We present an optical and photoelectron spectroscopic study to elucidate the interfacial electronic properties of organic-inorganic semiconductor heterojunctions formed in a kinetically blocked heptazethrene triisopro...We present an optical and photoelectron spectroscopic study to elucidate the interfacial electronic properties of organic-inorganic semiconductor heterojunctions formed in a kinetically blocked heptazethrene triisopropylsilyl ethynylene (HZ-TIPS) and its homologue,octazethrene (OZ-TIPS) on an all-inorganic perovskite cesium lead bromide (CsPbBr3) surface.The photoluminescence behavior of the underlying perovskites upon differing molecular doping conditions was examined.It turns out that the charge transfer dynamics of thermally-evaporated OZ-TIPS molecule exhibited a faster average lifetime than that of the HZ-TIPS case suggesting the importance of the biradical state in the former molecule.An interfacial dipole was formed at the interface due to the competing interaction between the dispersion force of the bulky TIPS-substituent group and the attractive van der Waals interaction at the first few layers.Photoemission spectroscopy of the physisorbed HZ-TIPS shows chemical shifts,which indicates electron transfer from HZ-TIPS molecules to the CsPbBr3 perovskite single crystal.In contrast,the adsorbed OZ-TIPS molecular layer on CsPbBr3 demonstrates the opposite trend indicating a hole transfer process.The average molecular orientation as determined by near edge X-ray absorption fine structure (NEXAFS) suggests that the HZ-TIPS molecular plane is generally lifted with respect to the perovskite surface.We suggest that the nature of the closed-shell electronic ground state of HZ-TIPS could contribute to the formation of interfacial dipole at the molecule/perovskite interface.展开更多
Optical barcodes have demonstrated a great potential in multiplexed bioassays and cell tracking for their distinctive spectral fingerprints.The vast majority of optical barcodes were designed to identify a specific ta...Optical barcodes have demonstrated a great potential in multiplexed bioassays and cell tracking for their distinctive spectral fingerprints.The vast majority of optical barcodes were designed to identify a specific target by fluorescence emission spectra,without being able to characterize dynamic changes in response to analytes through time.To overcome these limitations,the concept of the bioresponsive dynamic photonic barcode was proposed by exploiting interfacial energy transfer between a microdroplet cavity and binding molecules.Whispering-gallery modes resulting from cavity-enhanced energy transfer were therefore converted into photonic barcodes to identify binding activities,in which more than trillions of distinctive barcodes could be generated by a single droplet.Dynamic spectral barcoding was achieved by a significant improvement in terms of signal-to-noise ratio upon binding to target molecules.Theoretical studies and experiments were conducted to elucidate the effect of different cavity sizes and analyte concentrations.Timeresolved fluorescence lifetime was implemented to investigate the role of radiative and non-radiative energy transfer.Finally,microdroplet photonic barcodes were employed in biodetection to exhibit great potential in fulfilling biomedical applications.展开更多
文摘We present an optical and photoelectron spectroscopic study to elucidate the interfacial electronic properties of organic-inorganic semiconductor heterojunctions formed in a kinetically blocked heptazethrene triisopropylsilyl ethynylene (HZ-TIPS) and its homologue,octazethrene (OZ-TIPS) on an all-inorganic perovskite cesium lead bromide (CsPbBr3) surface.The photoluminescence behavior of the underlying perovskites upon differing molecular doping conditions was examined.It turns out that the charge transfer dynamics of thermally-evaporated OZ-TIPS molecule exhibited a faster average lifetime than that of the HZ-TIPS case suggesting the importance of the biradical state in the former molecule.An interfacial dipole was formed at the interface due to the competing interaction between the dispersion force of the bulky TIPS-substituent group and the attractive van der Waals interaction at the first few layers.Photoemission spectroscopy of the physisorbed HZ-TIPS shows chemical shifts,which indicates electron transfer from HZ-TIPS molecules to the CsPbBr3 perovskite single crystal.In contrast,the adsorbed OZ-TIPS molecular layer on CsPbBr3 demonstrates the opposite trend indicating a hole transfer process.The average molecular orientation as determined by near edge X-ray absorption fine structure (NEXAFS) suggests that the HZ-TIPS molecular plane is generally lifted with respect to the perovskite surface.We suggest that the nature of the closed-shell electronic ground state of HZ-TIPS could contribute to the formation of interfacial dipole at the molecule/perovskite interface.
基金We would like to thank the Centre of Bio-Devices and Bioinformatics and CNRS International—Nanyang Technological University-Thales Research Alliance(CINTRA)for lab supportWe would also like to thank NTU for the startup grant(SUG-M4082308.040).
文摘Optical barcodes have demonstrated a great potential in multiplexed bioassays and cell tracking for their distinctive spectral fingerprints.The vast majority of optical barcodes were designed to identify a specific target by fluorescence emission spectra,without being able to characterize dynamic changes in response to analytes through time.To overcome these limitations,the concept of the bioresponsive dynamic photonic barcode was proposed by exploiting interfacial energy transfer between a microdroplet cavity and binding molecules.Whispering-gallery modes resulting from cavity-enhanced energy transfer were therefore converted into photonic barcodes to identify binding activities,in which more than trillions of distinctive barcodes could be generated by a single droplet.Dynamic spectral barcoding was achieved by a significant improvement in terms of signal-to-noise ratio upon binding to target molecules.Theoretical studies and experiments were conducted to elucidate the effect of different cavity sizes and analyte concentrations.Timeresolved fluorescence lifetime was implemented to investigate the role of radiative and non-radiative energy transfer.Finally,microdroplet photonic barcodes were employed in biodetection to exhibit great potential in fulfilling biomedical applications.
