The near-infrared (NIR) spectra of powdered calcite in the 3 to 121μm mode particle size range

The near-infrared (NIR) spectra of powdered carbonate minerals is of significant multidisciplinary interest. However, there is a paucity of accounts of the behaviour of NIR bands as a function of particle size in well-constrained experimental settings, although such studies may hold promise in revealing band-specific traits and identifying spectral features amenable to quantified measurement of particle size fractions. To these ends, this study examines the NIR spectral response in the 2.5 to 1.66μm wavelength (4000-6000cm-1 wave number) region from powdered calcite in size fractions ranging from 3 to 121μm mode particle sizes. Results show that the behavioural response of the NIR spectra is varied. Those assigned to 3v3: 2.34μm (4270cm-1) and 2.3μm (4350cm-1) wavelengths show a linear relationship (r2 = 0.9992), with decreasing particle size and absorption intensity. Bands at 2μm (5007cm-1), 1.96μm (5109cm-1) and 1.87μm (5336cm-1) assigned to combinations between v3 overtones and v1 and its overtone show an initial decrease in absorption intensity, but an increase in absorption intensity in the 3μm mode particle size powder relative to the 5μm mode powder. The differing behaviours of 3v3 overtone related bands with respect to combinations containing v1 or its overtone occur at particle size ranges in which the optical thick to thin transition occurs at mid-infrared (MIR) frequencies. The separate NIR behavioural responses of specific bands are qualitatively reminiscent of MIR types 1 and 2 behaviour of [CO32-] anion internal modes at the optical thick to thin transition

The near-infrared spectra of the alkali carbonates

This study presents the first account of the near-infrared (NIR) spectra of the alkali carbonates: [Cs2CO3] [Rb2CO3] [K2CO3] [Na2CO3] and [Li2CO3]. Seven NIR bands (labelled [A] to [G] inclusive) within the [4000-6000cm-1] (2.5 – 1.66μm) region of interest are common to the five spectra examined, of which six bands [A-C] and [E-G] proved amenable to quantitative study. The first three occur in the range 4067-4493cm-1 (2.458-2.226μm) and are assigned to a [CO32-] 3v3 overtone, Bands [E] and [F] are centred at ca 4902cm-1 (2.04 μm) and ca 5034cm-1 (1.98 μm) respectively and are assigned to a (2v1 + 2v3) combination. Band [G] centred at ca 5190 cm-1 (1.92 μm) is assigned to a (v1 + 3v3) combination. One additional band (Band [X]) centred in the vicinity of ca 4080cm-1 (2.45μm) in all spectra other than [Cs2CO3] is assigned to (2v3 + 2v4). The data is compared with the corresponding additive sum of the mid-infrared (MIR) fundamental, or in the case of combinations, Raman and MIR fundamentals. The quantified differences between NIR band frequency and that of the corresponding MIR derived overtone or combination in the case of [Li2CO3] and [Rb2CO3] closely coincide with Raman active lattice modes of rotary origin. From which it is argued that vibration - libration combinations may operate across a range of NIR frequencies for these mineral types. NIR data from [K2CO3], [Cs2CO3] and [Na2CO3] are discussed in the light of these findings. The influences of differences in atomic mass and space group effects on the NIR spectra of the alkali carbonates are also demonstrated

Nanostructured DPA-MPC-DPA triblock copolymer gel for controlled drug release of ketoprofen and spironolactone

Objective: Uncontrolled rapid release of drugs can reduce their therapeutic efficacy and cause undesirable toxicity; however, controlled release from reservoir materials helps overcome this issue. The aims of this study were to determine the release profiles of ketoprofen and spironolactone from a pH-responsive self-assembling DPA-MPC-DPA triblock copolymer gel, and elucidate underlying physiochemical properties. Methods Drug release profiles from DPA50-MPC250-DPA50 gel (pH 7.5), over 32 hours (37 °C), were determined using UV-Vis spectroscopy. Nanoparticle size was measured by dynamic light scattering (DLS), and critical micelle concentration (CMC) by pyrene fluorescence. Polymer gel viscosity was examined via rheology, nanoparticle morphology investigated using scanning transmission electron microscopy (STEM), and the gel matrix observed using cryo-scanning electron microscopy (Cryo-SEM). Key Findings DPA50-MPC250-DPA50 copolymer (15 % w/v) formed a free-standing gel (pH 7.5) that controlled drug release relative to free drugs. The copolymer possessed a low CMC, nanoparticle size increased with copolymer concentration, and DLS data was consistent with STEM. The gel displayed thermostable viscosity at physiological temperatures, and the gel matrix was a nanostructured aggregation of smaller nanoparticles. Conclusions The DPA50-MPC250-DPA50 copolymer gel could be used as a drug delivery system to provide the controlled drug release of ketoprofen and spironolactone. Keywords DPA-MPC-DPA, pH sensitive, Nanoparticles, Polymer gel, Drug delivery system, Controlled releas

Sourcing limestone masonry for restoration of historic buildings: a spectroscopic study

This study presents a combined Fourier transform (FT) mid-infrared, laser Raman and Commission internationale d’éclairage (CIE) L*a*b*system analysis of quarry-derived impure limestone and fallen masonry from a medieval listed building situated in the south east of England, to ascertain how spectroscopic information can be collectively employed to identify the most exacting possible replacement stone source.Data shows that subtle differences in [Al] and [Fe3+] octahedral and tetrahedral site occupancy in glauconite group clays registered in the mid-infrared [3530 cm−1/3620 cm−1] absorption ratio exerts some influence on L*Cab*hab*values. Increases in L*and Cabare associated with decreasing clay content. Theoverall weakness of correlations between infrared and visible range spectral attributes indicates multiple contributing sources to overall color. Evidence indicates that the degree of laser Raman induced background noise is related to the overall calcite content and that activators of fluorescence at 785 nmexcitation wave length may also contribute to rock color. The results are utilized to define closest matching quarry samples to the fallen masonry