Fs5 spectrophotometer

The synthesized catalysts were analyzed for structural information using an X-ray diffractometer (Panalytical’s X’Pert Pro, Malvern, UK) with a Cukα radiation source. The experiments were performed in the 2θ scanning range of 20–70 degrees with step size of 0.02°. The particle size of catalysts was obtained with the help of a transmission electron microscope (EM-410 LS, Philips, Amsterdam, The Netherlands). The surface morphology of the catalysts was examined using a scanning electron microscope (SEM, Hitachi, Tokyo, Japan). X-ray photoelectron spectroscopy (Thermofisher Scientific, Nexsa base, Waltham, MA, USA) was employed for the determination of elemental presence and their valence states. The metal-stretching vibrations in the synthesized catalysts were performed with the help of a Raman spectrometer (Raman Horiba, Lab RAM HR evolution). The bandgap estimation was performed by analysis of the absorbance spectra recorded using a UV-VIS-NIR spectrophotometer (Perkin Elmer, Waltham, MA, USA). The magnetic properties of the catalysts were investigated using a vibrating sample magnetometer (Micrösense, EV7) to record the room temperature M-H loop at a field strength of 15,000 Oe. Photoluminescence (PL) spectra were recorded on a FS5 spectrophotometer (Edinburgh Instruments, Edinburgh, UK).

Emission and excitation spectra of purified GECIs in buffer A were recorded with a FS5 spectrophotometer (Edinburgh Instruments) controlled by Fluoracle. Absorption spectra were recorded with UV2600 spectrophotometer (Shimadzu) controlled by UVprobe. Quantum yields (Φ) were determined with FS5 using 1 cm quartz cuvette. The fluorescence spectra of GECIs with different concentrations were recorded to calculate the corresponding total integrated fluorescence intensities (TIF). Linear regression of TIF minus absorbance curves were used to derive the slopes (S) of GECIs. Φ was then calculated as: Φ_protein = Φ_standard × (S_protein/S_standard) (ref. ^{5 (link)}). For anionic chromophore 470 nm excitation; reference, fluorescein (fluo) in 0.1 M NaOH (φ = 0.925)³⁰ . For neutral chromophore, 405 nm excitation, TOLLES (φ = 0.79) (ref. ^{31 (link)}).

The samples’ morphologies were examined using a transmission electron microscope (FEI TecnaiG2F30; 200 kV). Thermo Fisher Scientific’s ESCALAB 250Xi photoelectron spectrometer was used to perform X-ray photoelectron spectroscopy with Mo as the excitation source. A JASCO V-770 spectrophotometer was used to acquire UV-vis absorption spectra. Ocean Optics QE Pro spectrofluorometer was used to measure the PL spectra. An Edinburgh FS5 spectrophotometer was used to measure the PL lifetime and PLQY. The fundamental-frequency 800 nm femtosecond laser pulse was generated by the Coherent Legend regenerative amplifier (100 fs, 1 kHz) which is seeded by a Coherent Vitesse oscillator (100 fs, 80 MHz). An automated optical parametric amplifier (Light Conversion, TOPAS Prime) pumped by the fundamental-frequency 800 nm femtosecond laser pulse was used to obtain the 1150 and 1500 nm femtosecond lasers employed in multiphoton FL. The two-photon and three-photon FL signals were collected by a spectrometer (ANDOR, Shamrock 303i) coupled with CCD (ANDOR, Newton DU920P). An Ultrafast System HELIOS spectrometer in a nondegenerate pump-probe configuration was used to measure TA. The 400 nm pump laser was obtained by propagating the 800 nm fundamental-frequency femtosecond laser pulse through a 0.5 mm thick BBO single crystal.

Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were obtained using a JEOL JEM-2100 microscope (JEOL, Japan) at an acceleration voltage of 80 kV or 200 kV, respectively. X-ray diffraction (XRD) characterizations were obtained using a Bruker D8 Advance diffractometer with a copper Ka (k = 0.154056 nm) radiation source. X-ray photoelectronspectroscopy (XPS) measurements were obtained using a PHI5000 Versaprobe-II spectrometer (ULVAC-PHI, Japan) with a monochromatic Al Ka (1486.6 eV) source. The UV absorption spectra were obtained with a UV-6300 spectrophotometer (Mapada instruments Ltd., Shanghai, China). The photoluminescence spectra were obtained using an FS5 spectrophotometer (Edinburgh instruments Ltd., Livingston, UK). The fluorescence images were obtained with an upright fluorescence microscope (i203 type, Chongqing UOP, Chongqing, China) and an Eclipse Ni-U (Nikon Ltd., Tokyo, Japan) fluorescence microscope. Fourier-transform Infrared Spectrometer (FTIR, Thermo Fisher Scientific Ltd., Waltham, MA, USA) was employed to carried out IR spectra. Atomic force microscope (AFM, Dimension Icon, Bruker Co. Ltd., USA) was used to obtain AFM images. The particle size distribution and zeta potential were studied by dynamic light scattering (DLS) using Malvern Zetasizer (Malvern Instruments Ltd., Malverm, UK).