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We report the rational design of the matrix‐free carbon dots (C‐dots) with long wavelength and wavelength‐tunable room‐temperature phosphorescence (RTP). Taking advantage of microwave‐assisted heating treatment, three RTP C‐dots in boric acid (BA) composites are synthesized by using diethylenetriaminepentakis (methylphosphonic acid) as a multiple‐sites crosslink agent, a moderately acid catalyst and P source; phenylenediamines (either o‐PD, m‐PD, or p‐PD, respectively) as building block while BA as a carbonization‐retardant matrix. After the water‐soluble BA matrix is removed by dialysis, three matrix‐free C‐dots are obtained with RTP emission at 540, 550 and 570 nm under an excitation wavelength of 365 nm. Alterations of RTP emission of three matrix‐free C‐dots are ascribed to the difference in their particle size and band gap from n‐π* transition. Furthermore, the application of three matrix‐free C‐dots are successfully performed in information encryption and decryption. [ABSTRACT FROM AUTHOR]

A label‐free electrochemical aptasensor was fabricated for the determination of serotonin (5‐HT) by the employment of specific binding between 5‐HT and aptamer and directly electrochemical measurement of 5‐HT oxidation. The comparison between two aptasensors and two strategies was studied. An electrochemical aptasensor fabricated using 57‐mer aptamer was facilely used to determine 5‐HT in the range from 1 μM to 100 μM with detection limit of 0.3 μM via one step recognition and detection. This work demonstrates that electrochemical method combing aptamer recognition and 5‐HT oxidation provides an alternative and promising method for the determination of 5‐HT with good selectivity and simplicity. [ABSTRACT FROM AUTHOR]

Designing efficient room‐temperature phosphorescence (RTP) carbon dots (C‐dots) without the need of an additional matrix is important for various applications. Herein, matrix‐free and highly efficient C‐dots with yellow‐green RTP emission have been successfully synthesized towards information encryption and decryption. Phytic acid (PA) and triethylenetetramine are used as molecular precursors, and a facile microwave‐assisted heating method is selected as synthesis method. The obtained C‐dots exhibit a maximum phosphorescence emission at around 535 nm under an excitation wavelength of 365 nm and a long average lifetime up to 750 ms (more than 9 s to the naked eye). PA containing six phosphate groups and serving as P source plays a significant role in producing the RTP C‐dots. Furthermore, potential applications of the RTP C‐dots in the field of information encryption and decryption are successfully demonstrated. [ABSTRACT FROM AUTHOR]

The development of new methods for the detection of redox cycle is important for biological and clinical diagnoses. Here, a new cyclometalated iridium complex, (4-(2-pyridyl) benzaldehyde)2Ir (5-chloro-1,10-phenanthroline) ([(4-pba)2Ir(5-Cl-phen)]PF6, probe 1), has been synthesized and applied to rapid, sensitive, and reversible detection and imaging of redox cycle HSO 3 - /H2O2 in living cells. The probe 1 is synthesized by using 4-(2-pyridyl) benzaldehyde as main ligand and 5-chloro-1,10-phenanthroline as ancillary ligand. Probe 1 exhibited "off–on–off" photoluminescence (PL) signal change in response to HSO 3 - and H2O2 in aqueous solution within 1 min. The change of PL intensity is proportional to HSO 3 - concentration from 40 μM to 300 μM and to H2O2 concentration from 40 μM to 260 μM. The detection limit is 10 μM for HSO 3 - and 20 μM for H2O2. Additionally, probe 1 was applied to detect HSO 3 - in food samples with satisfactory results. More importantly, PL imaging of HeLa cells indicates that probe 1 is able to image redox cycle HSO 3 - /H2O2 in living cells. [ABSTRACT FROM AUTHOR]

We report a self-terminated electroless deposition method to prepare surfactant-free and monodispersed Pt nanoparticle (NP)-modified carbon fiber microelectrodes (Pt NP/CFEs) for electrochemical detection of hydrogen peroxide (H 2 O 2 ) released from living cells. The surfactant-free and monodispersed Pt NPs with a uniform size of 65 nm are spontaneously deposited on a CFE surface by immersing an exposed carbon fiber (CF) of CFE in the PtCl 4 2- solution, in which an exposed CF can be used as the reducing agent and stabilizer. A self-terminated electroless deposition method is demonstrated, in which the density and size of Pt NPs on a CFE surface do not increase when the reaction time increases from 20 to 60 min. The self-terminated electroless deposition process not only can effectively avoid any manual electrode modification and thus largely minimize person-to-person and electrode-to-electrode deviations but also can avoid the use of any extra reductant or surfactant in the fabrication process. Therefore, Pt NPs/CFEs, with good reproducibility and sensitivity, not only exhibit high electrocatalytic activity toward the oxidation of H 2 O 2 but also maintain the spatial resolution of CFEs. Moreover, Pt NPs/CFEs can detect H 2 O 2 with a wide linear range of 0.5-80 μM and a low detection limit of 0.17 μM and then can be successfully applied in the monitoring of H 2 O 2 released from RAW 264.7 cells. The self-terminated electroless deposition method can also be extended to selectively prepare other metal NP-modified CFEs, such as Au NPs/CFEs or Ag NPs/CFEs, by choosing the metal ions with higher reduction potential as precursors. This work provides a simple, straightforward, and general method for the preparation of small, surfactant-free, and monodispersed metal NP-modified CFEs with high sensitivity, reproducibility, and spatial resolution.

We report a facile strategy for the synthesis of surfactant-free, small and highly dispersive Pt-Pd nanoparticles on graphene oxide (Pt-Pd NPs/GO) by an electroless deposition method, which is sheathed on carbon fiber microelectrodes (CFMs) as an electrochemical sensing platform for highly sensitive and selective detection of hydrogen peroxide (H 2 O 2 ) released from the living cells. GO serves as the reducing agent and stabilizer for electroless deposition of Pd NPs on the surface of GO owing to its low work function (4.38 eV) and highly conjugated electronic structure. The obtained Pd NPs/GO have a relatively high work function (4.64 eV), and thereby could be used as stabilizer for synthesis of surfactant-free, small and highly dispersive Pt-Pd NPs/GO by chemical reduction of K 2 PtCl 4 . The obtained Pt-Pd NPs have a uniform size of 4.0 ± 0.6 nm on the surface of GO. Moreover, the Pt-Pd NPs/GO sheathed CFMs exhibit an excellent electrocatalytic activity for the reduction of H 2 O 2 with a low detection limit of 0.3 μM and good selectivity. These good properties enable the modified microelectrode to detect the H 2 O 2 released from living cells.

The development of new methods for the detection of redox cycle is important for biological and clinical diagnoses. Here, a new cyclometalated iridium complex, (4-(2-pyridyl) benzaldehyde) 2 Ir (5-chloro-1,10-phenanthroline) ([(4-pba) 2 Ir(5-Cl-phen)]PF 6 , probe 1 ), has been synthesized and applied to rapid, sensitive, and reversible detection and imaging of redox cycle HSO 3 - /H 2 O 2 in living cells. The probe 1 is synthesized by using 4-(2-pyridyl) benzaldehyde as main ligand and 5-chloro-1,10-phenanthroline as ancillary ligand. Probe 1 exhibited "off-on-off" photoluminescence (PL) signal change in response to HSO 3 - and H 2 O 2 in aqueous solution within 1 min. The change of PL intensity is proportional to HSO 3 - concentration from 40 μM to 300 μM and to H 2 O 2 concentration from 40 μM to 260 μM. The detection limit is 10 μM for HSO 3 - and 20 μM for H 2 O 2 . Additionally, probe 1 was applied to detect HSO 3 - in food samples with satisfactory results. More importantly, PL imaging of HeLa cells indicates that probe 1 is able to image redox cycle HSO 3 - /H 2 O 2 in living cells.