Effective electrically tunable infrared reflectors based on polymer stabilised cholesteric liquid crystals

Electrically tunable infrared (IR) reflectors based on polymer stabilised cholesteric liquid crystals (PSCLC) have been fabricated. The influence of polymerisation time on bandwidth broadening and response time of the IR reflector was investigated. Such IR reflector can reflect broad band of infrared light from 725 to 1435 nm upon application of a DC electric field, while remaining predominantly transparent in the visible region, with the transmittance in the region of 400–700 nm being above 90%. Bandwidth broadening was induced using low operational power with acceptable switching speeds. Model tests reveal that this IR reflector can effectively control the indoor temperature. The distinct properties of such IR reflector make it a good candidate for smart windows of automobiles and buildings to control interior temperature and save energy.     

Preparation of Monolithic Ti‐incorporated Mesoporous Silica Materials via Tartaric Acid Templated Sol‐gel Process

Monolithic and transparent Ti‐incorporated mesoporous silica materials of large size (e.g. 2 mm) in dimension have been prepared with tartaric add (TA) as template via sol‐gel reactions of tetraethyl orthosilicate (TEOS) and tetrabutyl titanate (TBT). The materials are characterized by infrared (IR), nitrogen adsorption‐desorption isotherms, powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the monolithic materials exhibit large specific surface areas (ca. 1200 mVg) and pore volumes (ca. 0.900 cm³/g).     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

Summary. In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Vibrational and electronic absorption spectroscopy of dibenzo[b,def]chrysene and its ions

The vibrational and electronic absorption spectra of dibenzo[b,def]chrysene (DBC) and its ions in argon matrixes have been recorded. Assignment of the observed infrared (IR) bands has been made by comparison with the density functional theory (DFT) computations of harmonic vibrational frequencies (with 6-31G(d,p) or 6-311+G(d,p) basis sets). Extensive time-dependent (TD) DFT calculations of vertical excitation energies have aided in the assignment of the experimental electronic absorption transitions. In general, the theoretical predictions are in good agreement with the observed ultraviolet and visible bands. By correlating IR and UV-visible band intensities (after UV photolysis), it has been shown that both DBC cations and anions are formed. The IR band intensity distributions of the DBC ions differ markedly from neutral DBC. A synthetic spectrum composed of neutral, cationic, and anionic DBC contributions compares reasonably well with the interstellar features of the "unidentified infrared" (UIR) bands from the reflection nebula NGC 7023. Finally, it is shown that the electronic absorption bands of the DBC ions lie in close proximity to several of the diffuse interstellar visible absorption bands (DIBs).     

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1'-Binaphthyl-2,2'-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman (UVRR) spectra of 1,1'-binaphthyl-2,2'-diamine (BINAM) were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.     

The mechanism of the dissolution,spray and deposition technique--a novel infrared sampling method

The dissolution, spray and deposition (DSD) technique, a novel infrared (IR) sampling technique, gives very sharp spectra for amino acids and peptides. The mechanism of this unique technique has been established by scanning electron microscopy (SEM) studies and found to be due to the formation of several layers of fairly large KBr crystals in situ on an IR transparent window. The zwitterions of the amino acids and dipeptides are adsorbed on the surface of these large KBr crystals, which ensures the isolation of monomers of the amino acid or dipeptide zwitterions in the KBr matrix, thereby leading to sharp and well-resolved IR spectra. This methodology provides a powerful IR sampling technique, akin to matrix isolation, with the added advantage of being extremely cost effective as it does not require low-temperatures or a sophisticated experimental set up.     

Density functional theory study of the interaction between formamide and uracil

The hydrogen bonding of complexes formed between the formamide and uracil molecule has been fully investigated in the present study using the density functional theory (DFT) method at varied basis set levels from 6‐31G to 6‐311++G(d,p). Eight stable cyclic structures with two hydrogen bonds involved in the interaction are found on the potential energy surface (PES). The four structures are seven‐membered rings; the others are eight‐membered rings. The eight‐membered ring is preferred over the seven‐membered one by analyzing the hydrogen bond lengths and the interaction energies. The infrared (IR) spectrum frequencies, IR intensities, and the vibrational frequency shifts are reported. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Synthesis,spectroscopy, X-ray crystal structure,and DFT studies on a platinum(II) Schiff-base complex

[PtCl₂(SMe₂)₂] reacts with (N,N′-bis(salicylidene)-1,2-cyclohexanediamine) to give (N,N′-bis(salicylidene)cyclohexane-1,2-diamine)platinum(II). The complex has been characterized by elemental analysis, infrared (IR), UV-Vis, and single-crystal X-ray diffraction. Pt(II) is in a square-planar environment, coordinated by a chelating N₂O₂ donor. Density functional theory (DFT) calculations such as geometry optimization, vibrational frequency, electronic properties, and natural bond orbital (NBO) have been performed for the platinum compound using the OLYP method at TZP(6-311G*) basis set. The optimization calculation shows that the geometry parameters can be reproduced with the OLYP/TZP basis set. Experimental IR frequencies and calculated vibrational frequencies support each other. Time-dependent DFT has been used for absorption wavelengths and results were compared with experimental data. Moreover, NBO analysis has been performed.     

过渡金属表面α-吡啶基的振动光谱学判据

基于簇模型采用密度泛函理论在B3LYP/6-311+G^**/LANL2DZ(metal)基组水平上计算了吡啶及α-吡啶基吸附于Pt、Pd、Rh、Ni四种金属表面的红外和拉曼光谱. 通过详细地分析和比较计算结果与文献报道的实验谱图, 提出了以N端吸附的吡啶分子和α-吡啶基这两种表面物种各自存在的谱学判据. 计算结果表明在以上四种金属表面, α-吡啶基的拉曼活性比吡啶的小, 而特征谱峰的红外强度与吡啶相当. 该结果表明红外光谱是检测金属表面α-吡啶基的有效手段, 也解释了采用表面增强拉曼光谱和红外光谱研究吡啶吸附在金属表面得出不同结构的原因.     

Synthesis and properties of the addition polymer of benzenedithiol with divinylbenzene

Polyaddition of 1,4-benzenedithiol (BDT) to 1,4-divinylbenzene (DVB) was carried out with 2,2′-azobisisobutyronitrile initiator in toluene at 75°C under a nitrogen atmosphere. The polymerization proceeded without an induction period, to give a white polymer with a high molecular weight (M?_w = 110,000) in ca. 90% yield for 2 hr. It was confirmed by ¹H-NMR (nuclear magnetic resonance), IR (infrared) and sulfur contents that the polymer had an alternating structure of DVB and BDT units. The end-capping reaction of the polymer was also achieved by addition of thiophenol and/or styrene to the polymerization solution at a final stage of the polymerization. The polymer film exhibited a reversible phase transition between a transparent state and an opaque one by thermal mode. The thermal property of the polymer was studied by differential scanning calorimetry (DSC) analysis and polarized optical microscope observation with the polymer film. The detailed DSC analysis showed that the end-capped polymer with a relatively low molecular weight (M?_W = 4400–9600) exhibited similar to liquid crystalline behavior. A diffuse reflectance spectrum of the polymer coated on an aluminum plate showed a marked difference in reflective light intensity in the ultraviolet and visible regions: the reversible phase transition between an opaque and a transparent polymer layers was induced by thermal mode. The light transmittance of the polymer film, which was measured by depolarized light intensity method, was very sensitive toward the temperature variation.     

Effect of dehydration on sulfate coordination and speciation at the Fe-(hydr)oxide-water interface: a molecular orbital/density functional theory and Fourier transform infrared spectroscopic investigation

The effect of dehydration on the coordination and speciation of sulfate at the Fe-(hydr)oxide-H2O interface was investigated using molecular orbital/density functional theory (MO/DFT) and Fourier transform infrared (FTIR) spectroscopy. IR frequency calculations were performed at the UB3LYP/6-31+G(d) level of theory for potential sulfate (bidentate bridging, monodentate, and H-bonded) and bisulfate (bidentate bridging and monodentate) surface complexes. MO/DFT calculated IR frequencies were compared to available IR literature results and attenuated total reflectance (ATR) FTIR spectra collected in our laboratory of sulfate adsorbed at the hematite-H2O interface. IR frequency calculations performed using the larger 6-311+G(d,p) basis set resulted in minor frequency shifts that did not dramatically alter the agreement with experiment. This investigation proposes that sulfate undergoes a speciation change as a function of surface dehydration. A generalized model for the speciation change is proposed as follows. (1) At the Fe-(hydr)oxide-H2O interface, sulfate adsorbs as a bidentate bridging or monodentate surface complex under most experimental conditions. (2) Upon surface dehydration, sulfate changes speciation to form bidentate bridging and/or monodentate bisulfate. However, surface dehydration does not yield 100% speciation change but leads to a mixture of sulfate and bisulfate. (3) The speciation change is reversible as a function of rehydration. The reversibility of the sulfate-bisulfate speciation change is chiefly determined by the local hydration environment of the O-H bond in bisulfate. Under dehydrated conditions, the O-H bond length is approximately 0.98 A. The bond length substantially increases (bond strength decreases) to approximately 1.03 A when the initial H-bond network is re-established through hydration, likely leading to deprotonation upon full mineral surface hydration.     

CO2 sorption on MgO and CaO surfaces: a comparative quantum chemical cluster study

A comparative quantum chemical study of CO2 adsorption on MgO and CaO has been carried out. Theoretical infrared (IR) frequencies are calculated and compared with IR experiments from the literature. The results show that CO2 adsorbs as monodentate on edge sites and bidentate on corner sites on MgO. The former assignment contradicts the common assumption of adsorption of CO2 in a bidentate configuration. On CaO, CO2 adsorbs as monodentate on both edge and corner sites, which is a reinterpretation of earlier experimental work. On terrace (100) sites, none of the adsorption modes on MgO or CaO possess calculated frequencies in agreement with the experimental IR spectra. These experimental bands were tentatively assigned to some slightly perturbed double negatively charged carbonate ions at the surface, rather than the monodentate structure suggested in the literature.     

Basis set effects and the choice of reference geometry in ab initio calculations of vibrational spectra

Tatewaki and Huzinaga's [J. Comput. Chem. 1 , 205 (1980)] basis sets, constructed to minimize superposition error, were used to calculate infrared (IR) frequencies and intensities. They were found inferior to Pople bases such as 3–21G and 6–31G*. The question of whether a theoretical vibrational spectrum should be computed at experimental or theoretical bond lengths was also investigated. If the magnitude of the correlation energy increases with bond length, Hartree-Fock bond lengths are expected to be shorter than experimental, and frequencies computed there will be higher than those computed at experimental lengths. Conversely, if this magnitude decreases with R, computed lengths should be longer than experimental and should give lower computed frequencies.     

Study of structure and spectral characteristics of the binuclear zinc complex with (<Emphasis Type="Italic">E</Emphasis>)-2-({2-[3-(pyridin-2-yl)-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-5-yl]phenylimino}methyl)phenol

A study of the structure and spectral properties of the compound (E)-2-({2-[3-(pyridin-2-yl)-1H-1,2,4-triazol-5-yl]phenylimino}methyl)phenol and its binuclear complex with zinc was carried out by the quantum-chemical calculations at a level of density functional theory. Within the framework of the time-dependent density functional theory were calculated electron spectra of both compounds, which gave good agreement with experiment, and was revealed the nature of the absorption bands in the visible and near UV region taking into account the solvent effect. Complete interpretation of the absorption bands in the infrared spectra of the complex and protonated ligand was given, and the frequency shift and changes in the intensities of IR bands of the ligand at the complex formation were analyzed.     

Spectroscopy of Dibenzorubicene: Experimental Data for a Search in Interstellar Spectra

We report on the characterization of dibenzo[cde,opq]rubicene (C₃₀H₁₄). The molecule was studied in solution at room temperature with absorption spectroscopy in the visible (vis) and ultraviolet (UV) wavelength ranges, and with emission spectroscopy. The infrared (IR), visible, ultraviolet, and vacuum ultraviolet (VUV) absorption spectra of a thin film were measured also at room temperature. In addition, the UV/vis absorption spectrum was measured at cryogenic temperatures using the matrix isolation spectroscopy technique. The interpretation of spectra was supported by theoretical calculations based on semiempirical and ab initio models, as well as on density functional theory. Finally, the results of the laboratory study were compared with interstellar spectra.     

Non-coherent visible and infrared radiation increase survival to UV (254 nm) in Escherichia coli K12

Interactions between visible or infrared (IR) and ultraviolet (UV, 254 nm) radiation have been studied in E. coli. Pre-illumination with non-coherent monochromatic 446, 466, 570 and 685 nm radiation, as well as with polychromatic red and IR radiation at room temperature, leads to increased cell survival after a subsequent irradiation with UV light. In the thermic range of the spectrum (red and IR), IR but not red light pre-treatment is able to increase cell survival to a subsequent lethal heat (51 degrees C) challenge, suggesting that increased UV survival may be due to IR-induced heat-shock response. On the other hand, visible-light-induced resistance may be due to a different mechanism, possibly involved with unknown bacterial light receptors.     

Preparation of photoluminescent nanocomposite ink toward dual-mode secure anti-counterfeiting stamps

Fluorescent photochromism has been applied as an attractive approach for the production of effective authentication substrates to show dual-mode secure encoding. In the current study, novel photochromic and fluorescent nanocomposite ink was developed to introduce a stamped film with strong dual-mode emission for anti-counterfeiting purposes. Inorganic/organic nanocomposite ink was developed from lanthanide-doped aluminate (LDA) dispersed in poly(acrylic acid)-based binder. To produce a transparent film, LDA must be dispersed well in the poly(acrylic acid)-based ink solution. The fluorescent and photochromic nanocomposite ink was stamped effectively onto cellulose documents followed with thermal fixation. Homogeneous fluorescent and photochromic layer was stamped onto paper surface providing a transparent look with the ability to switch to green beneath ultraviolet as illustrated by CIE Lab. The stamped documents were studied by photoluminescence spectra to show an absorption peak at 364 nm, and fluorescence band at 438 nm. The induced security encoding was transparent beneath visible light turning into visible greenish-yellow beneath ultraviolet light indicating a bathochromic shift. LDA was synthesized in the nanoparticle form and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The morphological properties of the stamped documents were examined by infrared spectroscopy (FTIR), scan electron microscope (SEM), EDS, and X-ray fluorescence (XRF). The stamped paper sheets displayed an efficiently reversible photochromism without fatigue under visible and ultraviolet lights. The rheologies of the prepared photoluminescent nanocomposite inks as well as the mechanical performance of the stamped sheets were investigated.     

Theoretical prediction of the Infrared and Raman spectra of O-ethyl S-2-diisopropylaminoethylmethylphosphonothiolate

We have extended our computations of the structure and of the infrared and Raman spectra of methylphosphonates and related compounds to the O-ethyl S-2-diisopropylaminoethylmethylphosphonothiolate molecule (we abbreviate the name to ESD). We have computed the optimized geometry and the vibrational infrared and Raman frequencies of ESD by means of the Guassian 92 Program Package using 6–31G * basis sets. We assign the vibrational frequencies and we correct each frequency by multiplying it with a previously derived 6–31G * correction factor. The result is a computer-generated prediction of the IR and Raman spectra of ESD . The agreement between our theoretical predictions and the experimental IR spectrum of ESD is surprisingly good. © 1994 John Wiley & Sons, Inc.     

Alkali‐treated semiconducting polypyrrole for infrared detection

A simple treatment of a polypyrrole (PPy) film with sodium hydroxide (NaOH) solutions reduces the conductivity (i.e., increased the resistance) and makes the film heat sensitive in the infrared (IR) spectrum with wavelength from 2.5 to 15.4 μm. The IR sensitivity increases with increasing treatment time in NaOH solutions and increasing exposed area to the radiation. The temperature coefficient of resistance, α, quantifying the sensitivity to IR, of the NaOH‐treated PPy is comparable with that of silicon and other conventional materials. The reduction and recovery of resistance due to IR on/off exposure exhibit a t^β dependence, where t is the time and β is determined to be around 0.5. This implies that the response of the material is controlled by diffusion of heat flux into and out of the sample. It is also observed that thermal ageing of the NaOH‐treated PPy film enhances the IR sensitivity. The sensing response of the treated films is observed beyond the thermal IR region to ultraviolet–visible wavelengths. Thus, the NaOH‐treated PPy appears to be a broadband sensing material. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012