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We report the synthesis, electrochemistry, and electrogenerated chemiluminescence of a series of star-shaped donor-acceptor (D-A) molecules. The star-shaped molecules consist of an electron-deficient 1,3,5-triazine core with three fluorene arms substituted with diarylamino (TAM1-TAM3) or carbazolyl (TAM4) electron donors. Cyclic voltammetry of TAM1-TAM3 shows that the reduction consists of one wave of single electron transfer to the core, while the oxidation exhibits a single peak of three sequential electron-transfer processes, with the formation of a trication. The carbazole-containing molecule TAM4 after oxidation undergoes a subsequent rapid chemical reaction to produce a dimer (via the overall coupling of two radical cations with the loss of two protons). The dimer electrooxidizes more easily than the monomer of TAM4. With continuous cycling on the oxidation side, a conductive polymer film is formed on the surface of the working electrode. Because of the presence of the acceptor (triazine) center and strong donors in the arms (diarylamine or carbazole), TAM1-TAM3 exhibit large solvatochromic effects with emissions ranging from deep blue (428 nm) to orange-red (575 nm) depending on the solvent polarity. These star-shaped molecules show high PL quantum yields of 0.70-0.81. The electrogenerated chemiluminescence (ECL) of TAM1-TAM3 in nonaqueous solutions showed strong ECL that could be seen with the naked eye in a well-lit room. Because the enthalpy of annihilation is higher than the energy required for formation of the singlet excited state, the ECL emission is believed to be generated via S-route annihilation. However, TAM4 shows weak annihilation ECL because of the production of polymer film on the electrode surface during oxidation cycles. However, by limiting the potential region only to the reduction side and using benzoyl peroxide (BPO) as a coreactant, strong ECL of TAM4 can be obtained.

A new D-A-π-A-D molecule (Spiro-BTA) containing two 2,1,3-benzothiadiazole (BTA) as the acceptor (A) and triphenylamine as the donor (D) bridged by a spirobifluorene moiety has been synthesized. The novel D-A molecule shows intense red emission (612 nm) with a high PL quantum yield (Φ(PL) = 0.51) in a solid film. A cyclic voltammogram of Spiro-BTA in 1:2 MeCN:benzene/0.1 M Bu(4)NPF(6) shows two reversible oxidation waves and one reversible reduction wave. The first oxidation wave and reduction wave were assigned as two successive electron transfer peaks separated by ∼50 mV related to the oxidation of the two noninteracting donors and the reduction of the two noninteracting acceptors, respectively. Electrogenerated chemiluminescence (ECL) of Spiro-BTA upon cyclic oxidation and reduction in MeCN:benzene 1:2 shows a very bright and stable red emission that could be seen in a well-lit room. Using a reprecipitation method, well-dispersed organic nanoparticles (NPs) of the Spiro-BTA were prepared in aqueous solution. The nanoparticles were analyzed by dynamic light scattering (DLS) and scanning electron microscopy (SEM), yielding a NP size (without surfactant) of 130 ± 20 nm, while with surfactant, 100 ± 20 nm. Bathochromic shifts of absorption spectra (∼16 ± 2 nm), as compared to that of the dissolved Spiro-BTA in THF, were observed for both NPs in water and as a thin film. While blue shifts (14 ± 2 nm) were observed for the photoluminescence (PL). The PL intensity of the Spiro-BTA nanoparticles was slightly enhanced (Φ(PL) of nanoparticles in water = 48%) over that of the dissolved Spiro-BTA in THF. The ECL of the organic Spiro-BTA nanoparticles in aqueous solution could be observed upon oxidation with tri-n-propylamine as a coreactant.

We report the preparation, characterization, and electrogenerated chemiluminescence (ECL) of rubrene nanoparticles (NPs) and 9,10-diphenylanthracene (DPA) nanorods. The organic NPs were prepared in an aqueous phase using a simple reprecipitation method, i.e., injecting a solution of the hydrocarbon in an organic solvent into water. The resulting NPs can be collected and redispersed to form stable colloidal solutions in water. Rubrene forms spherical nanoparticles (NPs) (diameter ∼50 nm), while DPA initially forms nanorods with an average size of ∼500 nm in length and ∼50 nm in diameter. DPA nanorods grew gradually with time into wires with diameters of ∼1 μm and lengths of ∼10 μm. ECL emission from these NPs was observed upon electrochemical oxidation in aqueous solutions containing different co-reactants, such as tri-n-propylamine for rubrene and an oxalate ion for DPA NPs. The ECL intensity from rubrene NPs was significantly higher than that from DPA NPs because of the smaller size, and thus there is a higher diffusion coefficient for rubrene as compared to that of DPA NPs.

The single crystalline nanobelts were successfully fabricated with an ionic compound by a simple reprecipitation method. The compound used is the water-insoluble derivative of tris(bipyridine) Ru(II), [Ru(bpy)2(4,4'-(CH3(CH2)14COO)2-bpy)](ClO4)2. The prepared nanobelts show an enhanced fluorescence emission and relatively strong electrogenerated chemiluminescence (ECL), that have potential analytical applications. More interesting, ECL of a single nanobelt deposited on an ultramicroelectrode was observed. The observation of ECL in such nanostructures leads to the development of a new class of ECL systems that may prove useful for a variety of purposes.

Dual functional fluorescence nanosensors have many potential applications in biology and medicine. Monitoring temperature with higher precision at localized small length scales or in a nanocavity is a necessity in various applications. As well as the detection of biologically interesting metal ions using low-cost and sensitive approach is of great importance in bioanalysis. In this paper, we describe the preparation of dual-function highly fluorescent B, N-co-doped carbon nanodots (CDs) that work as chemical and thermal sensors. The CDs emit blue fluorescence peaked at 450 nm and exhibit up to 70% photoluminescence quantum yield with showing excitation-independent fluorescence. We also show that water-soluble CDs display temperature-dependent fluorescence and can serve as highly sensitive and reliable nanothermometers with a thermo-sensitivity 1.8% °C −1 , and wide range thermo-sensing between 0-90 °C with excellent recovery. Moreover, the fluorescence emission of CDs are selectively quenched after the addition of fe 2+ and fe 3+ ions while show no quenching with adding other common metal cations and anions. The fluorescence emission shows a good linear correlation with concentration of fe 2+ and fe 3+ (R 2 = 0.9908 for Fe 2+ and R 2 = 0.9892 for Fe 3+) with a detection limit of of 80.0 ± 0.5 nM for fe 2+ and 110.0 ± 0.5 nM for Fe 3+. Considering the high quantum yield and selectivity, CDs are exploited to design a nanoprobe towards iron detection in a biological sample. The fluorimetric assay is used to detect fe 2+ in iron capsules and total iron in serum samples successfully. Improvements in creating innovative sensors for detecting multiple parameters have grown much attention because they are more proficient than the sensors for a single objective 1. Currently, various fluorescent sensors for the simultaneous detection of two or more analytes or other parameters such as pH, temperature, and UV-light have been reported 2-6. Temperature is an essential thermodynamic variable that affects biochemical and physiological processes intensely 7. High-precision determination of temperature is of infinite importance owing to the widespread applications in human life, research studies, and industrial fields. An optical temperature sensor has the benefits of contactless detection, a high-temperature resistance, a diverse temperature range, not interfering with the original temperature, and prompt response 8. Some classes of luminescent nanomaterials such as, quantum dots, carbon dots, polymer dots, and nanodiamonds displayed temperature-dependent luminescence 9-11. Carbon dots take the lead as temperature detectors establishing great potential as a probe for the detection of temperature in complicated environments such as biological media due to their unique properties and small size comparing to the other nanomaterials 6,12-14. Iron homeostasis disorders are one of the utmost regular diseases of humans and cover an expansive range of diseases with various signs and symptoms, starting from anemia to excesses of iron, li...

We report electrochemical studies, spectroscopy, and electrogenerated chemiluminescence (ECL) of four monodisperse star-shaped truxene core-oligofluorene compounds (T1-T4). All oligomers produced stable radical anions and radical cations and showed blue ECL by ion annihilation with an intensity that could be seen with the naked eye. ECL spectra showed that all ECL emissions were at the same position as the fluorescence emission, except for T1, the compound with the shortest fluorene arms that produced some longer wavelength emission in addition to that seen in the fluorescence spectrum. When tetra-n-butylammonium oxalate was used as a coreactant for T1, the emission was much weaker than that in ion annihilation with the same long-wavelength emission observed, making it unlikely that this emission can be ascribed to excimer formation. The ECL intensity of T4 was about 80% of the common blue ECL emitter, 9,10-diphenylanthracene (DPA), under similar conditions.

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