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Van der Waals (vdW) heterojunctions, with their unique electronic and optoelectronic properties, have become promising candidates for photodetector applications. Amplifying the contribution of the depletion region in vdW heterojunction, which would enhance both of the collection efficiency and speed of the photogenerated carriers, presents an effective strategy for achieving high performance vdW heterojunction photodetectors. Herein, a fully depleted vdW heterojunction photodetector is built on two-dimensional (2D) semiconductor materials (GaTe and InSe) layered on a pattered bottom electrode in vertical structure, in which the generation and motion of carriers are exclusively achieved in the depletion region. Attributed to the intrinsic built-in electric field, the elimination of series resistance and the depletion region confinement of carriers, the as-fabricated photodetector exhibits prominent photovoltaic properties with a high open-circuit voltage of 0.465 V, as well as photoresponse characteristics with outstanding responsivity, detectivity and photoresponse speed of 63.7 A/W, 3.88 × 1013 Jones, and 32.7 μs respectively. The overall performance of this fully depleted GaTe/InSe vdW heterojunctions photodetectors are ranking high among the top level of 2D materials based photodetectors. It indicates the device architecture can provide new opportunities for the fabrication of high-performance photodetectors.

Abstract Since the end of 2019, a highly contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has deprived numerous lives worldwide, called COVID-19. Up to date, omicron is the latest variant of concern, and BA.5 is replacing the BA.2 variant to become the main subtype rampaging worldwide. These subtypes harbor an L452R mutation, which increases their transmissibility among vaccinated people. Current methods for identifying SARS-CoV-2 variants are mainly based on polymerase chain reaction (PCR) followed by gene sequencing, making time-consuming processes and expensive instrumentation indispensable. In this study, we developed a rapid and ultrasensitive electrochemical biosensor to achieve the goals of high sensitivity, the ability of distinguishing the variants, and the direct detection of RNAs from viruses simultaneously. We used electrodes made of MXene-AuNP (gold nanoparticle) composites for improved sensitivity and the CRISPR/Cas13a system for high specificity in detecting the single-base L452R mutation in RNAs and clinical samples. Our biosensor will be an excellent supplement to the RT-qPCR method enabling the early diagnosis and quick distinguishment of SARS-CoV-2 Omicron BA.5 and BA.2 variants and more potential variants that might arise in the future.

An increased demand for iron is a hallmark of cancer cells and is thought necessary to promote high cell proliferation, tumor progression and metastasis. This makes iron metabolism an attractive therapeutic target. Unfortunately, current iron-based therapeutic strategies often lack effectiveness and can elicit off-target toxicities. We report here a dual-therapeutic prodrug, DOXjade, that allows for iron chelation chemo-photothermal cancer therapy. This prodrug takes advantage of the clinically approved iron chelator deferasirox (ExJade®) and the topoisomerase 2 inhibitor, doxorubicin (DOX). Loading DOXjade onto ultrathin 2D Ti3C2 MXene nanosheets produces a construct, Ti3C2-PVP@DOXjade, that allows the iron chelation and chemotherapeutic functions of DOXjade to be photo-activated at the tumor sites, while potentiating a robust photothermal effect with photothermal conversion efficiencies of up to 40%. Antitumor mechanistic investigations reveal that upon activation, Ti3C2-PVP@DOXjade serves to promote apoptotic cell death and downregulate the iron depletion-induced iron transferrin receptor (TfR). A tumor pH-responsive iron chelation/photothermal/chemotherapy antitumor effect was achieved both in vitro and in vivo. The results of this study highlight what may constitute a promising iron chelation-based phototherapeutic approach to cancer therapy.

Infectious diseases severely threaten public health and global biosafety. In addition to transmission through the air, pathogenic microorganisms have also been detected in environmental liquid samples, such as sewage water. Conventional biochemical detection methodologies are time-consuming and cost-ineffective, and their detection limits hinder early diagnosis. In the present study, ultrafine plasmonic fiber probes with a diameter of 125 μm are fabricated for clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas)-12a-mediated sensing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Single-stranded DNA exposed on the fiber surface is trans-cleaved by the Cas12a enzyme to release gold nanoparticles that are immobilized onto the fiber surface, causing a sharp reduction in the surface plasmon resonance (SPR) wavelength. The proposed fiber probe is virus-specific with the limit of detection of ~2,300 copies/ml, and genomic copy numbers can be reflected as shifts in wavelengths. A total of 21 sewage water samples have been examined, and the data obtained are consistent with those of quantitative polymerase chain reaction (qPCR). In addition, the Omicron variant and its mutation sites have been fast detected using S gene-specific Cas12a. This study provides an accurate and convenient approach for the real-time surveillance of microbial contamination in sewage water.

Flexible acoustic sensors with high sensitivity, excellent mechanical strength, and easy integration are urgently needed for wearable electronics. MXene holds great promise as a sensing material for this application. However, low flexibility and stability limit the performance of MXene‐based composites. To alleviate the aforementioned issue, a flexible pressure sensor based on MXene/poly(3,4‐ethylenediox‐ythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) is fabricated and used as an acoustic sensor inhibiting high sensitivity, fast response time (57 ms), ultra‐thin thickness (30 μm), and remarkable stability. Excellent performance enables the sensor to detect and identify weak muscle movements and skin vibrations, such as word pronunciation and carotid artery pulse. Furthermore, by combining the proposed deep learning model based on number recognition convolutional neural network (NR‐CNN), speech recognition toward different pronunciations of numbers that appear frequently in daily conversations can be realized. High recognition accuracy (91%) is achieved by training and testing the proposed NR‐CNN with large amounts of data recorded by the sensor. Results demonstrate that the flexible and wearable MXene/PEDOT:PSS acoustic sensor accelerates intelligent artificial acoustics and possesses great potential for applications involving speech recognition and health monitoring.

Conventional strategies against hepatocellular carcinoma (HCC) remain unsatisfactory due to its invasiveness and poor prognosis. Herein, it is utmost imperative to require alternative modalities with less invasiveness, good clinical efficacy, and low side effects. A combination of photothermal therapy (PTT) and photodynamic therapy (PDT) is an emerging modality against refractory HCC. To date a majority of PTT/PDT paradigms has a disappointing therapeutic efficiency, owing to low targeting ability of nanotheranostic agents or imprecise irradiation of lasers. In this study, HCC‐specific targeting aptamer and chlorine e6 (Ce6)‐modified polydopamine (PDA) nanospheres with decoration of Pt quantum dots (termed Apt‐Ce6‐PDA@Pt bioconjugates) are explored to combat HCC in vivo by synergy of PTT and PDT modalities. The Apt‐Ce6‐PDA@Pt bioconjugates can effectively accumulate into tumor sites by specifically binding Glypican‐3 (GPC3)‐positive tumor cells, and core of PDA exerts strong optical absorption in near‐infrared (NIR) region to enable photothermal performance. Meanwhile, the moieties of Ce6 subsequently serve as photosensitizers and fluorophores to generate reactive oxygen species (ROS) and guide phototherapeutics, respectively. The current study finally suggests that Apt‐Ce6‐PDA@Pt bioconjugates can act as a protocol for programmable ablation of HCC and it is believed that it will have a significant impact on clinical translation of promising therapy.

Photonic and optoelectronic devices have been limited in most two-dimensional (2D) materials. Researchers have attempted diverse device structures, such as introducing some ferroelectric materials to form new hybrid materials that could improve the performance of these 2D devices. Ferroelectrics might adjust the carrier concentration, mobility, and bandgap of 2D materials to achieve non-volatile control of the photonic and optoelectronic properties. On the other hand, ferroelectrics have a spontaneous electric polarization that occurs below the Curie temperature and reverses under an applied electric field. The polarization can be modulated via incident light, while the light wavelengths can be tuned through switching the electric polarization. This could improve the performance of 2D photonic and optoelectronic devices. We believe that 2D materials, as an emerging member of 2D/ferroelectric hybrid materials, will have great potential in photonics and optoelectronics thanks to their tunable bandgap. Here, we provide a perspective of ferroelectrics on 2D materials for photonics and optoelectronics. We discuss the concept of ferroelectrics and their fundamentals and then present their unique advantages in optoelectronic devices.

Solvent evaporation and leakage of liquid electrolytes that restrict the practicality of dye-sensitized solar cells (DSSCs) motivate the quest for the development of stable and ionic conductive electrolyte. Gel polymer electrolyte (GPE) fits the criteria, but it still suffers from low efficiency due to insufficient segmental motion within the electrolytes. Therefore, incorporating metal oxide nanofiller is one of the approaches to enhance the performance of electrolytes due to the presence of cross-linking centers that can be coordinated with the polymer segments. In this research, polymer composite gel electrolytes (PCGEs) employing poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (P(VB-co-VA-co-VAc)) terpolymer as host polymer, tetrapropylammonium iodide (TPAI) as dopant salt, and copper oxide (CuO) nanoparticles as the nanofillers were produced. The CuO nanofillers were synthesized by sonochemical method and subsequently calcined at different temperatures (i.e., 200, 350, and 500 °C), denoted as CuO-200, CuO-350, and CuO-500, respectively. All CuO nanoparticles have different shapes and sizes that are connected in a chain which impact the amorphous phase and the roughness of the surface, proven by the structural and the morphological analyses. It was found that the PCGE consisting of CuO-350 exhibited the highest ionic conductivity of 2.54 mS cm−1 and apparent diffusion coefficient of triiodide of 1.537 × 10−4 cm2 s−1. The enhancement in the electrochemical performance of the PCGEs is correlated with the change in shape (rod to sphere) and size of CuO particles which disrupted the structural order of the polymer chain, facilitating the redox couple transportation. Additionally, a DSSC was fabricated and achieved the highest power conversion efficiency of 7.05% with JSC of 22.1 mA cm−2, VOC of 0.61 V, and FF of 52.4%.

Since atomically thin two-dimensional (2D) graphene was successfully synthesized in 2004, it has garnered considerable interest due to its advanced properties. However, the weak optical absorption and zero bandgap strictly limit its further development in optoelectronic applications. In this regard, other 2D materials, including black phosphorus (BP), transition metal dichalcogenides (TMDCs), 2D Te nanoflakes, and so forth, possess advantage properties, such as tunable bandgap, high carrier mobility, ultra-broadband optical absorption, and response, enable 2D materials to hold great potential for next-generation optoelectronic devices, in particular, mid-infrared (MIR) band, which has attracted much attention due to its intensive applications, such as target acquisition, remote sensing, optical communication, and night vision. Motivated by this, this article will focus on the recent progress of semiconducting 2D materials in MIR optoelectronic devices that present a suitable category of 2D materials for light emission devices, modulators, and photodetectors in the MIR band. The challenges encountered and prospects are summarized at the end. We believe that milestone investigations of 2D materials beyond graphene-based MIR optoelectronic devices will emerge soon, and their positive contribution to the nano device commercialization is highly expected.

Light-emitting diodes based on quantum dots as an active emission can be considered as a promising next generation for application in displays and lighting. We report a theoretical investigation of green emission at 550 nm of microcavity inorganic–organic light-emitting devices based on Zn (Te, Se) alloy quantum dots as an active layer. Distributed Bragg Reflector (DBR) has been applied as a bottom mirror. The realization of high-quality DBR consisting of both high and low refractive index structures is investigated. The structures applied for high refractive index layers are (ZrO2, SiNx, ZnS), while those applied for low index layers are (Zr, SiO2, CaF2). DBR of ZnS/CaF2 consisting of three pairs with a high refractive index step of (Δn = 0.95) revealed a broad stop bandwidth (178 nm) and achieved a high reflectivity of 0.914.

In this study, a novel label-free immunosensor platform is developed to exploit the localized surface plasmon resonance (LSPR) phenomenon. The LSPR solution-based platform is designed by a gold nanospheres probe, functionalized with monoclonal anti-dengue antibody (IgG). Numerical calculations are performed to assess the LSPR extinction spectrum and spatial near electric field distribution around the nanoparticle surface. Important parameters that govern sensor performance, molecular and refractive index sensitivity are evaluated. On the evaluation of the platform as a molecular sensor, the detection of dengue NS1 antigens is presented. The results are consistent with the numerical simulations, which depicts the system’s ability to identify dengue NS1 antigen concentrations as low as 0.07 ± 0.01 µg/mL, along with fosters its potential application in plasmonic sensing.

The luminescent properties and mechanisms of non-carrier injection (NCI) mode quantum dot light-emitting diodes (QLEDs) are explored in this work. The intermediate insulator electric layer, Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), effectively blocks carrier injection from the electrodes. Carriers for radiative recombination in the quantum dot (QD) layer are generated by the corresponding carrier generation complex layer under an AC electric field. In this investigation, the emission layer (EML), comprising distinct layers of Cd-based quantum dots, is precisely regulated using the spontaneous spreading (SS) method. The work reveals that the thickness of the QDs in NCI-QLEDs significantly influences the device’s luminescent performance. In NCI-QLEDs with a double QD layer as the EML, the device exhibits a maximum brightness of 1003.6 cd m−2 and a start-up voltage of 7 root mean square voltage (VRMS). This brightness level represents the highest reported for vertical emission NCI-QLEDs. All devices exhibit a broad range of driven voltages. Interestingly, luminescence is detected only during a half-cycle of the driven signal, as indicated by transient time-resolved spectrum test results. A system is established to analyze the luminescence mechanism comprehensively. Finally, a proposed carrier compounding mechanism sheds light on the behavior of NCI-QLED devices. [ABSTRACT FROM AUTHOR]

We present a detailed analysis and computations of the emitted radiation spectrum for quantum dots (QDs) microcavity light-emitting device, where the total physical thickness of the cavity spacer was kept at 254 nm which corresponds to the wavelength of the mode number (m) = 1 resonant mode of the cavity. Our calculation gives good results for QD diameter only from 1.2 to 6.4 nm. The computations are used to examine how the emitted radiation spectrum can be optimized by varying the position of the light-emitting layer, the type of cathode material, the choice of hole transport layer material, and the thickness of electron transport layer, QD layer, and hole transport layer. These studies showed that the variation of layers geometry and the position of the light-emitting layer will optimize the output intensity and the radiation spectrum and varying the ETL and QD layer thickness will have a more effect on the emitted spectrum than varying HTL thickness. In addition, we have examined the effect of using different quantum dots sizes in emission layer. On the other hand, we have investigated the difference between the electroluminescence (EL) emissions for microcavity device in comparison with the non-cavity device, and we have found that the full width at half maximum (FWHM) of the EL is reduced from 45 nm for the QD non-cavity LED to 30 nm for the output of a resonant microcavity device. Finally, we have investigated the compatibility between our calculation and the experimental results and found a fairly good agreement between them. [ABSTRACT FROM AUTHOR]

The mitigation of interfacial charge accumulation in solution-processed organic light-emitting diodes (s-OLEDs) is an effective method to improve device performance. In this study, the polar solvent vapor annealing (PSVA) method was used to treat two layers in s-OLED, PEDOT:PSS and mCP:DMAC-DPS emitting layers, separately, to optimize the carrier transmission and balance. After the double-layer PSVA treatment, the current efficiency increased, the lifetime of the device is improved, the efficiency roll-off alleviated from 33.3% to 26.6%, and the maximum brightness increased by 31.3%. It is worth mentioning that the work function of the EML interface reduced by 0.36 eV, and the initial injection voltage of the electrons also reduced. Simulating the solubility of the LUMO and HOMO molecule parts of the mCP and DMAC-DPS, it was found that the LUMO parts had stronger polarity and higher solubility in polar solution than the HOMO parts. By comparing the untreated luminescent layer films, it was found that the PSVA treatment improved the uniformity of the film morphology. We may infer that a more ordered molecular arrangement enhances carrier transport as the LUMO parts tend to be close to the surface and the reduced local state traps on the EML surface promote electron injection. According to the experimental results, the injection of holes and electrons is enhanced from both sides of the EML, respectively, and the charge accumulated at the interface of s-OLEDs is significantly reduced due to the improvement of carrier-transported characteristics. [ABSTRACT FROM AUTHOR]

Abstract Vanadium disulfide (VS2), a typical layered transition‐metal dichalcogenide, has drawn extensive attention in energy storage devices, catalysts as well as sensors due to its intriguing electronic peculiarities, whereas its chemiresistive gas sensing properties have seldom been investigated. In this contribution, first the ammonia sensing properties of VS2 nanosheets (NSs)‐based chemiresistive gas sensor are reported. VS2 NSs are synthesized through facile liquid‐phase exfoliation, and their crystal structure, micromorphology, and elemental component are characterized. Density functional theory calculation has revealed that VS2 (100) is highly affinitive to ammonia molecule, and sufficient electron transfers from ammonia to VS2, which implies VS2 NSs possess high potential for ammonia sensing. The computational results are verified by gas sensing measurement that the resistance of VS2 NSs remarkably increases upon injecting ammonia gas at low working temperature of 40 °C. Additionally, the VS2 NSs exhibit superb selectivity to ammonia. The probable mechanism for ammonia sensing can be that ammonia molecule absorbed at edge sites of VS2 NSs transfers electron to p‐type VS2 NSs, reduces hole concentration in the NSs, and thus leads to resistance enhancement of VS2 NSs.

The rapid development of luminescent solar concentrators (LSCs) is largely attributable to their advantageous features including colorful aesthetics, design flexibility, and their ability to harvest both outdoor (solar) and indoor (light emitting diodes (LD)) light. In this study, we fabricated and characterized a highly efficient LSC containing a newly synthesized pyrrolopyrazine-based aggregation-induced emissive fluorophore (PP1). PP1 comprises a central pyrrolopyrazine stator surrounded by three phenyl rotors proportionally end-capped with electron-donating dimethylamines and electron-accepting cyano moieties. Due to the high photoluminescence quantum yield (75%) of PP1 in polymethyl methacrylate matrix and a large Stokes shift, the fabricated LSCs showed the external photon efficiency (η ext) as high as 5.3% under 1 sun and 8.3% under LED illumination. Additionally, a theoretical model was employed to estimate the η ext of large-area (up to 100 cm length) PP1 LSCs. Photovoltaic measurements under 1 sun revealed that the champion device displayed a power conversion efficiency (η PCE) of 1.68% with scattering background and 0.95% without scattering background, the highest recorded η PCE among the aggregation-induced emission based LSCs. While the η PCE of the same LSC under LED illumination was 1.05% and 0.67% with and without scattering background, respectively. Collectively, this work demonstrates a substantial step forward toward the realization of highly efficient aggregation-induced emissive fluorophores based LSCs, that can be utilized not only as power producing building windows but also as the aesthetically appealing "wireless power suppliers" for uninterrupted functioning of various indoor electronic devices such as Internet-of-Things (IoT) and network sensors. [Display omitted] • Indoor/outdoor light harvesting LSC is fabricated. • PP1 LSCs showed η ext 5.3% and 8.3% under 1 Sun and LED light. • PP1 LSC showed η PCE of 0.95% and 0.67% (without scattering background) under 1 sun and LED light. [ABSTRACT FROM AUTHOR]