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Indole is an interesting molecule that exists in nature as a part of several important biomolecules including melatonin — a chemical that maintains the circadian rhythm in human body, serotonin — a chemical carrying messages through nerve cells, and tryptophan — an amino acid. It has a benzene ring fused with a pyrrole ring. Similar molecules containing cycloheptene ring fused with pyrrole — called azulene, cyclohepta[b]pyrrole and dihydrocyclohepta[b]pyrrole — also exist. It would be very interesting to see the effect on different properties of the above-mentioned biomolecules, if indole is replaced by azulene or cyclohepta[b]pyrrole or dihydro-cyclohepta[b]pyrrole. This paper precisely investigates such interesting substitutions. We replaced indole in the three biomolecules by azulene, cyclohepta[b]pyrrole, and dihydrocyclohepta[b]pyrrole and studied the corresponding change in acid-dissociation constant, static polarizabilities, first and second hyperpolarizabilities, absorption spectra, fluorescence, charge-transfer, and nature of the first two singlet, and the first two triplet states, using the state-of-the-art (time-dependent) density functional theory. The results are compared with the values obtained for the indole analogues calculated at the same level of theory.

A series of phosphorus(V) porphyrins functionalized with meso-phenyl, tolyl, or 4-methoxyphenyl groups and axial-ethoxy, trifluoroethoxy, or ethylene glycoxy groups have been synthesized and their spectroscopic, redox, and optical properties were investigated. The X-ray crystal structures revealed a significant saddling in porphyrin molecular structures due to the presence of a small P(+5) ion in the cavity. The absorption and fluorescence properties are less sensitive to the meso-functionality, with small redshifts observed when moving from phenyl to tolyl and then to 4-methoxyphenyl on the phosphorus(V) porphyrin. In contrast, the meso- and axial-functionalities significantly influenced the redox properties. Specifically, the meso-4-methoxy phenyl group lowered the oxidation potentials, while the axial trifluoroethoxy units reduced the reduction potentials. This study demonstrates that by carefully choosing the axial and meso-substitutions, it is possible to selectively tune the redox potentials with minimal impact on optical properties. Steady-state and time-resolved measurements revealed relatively high fluorescence quantum yields, with lifetimes ranging from 2 to 4 ns. Together, the high fluorescence quantum yields and tunable redox potentials suggest that the investigated porphyrins could serve as excellent photosensitizers in model compounds for artificial photosynthesis and molecular electronic and photonic devices.

Nanodiamonds (NDs) have unique optical and mechanical characteristics, surface chemistry, extensive surface area and biocompatibility, and they are nontoxic, rendering them suitable for a diverse range of applications. Recently, NDs have received significant attention in nano-biomedical engineering. This review discusses the recent advancement of NDs’ biomedical engineering, historical background, basic introduction to nanoparticles and development. We summarize NDs’ synthesis technique, properties and applications. Two methodologies are used in ND synthesis: bottom-up and top-down. We cover synthesis methods, including detonation, ball milling, laser ablation, chemical vapor deposition (CVD) and high pressure and high temperature (HPHT); discuss the properties of NDs, such as fluorescence and biocompatibility. Due to these properties, NDs have potential applications in biomedical engineering, including bioimaging, biosensing, drug delivery, tissue engineering and protein mimics. Further, it provides an outlook for future progress, development and application of NDs in biological and biomedical areas.

Nanobodies have been extensively demonstrated in biomedical imaging and therapy. However, nanobody probes often suffer from rapid renal clearance due to its small size. Herein, we reported a recombinant nanobody with a 200 amino-acid polypeptide chain consisting of Pro, Ala, and Ser (PAS) at the C-terminal, which can be easily expressed in Escherichia coli with a high yield. The PASylated nanobody was functionalized with a fluorescent dye and the cell labeling properties were characterized by flow cytometry and confocal microscopy. In vivo fluorescence imaging indicated that the PASylated nanobody showed comparable blood circulation time, but $\sim 1.5$ times higher tumor targeting ability as compared to the PEGylated nanobody of comparable molecular weight. Our findings demonstrate that nanobody PASylation is a promising approach to produce long-circulating nanobody probes for imaging and therapeutic applications.

The interaction of cationic surfactants such as CTAB (cetyl trimethyl ammonium bromide) with tetrakis-(4-sulfonato phenyl) porphine (H₄TPPS²⁻), a dianion, leads to the formation of two premicellar aggregates of porphyrin when [CTAB] is below CMC (critical micelle concentration) and a micellized monomer when [CTAB] is above CMC. The premicellar aggregates are labeled as J- and H-aggregates because of their characteristic spectroscopic properties. Simple inorganic cations such as K⁺, Ba²⁺, Ca²⁺ and Zr⁴⁺ also induce the formation of the J-aggregate but not of the H-aggregate. The formation of the J-aggregate is preceded by kinetic intermediates, while no intermediate was observed prior to the formation of the H-aggregate. The rate of formation of the H-aggregate was faster than that of the J-aggregate. The fluorescence depolarization (anisotropy) properties of the monomer and the H- and J-aggregates were studied and compared. The size and structure of the J-aggregate were examined by transmission electron microscopy (TEM). The structure of the J-aggregate reveals a fiber-like (linear stacking) or domain-like (helical stacking) arrangement of the porphyrin molecules.

The singlet and triplet excited state properties of two diporphyrins, H₂-H and Zn-H, are described. Steady state fluorescence studies indicate that the emission of the H₂-H diporphyrin is dependent on the excitation wavelength and is dominated by the emission of the individual constituent monomers at their respective excitation. Time-resolved studies show two lifetimes ascribable to the normal and thiaporphyrin subunits. However, the emission of the Zn-H diporphyrin is dominated by the thiaporphyrin subunit irrespective of the wavelength of excitation, suggesting an energy transfer from the Zn porphyrin subunit to the thiaporphyrin subunit. Lifetime measurements in toluene show two lifetimes due to open and folded conformations, while in DMF an additional component due to axial ligation is observed. The efficiency of energy transfer is moderately higher in DMF (72%) than in toluene (68%). Triplet ESR studies on the H₂-H dimer reveal a localized triplet with ZFS parameters and ESP pattern the same as for the individual monomers. On the other hand, triplet ESR of the Zn-H diporphyrin reveals triplet characteristics of the thiaporphyrin subunit, indicating an energy transfer in the triplet state.

Vinylporphyrins containing one vinyl group at the pyrrole or benzene ring and their complexes with Cu²⁺ and Zn²⁺ have been obtained by the Wittig reaction. The compounds obtained were characterized by physicochemical methods. X-ray diffraction analysis of 5-(4-vinylphenyl)-10,15,20-triphenylporphyrin has been carried out. It is likely that the inclusion of the vinyl group is accompanied by weak electron effects on the macrocycles. The radical-induced copolymerization of meso-tetraphenylporphyrin monomers with the vinyl group in a benzene or pyrrole ring and their copper and zinc complexes with styrene and methacrylate was studied. Porphyrin comonomers decrease the overall polymerization rate and the number-average molecular weight of the products formed compared with the weight of polystyrene obtained under similar conditions. The main reasons for termination of chain growth by vinylporphyrins were revealed and some quantitative parameters of these reactions were obtained. IR and electronic absorption spectra of porphyrin-containing copolymers are discussed. According to the ESR spectra, the copper-containing centres in the copolymers are fairly remote from each other, and the metal-containing polymeric systems are magnetically dilute. The spectral luminescence properties of solutions of zinc 5-(4-vinylphenyl)-10,15,20-triphenylporphyrin–methyl methacrylate copolymers with various contents of porphyrin groups were studied. It was shown that a new long-wave band appears in the absorption spectra of the copolymers, the intensity of which depends on the copolymer composition, and the quantum yield of fluorescence decreases with increasing molar fraction of porphyrin groups.

The binding of meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (T4CPP), meso-tetrakis[3-(carboxymethyleneoxy)phenyl]porphyrin (T3CPP) and meso-tetrakis[3,4-bis(carboxymethyl-eneoxy)phenyl]porphyrin (T3, 4BCPP) with bovine serum albumin (BSA) at pH 7.4 has been studied at 420 nm in detail. The results show hypochromicity along with a red shift in the Soret band of the porphyrins. This suggests that these porphyrins bind to BSA as monomers. Further analysis of these data supports the non-interactive binding of T4CPP and T3CPP with BSA and the cooperative binding of T3, 4BCPP with BSA. These binding data have been interpreted in terms of one specific binding site and several non-specific binding sites on BSA for the porphyrins. The absorption spectral changes of the porphyrins between 400 and 450 nm when titrated with BSA suggest that there is another specific binding site on BSA for the porphyrins. These two specific binding sites have also been supported by circular dichroism (CD) studies. The absorption spectral and CD studies on the interactions of the porphyrins with BSA further suggest that these interactions are dependent on the number and configuration of substituents in the phenyl groups of the porphyrins. The contact energy transfer from the aromatic amino acid residues tryptophan and tyrosine of BSA to the porphyrins in the BSA–porphyrin complexes has also been studied using fluorescence spectroscopy. These energy transfer data show the energy transfer from tryptophan to the porphyrins for their binding to site I of BSA and from tyrosine to the porphyrins for their binding to site II of BSA. Unfolding studies of the BSA–porphyrin systems indicate that the tertiary structure is essential for the binding of the porphyrins. A correlation between the accumulation of ^99mTc-labelled T4CPP and T3, 4BCPP in tumour tissue and their binding at site II of BSA is possible. The interaction of the porphyrins can also be used as a model for mitochondrial interactions.

Series of 5,10,15,20-tetraarylporphyrins 1 and 5,10,15,20-tetrakis[4-(arylethynyl)phenyl]porphyrins 2 were prepared via condensation of pyrrole with the appropriate benzaldehyde or 4-(arylethynyl)benzaldehyde derivative (3). Condensation of meso-phenyldipyrromethane with mixtures of benzaldehyde and 4-(trimethylsilyl-ethynyl)benzaldehyde gave a separable mixture of mono- (6), bis- (both cis-7 and trans-8) and tris[4-(trimethylsilylethynyl)phenyl]porphyrin (9). Following removal of the trimethylsilyl groups of 6–9, the 4-ethynylphenyl groups of 11–14 were coupled to 1-iodo-3,5-di(trifluoromethyl)benzene with Pd(OAc)₂ to give 15–18 bearing one, two (both cis- and trans-) and three 4-[bis-3,5-(trifluoromethyl)phenylethynyl]phenyl groups respectively. Coupling of 11 and 1-iodo-4-nitrobenzene with Pd(OAc)₂ gave porphyrin 19 with one 4-(4-nitrophenylethynyl)phenyl group. Porphyrin 24 with a p-quinone linked to the porphyrin core via a phenylethynyl group was prepared via similar chemistry. The absorbance spectra, emission maxima, excited-state fluorescence lifetimes, quantum yields of fluorescence, rates of fluorescence and rates of non-radiative decay were measured for each of the porphyrins. Absorbance spectra and emission maxima were nearly identical for all the porphyrins of this study, which suggests that the aryl groups and 4-(arylethynyl)phenyl groups are not strongly coupled to the porphyrin core in these metal-free compounds. Fluorescence quantum yields and rates of radiative decay were larger for porphyrins bearing 4-(arylethynyl)phenyl groups, while excited-state fluorescence lifetimes were somewhat shorter. These effects were additive for each additional 4-(arylethynyl)phenyl group.

The preparation and luminescence properties of a dipalladium cofacial porphyrin dimer (DPA)Pd₂ (where DPA is the tetraanion of 1,8-bis(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin-5-yl)anthracene) are reported and compared together with the photophysical behavior of the known monomeric (OEP)Pd and (TPP)Pd complexes. The effect of dioxygen in the presence and in the absence of the very bulky base, 1-t-butyl-5-phenylimidazole, is also investigated. The title dimer, (DPA)Pd₂, shows fluorescence and phosphorescence in the ps and ms time scale, respectively, with a global intensity lower than that of the porphyrin monomer analogues. The fluorescence sensitivity towards dioxygen quenching appears greater for the dipalladium complex than that of the monoporphyrin derivatives. In the presence of the bulky base, this sensitivity shows a dramatic decrease.

The fluorescence quenching of a Zn(II) porphyrin linked to Cu(I)catenates relative to a model compound without Cu(I) was attributed to energy transfer from the Zn(II) porphyrin to the metal-to-ligand charge transfer (MLCT) state of the Cu(I)(phenanthroline)₂ center at the core of the molecules. The similarity of the fluorescence spectra and fluorescence decays of a Zn(II) porphyrin linked to an Au(III) porphyrin, a Zn(II) porphyrin or a benzoate moiety through the catenate framework suggested that no fluorescence quenching by electron transfer to the Au(III) porphyrin occurred and that the copper(I) (phenanthroline)₂ center acts as an energy sink. The value of the critical distance for Förster type energy transfer, determined from spectral data is compatible with the observed rate constants for energy transfer and dimensions of the macrocycle. The multi-exponential nature of the fluorescence decay is attributed to the presence of different slowly interconverting conformations of the macrocycle to which the porphyrins are attached.

The stand-off detection classification by laser induced fluorescence is the objective of the Biosense project. The sensor will perform the monitoring of a defined area around its location using an elastic lidar detector for particles cloud. The detection of cloud will trigger fluorescence probing of the cloud. To perform this task the area fluorescence background will be monitored in order to evaluate if a return signal changed. Using a simple signal model built with experimental data, we designed a detection and monitoring procedure for the fluorescence at a single location. Signal simulations have been performed to verify the operation of the system. The results of the simulation indicate the system is able to detect anomaly with small contrast between a signal and the background. The results will have to be extended to area surveillance and a more complete signal model for various environments in natural conditions is required

Threats associated with bioaerosol weapons have been around for several decades. However, with the recent political developments that changed the image and dynamics of the international order and security, the visibility and importance of these bioaerosol threats have considerably increased. Over the last few years, Defence Research and Development Canada has investigated the spectrometric LIDAR-based standoff bioaerosol detection technique to address this menace. This technique has the advantages of rapidly monitoring the atmosphere over wide areas without physical intrusions and reporting an approaching threat before it reaches sensitive sites. However, it has the disadvantages of providing a quality of information that degrades as a function of range and bioaerosol concentration. In order to determine the importance of these disadvantages, Canada initiated in 1999 the SINBAHD (Standoff Integrated Bioaerosol Active Hyperspectral Detection) project investigating the standoff detection and characterization of threatening biological clouds by Laser-Induced Fluorescence (LIF) and intensified range-gated spectrometric detection techniques. This article reports an overview of the different lessons learned with this program. Finally, the BioSense project, a Technology Demonstration Program aiming at the next generation of wide area standoff bioaerosol sensing, mapping, tracking and classifying systems, is introduced.

Terahertz (THz) gas photonics uses gas as THz emitter and sensor for time-domain spectroscopy. Unique properties of the gas promise scalable, strong THz wave generation with broad spectral range covering the entire THz gas (0.3 THz to 35 THz). The systematic study of THz wave generation and detection in different gases shows that the generation efficiency is monotonically decreasing with the ionization potential of the gas molecules while the detection efficiency is linearly proportional to the third order nonlinear coefficient of the gas molecules. We also discuss the development of THz wave detection using laser-induced fluorescence and coherent control with THz gas photonics.

The physics of Cosmic Rays of Extreme Energy will be deeply investigated by the next generation of fluorescence space detectors. For the Extreme Energy Neutrino Astronomy such detectors will probably exhibit a lack of statistics and a further increase of sensitivity will be necessary for this goal. The critical items in designing a future Neutrino Space Observatory suited for Neutrino Astronomy are discussed.

We report the development of laboratory astrophysics program in Taiwan. We begin with outlining Taiwan's participation in the FLASH collaboration for measuring the fluorescence yield using SLAC 28.5 GeV electron beam. We then report the domestic effort of studying cosmic ray shower properties using NSRRC 1.5 GeV electron beam.

Hybrid hydrogels are a new class of composite materials. Polyacrylamide (PAAm) hydrogels are mainly produced by free radical crosslinking copolymerization (FCC) of AAm in the presence of N, N′-methylene bis (acrylamide) (BIS) as the crosslinker. Pyranine doped PAAm-poly (N-vinyl pyrrolidone) (PVP) composite were prepared with different amounts of PVP varying in the range between 0.0015 and 0.1 gr. It was observed that pyranine molecules as a fluoroprobe bind to AAm and PVP chains upon the initiation of the polymerization, causing the fluorescence spectra of the bonded pyranines shift to the shorter wavelengths. The sol–gel phase transition and its universality were monitored and tested as a function of PVP contents. Observations around the critical point show that the gel fraction exponent, β, agreed with the percolation result for below 0.025 gr PVP contents. However, classical result was observed above 0.0125 gr PVP content.

In this paper, combining phosphorescence and fluorescence to form white light was realized based on DCJTB:PMMA/ITO/NPB/TCTA/FIrpic:TCTA/TPBi/Ir(ppy)3:TPBi/TPBi/Cs₂CO₃/Al. The effects of red fluorescence on this white light device was studied by adjusting the concentration of DCJTB. The study shows that the device with a DCJTB concentration of 0.7% in the color conversion layer (CCL) generates a peak current efficiency and power efficiency of 23.4 cd ⋅ A${}^{-1}$ and 7.5 lm ⋅ W${}^{-1}$, respectively. And it is closest to the equal-energy white point of (0.33, 0.33) which shows a CIE (Commission Internationale de L’Eclairage) coordinate of (0.35, 0.43) and a color rendering index (CRI) of 70 at current density of 10 mA ⋅ cm${}^{-2}$. In order to improve the efficiency, we design and fabricate both high efficient and pure white organic light-emitting diode (WOLED) by replacing the single blue emission layer (EML) with double EMLs of FIrpic:TCTA and FIrpic:TPBi. The further study shows that, when the layers of EML is three and the concentration of DCJTB at 0.7%, the device exhibits good performance specifically, at current density of 10 mA ⋅ cm${}^{-2}$, the current efficiency of 28.2 cd ⋅ A${}^{-1}$ (power efficiency of 10.3 lm ⋅ W${}^{-1}$), and the CIE coordinate of (0.33, 0.31) (CRI of 80.38).

In this work, Mn${}^{2+}/$Eu${}^{3+}$ co-doped Zn₂GeO₄ (Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+})$ was prepared by high-temperature solid phase method. Compared with common fluorescent materials Zn₂GeO₄:Mn${}^{2+}$, Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ could not only emit strong green fluorescence of 535 nm, but also maintain excellent persistent luminescence performance. Through Density Functional Theory calculation, we obtained the fine band structure of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$. The results of the band structure were consistent with the experimental spectral data. On this basis, we proposed a new luminescence mechanism model of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ to explain the phenomena observed in experiment reasonably, though which was not completely consistent with previous works. When Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ was excited, electron–hole separation occurred in the valence band (VB), and the electron transitioned to the conduction band (CB) directly. Through CB, the electron was trapped by trap levels (⁷F${}_0{\sim }^7$F₅ of Eu${}^{3+})$ and maintained metastable for a long time. Under the action of thermal stimulation, electron returned to CB from the trap level slowly. The electron was captured again by the ⁴T₂(D) level of Mn${}^{2+}$. Then the electron transitioned down toward VB and recombined with the previous hole and emitted a photon with 535 nm (afterglow). The samples were being irradiated, trap levels accommodated the excited electrons to saturation. More electrons excited into the CB could not be captured by the trap levels any more. They were captured directly by the ⁴T₂(D) and transitioned directly to VB, then emitted green fluorescence.

In this work, the mixed system composed of Zn₂GeO₄: Mn and MgGeO₃: Mn, Eu was synthesized by the high temperature solid phase method. Under the external excitation, visual color of samples was yellow. However, after the excitation was completed, visual color turned to be red. From luminescence spectrum, it was found that Zn₂GeO₄: Mn emitted green fluorescence of 534 nm under the excitation of 375 nm light. At the same time, MgGeO₃: Mn, Eu emitted both fluorescence and persistent luminescence (PersL) of 668 nm. Moreover, the properties of PersL present samples were superior to other red PersL materials. Fine band structures from density functional theory (DFT) indicated that there were different luminescent mechanisms of Zn₂GeO₄: Mn and MgGeO₃: Mn, Eu. When Zn₂GeO₄: Mn was excited, electron transitioned from VB to CB directly. Through CB, the electron was captured by the ⁴T₂(D) of Mn ion, then the electron jumped from ⁴T₂(D) to VB and recombined at once with the previous hole and emitted a 534 nm photon. When MgGeO₃: Mn, Eu was excited, electron transitioned from ⁶A₁(S) of Mn ion to CB and left a hole. Through CB, electron was captured by ⁷F₆ levels of Eu${}^{3+}$ and remained metastable for a long time, which slowed down the recombined rate between electron and hole. Under thermal stimulation, the captured electron returned to CB from ⁷F₆ levels and was recaptured by the ⁴T₂(D) of Mn. The electron transitioned down toward ⁶A₁(S) and recombined with the hole immediately, then emitted a photon with 668 nm.