Ultra-broad spectral detection is critical for several technological applications in imaging, sensing, spectroscopy, and communication. Carbon nanotube (CNT) films are a promising material for ultra-broadband photodetectors because their absorption spectra cover the entire ultraviolet to the terahertz range. However, because of the high binding energy of excitons, photodetectors based on CNT films always require a strong electric field, asymmetric electrical contacts, or hybrid structures with other materials. Here, we report an ultra-broadband bolometric photodetector based on a suspended CNT film. With an abundant distribution of tube diameters and an appropriate morphology (spider web-like), the CNT films display a strong absorption spectrum from the ultraviolet up to the terahertz region. Under illumination, heat generated from the electron–photon interaction dominates the photoresponse of our devices. For small changes in temperature, the photocurrent shows a convincing linear dependence with the absorbed light’s power across 3 orders of magnitude. When the channel length is reduced to 100 μm, the device demonstrates a high performance with an ultraviolet responsivity of up to 0.58 A/W with a bias voltage of 0.2 V and a short response time of ∼150 μs in vacuum, which is better than that of many other photodetectors based on CNTs. Moreover, this performance could be further enhanced by optimization.

Fast switching of positive and negative photocurrents of a device under the modulation of different incident laser power densities.

Silver nanostructured films suitable for use as surface-enhanced Raman scattering (SERS) substrates are prepared in just 2 hours by the solid-state ionics method. By changing the intensity of the external direct current, we can readily control the surface morphology and growth rate of the silver nanostructured films. A detailed investigation of the surface enhancement of the silver nanostructured films using Rhodamine 6G (R6G) as a molecular probe revealed that the enhancement factor of the films was up to 1011. We used the silver nanostructured films as substrates in SERS detection of human red blood cells (RBCs). The SERS spectra of RBCs on the silver nanostructured film could be clearly detected at a laser power of just 0.05 mW. Comparison of the SERS spectra of RBCs obtained from younger and older donors showed that the SERS spectra depended on donor age. A greater proportion of the haemoglobin in the RBCs of older donors was in the deoxygenated state than that of the younger donors. This implies that haemoglobin of older people has lower oxygen-carrying capacity than that of younger people. Overall, the fabricated silver substrates show promise in biomedical SERS spectral detection.

Silver nanostructures were prepared by a solid-state ionics method using fast ionic conductor RbAg(4)I(5) films under a direct current electric field (DCEF). The surface morphology of the silver nanostructures grown under different constant current fields was characterized by scanning electron microscopy (SEM). Rhodamine 6G (R6G) aqueous solutions were used as probe molecules to detect the Raman enhancement performance of the silver nanostructure substrates. The effect of external electric field current intensity on the surface morphology of the silver nanostructures during the preparation was studied in detail. The enhancement effect of the silver nanostructure surface enhanced Raman scattering (SERS) substrates with different surface morphologies toward R6G was determined. We found that disordered silver nanowires (DSNW), ordered silver nanowires (OSNW), densely arranged silver nanobamboo arrays (SNBA) and compactly arranged silver nanobud clusters (SNBC) were respectively obtained when the constant current intensity was 3 μA, 5 μA, 8 μA and 12 μA under the same vacuum evaporation plating conditions. The limiting concentrations of R6G for these SERS substrates were found to be 10(-7) mol l(-1), 10(-13) mol l(-1), 10(-13) mol l(-1) and 10(-16) mol l(-1), respectively.

Eutectic gallium-indium (EGaIn) alloy is a kind of liquid metal and has attracted much attention due to good properties. In order to satisfy the trend of miniaturization and realize more practical applications, the exploration for preparation method and properties of EGaIn at nanoscale are very important. Here, facile vacuum thermal evaporation method is developed to fabricate EGaIn nanostructures. The EGaIn nanoparticle and nanofilm with naturally formed 5 nm thick oxide layers are well prepared. The oxide film formed on the EGaIn surface is an important factor, making the properties of the nanostructure different from the properties of the bulk. Compared with ignorance of oxide layer in bulk materials, the proportion of oxide layer increases evidently in nanostructures, which produce obvious influence on the electric and optical properties. The rectifying characteristic and optoelectronic performance are experimentally observed. The EGaIn nanostructures can generate evident photocurrent responses with good responsivities (∼1 mA W −1 ) and response speed (∼1 s) under irradiation of 206 nm, 405 nm, 532 nm, 635 nm, 808 nm, 1064 nm and 10.6 μm lasers. These properties are completely different from the metallic properties of EGaIn bulk material.