Polarization-sensitive photodetectors are highly desirable for high-performance optical signal capture and stray light shielding in order to enhance the capability for detection and identification of targets in dark, haze, and other complex environments. Usually, filters and polarizers are utilized for conventional devices to achieve polarization-sensitive detection. Herein, to simplify the optical system, a two-dimensional self-powered polarization-sensitive photodetector is fabricated based on a stacked GeSe/MoS2 van der Waals (vdW) heterojunction which facilitates efficient separation and transportation of the photogenerated carriers because of type-II band alignment. Accordingly, a high-performance self-powered photodetector is achieved with merits of a very large on–off ratio photocurrent at zero bias of currently 104 and a high responsivity (R λ) of 105 mA/W with an external quantum efficiency of 24.2%. Furthermore, a broad spectral photoresponse is extended from 380 to 1064 nm owing to the high absorption coefficient in a wide spectral region. One of the key benefits from these highly anisotropic orthorhombic structures of layered GeSe is self-powered polarization-sensitive detection with a peak/valley ratio of up to 2.95. This is realized irradiating with a 532 nm wavelength laser with which a maximum photoresponsivity of up to 590 mA/W is reached when the input polarization is parallel to the armchair direction. This work provides a facile route to fabricate self-powered polarization-sensitive photodetectors from GeSe/MoS2 vdW heterojunctions for integrated optoelectronic devices.

DNA oligonucleotides can form multi-stranded structures such as a duplex, triplex, and quadruplex, while the double helical structure is generally considered as the canonical structure of DNA oligonucleotides. Guanine-rich or cytosine-rich oligonucleotides, which are observed in telomere, centromere, and other biologically important sequences in vivo, can form four-stranded G-quadruplex and I-motif structures in vitro. In this study, we have investigated the effects of pH and cation on the structures and their stabilities of d(G4T4G4) and d(C4A4C4). The CD spectra and thermal melting curves of DNAs at various pHs demonstrated that acidic conditions induced a stable I-motif structure of d(C4A4C4), while the pH value did not affect the G-quadruplex structure and stability of d(G4T4G4). The CD spectra of the 1:1 mixture of d(G4T4G4) and d(C4A4C4) indicated that the acidic conditions inhibit the duplex formation between d(G4T4G4) and d(C4A4C4). Isothermal titration calorimetry measurements of the duplex formation at various pHs also quantitatively indicated that the acidic conditions inhibit the duplex formation. On the other hand, the CD spectra and thermal melting curves of DNAs in the absence and presence of Ca2+ indicated that Ca2+ induces a parallel G-quadruplex structure of d(G4T4G4) and then inhibits the duplex formation. These results lead to the conclusion that both the pH and coexisting cation can induce and regulate the structural polymorphisms the oligonucleotides in which they form the G-quadruplex, I-motif, and duplex depending on the conditions. Thus, the results reported here indicate pivotal roles of pH and coexisting cations in biological processes by regulating the conformational switching between the duplex and quadruplexes structures of the guanine-rich or cytosine-rich oligonucleotides in vivo.

A design mode, in which a casing is filled with a charge initiated off‐centre (eccentric point initiation), is common in the field of explosion and structural protection. The fragment velocity distribution along the circumference of the casing is distinctly non‐uniform due to the difference in blast loading around the circumference of the casing. To quantify the fragment velocity distribution, two kinds of cylindrical rings with different structural parameters were adopted. Static explosive experiments with three eccentric coefficients (0, 0.5, 1.0) were conducted with pulsed X‐ray diagnostics. Using coefficients derived from experimental data and calculating the effects of both the eccentricity of initiation and angle around the circumference, an angle‐dependent ratio βθ of charge mass to casing mass has been derived as a mean to modify the fragment velocity formula of Gurney for this application. The derived formula was shown to correctly predict the fragment velocity distribution around the circumference of the cylindrical ring. The calculated velocity distributions show good agreement with the experimental results.

A variety of two-dimensional (2D) nanodevices with diverse optoelectronic properties have been successfully fabricated. A strategy for engineering 2D heterostructures high-performance devices rich in functions and adaptable for specific applications must be developed. Herein, two types of photodetectors fabricated through van der Waals interactions from vertically stacked MoSe 2 / MoO 2 heterostructures with the thickness of MoO 2 flakes at 25 and 105 nm, respectively, which exhibits metallic and semiconductor characteristics on elevation at thickness from 25 to 105 nm. A higher photoresponse can be obtained from the thin MoO 2 flake vertically stacked MoSe 2 /MoO 2 heterostructure with the merits of a photoresponsivity of 100.86 mA•W −1 and a detectivity of 23.4 × 10 9 Jones. The external quantum efficiency reaches 23.5% at bias of 3 V under the illumination of a monochromatic light at 532 nm, which is better than thick MoO 2 flake heterostructure (thickness ∼ 105 nm). The enhanced mechanism originates from high absorption efficiency, high carrier conductivity, and better contact of thin metallic MoO 2 flakes compared to the thick MoO 2 flakes heterostructure, which relates to various Fermi energy levels of the two different MoO 2 flakes photodetector. This work can provide an interesting route for engineering optoelectronic high-performance devices and developing a diverse photodetector on the basis of transition metal dichalcogenides (TMDs)/transition metal oxides (TMOs) heterojunction.

Waveguide near-eye displays (NEDs) consist of a planar waveguide combiner and a coupling-in projection system. A two-dimensional geometrical waveguide (TDGW) can achieve an ultra-thin, large exit pupil diameter (XPD), wide-angle NED. The design method of a single-layer TDGW is presented and discussed in detail in this paper. A high-precision processing technology that can effectively guarantee the parallelism accuracy is also presented. A miniature coupling-in projection optics is designed with a catadioptric structure and integrated with the waveguide accordingly. Finally, a TDGW with a thickness of 1.75 mm is designed and analyzed. The results show that the stray light over the normal light is less than 0.5%, and the illuminance uniformity is well optimized. The field of view is up to 55°, and the XPD exceeds 12 m m × 10 m m at an eye relief (ERF) of 18 mm. A proof-of-concept prototype was fabricated and demonstrated.