importance to unravel the complexity of these systems and to impact a multitude of technological applications ranging from integrated photonic devices to precise medicine. [1-3] Thermocouples and thermistors dominate the market but are inappropriate to probe temperature in live biological systems as physical contact with measured samples is a prerequisite, which disturbs the measurements at sub-millimeter scales. [4] Alternatively, luminescence nanothermometry is emerging as a noninvasive spectroscopic method that allow to probe temperature variation at nanometric spatial resolution and in remote distance, spurring wide interests. [5,6] The contactless and high-resolution nature makes them ideal candidates for temperature evaluation in the early diagnosis of several diseases as well as for providing real-time temperature feedback in thermal (hypothermia or hyperthermia) therapies of malignant cancers. [7-9] Indeed, the potential clinical and preclinical applications fuel a fast development of luminescence nanothermometers particularly for in vivo studies in the nearinfrared (NIR) range. [10] Light in the first biological window (NIR-I, 750-950 nm) or the second biological window (NIR-II, 1000-1700 nm) is known to have minimized scattering and absorption, thus allowing for maximized light Luminescence nanothermometry is promising for noninvasive probing of temperature in biological microenvironment at nanometric spatial resolution. Yet, wavelength-and temperature-dependent absorption and scattering of tissues distort measured spectral profile, rendering conventional luminescence nanothermometers (ratiometric, intensity, band shape, or spectral shift) problematic for in vivo temperature determination. Here, a class of lanthanide-based nanothermometers, which are able to provide precise and reliable temperature readouts at varied tissue depths through NIR-II luminescence lifetime, are described. To achieve this, an inert core/ active shell/inert shell structure of tiny nanoparticles (size, 13.5 nm) is devised, in which thermosensitive lanthanide pairs (ytterbium and neodymium) are spatially confined in the thin middle shell (sodium yttrium fluoride, 1 nm), ensuring being homogenously close to the surrounding environment while protected by the outmost calcium fluoride shell (CaF 2 , ≈2.5 nm) that shields out bioactive milieu interferences. This ternary structure enables the nanothermometers to consistently resolve temperature changes at depths of up to 4 mm in biological tissues, having a high relative temperature sensitivity of 1.4-1.1% °C −1 in the physiological temperature range of 10-64 °C. These lifetime-based thermosensitive nanoprobes allow for in vivo diagnosis of murine inflammation, mapping out the precise temperature distribution profile of nanoprobes-interrogated area.

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Highly ordered organic crystals are important building blocks for future highperformance organic nanodevices. Here we report a feasible way to produce arrays of wellordered 1D copper phthalocyanine (CuPc) nanocrystals by using molybdenum disulfide (MoS 2 ) or highly oriented pyrolytic graphite (HOPG) as substrates. The growth behaviors of CuPc on MoS 2 (0001) as well as on HOPG and corresponding effects of air exposure were systematically investigated by means of in situ photoemission spectroscopy (PES) and lowenergy electron diffraction (LEED), combined with ex situ atomic force microscopy (AFM), surface X-ray diffraction (SXRD), and Raman spectroscopy. PES and LEED results show that CuPc molecules adopt a face-on configuration at thickness up to 4.8 nm, while AFM and SXRD results show that they adopt an edge-on configuration to form 1D nanocrystals in films thicker than 2.4 nm. Detailed analyses show that the formation of these 1D nanocrystals is closely related to air exposure, thicknesses, and growth temperature. Such 1D CuPc nanocrystals can be further optimized by tuning growth conditions and may have great potential for use in high-performance organic devices.Article pubs.acs.org/JPCC

Combining ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), atomic force microscopy (AFM) and small angle X-ray diffraction (SAXD) measurements, we perform a systematic investigation on the correlations of the electronic structure, film growth and molecular orientation of 2,7-diocty[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) on silicon oxide (SiO). AFM analysis reveals a phase transition of disorderedly oriented molecules in clusters in thinner films to highly ordered standing-up molecules in islands in thicker films. SAXD peaks consistently support the standing-up configuration in islands. The increasing ordering of the molecular orientation with film thickness contributes to the changing of the shape and lowering of the leading edge of the highest occupied molecular orbital (HOMO). The end methyl of the highly ordered standing molecules forms an outward pointing dipole layer which makes the work function (WF) decrease with increasing thickness. The downward shift of the HOMO and a decrease of WF result in unconventional downward band bending and decreased ionization potential (IP). The correlations of the orientation ordering of molecules, film growth and interface electronic structures provide a useful design strategy to improve the performance of C8-BTBT thin film based field effect transistors.