Temperature-Dependent Photoluminescence of Cesium Lead Halide Perovskite Quantum Dots: Splitting of the Photoluminescence Peaks of CsPbBr₃ and CsPb(Br/I)₃ Quantum Dots at Low Temperature

We investigated the temperature-dependent photoluminescence (PL) properties of colloidal CsPbX₃ (X = Br, I, and mixed Br/I) quantum dot (QD) samples in the 30–290 K temperature range. Temperature-dependent PL experiments reveal thermal quenching of PL, blue shifting of optical band gaps, and line width broadening for all CsPbX₃ QD samples with increasing temperature. Interestingly, side-peak emissions that are spectrally separated from the excitonic PL peaks were observed for both CsPbBr₃ and CsPb­(Br/I)₃ QD samples at temperatures below ∼250 K. The side-peak emission for the CsPbBr₃ QD sample is located at a lower energy compared to the band-edge peak, whereas that of the Br-rich CsPb­(Br/I)₃ alloy QD sample is located at a higher energy than that of the band-edge peak. We found that the CsPbBr₃ QDs have two emissive states, a band-edge state, and one involving shallow defects, which can be spectrally separated by narrowing the emission line widths at low temperature. In the case of the Br-rich CsPb­(Br/I)₃ QD sample, the partial halide-segregation-induced heterogeneity of the alloy phase within the ensemble at low temperature leads to blue-shifted radiative recombination channels

Isomer-Specific Induced Circular Dichroism Spectroscopy of Jet-Cooled Phenol Complexes with (−)-Methyl l‑Lactate

Induced circular dichroism (ICD) is the CD observed in the absorption of an achiral molecule bound to a transparent chiral molecule through noncovalent interactions. ICD spectroscopy has been used to probe the binding between molecules, such as protein–ligand interactions. However, most ICD spectra have been measured in solution, which only exhibit the averaged CD values of all conformational isomers in solution. Here, we obtained the first isomer-selective ICD spectra by applying resonant two-photon ionization CD spectroscopy to jet-cooled phenol complexes with (−)-methyl l-lactate (PhOH-(−)­ML). The well-resolved CD bands in the spectra were assigned to two conformers, which contained different types of hydrogen-bonding interactions between PhOH and (−)­ML. The ICD values of the two conformers have different signs and magnitudes, which were explained by differences both in the geometrical asymmetries of PhOH bound to (−)­ML and in the electronic coupling strengths between PhOH and (−)­ML

Origin of Both Right- and Left-Handed Helicities in a Supramolecular Gel with and without Ni²⁺ at the Supramolecular Level

We demonstrate the different origins of helical directions in polymeric gels derived from a hydrazone reaction in the absence and presence of Ni²⁺. The right-handed helicity of polymeric gels without Ni²⁺ originates from the enantiomeric d-form alanine moiety embedded in the building block. However, the right-handed helicity is inverted to a left-handed helicity upon the addition of Ni²⁺, indicating that added Ni²⁺ greatly affects the conformation of the polymeric gel by overcoming the influence of the enantiomer embedded in the building block on the helicity at the supramolecular level. More interestingly, the ratio of the right-toleft-handed helical fibers varies with the concentration of Ni²⁺, which converts from 100% right-handed helical fiber to 90% left-handed helical fiber. In the presence of Ni²⁺, both right- and left-handed helical fibers coexist at the supramolecular level. Some fibers also exhibit both right- and left-handed helicities in a single fiber

Self-Assembled Tb³⁺ Complex Probe for Quantitative Analysis of ATP during Its Enzymatic Hydrolysis via Time-Resolved Luminescence in Vitro and in Vivo

To more accurately assess the pathways of biological systems, a probe is needed that may respond selectively to adenosine triphosphate (ATP) for both in vitro and in vivo detection modes. We have developed a luminescence probe that can provide real-time information on the extent of ATP, ADP, and AMP by virtue of the luminescence and luminescence lifetime observed from a supramolecular polymer based on a <i>C</i>₃ symmetrical terpyridine complex with Tb³⁺ (<b>S1-Tb</b>). The probe shows remarkable selective luminescence enhancement in the presence of ATP compared to other phosphate-displaying nucleotides including adenosine diphosphate (ADP), adenosine monophosphate (AMP), guanosine triphosphate (GTP), thymidine triphosphate (TTP), H₂PO₄^– (Pi), and pyrophosphate (PPi). In addition, the time-resolved luminescence lifetime and luminescence spectrum of <b>S1-Tb</b> could facilitate the quantitative measurement of the exact amount of ATP and similarly ADP and AMP within living cells. The time-resolved luminescence lifetime of <b>S1-Tb</b> could also be used to quantitatively monitor the amount of ATP, ADP, and AMP in vitro following the enzymatic hydrolysis of ATP. The long luminescence lifetime, which was observed into the millisecond range, makes this <b>S1-Tb</b>-based probe particularly attractive for monitoring biological ATP levels in vivo, because any short lifetime background fluorescence arising from the complex molecular environment may be easily eliminated