Microhr

Tissue autofluorescence was excited with 355 nm pulsed laser (<0.6 ns per pulse, >2 $\mathsf{\mu }$ J per pulse, repetition rate 4 kHz; TEEM photonics STV-02E, Meylan, France). A 400 $\mathsf{\mu }$ m core diameter multimode fiber placed perpendicular to the sample was used to deliver and collect the light. A second multimode fiber (600 $\mathsf{\mu }$ m in core diameter) was used to guide the tissue autofluorescence to a monochomator (MicroHR, Horiba, Kyoto, Japan). Light was detected with a gated microchannel plate photomultiplier tube (R5916U-50, Hamamatsu, Hamamatsu, Japan) connected to a high-speed amplifier (C5594, Hamamatsu), and digitized by an oscilloscope (DPO7254, Tektronix, Beaverton, OR, USA). The laser power at the sample plane was kept under 5 mW. Fluorescence decays were acquired from 370 to 600 nm with 2 nm increments and a 0.08 ns resolution. Each data point was an average of 64 decays.
Data were acquired from three points along the length of the colon corresponding to the proximal, the middle, and the distal ends. Three measurements were taken on each position. The results presented in Figure 2 represent the mean (solid thick line) over 4 independent samples (2 female and 2 male) and their corresponding standard deviation (shaded area). Samples were kept in phosphate buffer saline (PBS) for the duration of imaging.

All the performances measurements of the devices were done in ambient conditions at room temperature. The junction characteristics have been determined by two points resistivity measurements, tungsten needles as electrical leads. One of the contacts is positioned directly on the perovskite single crystal, whereas the second one touches the Ti foil as the back electrode. A Keithley 2400 source meter allowed us to measure the current with < 0.1 nA resolution, while tuning the applied bias voltage, in dark and under visible light illumination. Current-Voltage measurements were performed by sweeping the voltage from 0 to +2 V/-2 V and back, with a scan speed of 0.2 V/s. Photocurrent measurements at low light intensities were done by choosing 550 nm wavelength, within the spectral response of our device, enabling also to achieve high enough intensities of light that can be detected. The wavelength was set with a monochromator (Horiba Micro HR), while light intensity was adjusted by closing and opening slits in the light path.

Steady-state PL and PLE spectra have
been recorded using a xenon lamp as an excitation source, together
with a double monochromator (Jobin-Yvon Gemini 180 with a 1200 grooves/mm
grating), and recorded through a nitrogen-cooled CCD detector coupled
to a monochromator (Jobin-Yvon Micro HR). Under cw laser excitation, signals have been recorded using a nitrogen-cooled
CCD coupled with a double monochromator, Triax-190 (HORIBA Jobin-Yvon),
with a spectral resolution of 0.5 nm. The PL quantum yield of bare
NTs has been measured with relative methods using 2,5-diphenyloxazole
as a fluorescence standard.⁶⁶ All spectra
have been corrected for the setup optical response. Time-resolved
PL spectra have been recorded using a pulsed LED at 340 nm (3.65 eV,
EP-LED 340 Edinburgh Instruments, a pulse width of 700 ps) or a pulsed
laser at 405 nm (3.06 eV, EPL-405 Edinburgh Instruments, a pulse width
of 150 ps) as a light source. Data were obtained with an Edinburgh
Instruments FLS-980 spectrophotometer, with a 5 nm bandwidth and a
time resolution of 0.1 ns.