Electrolyte‐Gated n‐Type Transistors Produced from Aqueous Inks of WS2 Nanosheets

Solution‐processed, low cost thin films of layered semiconductors such as transition metal dichalcogenides (TMDs) are potential candidates for future printed electronics. Here, n‐type electrolyte‐gated transistors (EGTs) based on porous WS₂ nanosheet networks as the semiconductor are demonstrated. The WS₂ nanosheets are liquid phase exfoliated to form aqueous/surfactant stabilized inks, and deposited at low temperatures (T < 120 °C) in ambient atmosphere by airbrushing. No solvent exchange, further additives, or complicated processing steps are required. While the EGTs are primarily n‐type (electron accumulation), some hole transport is also observable. The EGTs show current modulations > 10⁴ with low hysteresis, channel width‐normalized on‐conductances of up to 0.27 µS µm^?1 and estimated electron mobilities around 0.01 cm² V^?1 s^?1. In addition, the WS₂ nanosheet networks exhibit relatively high volumetric capacitance values of 30 F cm^?3. Charge transport within the network depends significantly on the applied lateral electric field and is thermally activated, which supports the notion that hopping between nanosheets is a major limiting factor for these networks and their future application.     

Bottom‐Up Preparation of Fully sp2‐Bonded Porous Carbons with High Photoactivities

Porous carbons, possessing exceptional stability, high surface area, and electric conductivity, are broadly used as superior adsorbent, supporter, or electrode material for environmental protection, industrial catalysis, and energy storage and conversion. The construction of such kinds of materials with designable structures and properties will extremely extend their potential applications, but remains a huge synthetic challenge. Herein, a bottom‐up approach is presented to synthesize one type of fully sp² carbon–bonded frameworks by transition metal–catalyzed cross‐coupling of different polyphenylenes with electron‐withdrawing 9,9′‐bifluorenylidene (9,9′‐BF) through its 2,7‐position. The resulting porous polymeric carbons exhibit substantial semiconducting properties, such as strong light‐harvesting capabilities in the visible light region, likely due to their π‐extended backbones with donor–acceptor characters. Their electronic and porous structures can be finely tuned via the polyphenylene spacers. The intriguing properties allow these porous carbons to efficiently catalyze dye degradation under visible light or even natural sunlight with high reusability. Meanwhile, associated with their intrinsic structures, these porous carbons also exhibit highly selective degradation activities toward different dyes. In particular, the photodegradation mechanism involving oxygen and electron is elucidated for the first time for such kinds of materials, related to the presence of specific 9,9′‐BF units in their π‐conjugated skeletons.     

Semiconducting Nanocomposite with AIEgen‐Triggered Enhanced Photoluminescence and Photodegradation for Dual‐Modality Tumor Imaging and Therapy

Semiconducting polymer nanoparticles (SPNs) have potential in biological applications. While some SPNs have significant photothermal conversion efficiencies (PCEs) as photothermal and photoacoustic agents, other SPNs offer high fluorescence yields as photoluminescent agents. However, the energy balance distribution in SPNs inhibits their successful applications in photoluminescence/photoacoustic (PL/PA) dual‐modality imaging. Additionally, the ultrastability of SPNs in vivo may cause damage to organisms. This work reports nanocomposite semiconducting polymer and tetraphenylethene nanoparticles (STNPs) constructed by semiconducting polymers (SPs) and tetraphenylethene aggregation‐induced emission luminogens (TPE AIEgens). The SP SPC10 endows good photothermal conversion ability, and the AIEgen TPBM supports enhanced photoluminescence of the STNPs. The results show that the STNPs can act as PL/PA dual‐modality imaging agents. The signal‐to‐noise (S/N) ratio in the PL modality reaches 8.7, and the imaging depth in the PA modality is 5.8 mm. The SPC10 in the STNPs can be decomposed under 90 mW cm^?2 white light irradiation in 6 h without any other additional agents. Furthermore, the STNPs are sufficient for the treatment of xenograft 4T1 tumor‐bearing mice based on photothermal therapy. The nanocomposite STNPs achieve optimized dual‐modality PL/PA imaging and the AIEgen‐triggered in situ photodegradation of SPNs. These properties indicate the significant potential of STNPs in clinical diagnosis and noninvasive therapy.     

Spontaneous Phase Separation of Poly(3‐hexylthiophene)s with Different Regioregularity for a Stretchable Semiconducting Film

Highly regioregular (RR) poly(3‐hexylthiophene)s PHTs are known to exhibit excellent electrical properties in comparison to chemically identical but regiorandom (rr) PHTs. In this study, distinct RR (97% and 55%)‐graded PHTs are subjected to solution blending to spontaneously separate the high‐RR PHT chains from the low‐RR PHT media and develop highly conjugated nanodomains in both solution and film. In the spun‐cast blend films, the rr PHT matrix imparts sufficient deformability of the channel layer required for stretchable organic thin‐film transistors (OTFTs), compared to neat RR PHTs and blends with a deformable polymer. OTFTs including RR PHT/rr PHT blend films show excellent hole mobility (µ) values up to 0.13 cm² V^?1 s^?1, surpassing that of the best RR PHT films (0.026 cm² V^?1 s^?1) fabricated by ultrasound solution pretreatment. Furthermore, a 50% stretched RR PHT/rr PHT film maintains ≈55% of its µ value at no strain, while RR PHT films show a sudden decrease in µ even at 10% stretch. The simple blending approach imparts deformability to π‐conjugated polymer films for application in stretchable OTFTs.     

Van der Waals SnSe2(1−x)S2x Alloys: Composition‐Dependent Bowing Coefficient and Electron–Phonon Interaction

The design of advanced functional materials with customized properties often requires the use of an alloy. This approach has been used for decades, but only recently to create van der Waals (vdW) alloys for applications in electronics, optoelectronics, and thermoelectrics. A route to engineering their physical properties is by mixing isoelectronic elements, as done for the SnSe_2(1?x)S_2x alloy. Here, by experiment and first‐principles modeling, it is shown that the value of x can be adjusted over a wide range, indicating good miscibility of the SnS₂ and SnSe₂ compounds. The x‐dependence of the indirect bandgap energy from E_ind = 1.20 eV for SnSe₂ to E_ind = 2.14 eV for SnS₂, corresponds to a large bowing coefficient b ≈ 1 eV, arising from volume deformation and charge exchange effects due to the different sizes and orbital energies of the S‐ and Se‐atoms. This also causes composition‐dependent phonon energy modes, electron–phonon interaction, and temperature dependence of E_ind. The alloys are exfoliable into thin layers with properties that depend on the composition, but only weakly on the layer thickness. This work shows that the electronic and vibrational properties of the SnSe_2(1?x)S_2x alloy and its thin layers provide a versatile platform for development and exploitation.     

Ultrasmall Semiconducting Polymer Dots with Rapid Clearance for Second Near‐Infrared Photoacoustic Imaging and Photothermal Cancer Therapy

Phototheranostic agents in the second near‐infrared (NIR‐II) window (1000–1700 nm) are emerging as a promising theranostic platform for precision medicine due to enhanced penetration depth and minimized tissue exposure. The development of metabolizable NIR‐II nanoagents for imaging‐guided therapy are essential for noninvasive disease diagnosis and precise ablation of tumors. Herein, metabolizable highly absorbing NIR‐II conjugated polymer dots (Pdots) are reported for the first time for photoacoustic imaging guided photothermal therapy (PTT). The unique design of low‐bandgap D‐A π‐conjugated polymer (DPP‐BTzTD) together with modified nanoreprecipitation conditions allows to fabricate NIR‐II absorbing Pdots with ultrasmall (4 nm) particle size. Extensive experimental tests demonstrate that the constructed Pdots exhibit good biocompatibility, excellent photostability, bright photoacoustic signals, and high photothermal conversion efficiency (53%). In addition, upon tail‐vein intravenous injection of tumor‐bearing mice, Pdots also show high‐efficient tumor ablation capability with rapid excretion from the body. In particular, both in vitro and in vivo assays indicate that the Pdots possess remarkable PTT performance under irradiation with a 1064 nm laser with 0.5 W cm^?2, which is much lower than its maximum permissible exposure limit of 1 W cm^?2. This pilot study thus paves a novel avenue for the development of organic semiconducting nanoagents for future clinical translation.     

Functionalized NIR‐II Semiconducting Polymer Nanoparticles for Single‐cell to Whole‐Organ Imaging of PSMA‐Positive Prostate Cancer

Development of molecular probes holds great promise for early diagnosis of aggressive prostate cancer. Here, 2‐[3‐(1,3‐dicarboxypropyl) ureido] pentanedioic acid (DUPA)‐conjugated ligand and bis‐isoindigo‐based polymer (BTII) are synthesized to formulate semiconducting polymer nanoparticles (BTII‐DUPA SPN) as a prostate‐specific membrane antigen (PSMA)‐targeted probe for prostate cancer imaging in the NIR‐II window. Insights into the interaction of the imaging probes with the biological targets from single cell to whole organ are obtained by transient absorption (TA) microscopy and photoacoustic (PA) tomography. At single‐cell level, TA microscopy reveals the targeting efficiency, kinetics, and specificity of BTII‐DUPA SPN to PSMA‐positive prostate cancer. At organ level, PA tomographic imaging of BTII‐DUPA SPN in the NIR‐II window demonstrates superior imaging depth and contrast. By intravenous administration, BTII‐DUPA SPN demonstrates selective accumulation and retention in the PSMA‐positive tumor, allowing noninvasive PA detection of PSMA overexpressing prostate tumors in vivo. The distribution of nanoparticles inside the tumor tissue is further analyzed through TA microscopy. These results collectively demonstrate BTII‐DUPA SPN as a promising probe for prostate cancer diagnosis by PA tomography.     

Self‐Assembled Semiconducting Polymer Nanoparticles for Ultrasensitive Near‐Infrared Afterglow Imaging of Metastatic Tumors

Detection of metastatic tumor tissues is crucial for cancer therapy; however, fluorescence agents that allow to do share the disadvantage of low signal‐to‐background ratio due to tissue autofluorescence. The development of amphiphilic poly(p‐phenylenevinylene) derivatives that can self‐assemble into the nanoagent (SPPVN) in biological solutions and emit near‐infrared afterglow luminescence after cessation of light irradiation for ultrasensitive imaging of metastatic tumors in living mice is herein reported. As compared with the counterpart nanoparticle (PPVP) prepared from the hydrophobic PPV derivate, SPPVN has smaller size, higher energy transfer efficiency, and brighter afterglow luminescence. Moreover, due to the higher PEG density of SPPVN relative to PPVP poly(ethylene glycol), SPPVN has a better accumulation in tumor. Such a high sensitivity and ideal biodistribution allow SPPVN to rapidly detect xenograft tumors with the size as small as 1 mm³ and tiny peritoneal metastatic tumors that are almost invisible to naked eye, which is not possible for PPVP. Moreover, the oxygen‐sensitive afterglow makes SPPVN potentially useful for in vivo imaging of oxygen levels. By virtue of enzymatic biodegradability and ideal in vivo clearance, these organic agents can serve as a platform for the construction of advanced afterglow imaging tools.     

Control of Shell Morphology in p–n Heterostructured Water‐Processable Semiconductor Colloids: Toward Extremely Efficient Charge Separation

This article describes p–n heterostructured water‐borne semiconductor naonoparticles (NPs) with unique surface structures via control of shell morphology. The shell particles, comprising PC60–[6,6]‐phenyl‐C61‐butyric acid methyl ester (PC₆₁BM) composite, having n‐type semiconductor characteristics, notably influence the charge carrier behavior in the core–shell NPs. A one‐ or two‐phase methodology based on a PC60 surfactant‐water phase and PC₆₁BM n‐type semiconductor‐organic phase provides highly specific control over the shell structure of the NPs, which promote their superior charge separation ability when combined with poly‐3‐hexyl‐thiophene (P3HT). Moreover, the resulting water‐borne NP exhibits shell morphology‐dependent carrier quenching and stability, which is characterized via luminescence studies paired with structural analysis. Corresponding to the results, outstanding performances of photovoltaic cells with over 5% efficiency are achieved. The results suggest that the surrounding shell environments, such as the shell structure, and its electronic charge density, are crucial in determining the overall activity of the core–shell p–n heterostructured NPs. Thus, this work provides a new protocol in the current fields of water‐based organic semiconductor colloids.