehyde to phenolic groups. Resulting TPA-based phenolic polymers exhibited flexible structures and fluorescence due to charge transfer with acceptor molecules. Furthermore, TPA-based phenolic polymers' capacity to distinguish acceptor molecule sizes correlated with their molecular weight, reflecting upon donor-acceptor interactions. This novel optical trait in phenolic polymers holds potential for electronic components and conductive materials.

Design, synthesis, and density functional theory studies of a new selective chemosensor for Pb2

Herein, we have focused on a new colorimetric ligand synthesized from the reaction of 2-hydroxy-5-methylbenzene-1,3-dialdehyde with 2-amino-thiophenol, and investigated its activity as a sensor. In this regard, the sensory activity of the ligand towards different ions (Mn2+, Cu2+, Co2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Ag+, Na+, Cs+, Mg2+, Al3+, Ba2+, K+, and Pb2+) was studied. The specificity of ion bindings is discussed through UV-Vis analysis. The ligand that was synthesized showed remarkable sensitivity, with a detection limit of 0.001 ppb. Additionally, the presence of Pb2+ ions can be visually detected through a color change from colorless to yellow. In the last part of this work, we seek to predict the available experimental measurements. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) are employed to examine the bonding between the ligand and the Pb2+ ion. The effect of water solvent was thoroughly examined for all the steps via the conductor-like Polarizable Continuum Model (CPCM). The theoretical findings revealed that electronic properties, including energy gap, adsorption energy, charge/energy transfer, and optical characteristics, undergo significant changes when Pb2+ cations are present. Hence, it can be inferred that the newly synthesized chemosensor (NC) is highly efficient in detecting Pb2+.

Effect of Chalcogenophenes on Chiroptical Activity of Twisted Tetracenes: Computational Analysis, Synthesis and Crystal Structure Thereof

The synthesis of multiply substituted acenes is still a relevant research problem, considering their applications and future potential. Here we present an elegant synthetic protocol to afford tetra-peri-substituted naphthalene and tetracene from their tetrahalo derivatives by a Pd(0)-catalyzed C-C cross-coupling method in a single step. The newly synthesized tetracenes were characterized by NMR, HRMS, UV-vis spectrophotometry, and single-crystal X-ray diffraction (SCXRD). In addition, the first systematic computational study of the effect of chalcogenophenyl substitutions on the chiroptical properties of twistacenes was reported here. The gas phase computational studies using density functional theory (DFT) on a series of chalcogenophene-substituted tetracenes revealed that their chiroptical activity could be systematically increased via the atomistic tuning of peripheral substituents.

Hypsochromic Shift Donor-Acceptor NIR-II Dye for High-Efficiency Tumor Imaging

Nowadays, second near-infrared window (NIR-II) dyes' development focuses on pursuing a longer absorption/emission wavelength and higher quantum yield, which usually means an extended π conjugation system, resulting in an enormous molecular weight and poor druggability. Most researchers thought that the reduced π conjugation system would bring on a blueshift spectrum that causes dim imaging qualities. Little efforts have been made to study smaller NIR-II dyes with a reduced π conjugation system. Herein, we synthesized a reduced π conjugation system donor-acceptor (D-A) probe TQ-1006 (Em = 1006 nm). Compared with its counterpart donor-acceptor-donor (D-A-D) structure TQT-1048 (Em = 1048 nm), TQ-1006 exhibited comparable excellent blood vessels, lymphatic drainage imaging performance, and a higher tumor-to-normal tissue (T/N) ratio. An RGD conjugated probe TQ-RGD showed an extra high contrast tumor imaging (T/N ≥ 10), further proving D-A dyes' excellent NIR-II biomedical imaging applications. Overall, the D-A framework provides a promising approach to designing next-generation NIR-II fluorophores.

Non-Aufbau orbital ordering and spin density modulation in high-spin donor-acceptor conjugated polymers

High-spin ground-state organic materials with unique spin topology can significantly impact molecular magnetism, spintronics, and quantum computing devices. However, strategies to control the spin topology and alignment of the unpaired spins in different molecular orbitals are not well understood. Here, we report modulating spin distribution along the molecular backbone in high-spin ground-state donor-acceptor (D-A) conjugated polymers. Density functional theory calculations indicate that substitution of different heteroatoms (such as C, Si, N, and Se) alters the aromatic character in the thiadiazole unit of the benzobisthiadiazole (BBT) acceptor and modulates the oligomer length to result in high-spin triplet ground-state, orbital and spin topology. The C, Si, and Se atom substituted polymers show a localized spin density at the two opposite ends of the polymers. However, a delocalized spin distribution is observed in the N substituted polymer. We find that the hybridization (sp³vs. sp²) of the substituent atom plays an important role in controlling the electronic structure of these materials. This study shows that atomistic engineering is an efficient technique to tune the spin topologies and electronic configurations in the high-spin ground-state donor-acceptor conjugated polymers, compelling synthetic targets for room-temperature magnetic materials.

Materials and device design for advanced phototherapy systems

Phototherapy has recently emerged as a promising solution for cancer treatment due to its multifunctionality and minimal invasiveness. Notwithstanding the limited penetration depth of light through skin, the ability of photopharmaceutical device systems to deliver light to desired lesions is important. The device system deploys advanced biocompatible materials and fabrication technologies for electronics, and eventually enables more efficient phototherapy. In this review, we focus on diverse optical electronics to illuminate the lesion site with light. Then, moving on to the phototherapy, we highlight photo-thermal therapy with light absorbing materials, photo-activated chemotherapy with light sensitive materials, and photo-dynamic therapy using photosensitizers. Furthermore, we introduce a drug delivery system that can deliver these photopharmaceutical agents spatiotemporally to the tumor site. To this end, we provide a general overview of materials and devices for phototherapy and discuss critical issues and pending limitations of such phototherapy.

Multicomponent Reaction of Isocyanide, Ditelluride, and Mn(III) Carboxylate: Synthesis of N-Acyl Tellurocarbamate

A multicomponent reaction of isocyanides, ditellurides and manganese(III) carboxylates under mild reaction conditions leads to the synthesis of various N-acyl tellurocarbamates. This method demonstrates good functional tolerance and broad substrate scope and, as a result, is especially suitable for the postfunctionalization of complicated molecules such as drugs. The given method can be further extended to the synthesis of selenocarbamates.

Organosulfur/selenium-based Highly Fluorogenic Molecular Probes for Live-Cell Nucleolus Imaging

We present rationally designed cationic organochalcogens highly selective to RNA. We have demonstrated that the conformational dynamics and subsequently the optical properties of these dyes can be controlled to facilitate efficient bioimaging. We report organoselenium and organosulfur-based cell-permeable red-emissive probes bearing favorable cyclic sidearm with potential for selective and high contrast imaging of cell nucleoli. The probes exhibit high quantum yield upon interaction with RNA in an aqueous solution. An in-depth multiscale simulation study reveals that the prominent rotational freezing of the electron-donating sidearm of the probes in the microenvironment of RNA helps in attaining more planar conformation when compared to DNA. It exerts a greater extent of intramolecular charge transfer and hence leads to enhanced fluorescence emission. A systematic structure-interaction relationship study highlighted the impact of heavy-chalcogens toward the improved emissive properties of the probes.

PN-Doped tetraphenylnaphthalene: a straightforward synthetic strategy analogous to BN-annulation

Compared to BN heterocycles, few studies on PN heterocycles have been reported to date. Herein, we developed an efficient synthetic strategy analogous to BN-annulation to simultaneously incorporate a PN bond and a halogen group into the naphthalene core. Subsequently, we prepared PN-containing tetraphenylnaphthalene using this method, followed by palladium-catalyzed cross-coupling and reduction reactions. The prepared molecule was characterized via X-ray crystallography, NMR spectroscopy, UV-vis spectroscopy, and cyclic voltammetry.

Hybrid donor-acceptor polymer nanoparticles and combination antibiotic for mitigation of pathogenic bacteria and biofilms

Biofilms pose a significant clinical problem in skin and soft tissue infections. Their resistance to antibiotics has spurred investigations into alternative treatments, such as nanoparticle-mediated photothermal ablation. Non-toxic Hybrid Donor- Acceptor (DA) Polymer nanoParticles (H-DAPPs) were developed for fluorescence imaging (using poly(3-hexylthiophene-2,5 diyl) (P3HT)) and rapid, near-infrared photothermal ablation (NIR- PTA) (using poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe)). H-DAPPs were evaluated alone, and in combination with antibiotics, against planktonic S. aureus and S. pyogenes, and S. aureus biofilms. H-DAPPs NIR-PTA (15-700 μg/ mL) can generate rapid temperature changes of 27.6-73.1 °C, which can eradicate planktonic bacterial populations and reduce biofilm bacterial viability by more than 4- log (> 99.99%) with exposure to 60 s of 800 nm light. Reductions were confirmed via confocal analysis, which suggested that H-DAPPs PTA caused bacterial inactivation within the biofilms, but did not significantly reduce biofilm polysaccharides. SEM imaging revealed structural changes in biofilms after H-DAPPs PTA. S. aureus biofilms challenged with 100 μg/mL of H-DAPPs (H-DAPPs-100) to induce an average temperature of 55.1 °C, and the minimum biofilm eradication concentration (MBEC) of clindamycin, resulted in up to ~3- log decrease in bacterial viability compared to untreated biofilms and those administered H-DAPPs-100 PTA only, and up to ~2- log compared to biofilms administered only clindamycin. This study demonstrates that polymer nanoparticle PTA can mitigate biofilm infection and may improve antimicrobial efficacy.

Trends in Conjugated Chalcogenophenes: A Theoretical Study

Heavy atom substitution in chalcogenophenes is a versatile strategy for tailoring and ultimately improving conjugated polymer properties. While thiophene monomers are commonly implemented in polymer designs, relatively little is known regarding the molecular properties of the heavier chalcogenophenes. Herein, we use density functional theory (DFT) calculations to examine how group 16 heteroatoms, including the radioactive polonium, affect polychalcogenophene properties including bond length, chain twisting, aromaticity, and optical properties. Heavier chalcogenophenes are more quinoidal in character and consequently have reduced band gaps and larger degrees of planarity. We consider both the neutral and radical cationic species. Upon p-type doping, bond length rearrangement is indicative of a more delocalized electronic structure, which combined with optical calculations is consistent with the polaron-model of charge storage on conjugated polymer chains. A better understanding of the properties of these materials at their molecular levels will inevitably be useful in material design as the polymer community continues to explore more main group containing polymers to tackle issues in electronic devices.

Molecular engineering of diketopyrrolopyrrole-conjugated polymer nanoparticles by chalcogenide variation for photoacoustic imaging guided photothermal therapy

Photothermal therapy is promising for augmenting cancer therapeutic outcomes in cancer treatment. Diketopyrrolopyrrole (DPP)-conjugated polymer nanoparticles are in focus due to their dual photoacoustic imaging and photothermal therapy functions. Herein, the design and synthesis of three near-infrared absorbing conjugated polymers, named DPP-SO, DPP-SS and DPP-SSe, with heteroatom substitution of the thiophene moiety were developed for a photoacoustic imaging guided photothermal therapy. It was demonstrated that systematically changing only the heteroatom from O to S or Se could apparently adjust the absorption spectrum and energy gap of DPP-conjugated polymers to obtain the most suitable photothermal transduction agents (PTAs) for use in biomedicine. The characterization of photophysical properties proved that the photothermal conversion efficiency and absorption coefficient of DPP-SO nanoparticles under 808 nm irradiation was up to 79.3% and 66.51 L g^-1 cm^-1, respectively, which were much higher than those of DPP-SS and DPP-SSe nanoparticles. Remarkably, the IC₅₀ value of DPP-SO for killing A549 cells was half that of DPP-SS and DPP-SSe nanoparticles. Further in vivo works demonstrated efficient photothermal therapeutic effects of DPP-SO nanoparticles with the guidance of photoacoustic imaging. Thus, this is an efficient method to regulate the photothermal performance of DPP-conjugated polymers by changing the heteroatom in the molecular skeleton.

Fabrication of Alternating Copolymers Based on Cyclopentadithiophene-Benzothiadiazole Dicarboxylic Imide with Reduced Optical Band Gap: Synthesis, Optical, Electrochemical, Thermal, and Structural Properties

A series of alternating copolymers containing cyclopentadithiophene (CPDT) flanked by thienyl moieties as electron-donor units and benzothiadiazole dicarboxylic imide (BTDI) as electron-acceptor units were designed and synthesized for solar cell applications. Different solubilizing side chains, including 2-ethylhexyl chains and n-octyl chains were attached to CPDT units, whereas 3,7-dimethyloctyl chains and n-octyl chains were anchored to the BTDI moieties. The impact of these substituents on the solubilities, molecular weights, optical and electrochemical properties, and thermal and structural properties of the resulting polymers was investigated. PCPDTDTBTDI-EH, DMO was synthesized via Suzuki polymerization, whereas PCPDTDTBTDI-8, DMO, and PCPDTDTBTDI-EH, 8 were prepared through direct arylation polymerization. PCPDTDTBTDI-8, DMO has the highest number average molecular weight (Mn = 17,400 g mol-1) among all polymers prepared. The PCPDTDTBTDI-8, DMO and PCPDTDTBTDI-8, 8 which have n-octyl substituents on their CPDT units have comparable optical band gaps (Eg ~ 1.3 eV), which are around 0.1 eV lower than PCPDTDTBTDI-EH, DMO analogues that have 2-ethylhexyl substituents on their CPDT units. The polymers have their HOMO levels between -5.10 and -5.22 eV with PCPDTDTBTDI-EH, DMO having the deepest highest occupied molecular orbital (HOMO) energy level. The lowest unoccupied molecular orbital (LUMO) levels of the polymers are between -3.4 and -3.5 eV. All polymers exhibit good thermal stability with decomposition temperatures surpassing 350 °C. Powder X-ray diffraction (XRD) studies have shown that all polymers have the amorphous nature in solid state.

Three-Dimensional Spirothienoquinoline-Based Small Molecules for Organic Photovoltaic and Organic Resistive Memory Applications

A new electron-rich spirothienoquinoline unit, ^tBuSAF-Th, has been developed via incorporation of a thienyl unit instead of a phenyl unit into the six-membered ring of the spiroacridine (SAF) and utilized for the first time as a building block for constructing small-molecule electron donors in organic solar cells (OSCs) and as active layers in organic resistive memory devices. The resulting three-dimensional spirothienoquinoline-containing 1-4 exhibit high-lying highest occupied molecular orbital (HOMO) energy levels. By the introduction of electron-deficient benzochalcogenodiazole linkers, with the chalcogen atoms being varied from O to S and Se, a progressively lower lowest unoccupied molecular orbital (LUMO) energy level has been achieved while keeping the HOMO energy levels similar. This strategy has allowed an enhanced light-harvesting ability without compromising open-circuit voltage (V_oc) in vacuum-deposited bulk heterojunction OSCs using 1-4 as donors and C₇₀ as the acceptor. Good photovoltaic performances with power conversion efficiencies (PCEs) of up to 3.86% and high short-circuit current densities (J_sc) of up to 10.84 mA cm^-2 have been achieved. In addition, organic resistive memory devices fabricated with these donor-acceptor small molecules exhibit binary logic memory behaviors with long retention times and high on/off current ratios. This work indicates that the spirothienoquinoline moiety is a potential building block for constructing multifunctional organic electronic materials.

Highly-Sensitive Detection of Volatile Organic Compound Vapors by Electrospun PANI/P3TI/PMMA Fibers

Detection of volatile organic compounds (VOCs) is one of the essential concerns for human health protection and environmental monitoring. In this study, the blending fibers using a donor-acceptor copolymer were fabricated by electrospinning technique and subsequent UV/ozone treatment. The donor-acceptor polymers were polyaniline, P3TI, and poly(methyl methacrylate) (PANI/P3TI/PMMA) fibers with a cylindrical structure and uniform morphology. VOCs were directly adsorbed by the copolymer materials assembled onto a glass surface or metal framework scaffold. Under optimal conditions, the PANI/P3TI/PMMA fibers exhibit rapid response and high selectivity to VOC vapors within 30 min of UV/ozone treatment. Additionally, the optical transmittance changes of the freestanding fibers show significant improvement of more than 10 times to those fibers on glass substrates. It is speculated that the presence of P3TI leads to the formation of a heterojunction and increases the electron reception behavior. The modification of the electronic structure as exposed to VOC vapors tend to significantly alter the optical absorbance of the fibers, leading to the excellent sensing at low VOC concentration.

Conjugated polymer nano-systems for hyperthermia, imaging and drug delivery

Hyperthermia has shown tremendous therapeutic efficiency in the treatment of cancer due to its controllability, minimal invasiveness and limited side effects compared to the conventional treatment techniques like surgery, radiotherapy and chemotherapy. To improve the precision of hyperthermia specifically to a tumor location, near infra-red (NIR) light activatable inorganic metal nanoparticles have served as effective photothermal therapy materials, but toxicity and non-biodegradability have limited their clinical applications. Conjugated polymer nanoparticles have overcome these limitations and are emerging as superior photothermal materials owing to their excellent light harvesting nature, biocompatibility and tunable absorption properties. In this review we focus on the development of organic conjugated polymers (polyaniline, polypyrrole, polydopamine etc.) and their nanoparticles, which have broad NIR absorption. Such materials elicit photothermal effects upon NIR stimulation and may also serve as carriers for delivery of therapeutic and contrast agents for combined therapy. Subsequently, the emergence of donor-acceptor based semiconducting polymer nanoparticles with strong absorbance that is tunable across the NIR have been shown to eradicate tumors by either hyperthermia alone or combined with other therapies. The design of multifunctional polymer nanoparticles that absorb near- or mid- infrared light for heat generation, as well as their diagnostic abilities for precise biomedical applications are highlighted.

Narrow bandgap difluorobenzochalcogenadiazole-based polymers for high-performance organic thin-film transistors and polymer solar cells

A series of difluorobenzochalcogenadiazole-bithiophene copolymers are developed for high-performance organic semiconductors.

Water-Soluble Conjugated Organic Molecules as Optical and Electrochemical Materials for Interdisciplinary Biological Applications

Apart from the wide applications in the field of electronic and optoelectronic devices, conjugated molecules have been established as useful functional materials for biological applications. By introducing hydrophilic side chains to conjugated backbones, water-soluble conjugated polymers or oligomers (CPs or COs) inherit the attractive optical and electronic properties from conjugated molecules, while their water solubility ensures interaction with biological substrates such as biomacromolecules, microorganisms, and living cells for further biological applications. Benefiting from high brightness, large extinction coefficients, excellent photostability, low cytotoxicity, stability in bodily fluids, and versatile structural modifications, water-soluble conjugated polymers and oligomers have offered powerful alternatives in a variety of biological applications including biological and chemical sensors, fluorescence imaging, disease diagnostics, and therapy. This Account will focus on our recent advances in design, synthesis, and interdisciplinary biological applications of a series of new water-soluble CP and CO materials, starting with a brief introduction to water-soluble CPs and COs and various methods and strategies developed for the preparation of advanced water-soluble CPs and COs. Since their properties can be tuned by rational design and synthesis at the level of the conjugated repeat unit and versatile pendant groups, CPs and COs provide a diverse toolbox for satisfying interdisciplinary biological applications. The application of water-soluble CPs and COs in the past five years can be broadly categorized into four areas. Specifically, integrating the unique optoelectronic properties of water-soluble CPs and COs with self-assembly and supramolecular strategies, efficacy regulation of antibiotic and anticancer drugs has been achieved, meanwhile drug resistance could be overcome and drug resistant "superbacteria" can be inhibited. For applications regulating cellular functions and biological processes, we introduce CPs and COs with the ability to regulate intracellular oxidative stress, cell-cell communication, cellular proliferation, cell membrane permeability, and quorum sensing of bacteria cells. By covalent linkage of reactive groups upon CPs and COs, these molecules are endowed with abilities like disassembly of amyloid polypeptides, biased distribution in cells, selective imaging of organelles, and distinguished interactions with biomolecules. For photothermal therapy (PTT) applications, photothermal-responsive conjugated polymer materials have been utilized for remote control of gene expression in living cells and in vivo photothermal therapy of cancer. Beyond these applications, we have achieved new interdisciplinary applications of water-soluble CP and CO materials for biological optoelectronic devices including photosynthesis, photocatalysis, and bioenergy. Specific features or properties of water-soluble CPs and COs are leveraged to bring opportunities for each of these applications. These studies open a new frontier for development of new functional conjugated molecule materials and provide better understanding of their interactions with biological systems as well as structure/property relationships. Current limitations confronted by CPs and COs are raised, and developmental direction for the future is proposed.

Benzochalcogendiazole-based conjugated molecules: investigating the effects of substituents and heteroatom juggling

A convenient and effective synthetic approach for benzochalcogendiazole-based small molecules has been achieved using polyaniline (PANI)-anchored palladium as a heterogeneous catalyst. The photophysical properties of the synthesized benzochalcogendiazole-based small molecules, having different terminal substituents, have been compared. Moreover, the structural aspects, including the packing patterns and non-bonding interactions of the conjugated molecules, have been investigated using the single crystal X-ray diffraction (SCXRD) technique.

The Synthesis and Optoelectronic Applications for Tellurophene-Based Small Molecules and Polymers

Tellurophene-based small molecules and polymers have received great attentions owing to their applications in thin-film transistors, solar cells, and sensors. This article reviews the current progress of the synthesis and applications of tellurophene-based small molecules and polymers. The physicochemical properties and optoelectronic applications of tellurophene-based materials are summarized and discussed. In the end, the challenges and outlook of tellurophene-based materials are presented.

Synthesis of Tellurium-Containing π-Extended Aromatics with Room-Temperature Phosphorescence

A synthesis of tellurium-embedded π-extended aromatics from tellurium powder and readily available cyclic diaryliodonium salts has been developed. The versatility of this method has been demonstrated by the synthesis of various functionalized dibenzotellurophenes (DBTe's), a ladder-type π-system, and a heterosumanene. These compounds demonstrated good air/moisture stability and high thermal stability. Remarkably, many DBTe's exhibited interesting tunable room-temperature phosphorescence (RTP) in the solid state.

The Effect of Acceptor Structure on Emission Color Tuning in Organic Semiconductors with D-π-A-π-D Structures

A series of novel donor-acceptor D-π-A-π-D compounds were synthesized and characterized in order to determine the influence of different acceptor units on their properties. The introduction of acceptor moieties had a direct impact on the HOMO and LUMO energy levels. Fluorescence spectra of compounds can be changed by the choice of an appropriate acceptor and were shifted from the green to the near-infrared part of spectra. Due to observed concentration induced emission quenching, the green exciplex type host was used to evaluate the potential of synthesized molecules as emitters in organic light emitting diodes (OLEDs).

Molecular Engineering of a Donor-Acceptor Polymer To Realize Single Band Absorption toward a Red-Selective Thin-Film Organic Photodiode

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study. By employing PCZ-Th-DPP as a photoactive layer of Schottky OPD, to fully match its absorption characteristic to the spectral response of the red-selective OPD, we demonstrate a genuine red-selective specific detectivity in the order of 10¹² Jones while maintaining a thin active layer thickness of ∼300 nm. This work demonstrates the possibility of realizing a full color image sensor with a synthetic approach to the constituting active layers without optical manipulation.