Fluorescent Nanosensors for pH Detection and Imaging

Fluorescent nanosensors constitute a versatile class of analytical tools that exploit the optical response of nanometre‐scale materials to local proton concentrations. By integrating pH‐sensitive fluorophores within inert nano‐matrices or on the surface of nanoparticles, these sensors offer high spatial and temporal resolution for real‐time monitoring of acidity in diverse environments. The design of such nanosensors encompasses ratiometric schemes, dual‐fluorophore constructs and fluorescence lifetime imaging modalities, each tailored to enhance sensitivity, minimise background interference and extend dynamic range. Applications span intracellular mapping of organellar pH, in vivo biosensing, environmental monitoring of water bodies and industrial process control. Key performance metrics include photostability, fast response time and tunable pKa values, enabling measurement across physiological to highly alkaline regimes. Recent innovations have demonstrated imaging depths in biological tissues and two‐dimensional pH mapping in sediments, underscoring the global significance of these tools in both fundamental research and practical applications.

Research from Nature Portfolio

Researchers have developed a dual‐lumophore planar optode capable of high‐resolution two‐dimensional pH imaging in alkaline sediments and freshwater. The sensor film employs a proton‐permeable polymer matrix doped with two complementary dyes, yielding a sigmoid calibration curve over pH 7.5–10.5, negligible ionic‐strength interference and a spatial resolution of ~22 µm. Response times below 120 s and robust performance under varying temperatures enabled visualisation of photosynthesis‐driven pH gradients in natural sediments, demonstrating the sensor’s promise for field measurements of biogeochemical processes.

Fluorescent Nanosensors for pH Detection and Imaging publication trend

The graph below shows the total number of articles in fluorescent nanosensors for ph detection and imaging across all publications each year (not limited to Nature Index journals).

Technical terms

Fluorescent nanosensor: A nanoparticle or nanostructured material incorporating one or more fluorophores whose emission properties change in response to pH, enabling optical readout of acidity at the nanoscale.

Fluorescence lifetime imaging microscopy (FLIM): An imaging technique that maps the spatial distribution of fluorophore lifetimes, independent of intensity, to quantify environmental parameters such as pH or ion concentration.

Ratiometric sensing: A method that employs two fluorophores or dual‐emission bands to generate an intensity ratio, providing self‐referenced measurements that are less susceptible to probe concentration and excitation fluctuations.

Quantum dot: A semiconductor nanoparticle with size‐tunable emission wavelength and high photostability, often used as a fluorescent label or sensor platform.

Photoinduced electron transfer (PET): A quenching mechanism in which electron transfer between a receptor moiety and fluorophore is modulated by protonation state, providing pH‐dependent changes in fluorescence.

Dynamic range: The span of pH values over which a sensor provides a reliable and quantifiable optical response, typically defined by its lower and upper detection limits.

References

1. Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications. Chemical Reviews (2020).
2. Dual-fluorophore ratiometric pH nanosensor with tuneable p K a and extended dynamic range. Analyst (2011).
3. High-resolution Imaging of pH in Alkaline Sediments and Water Based on a New Rapid Response Fluorescent Planar Optode. Scientific Reports (2016).
4. Quinolinium-Based Fluorescent Probes for Dynamic pH Monitoring in Aqueous Media at High pH Using Fluorescence Lifetime Imaging. ACS Sensors (2023).
5. A Novel Quantum Dot-Based pH Probe for Long-Term Fluorescence Lifetime Imaging Microscopy Experiments in Living Cells. ACS Applied Materials & Interfaces (2022).
6. Blood-pH Optical Measurement: A Model to Compensate for the Effects of Temperature. IEEE Transactions on Instrumentation and Measurement (2023).