Smart luminescent materials that are responsive to external stimuli have received considerable interest. Here we report ionic iridium (III) complexes simultaneously exhibiting mechanochromic, vapochromic and electrochromic phosphorescence. These complexes share the same phosphorescent iridium (III) cation with a N-H moiety in the N^N ligand and contain different anions, including hexafluorophosphate, tetrafluoroborate, iodide, bromide and chloride. The anionic counterions cause a variation in the emission colours of the complexes from yellow to green by forming hydrogen bonds with the N-H proton. The electronic effect of the N-H moiety is sensitive towards mechanical grinding, solvent vapour and electric field, resulting in mechanochromic, vapochromic and electrochromic phosphorescence. On the basis of these findings, we construct a data-recording device and demonstrate data encryption and decryption via fluorescence lifetime imaging and time-gated luminescence imaging techniques. Our results suggest that rationally designed phosphorescent complexes may be promising candidates for advanced data recording and security protection. D ata recording, storage and security technologies have been widely utilized in economic and military fields as well as in our daily life. Smart luminescent materials that are responsive to external stimuli have received considerable attention in the construction of optical data recording and storage devices [1][2][3][4][5] . These materials have been classified on the basis of the types of external stimuli that they are responsive to. Mechanochromic materials show changes in emission colour in the presence of mechanical stimuli (for example, shearing, grinding and rubbing) because of the interruption of intermolecular interactions (for example, p-p stacking and hydrogen bonds) [6][7][8][9][10] . Vapochromic luminescence has been observed in materials that are responsive to volatile organic compounds 11,12 . Electric field is an important external stimulus. Electrochromism occurs in p-conjugated polymers because of the reversible transition between two redox states [13][14][15][16] . However, materials showing electrochromic luminescence, which is distinct luminescence colour responses to an electric field, are scarce. We envision the potential commercial applications of electrochromic luminescent materials because they can be conveniently integrated into semiconductor-based electronic devices. In addition, it is conceivable that compounds simultaneously showing mechanochromic, vapochromic and electrochromic luminescence are of great use to the development of multifunctional materials.Phosphorescent transition-metal complexes, such as those of Ir(III) and Pt(II), have been extensively studied for various photonic and electronic applications because of their rich excited-state properties, including high luminescence quantum yields, long emission lifetimes, large Stokes shifts, high photostability and various luminescence colours [17][18][19][20] . These complexes have also been utilized a...

Graphene, because of its excellent mechanical, electrical, chemical, physical properties, sparked great interest to develop and extend its applications. Particularly, graphene based field-effect transistors (GFETs) present exciting and bright prospects for sensing applications due to their greatly higher sensitivity and stronger selectivity. This Review highlights a selection of important topics pertinent to GFETs and their application in electronic sensors. This article begins with a description of the fabrications and characterizations of GFETs, and then introduces the new developments in physical, chemical, and biological electronic detection using GFETs. Finally, several perspective and current challenges of GFETs development are presented, and some proposals are suggested for further development and exploration.

A microfluidic device for performing single copy, emulsion Reverse Transcription Polymerase Chain Reaction (RT-PCR) within agarose droplets is presented. A two-aqueous-inlet emulsion droplet generator was designed and fabricated to produce highly uniform monodisperse picoliter agarose emulsion droplets with RT-PCR reagents in carrier oil. Template RNA or cells were delivered from one inlet with RT-PCR reagents/cell lysis buffer delivered separately from the other. Efficient RNA/cell encapsulation and RT-PCR at the single copy level was achieved in agarose-in-oil droplets, which, after amplification, can be solidified into agarose beads for further analysis. A simple and efficient method to graft primer to the polymer matrix using 5'-acrydite primer was developed to ensure highly efficient trapping of RT-PCR products in agarose. High-throughput single RNA molecule/cell RT-PCR was demonstrated in stochastically diluted solutions. Our results indicate that single-molecule RT-PCR can be efficiently carried out in agarose matrix. Single-cell RT-PCR was successfully performed which showed a clear difference in gene expression level of EpCAM, a cancer biomarker gene, at the single-cell level between different types of cancer cells. This work clearly demonstrates for the first time, single-copy RT-PCR in agarose droplets. We believe this will open up new possibilities for viral RNA detection and single-cell transcription analysis.

The application of a time‐resolved photoluminescence technique and fluorescence lifetime imaging microscopy for biosensing and bioimaging based on phosphorescent conjugated polyelectrolytes (PCPEs) containing Ir(III) complexes and polyfluorene units is reported. The specially designed PCPEs form 50 nm nanoparticles with blue fluorescence in aqueous solutions. Electrostatic interaction between the nanoparticles and heparin improves the energy transfer between the polyfluorene units to Ir(III) complex, which lights up the red signal for naked‐eye sensing. Good selectivity has been demonstrated for heparin sensing in aqueous solution and serum with quantification ranges of 0–70 μM and 0–5 μM, respectively. The signal‐to‐noise ratio can be further improved through time‐resolved emission spectra, especially when the detection is conducted in complicated environment, e.g., in the presence of fluorescent dyes. In addition to heparin sensing, the PCPEs have also been used for specific labeling of live KB cell membrane with high contrast using both confocal fluorescent cellular imaging and fluorescence lifetime imaging microscopies. This study provides a new perspective for designing promising CPEs for biosensing and bioimaging applications.