Note: A variable temperature cell for spectroscopy of thin films

Abstract

We report the design and construction of a cell that enables precisely controlled measurement of UV∕Vis spectra of thin films on transparent substrates at temperatures up to 800 K. The dimensions of the setup are accommodated by a standard Varian Cary 5E spectrophotometer allowing for widespread use in standard laboratory settings. The cell also fits in a Bio-Rad IR-spectrometer. The cell is constructed with an outer water cooled heat shield of aluminum and an inner sample holder with heating element, thermo-resistor and windows, made from nickel coated copper. The cell can operate both in air, and with an inert gas filling. We illustrate the utility of the cell by characterization of three commercially available near infrared absorbers that are commonly used for laser welding of plastics and are known to possess high thermal stability.

Croconaine Dyes – the Lesser Known Siblings of Squaraines

“…[73] A second more extensive examination of type 31 croconaine rotaxanes was reported in 2014 [74] with efficient photothermal performance in both organic and aqueous environments as well as the preparation of croconaine-doped silicate micelle nanoparticles. A patent from the University of Copenhagen [77] covered a type 13 croconaine as a near-infrared--absorbing (near-infrared = NIR) additive in plastics to aid the laser welding of these materials. [75] The only paper from 2015 [76] reported the use of the same water-soluble type 16 croconaine [λ max = 798 nm (EtOH/H 2 O = 4:1 v/v)] synthesized according to Song and Foley, [66] as a dualchannel colorimetric and fluorescent probe for metal ions in ethanol/water (4:1 v/v) solution with particular sensitivity and selectivity towards Fe 3+ and Cu 2+ (Scheme 14).…”

“…Similar to their squaraine counterparts, croconaines have primarily, although not exclusively, been made in short-chain alcohols or solvent mixtures containing such alcohols. Type 4 croconaines have primarily been prepared in butanol/ toluene mixtures, [77] in most cases with the azeotropic removal of water, [44,57,79] whereas type 4b required pyridine. Syntheses of the more frequently studied croconaines are illustrated in the following examples, which were taken from the stated publications that reported full experimental details.…”

“…of Figure 6, was that substituents induced a red shift of the λ max value as observed for both 2a and 4b relative to 2 and 4 croconaines, respectively. [77] Apart from these two, λ max of compound 30 [71] was examined in three solvents (Table 1), and four type 16 croconaines were examined in four amount of Pb 2+ to a THF solution of 33 gave a 26-fold enhancement of the fluorescence intensity, while Cd 2+ gave a 14-fold increase. Larger aromatic substituents also generally increased the λ max value further than smaller substituents.…”

“…The use of croconaine dyes in optical-information recording media was not only examined because of their suitability for data recording by a high wavelength laser but also because they were stable to heat and regeneration light. [77] Croconaines have been covered in patents simply because of their NIR absorbing properties. This commonly consisted of dip-coated or solvent-cast thin films although one patent reported vapour deposition.…”

“…[74] [60] [c] Type 13 croconaine (R 1 and R 2 = C 12 H 25 ; shown in Scheme 18). [77] [d] Compound 30. [71] There is also scant evidence within the literature that the visible absorption strength of croconaine dyes is less in comparison to the analogous squaraine dyes.…”