KNEIPP J, KNEIPP H, WITTIG B, et al.. Novel optical nanosensors for probing and imaging live cells[J].Nanomed.:Nanotechnol., Biol. Med., 2010, 6(2):214-226.

ISLAM S, BIDIN N, RIAZ S, et al.. Sol-gel based fiber optic pH nanosensor:structural and sensing properties[J].Sens. Actuators A Phys., 2016, 238:8-18.

WANG X D, STOLWIJK J A, LANG T, et al.. Ultra-small, highly stable, and sensitive dual nanosensors for imaging intracellular oxygen and pH in cytosol[J].J. Am. Chem. Soc., 2012, 134(41):17011-17014.

FUJISAKU T, TANABE R, ONODA S, et al.. pH nanosensor using electronic spins in diamond[J].ACS Nano, 2019, 13(10):11726-11732.

SHAMSIPUR M, BARATI A, NEMATIFAR Z. Fluorescent pH nanosensors:design strategies and applications[J].J. Photochem. Photobiol. C Photochem. Rev., 2019, 39:76-141.

WENCEL D, ABEL T, MCDONAGH C. Optical chemical pH sensors[J].Anal. Chem., 2014, 86(1):15-29.

PENG H S, STOLWIJK J A, SUN L N, et al.. A nanogel for ratiometric fluorescent sensing of intracellular pH values[J].Angew. Chem. Int. Ed., 2010, 49(25):4246-4249.

LU H G, JIN Y G, TIAN Y Q, et al.. New ratiometric optical oxygen and pH dual sensors with three emission colors for measuring photosynthetic activity in cyanobacteria[J].J. Mater. Chem., 2011, 21(48):19293-19301.

SCHREML S, MEIER R J, WOLFBEIS O S, et al.. 2D luminescence imaging of pH in vivo[J].Proc. Natl. Acad. Sci. USA, 2011, 108(6):2432-2437.

WANG X D, MEIER R J, WOLFBEIS O S. A fluorophore-doped polymer nanomaterial for referenced imaging of pH and temperature with sub-micrometer resolution[J].Adv. Funct. Mater., 2012, 22(20):4202-4207.

WANG C, OTTO S, DORN M, et al.. Luminescent TOP nanosensors for simultaneously measuring temperature, oxygen, and pH at a single excitation wavelength[J].Anal. Chem., 2019, 91(3):2337-2344.

WANG X H, PENG H S, YANG L, et al.. Targetable phosphorescent oxygen nanosensors for the assessment of tumor mitochondrial dysfunction by monitoring the respiratory activity[J].Angew. Chem. Int. Ed., 2014, 53(46):12471-12475.

SHI W, LI X H, MA H M. Fluorescent probes and nanoparticles for intracellular sensing of pH values[J].Methods Appl. Fluoresc., 2014, 2(4):042001.

MA T C, MA Y, LIU S J, et al.. Dye-conjugated upconversion nanoparticles for ratiometric imaging of intracellular pH values[J].J. Mater. Chem. C, 2015, 3(26):6616-6620.

NÄREOJA T, DEGUCHI T, CHRIST S, et al.. Ratiometric sensing and imaging of intracellular pH using polyethylenimine-coated photon upconversion nanoprobes[J].Anal. Chem., 2017, 89(3):1501-1508.

BRUNI F, PEDRINI J, BOSSIO C, et al.. Two-color emitting colloidal nanocrystals as single-particle ratiometric probes of intracellular pH[J].Adv. Funct. Mater., 2017, 27(12):1605533-1-9.

FULAZ S, HIEBNER D, BARROS C H N, et al.. Ratiometric imaging of the in situ pH distribution of biofilms by use of fluorescent mesoporous silica nanosensors[J].ACS Appl. Mater. Interfaces, 2019, 11(36):32679-32688.

WANG X H, YU Y X, CHENG K, et al.. Polylysine modified conjugated polymer nanoparticles loaded with the singlet oxygen probe 1, 3-diphenylisobenzofuran and the photosensitizer indocyanine green for use in fluorometric sensing and in photodynamic therapy[J].Microchim. Acta, 2019, 186(12):842-1-8.

WANG X H, PENG H S, YANG W, et al.. Indocyanine green-platinum porphyrins integrated conjugated polymer hybrid nanoparticles for near-infrared-triggered photothermal and two-photon photodynamic therapy[J].J. Mater. Chem. B, 2017, 5(9):1856-1862.

GE J Y, FAN L, ZHANG K, et al.. A two-photon ratiometric fluorescent probe for effective monitoring of lysosomal pH in live cells and cancer tissues[J].Sens. Actuators B Chem., 2018, 262:913-921.