This paper presents a piezoresistive differential pressure sensor based on a silicon-on-insulator (SOI) structure for low pressure detection from 0 to 30 kPa. In the design phase, the stress distribution on the sensing membrane surface is simulated, and the doping concentration and geometry of the piezoresistor are evaluated. By optimizing the process, the realization of the pressure sensing diaphragm with a controllable thickness is achieved, and good ohmic contact is ensured. To obtain higher sensitivity and high temperature stability, an SOI structure with a 1.5 µm ultra-thin monocrystalline silicon layer is used in device manufacturing. The device diaphragm size is 700 µm × 700 µm × 2.1 µm. The experimental results show that the fabricated piezoresistive pressure sensor has a high sensitivity of 2.255 mV/V/kPa and a sensing resolution of less than 100 Pa at room temperature. The sensor has a temperature coefficient of sensitivity (TCS) of −0.221%FS/°C and a temperature coefficient of offset (TCO) of −0.209%FS/°C at operating temperatures ranging from 20 °C to 160 °C. The reported piezoresistive microelectromechanical systems (MEMS) pressure sensors are fabricated on 8-inch wafers using standard CMOS-compatible processes, which provides a volume solution for embedded integrated precision detection applications of air pressure, offering better insights for high-temperature and miniaturized low-pressure sensor research.

Through a new synthetic route, three ruthenium-phenanthroline porphyrins (RPP1, RPP2 and RPP3) were prepared. Their photophysical and photochemical properties, such as DNA photocleavage activity, singlet-oxygen photogeneration and two-photon absorption (2PA) were evaluated. These porphyrins 1–3 had substantial photocleavage activities, with 71%, 74% and 38% observed at 20 μM. The porphyrins with different substituents on phenathroline group had similar singlet oxygen quantum yields, with ΦΔ values at 0.52, 0.47 and 0.41, respectively. The 2PA cross-section (σ(2)) values of RPP 1–3, measured by the Z-scan method, were calculated to be 152, 172 and 135 GM, respectively, which were around 5-fold higher than that of H2TPP . Thus, these porphyrins, with their good photocleavage activities, 1 O 2 quantum yields and high 2PA cross section, suggest great potential as photodynamic therapeutic agents.

Three azobisporphyrins (Por1, Por2 and Por3) were synthesized by coupling two molecules of (4-nitrophenyl/pyridyl) porphyrins in the presence of KOH/butanol. The structures of porphyrins were confirmed by UV, IR, NMR and mass spectra and elemental analysis. With tetraphenylporphyrin (H2TPP) as a control, the singlet oxygen (1O[Formula: see text] generation of porphyrins was evaluated through 1,3-diphenylisobenzofuran (DPBF) method. The order of ability to generate 1O2 for three azobisporphyrins was Por 1 [Formula: see text]Por 2 > Por 3[Formula: see text] H2TPP. The photocytotoxicity and sub-cellular localization of azobisporphyrins over Hela cells were studied through MTT analysis and confocal laser scanning microscope, respectively. The results indicated Por 1 and Por 2 displayed the low dark-cytotoxicity, while Por 3 induced a concentration-dependent cytotoxicity to Hela cells with the concentration of porphyrins ranging from 1 to 100 [Formula: see text] M. With the light dose at 4 J/cm2, Por 3 killed more than 60% Hela cells at 2 [Formula: see text] M, indicating a high photocytoxicity. As seen from the laser scanning confocal microscopy images, Por 3 was mainly localized in cell membrane, while Por 1 and Por 2 do not displayed significant fluorescent emission in Hela cells. These results suggest the synthesized cationic azobisporphyrin could be used as a potential therapeutic agent for photodynamic therapy of cancers.

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