Dorothy Duo Duo Ma

Ag-modified silicon nanowires substrate for ultrasensitive surface-enhanced raman spectroscopy

We report a unique substrate for surface-enhanced raman spectroscopy (SERS) based on silver nanoparticles-embedded silicon nanowires (SiNWs). The SiNWs were prepared by thermal evaporation of SiO powder via oxide-assisted growth, oxide removed with HF, and then used to reduce silver ions to form a highly decorated Ag-embedded surface. Such modified SiNWs substrates yielded ultrahigh SERS sensitivity, which could detect 25μl of 1×10−16M Rhodamine 6G, 1×10−16M crystal violet, and 1×10−14M nicotine in methanol solutions. An Ag-modified SiNW strand could also enable SERS detection of 25μl of 1×10−8mg∕ml calf thymus DNA. The possible mechanisms for the ultrahigh SERS sensitivity were discussed.

Silicon nanowires with permanent electrostatic charges for nanogenerators.

Electrets are dielectric materials possessing a quasi-permanent electric charge or dipole polarization. Frequently, the electrets are adversely affected by environmental temperature and humidity, leading to charge instability, which severely restricts applications. Here we show that silicon nanowires (SiNWs) via modified oxide-assisted growth can surprisingly serve as electrets with permanent electrostatic charges and surface potential up to 7.7 mV. Significantly, the extraordinary electret behavior of SiNWs is extremely robust, remaining stable against immersion in water for over 2 months. The SiNWs were utilized to fabricate a nanogenerator, which yielded an output electrical power of 2.19 × 10(-11) W with a conversion efficiency of 2.2%. The nanogenerator consists of only one movable part, giving highly sustainable and stable output signals, and thus holds promise for various self-powered applications. The permanent electrostatic charges on SiNWs are attributed to the formation of α-quartz in SiNWs.

The mutual promotional effect of Au–Pd bimetallic nanoparticles on silicon nanowires: A study of preparation and catalytic activity

Au–Pd nanoparticles were synthesized on the surface of silicon nanowires and used in the degradation of the p-nitroaniline, which exhibited the mutual promotional effect compared with Au/Si and Pd/Si catalysts. This synergistic effect factor was calculated as 2.35. The Au–Pd/Si catalysts might be recycled and used again. The catalytic rate of the catalysts only decreased by 20% after recycling for five times.

SnO2 nanowires with strong yellow emission and their application in photoswitches

SnO2 nanowires with strong yellow emission centered at 550 nm were obtained by a high-temperature reaction via controlled oxygen flux. Characterization indicated that the products had a tetragonal SnO2 structure with an average diameter of 100 nm and length up to 100 μm. They also exhibited high photoresponse under an incandescent light, and may have potential application as photoswitches.

Silicon nanowires for high-specificity and high-selectivity sensors under low-frequency scanning

The high specificity and selectivity of H–Si nanowire bundles, which are single crystalline and composed of pure Si without oxygen, for detecting water (peak at 12 Hz) and ethanol (peak at 70 Hz) in their mixture are measured by a frequency scanning test. The signal amplitude deduced between the work channel and the reference channel {[(VR-VS)/VR]×100%} is defined as the impedance recorded under different scanning frequencies.

Strong and stable blue photoluminescence: The peapodlike SiOx@Al2O3 heterostructure

Peapodlike heterostructure composed of SiOx particles orderly embedded in the high-crystalline α-Al2O3 nanoribbons was fabricated via a two-step thermal reaction route. The room temperature photoluminescence spectrum of the products showed a strong and stable blue emission centered at 467 nm under excitation at 320 nm, which was attributed to the especial heterostructure. This technique also provided a general and convenient approach for preparing even more complex heterostructures and would be useful in improving the properties of materials.

Large-scale silica nanowire array grown on liquid tin and its applications as Hg (II) scavenger

Silica (SiO2) nanowire array has been prepared in large scale through thermal evaporation of SiO via oxide-assisted growth on Sn substrate. During growth the Sn substrate became a liquid, whose fluid surface induced the growth of SiO2 (from SiO disproportionation) into an aligned nanowire array on Sn surface. The liquid Sn itself further served as the solvent to dissolve elemental Si produced from SiO disproportionation. The high-density nanowire array is a type of microporous silica with a large surface area, which can serve as an efficient absorbent for scavenging heavy metal ions such as Hg (II) from water after surface modification with mercapto groups (–SH).