Highly Sensitive Dual-Phase Nanoglass-Ceramics Self-Calibrated Optical Thermometer

A strategy to achieve high sensitivity of noncontact optical thermometer via the structure design of nanoglass-ceramic and the usage of Ln³⁺ (Ln = Eu, Tb, Dy) luminescence as reference signal and Cr³⁺ emission as temperature signal was provided. Specifically, the synthesized dual-phase glass-ceramics were evidenced to enable spatially confined doping of Ln³⁺ in the hexagonal GdF₃ nanocrystals and Cr³⁺ in the cubic Ga₂O₃ nanoparticles, being beneficial to suppressing detrimental energy transfer between Ln³⁺ and Cr³⁺ and thus significantly enhancing their luminescence. As a consequence, completely different temperature-sensitive luminescence of Ln³⁺4f → 4f transition and Cr³⁺ 3d → 3d transition in the present glass-ceramic resulted in obvious variation of Cr³⁺/Ln³⁺ fluorescence intensity ratio with temperature and strikingly high detecting temperature sensitivity of 15–22% per K. We believe that this preliminary study will provide an important advance in exploring other innovative optical thermometry

EuF₃/Ga₂O₃ Dual-Phase Nanostructural Glass Ceramics with Eu²⁺/Cr³⁺ Dual-Activator Luminescence for Self-Calibrated Optical Thermometry

To circumvent the requirement of small energy gap between thermally coupled levels of lanthanide probes in optical thermometry, a strategy using dual-activator fluorescence intensity ratio as temperature signal in dual-phase nanostructural glass ceramics was reported. Specifically, oxyfluoride glass with specially designed composition of SiO₂–Al₂O₃–LiF–EuF₃–Ga₂O₃–Cr₂O₃ was fabricated, and subsequently glass crystallization was used to induce homogeneous precipitation of hexagonal EuF₃ and cubic Ga₂O₃ nanocrystals among the glass matrix. Impressively, Eu²⁺ activators were produced after glass crystallization in an air atmosphere, and the Cr³⁺ emitting center was evidenced to incorporate into Ga₂O₃ crystalline lattice. As a result, temperature determination with high sensitivity of 0.8% K^–1, large energy gap of 8500 cm^–1, and superior thermal stability were realized by taking advantage of the fluorescence intensity ratio between Eu²⁺ and Cr³⁺ as detecting parameter, which exhibited a linear dependence on temperature. We believe that this preliminary investigation will provide a practical approach for developing a high-performance self-calibrated optical thermometer

Effects of Feedstock and Pyrolysis Temperature on Biochar Adsorption of Ammonium and Nitrate

<div><p>Biochar produced by pyrolysis of biomass can be used to counter nitrogen (N) pollution. The present study investigated the effects of feedstock and temperature on characteristics of biochars and their adsorption ability for ammonium N (NH₄⁺-N) and nitrate N (NO₃⁻-N). Twelve biochars were produced from wheat-straw (W-BC), corn-straw (C-BC) and peanut-shell (P-BC) at pyrolysis temperatures of 400, 500, 600 and 700°C. Biochar physical and chemical properties were determined and the biochars were used for N sorption experiments. The results showed that biochar yield and contents of N, hydrogen and oxygen decreased as pyrolysis temperature increased from 400°C to 700°C, whereas contents of ash, pH and carbon increased with greater pyrolysis temperature. All biochars could sorb substantial amounts of NH₄⁺-N, and the sorption characteristics were well fitted to the Freundlich isotherm model. The ability of biochars to adsorb NH₄⁺-N followed: C-BC>P-BC>W-BC, and the adsorption amount decreased with higher pyrolysis temperature. The ability of C-BC to sorb NH₄⁺-N was the highest because it had the largest cation exchange capacity (CEC) among all biochars (e.g., C-BC400 with a CEC of 38.3 cmol kg⁻¹ adsorbed 2.3 mg NH₄⁺-N g⁻¹ in solutions with 50 mg NH₄⁺ L⁻¹). Compared with NH₄⁺-N, none of NO₃⁻-N was adsorbed to biochars at different NO₃⁻ concentrations. Instead, some NO₃⁻-N was even released from the biochar materials. We conclude that biochars can be used under conditions where NH₄⁺-N (or NH₃) pollution is a concern, but further research is needed in terms of applying biochars to reduce NO₃⁻-N pollution.</p></div

FT-IR spectrum of wheat-straw biochar (W-BC), corn-straw biochar (C-BC) and peanut-shell biochar (P-BC) at different pyrolytic temperatures and the biochars with different treatments at 500°C (a: W-BC, b: C-BC, c: P-BC, d: W-BC500 with acid- and DI water-washed treatments, e: C-BC500 with acid- and DI water-washed treatments, f: P-BC500 with acid- and DI water-washed treatments).

<p>FT-IR spectrum of wheat-straw biochar (W-BC), corn-straw biochar (C-BC) and peanut-shell biochar (P-BC) at different pyrolytic temperatures and the biochars with different treatments at 500°C (a: W-BC, b: C-BC, c: P-BC, d: W-BC500 with acid- and DI water-washed treatments, e: C-BC500 with acid- and DI water-washed treatments, f: P-BC500 with acid- and DI water-washed treatments).</p

Correlations between mass of NH₄⁺-N adsorbed per mass of biochar at equilibrium (Qe) and content of C (a), content of O (b), atomic ratio O/C (c), atomic ratio H/C (d), atomic ratio (O+N)/C (e) and CEC of corn-straw biochar (f), respectively.

<p>The symbols ▪, , ▴ and ▾ represented pyrolysis temperatures at 400°C, 500°C, 600°C and 700°C, respectively.</p

Sorption of NH₄⁺-N and NO₃⁻-N by W-BC500, C-BC500 and P-BC500 with different treatments in 50 mg L⁻¹ aqueous solutions.

<p>Note: Different letters indicate significant difference for the results and the adsorbed amounts of NH₄⁺-N and NO₃⁻-N were compared separately.</p><p>Sorption of NH₄⁺-N and NO₃⁻-N by W-BC500, C-BC500 and P-BC500 with different treatments in 50 mg L⁻¹ aqueous solutions.</p

pH values, electrical conductivity (EC), ash content, cation exchange capacity (CEC), BET surface area, pore volume and pore size of W-BC, C-BC and P-BC at different pyrolytic temperatures.

<p>Note: Different letters indicate significant difference for the results in the same column.</p><p>pH values, electrical conductivity (EC), ash content, cation exchange capacity (CEC), BET surface area, pore volume and pore size of W-BC, C-BC and P-BC at different pyrolytic temperatures.</p

Sorption isotherms of NO₃⁻-N on wheat-straw biochar (W-BC), corn-straw biochar (C-BC) and peanut-shell biochar (P-BC) at different pyrolytic temperatures (Q_e: the amount of NO₃⁻-N sorbed by per unit mass of biochar at equilibrium; Ce: concentration of NO₃⁻-N in the solution at equilibrium).

<p>Bars indicate standard deviation of three replicates.</p

Sorption isotherms of NH₄⁺-N on wheat-straw biochar (W-BC), corn-straw biochar (C-BC) and peanut-shell biochar (P-BC) at different pyrolytic temperatures (Q_e: the amount of NH₄⁺-N sorbed by per unit mass of biochar at equilibrium; Ce: concentration of NH₄⁺-N in the solution at equilibrium).

<p>Bars indicate standard deviation of three replicates.</p

Regression parameters of isotherms for expressing adsorption of solution NH₄⁺-N to W-BC, C-BC and P-BC at different pyrolytic temperatures.

<p>Regression parameters of isotherms for expressing adsorption of solution NH₄⁺-N to W-BC, C-BC and P-BC at different pyrolytic temperatures.</p