A Protein‐Nanocellulose Paper for Sensing Copper Ions at the Nano‐ to Micromolar Level

Tracing heavy metals is a crucial issue in both environmental and medical samples. In this work, a sensing biomolecule, the cyanobacterial C‐phycocyanin (CPC), is integrated into a nanocellulose matrix, and with this, a biosensor for copper ions is developed. The assembly of CPC‐functionalized nanocellulose into a red‐fluorescent, copper‐sensitive hybrid film “CySense”, enhances protein stability and facilitates the reuse and the regeneration of the sensor for several cycles over 7 days. CySense is suitable for the analysis of complex medical samples such as human serum filtrate. The reported biosensor reliably detects copper ion contents with a lower detection limit of 200 × 10^?9m and an IC50 of 4.9 × 10^?6m as changes in fluorescence emission intensity that can be measured with a fluorimeter or a microarray laser scanner.     

Selective Determination of Dopamine on a Boron‐Doped Diamond Electrode Modified with Gold Nanoparticle/Polyelectrolyte‐coated Polystyrene Colloids

Negatively charged gold nanoparticles (AuNPs) and a polyelectrolyte (PE) have been assembled alternately on a polystyrene (PS) colloid by a layer‐by‐layer (LBL) self‐assembly technique to form three‐dimensional (Au/PAH)₄/(PSS/PAH)₄ multilayer‐coated PS spheres (Au/PE/PS multilayer spheres). The Au/PE/PS multilayer spheres have been used to modify a boron‐doped diamond (BDD) electrode. Cyclic voltammetry is utilized to investigate the properties of the modified electrode in a 1.0 M KCl solution that contains 5.0 × 10^?3 M K₃Fe(CN)₆, and the result shows a dramatically decreased redox activity compared with the bare BDD electrode. The electrochemical behaviors of dopamine (DA) and ascorbic acid (AA) on the bare and modified BDD electrode are studied. The cyclic voltammetric studies indicate that the negatively charged, three‐dimensional Au/PE/PS multilayer sphere‐modified electrodes show high electrocatalytic activity and promote the oxidation of DA, whereas they inhibit the electrochemical reaction of AA, and can effectively be used to determine DA in the presence of AA with good selectivity. The detection limit of DA is 0.8 × 10^?6 M in a linear range from 5 × 10^?6 to 100 × 10^?6 M in the presence of 1 × 10^?3 M AA.     

Plasmon‐Enhanced Fluorescence‐Based Core–Shell Gold Nanorods as a Near‐IR Fluorescent Turn‐On Sensor for the Highly Sensitive Detection of Pyrophosphate in Aqueous Solution

Developing plasmon‐enhanced fluorescence (PEF) technology for identifying important biological molecules has a profound impact on biosensing and bioimaging. However, exploration of PEF for biological application is still at a very early stage. Herein, novel PEF‐based core–shell nanostructures as a near‐infrared fluorescent turn‐on sensor for highly sensitive and selective detection of pyrophosphate (PPi) in aqueous solution are proposed. This nanostructure gold nanorod (AuNR)@SiO₂@meso‐tetra(4‐carboxyphenyl) porphyrin (TCPP) contains a gold nanorod core with an aspect ratio of 2.3, a silica shell, and TCPP molecules covalently immobilized onto the shell surface. The silica shell is employed a rigid spacer for precisely tuning the distance between AuNR and TCPP and an optimum fluorescence enhancement is obtained. Due to the quenching effect of Cu²⁺, the copper porphyrin (TCPP‐Cu²⁺) results in a weak fluorescence. In the presence of PPi, the strong affinity between Cu²⁺ and PPi can promote the disassembly of the turn‐off state of TCPP‐Cu²⁺ complexes, and therefore the fluorescence can be readily restored. By virtue of the amplified fluorescence signal imparted by PEF, this nanosensor obtains a detection limit of 820 × 10^?9m of PPi with a good selectivity over several anions, including phosphate. Additionally, the potential applicability of this sensor in cell imaging is successfully demonstrated.     

Scissor‐Like Chiral Metamolecules for Probing Intracellular Telomerase Activity

A DNA‐driven gold (Au) heterodimer for intracellular telomerase detection is fabricated. The highly biocompatible and intracellularly stable probe shows an active chiroptical property in the visible region, due to the scissor‐like configuration formed by prolate nanoparticles. Importantly, the telomerase activity is specifically quantified using circular dichroism intensity in situ after internalization of the heterodimer into cancer cells. Moreover, the results clearly illustrate that this method has a remarkable linear range from 0.8 × 10^?12 to 32 × 10^?12 IU, and the limit of detection for telomerase activity is 1.7 × 10^?15 IU in a single HeLa cell. This strategy paves the way for chirality‐based ultrasensitive detection of intracellular cancer markers.     

2D Colloidal Array of Glucose‐Conjugative Conductive Microparticles for a Pressure‐Mediated Chemiresistive Sensor Platform

A platform is introduced for pressure‐mediated chemiresistive glucose sensing based on a 2D array of glucose‐conjugating silver nanowire (AgNW)‐deposited conductive microparticles (AgCMPs). Glucose‐conjugating AgCMPs, as transducers of the sensors, are fabricated by decorating the surface of monodisperse polyurethane elastomeric MPs with AgNWs by layer‐by‐layer deposition. Then, the AgNWs are covalently bonded to 4‐mercaptophenylboronic acid (4‐MPBA) to endow them with chemiresistive glucose sensing property against the applied pressure. The 4‐MPBA‐functionalized AgCMPs are positioned with high accuracy on a hole‐patterned stencil film placed between electrodes. Using this sensor system, it is shown that the current induced by the application of constant pressure to the sensor film at a given supply voltage varies linearly with the glucose concentration before and after critical glucose bridging concentration. Notably, the AgCMP‐based chemiresistive sensors could detect glucose over a wide concentration range from 0.56 × 10^?6 m to 56 × 10^?3 m with remarkable sensitivity and selectivity.     

Detection of Glioma‐Derived Exosomes with the Biotinylated Antibody‐Functionalized Titanium Nitride Plasmonic Biosensor

Titanium nitride (TiN), as an excellent alternative plasmonic supporting material compared to gold and silver, exhibits tunable plasmonic properties in the visible and near‐infrared spectra. However, label‐free surface plasmon resonance biosensing with TiN is seldom reported due to lack of proper surface functionalization protocols. Herein, this study reports biotinylated antibody‐functionalized TiN (BAF‐TiN) for high‐performance label‐free biosensing applications. The BAF‐TiN biosensor can quantitatively detect exosomes of 30–200 nm extracellular vesicles, isolated from a human glioma cell line. The limit of detection for an exosomal membrane protein with the BAF‐TiN biosensor is found to be 4.29 × 10^?3µg mL^?1 for CD63, an exosome marker, and 2.75 × 10^?3µg mL^?1 for epidermal growth factor receptor variant‐III, a glioma specific mutant protein, respectively. In conclusion, combining the biocompatibility, high stability, and excellent label‐free sensing performance of TiN, the BAF‐TiN biosensor could have great potential for the detection of cancer biomarkers, including exosomal surface proteins.     

Size Switchable Nanoclusters Fueled by Extracellular ATP for Promoting Deep Penetration and MRI‐Guided Tumor Photothermal Therapy

Protein‐based theranostic agents (PBTAs) exhibit superior performance in the diagnosis and therapy of cancers. However, the in vivo applications of PBTA are largely limited by undesired accumulation, penetration, or selectivity. Here, an ATP‐supersensitive protein cluster is fabricated for promoting PBTA delivery and enhancing magnetic resonance imaging (MRI)‐guided tumor photothermal therapy. Gd³⁺‐ and CuS‐coloaded small bovine serum albumin nanoparticles (GdCuB) are synthesized as the model protein with a size of 9 nm and are encapsulated into charge switchable polycations (DEP) to form DEP/GdCuB nanoclusters of 120 nm. In blood circulation, DEP/GdCuB significantly extends the half‐lifetime and thereby enhances the tumor accumulation of GdCuB. When the clusters reach the tumor site, the extracellular adenosine triphosphate (ATP) can effectively trigger the release of GdCuB, resulting in tumoral deep penetration as well as the activation of T₁‐weighted MRI (r₁ value switched from 2.8 × 10^?3 to 11.8 × 10^?3 m ^?1 s^?1). Furthermore, this delivery strategy also improves the tumoral photothermal therapy efficacy with the MRI‐guided therapy. The study of ATP‐activated nanoclusters develops a novel strategy for tumor deep penetration and on/off imaging of PBTA by size switchable technology, and reveals the potential for MRI‐guided therapy of cancers.     

Highly Reproducible Surface‐Enhanced Raman Scattering on a Capillarity‐Assisted Gold Nanoparticle Assembly

A facile method based on capillarity‐assisted assembly is used to fabricate high‐performance surface‐enhanced Raman scattering (SERS) substrates employing clean Au nanoparticles (NPs). This method is better than micro‐channel way because the former may supply large‐area uniform assembly and overcome the uneven radial distribution. Such densely‐arranged assembly of Au NPs exhibits high reproducibility and large Raman enhancement factors of 3 × 10¹⁰, arising from strong electromagnetic field coupling induced by adjacent Au NPs. The spot‐to‐spot SERS signals show that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1310, 1361, 1509, 1650 cm^?1) of Rhodamine 6G at a concentration of 1 × 10^?10 M are consistently less than 20%, demonstrating good spatial uniformity and reproducibility. The SERS signals of sudan dye at a 1 × 10^?8 M concentration also shows high reproducibility with a low RSD of <20%. Further, the assembly substrate is stable, retaining excellent uniformity and sensitivity after storage for months. This assembly strategy integrating the advantages of low‐cost production, high sensitivity, and reproducibility would significantly facilitate practical SERS detection.     

Thermo‐Switchable Charge Transport and Electrocatalysis Using Metal‐Ion‐Modified pNIPAM‐Functionalized Electrodes

Metal ions (Ag⁺, Cu²⁺, Hg²⁺) are incorporated into an electropolymerized, poly(N‐isopropyl acrylamide), pNIPAM, thermosensitive polymer associated with an electrode using the “breathing‐in” method. The ion‐functionalized pNIPAM matrices reveal ion‐dependent gel‐to‐solid phase‐transition temperatures (28 ± 1 °C, 25 ± 1 °C, 40 ± 1 °C for the Ag⁺, Cu²⁺, and Hg²⁺‐modified pNIPAM, respectively). Furthermore, the ion‐functionalized polymers exhibit quasi‐reversible redox properties, and the ions are reduced to the respective Ag⁰, Cu⁰, and Hg⁰ nanocluster‐modified polymers. The metal‐nanocluster‐functionalized pNIPAM matrices enhance the electron transfer (they exhibit lower electron‐transfer resistances) in the compacted states. The electron‐transfer resistances of the metal‐nanocluster‐modified pNIPAM can be cycled between low and high values by temperature‐induced switching of the polymer between its contracted solid and expanded gel states, respectively. The enhanced electron‐transfer properties of the metal nanocluster‐functionalized polymer are attributed to the contacting of the metal nanoclusters in the contracted state of the polymers. This temperature‐switchable electron transfer across a Ag⁰‐modified pNIPAM was implemented to design a thermo‐switchable electrocatalytic process (the temperature‐switchable electrocatalyzed reduction of H₂O₂ by Ag⁰‐pNIPAM).     

High‐Performance UV–Vis–NIR Phototransistors Based on Single‐Crystalline Organic Semiconductor–Gold Hybrid Nanomaterials

Hybrid materials in optoelectronic devices can generate new functionality or provide synergistic effects that enhance the properties of each component. Here, high‐performance phototransistors with broad spectral responsivity in UV–vis–near‐infrared (NIR) regions, using gold nanorods (Au NRs)‐decorated n‐type organic semiconductor and N ,N ′‐bis(2‐phenylethyl)‐perylene‐3,4:9,10‐tetracarboxylic diimide (BPE‐PTCDI) nanowires (NWs) are reported. By way of the synergistic effect of the excellent photo‐conducting characteristics of single‐crystalline BPE‐PTCDI NW and the light scattering and localized surface plasmon resonances (LSPR) of Au NRs, the hybrid system provides new photo‐detectivity in the NIR spectral region. In the UV–vis region, hybrid nanomaterial‐based phototransistors exhibit significantly enhanced photo‐responsive properties with a photo‐responsivity (R ) of 7.70 × 10⁵ A W^?1 and external quantum efficiency (EQE) of 1.42 × 10⁸% at the minimum light intensity of 2.5 µW cm^?2, which are at least tenfold greater than those of pristine BPE‐PTCDI NW‐based ones and comparable to those of high‐performance inorganic material‐based devices. While a pristine BPE‐PTCDI NW‐based photodetector is insensitive to the NIR spectral region, the hybrid NW‐based phototransistor shows an R of 10.7 A W^?1 and EQE of 1.35 × 10³% under 980 nm wavelength‐NIR illumination. This work demonstrates a viable approach to high‐performance photo‐detecting systems with broad spectral responsivity.     

Large‐Area Silver‐Coated Silicon Nanowire Arrays for Molecular Sensing Using Surface‐Enhanced Raman Spectroscopy

A new and facile method to prepare large‐area silver‐coated silicon nanowire arrays for surface‐enhanced Raman spectroscopy (SERS)‐based sensing is introduced. High‐quality silicon nanowire arrays are prepared by a chemical etching method and used as a template for the generation of SERS‐active silver‐coated silicon nanowire arrays. The morphologies of the silicon nanowire arrays and the type of silver‐plating solution are two key factors determining the magnitude of SERS signal enhancement and the sensitivity of detection; they are investigated in detail for the purpose of optimization. The optimized silver‐coated silicon nanowire arrays exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability, and reproducibility. Their further applications in rapidly detecting molecules relating to human health and safety are discussed. A 10 s data acquisition time is capable of achieving a limit of detection of approximately 4 × 10^?6 M calcium dipicolinate (CaDPA), a biomarker for anthrax. This value is 1/15 the infectious dose of spores (6 × 10^?5 M required), revealing that the optimized silver‐coated silicon nanowire arrays as SERS‐based ultrasensitive sensors are extremely suitable for detecting Bacillus anthracis spores.     

Position‐Sensitive Array Photodetector Based on Comb‐Like CdS Nanostructure with Cone‐Shape Branches

2D microscale position‐sensitive detectors (PSDs) are highly desirable with the degree of integration increase and the size reduction of nanodevices, which are still unavailable. Multichannel devices with outstanding photoelectric properties attract considerable interest as powerful building blocks to be applied in on‐chip systems. Here, based on a highly ordered comb‐like CdS nanowire array with cone‐shape branches through a one‐step synthesis strategy, a high‐resolution 2D position‐sensitive photodetector is realized through variable resistance in different transportation routes and variable optical responses at different parts of the cone‐shape branches, which enable accurate position identification of incident light in various zones of nanowire arrays according to photocurrent changes. In a broadband from 310 to 560 nm, the PSD exhibits high sensitivity with 85 and 58 KΩ µm^?1 in the trunk and branch part, respectively, and an ultrafast optical response shorter than tens of millisecond. Moreover, a lower conductivity change rate per unit temperature of the PSD (1.625 × 10^?9 A V^?1 K^?1) than that of commercial Si‐based PSDs (≈6.67 × 10^?7 A V^?1 K^?1) reveals outstanding low‐temperature performance. Finally, the multichannel nanostructure based PSD with nanoscale resolution is applied to high‐accuracy quadrant photodetectors.     

A Ratiometric Near‐Infrared Fluorescent Probe for Quantification and Evaluation of Selenocysteine‐Protective Effects in Acute Inflammation

Selenocysteine (Sec) is a primary kind of reactive selenium species in cells whose antioxidant roles in a series of liver diseases have been featured. However, it is difficult to determine Sec in living cells and in vivo due to its high reactivity and instability. This work reports a ratiometric near‐infrared fluorescent probe (Cy‐SS) for qualitative and quantitative determination of Sec in living cells and in vivo. The probe is composed of heptamethine cyanine fluorophore, the response unit bis(2‐hydroxyethyl) disulfide, and the liver‐targeting moiety d ‐galactose. Based on a detection mechanism of selenium–sulfur exchange reaction, the concentrations of Sec in HepG2, HL‐7702 cells, and primary mouse hepatocytes is determined as 3.08 ± 0.11 × 10^?6m , 4.03 ± 0.16 × 10^?6m and 4.34 ± 0.30 × 10^?6m , respectively. The probe can selectively accumulate in liver. The ratio fluorescence signal of the probe can be employed to quantitatively analyze the fluctuation of Sec concentrations in cells and mice models of acute hepatitis. The experimental results demonstrate that Sec plays important antioxidant and anti‐inflammatory roles during inflammatory process. And the levels of intracellular Sec have a close relationship with the degree of liver inflammation. The above imaging detections make this new probe a potential candidate for the accurate diagnosis of inflammation.     

Spectral efficiency improvement with SISO and SIMO in M‐QAM over millimeter‐wave links

This paper proposes a spectral efficiency improvement technique for millimeter wave (mmWave) links. The proposed technique provides an efficient utilization of the mmWave link capacity. This technique is applied in three cases the single‐input single‐output (SISO), single‐input multiple‐output (SIMO) with the maximal ratio combining and with the equal gain combining. The M‐ary quadrature amplitude modulation scheme is used in our work. The power series expansion is used for deriving closed‐form expressions for bit error rate (BER) performances in all studied cases. The BER closed‐form expressions are confirmed by the numerical solution of the integral equations. The simulation results show that a high spectral efficiency can be accomplished by the proposed technique. As well as the derived expressions closely match with the numerical solution of integration expressions at different values of modulations order the Rician factor. For instance, the spectral efficiency gain achievement is 8 at signal‐to‐noise ratio (SNR) equals 34 dB in the case of SISO system whereas in the case of SIMO system, the same gain is achieved at SNR equals 24 dB. As well as the BER performance is enhanced from 1.188 × 10^?4, 7.112 × 10^?4, 4.164 × 10^?3, and 3.286 × 10^?2 to 8.717 × 10^?16, 1.119 × 10^?12, 1.308 × 10^?9, and 4.905 × 10^?6 for M = 4, 16, 64, and 256, respectively, at SNR equals 30 dB.     

A surface plasmon resonance sensor based on a multi-core photonic crystal fiber

A surface plasmon resonance(SPR) sensor based on a multi-core photonic crystal fiber(PCF) is presented in this paper.There is only one analyte channel positioned in the center of the PCF cross section,rather than several closely arranged analyte channels around the central core.So the design of this sensor not only reduces the consumption of gold and samples,but also effectively avoids the interference between neighboring analyte channels.Optical field distributions of this fiber at different wavelengths and the sensing properties of this sensor are theoretically analyzed and discussed using finite element method(FEM).Simulation results confirm that both the thickness of metallic layer and the fiber structural parameters have significant effect on sensing performance.The amplitude sensitivity of the sensor is found to be 1.74×10-5RIU,and the spectral sensitivity is 3300 nm/RIU,corresponding to a resolution of 3.03×10-5 RIU.Finally,in order to achieve PCF-SPR sensing characteristics,an experiment design scheme based on spectroscopic detection method is proposed.     

Gold Core‐DNA‐Silver Shell Nanoparticles with Intense Plasmonic Chiroptical Activities

The strong plasmonic chiroptical activities of gold core‐DNA‐silver shell nanoparticles (NPs) are reported for the first time, using cytosine‐rich single‐stranded DNA as the template for the guidance of silver shell growth. The anisotropy factor of the optically active NPs at 420 nm reaches 1.93 × 10^?2. Their chiroptical properties are likely induced by the DNA–plasmon interaction and markedly amplified by the strong electromagnetic coupling between the gold core and silver shell.     

High‐Performance SiC Nanobelt Photodetectors with Long‐Term Stability Against 300 °C up to 180 Days

In the present work, high‐performance photodetectors (PDs) based on a single B‐doped 3C‐SiC nanobelt, which are synthesized via catalyst‐free pyrolysis of polymeric precursors of polysilazane, are reported. The as‐built PDs have a high responsivity and external quantum efficiency of 6.37 × 10⁵ A · W^?1 and 2.0 × 10⁸% under 405 nm light with a power density of 0.14 mW · cm^?2 at 5 V, respectively. The detectivity of the PDs is measured to be of 6.86 × 10¹⁴ Jones. Moreover, the B‐doped 3C‐SiC nanobelt PDs exhibit a long‐term stability against 300 °C up to 180 days, suggesting their promising applications to be served under harsh conditions.     

N‐Type Self‐Assembled Monolayer Field‐Effect Transistors and Complementary Inverters

This work describes n‐type self‐assembled monolayer field‐effect transistors (SAMFETs) based on a perylene derivative which is covalently fixed to an aluminum oxide dielectric via a phosphonic acid linker. N‐type SAMFETs spontaneously formed by a single layer of active molecules are demonstrated for transistor channel length up to 100 μm. Highly reproducible transistors with electron mobilities of 1.5 × 10^?3 cm² V^?1 s^?1 and on/off current ratios up to 10⁵ are obtained. By implementing n‐type and p‐type transistors in one device, a complimentary inverter based solely on SAMFETs is demonstrated for the first time.     

Humidity‐Driven Mechanical and Electrical Response of Graphene/Cloisite Hybrid Films

Humidity‐driven and electrically responsive graphene/cloisite hybrid films are obtained by casting water dispersions of graphene oxide and cloisite Na⁺. Coupling hydrophilicity and a high water vapor barrier in a homogenous film enables to realize humidity‐driven actuators which exploit the water gradient generated across the film section under asymmetric exposure to humidity. The hybrid films are self‐standing, flexible, and exhibit fast humidity‐triggered bidirectional bending up to 75°, which is tuned by varying the relative amount of the two components. Up to 60% of the bending angle can be preserved at the steady state, providing a large and reliable response to humidity. Moreover, thermal treatment results in the reduction of graphene oxide, endowing the films with humidity‐dependent electrical conductivity, which increases from 1.5 × 10^?6 S at 20% relative humidity (RH) up to 2.7 × 10^?5 S at 90% RH. The films are used to realize a humidity‐sensitive electrical switching system in which the reversible actuation is due to water desorption induced by the Joule effect. Due to their ease of preparation and tunable properties, this new class of graphene‐based materials is suitable for the realization of humidity‐driven and electrically responsive actuators and sensors.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.