Change In Crystal Structure Research Articles

One-pot hydrothermal synthesis of carbon dots-immobilized hydrozincite for ZnO-based nanocomposite lighting applications

ABSTRACT The immobilization of fluorescent nanomaterials in host–guest systems is one of the important factors for the further development of light-emitting properties in nanocomposite materials. In this study, one-pot hydrothermal synthesis was performed to generate advanced fluorescent nanocomposite by immobilizing carbon dots (C-dots) in a layered hydrozincite matrix while synthesizing them in a reaction solution. The one-pot reaction was performed by hydrothermal treatment starting from zinc acetate, urea, and diammonium hydrogen citrate in solution as precursor. The reaction condition that C-dots and hydrozincite could be synthesized together in a one-pot hydrothermal reaction at 200°C was investigated by adjusting the pH of the precursor, and the formation criteria depending on the pH were discussed. Based on the changes in crystal structure and in the surface state of the resulting composite powder compared with the single hydrozincite powder, the interaction that contributed to the immobilization of carbon dots was discussed. The fluorescence properties of the C-dots immobilized zinc compounds were characterized. Further sintering under an appropriate condition for the C-dots–hydrozincite composite allowed conversion into the C-dots–zinc oxide composite exhibiting quite different fluorescent characteristics.

შენადნობები ფორმის მეხსიერებით და შესაძლებლობები

The article contains the list of alloys with shape memory and given their structural formulations. As an example, an alloy of nickel and titanium, named Nitinol ({Ni}_3Ti), characterized by the highest shape storage index. Here in the work, the analysis of changes in crystal structure of this alloy is made, at ground temperatures of material heating and cooling.

Cathodic reduction of oxidizing gas generated by low‐temperature decomposition of hydrated calcium hypochlorite for flow cell

AbstractIn this study, we investigated the oxidizing gas generated from the low‐temperature decomposition of hydrated calcium hypochlorite and evaluated its possible use in the cathode reaction of polymer electrolyte fuel cells. The cathodic reduction of the oxidizing gas generated from hydrated calcium hypochlorite was performed at <80°C using an electrochemical method comprising a combination of a Pt millidisc and a Pt microdisc in a non‐aqueous solution as an aprotic polar solvent. In addition, we proposed a low‐temperature mechanism for the decomposition of hydrated calcium hypochlorite and assessed the crystal structure change using X‐ray diffraction. Overall, the results indicate that the oxidizing gas exhibited sufficient electrochemical activity. At each decomposition temperature, the waveform changed, and at 30°C approximately two reactive electrons were present in a typical reduction wave. The main reactant in the cathodic reaction was chlorine oxyacid, and the low‐temperature decomposition of hydrated calcium hypochlorite was found to be strongly related to water crystallization.

Effect of water medium on material removal and sub-surface defect evolution in nano-cutting of single-crystal γ-TiAl alloy

ABSTRACT In this paper, molecular dynamics (MD) simulation has been applied to study the influence of water medium on the nano-cutting process and the evolution of sub-surface defects of single-crystal γ-TiAl alloy. The effect of water medium in the result of cutting force and cutting temperature have been analysed and discussed in the machining process, while the function of common neighbour analysis (CNA) method has been used to research the chip removal mechanism, sub-surface defects and crystal structure changes. The results showed that the extrusion and shear effects of tool removed atoms from the surface of the workpiece. In the meantime, the cooling and lubricating effect of the water medium reduces the cutting temperature and cutting force. Especially, the temperature of the workpiece has a diffusion effect in the cutting process in the absence of the water medium. Some heat was taken away by the water medium, which lead to insufficient nucleation and migration of the dislocation, and high compressive stress was formed during cutting of water-bearing medium.

Heat accumulation during femtosecond laser treatment at high repetition rate – A morphological, chemical and crystallographic characterization of self-organized structures on Ti6Al4V

This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti3Al), sub-oxides and oxides (Ti6O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material.

Simultaneous Control of Formation and Growth of Asphaltene Solids and Wax Crystals Using Single-Walled Carbon Nanotubes: an Experimental Study under Real Oilfield Conditions

Asphaltene and wax depositions in oil production systems have been recognized as the most serious flow assurance concern of petroleum engineering. Despite the several chemicals offered for treatment of issues induced by these organic deposits, proposing a single efficient chemical to control simultaneously both asphaltene and wax precipitation has not been attended yet. Here, single-walled carbon nanotubes (SWCNTs) were synthesized to assess their effects on controlling the formation and size growth of asphaltene particles and wax crystals in live oil under realistic production conditions. SDS experiments showed that during depressurization at 125 °C, the asphaltene onset pressure decreased from 5946 psi in untreated live oil to 4375 in treated live oil with 100 ppm SWCNTs. High-pressure microscopy revealed that SWCNTs efficiently controlled the growth of asphaltene aggregates and reduced the size of asphaltenes in live oil during depressurization at 125 °C. This is ascribed to the strong π–π interactions between the aromatic rings of SWCNTs and electron clouds of asphaltenes. Results of cross-polarized microscopy showed that SWCNTs at an optimum concentration of 75 ppm postponed the wax formation temperature and gelation point from 32.6 and 21.5 °C to 23.2 and 14.7 °C, respectively. In addition, the morphology of the wax crystals with an average size of 756 nm in untreated oil changed from dense spherical-like into thin needle-like with an average size of 86 nm in treated oil with SWCNTs at 75 ppm. The changes in the wax crystal size and structure via X-ray powder diffraction analysis after crude oil treatment with SWCNTs confirm interactions between the carbon nanotubes and active sites of the wax crystals. The findings of this research prove that synthesized carbon nanotubes can be used as efficient inhibitor and dispersant agents for stabilizing the waxes and asphaltenes in live oil with controlling the rate of aggregation under high-pressure–high-temperature conditions.

Ferroelectric Aspect and Phase Transitions of Solid Solution of Cadmium Acetate with Aluminium (III) Oxide

The behavior of variation of dielectric constant with temperature of solid solution of Cadmium Acetate Cd(C2H3O2)2 with Aluminium (III) Oxide Al2O3 and other dielectric parameters have been measured between the temperatures 35°C to 100°C using the capacitance bridge model ZENITH-FM89A and Q meter at the frequency of 2000 Hz. In the measurement, it have been observed that the compound has lower value of dielectric constant (ε = 1580) below 36ºC, which rises upto a value of 5600 at the moderate temperature of 45ºC. After this temperature, the dielectric constant of compound decreases upto the value of nearly 3521 at the temperature of 75ºC and a high peak at the temperature of 76°C (ε = 7000) in the heating cycle curve with some fluctuations.. When the variation of dielectric constant was studied in cooling cycle the peak was observed at 62ºC(ε = 6500), above and below this temperature dielectric constant decreases with some intermediate fluctuations and by increasing aluminium oxide content in the mother compound, its quality factor also increases with a little effect on dielectric constant. The cooling cycle curve does not follow heating curve because of the relaxor behaviour of the compound. The results have been explained on the basis of crystal structure changes and the possibility of free internal rotation of acetate groups within the crystal lattice at elevated temperature. One of the advantages of Cd(C2H3O2)2 with Al2O3 is that by varying the Aluminium Oxide content, one can control temperature coefficient of resonant frequency τf without affecting the other properties. This is important for many ferroelectric applications because τf of near about low value is not always required. A non-zero τf is often preferable to compensate for frequency variation due to the effect of temperature change on the resonator housing and dielectric support structure. Solid solution of Cadmium Acetate with Aluminium Oxide suggests for its valuable applications as dielectric material with excellent properties useful in ceramics engineering and communication system. KEY WORDS: Polarization, Quality Factor, Dielectric Constant, Phase Transition, Curie temperature, Resonant Frequency and Ceramics Engineering.

Preparation and growth mechanism of micro spherical ammonium dinitramide crystal based on ultrasound-assisted solvent-antisolvent method

Micro-sized spherical ammonium dinitramide (ADN) crystals are successfully prepared by a facile ultrasound-assisted solvent-antisolvent recrystallization method without introducing any additives. The influences of the volume ratio of solvent to antisolvent, the antisolvent temperature and the ultrasound power on the micro-morphologies and properties of ADN crystals are studied systematically. The changes of morphology, particle size, crystal structure and melting point of the ADN crystals are characterized through scanning electron microscopy (SEM), laser particle size analyzer (LPSA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The results show that the optimal experimental parameters for the ADN crystal of spherical morphology are as follows: the volume ratio of solvent to antisolvent is 1:50, the antisolvent temperature is 20 ℃, and the ultrasound power is 70 W. The predicted hexagonal-flake and spherical morphologies for the ADN are close to the experimental morphologies. The growth mechanism of the spherical ADN crystal changes with supersaturation of the ADN solution. As the degree of supersaturation increases, the growth models of the spherical ADN change from the spiral growth to the rough growth, and the morphologies of ADN change from the large-sized ADN ball to the small-sized ADN ball.

Hollow zeolitic imidazolate framework-7 coated stainless steel fiber for solid phase microextraction of volatile biomarkers in headspace gas of breast cancer cell lines

In this work, we reported the preparation of the hollow zeolitic imidazolate framework-7 (ZIF-7) via etching ZIF-7 with tannic acid, and further fabricated the hollow ZIF-7 coated fiber for the solid phase microextraction (SPME) of the five volatile biomarkers (acetone, isopropanol, hexanal, hexanol and decanal) generated from breast cancer cell lines. The hollow structure not only endowed higher extraction performance for the SPME of analytes, but also improved the diffusion rate of the analytes inside the hollow ZIF-7. Under the optimal conditions, the hollow ZIF-7 coated fiber offered high extraction capacity (25–153 mg g−1) and enhancement factors (EFs, 2023–11250) for the five biomarkers, good linearity (R2 > 0.9918) of acetone and isopropanol (2.5–500 μg L−1) and hexanol, hexanal, and decanal (1.0–100 μg L−1), low limits of detection (S/N = 3) of 0.07–0.53 μg L−1 and the limit of quantifications (LOQs, S/N = 10) of 0.23–1.76 μg L−1. The precisions (RSDs, %) for intra-day (n = 6), inter-day (n = 5) and fiber-to-fiber (n = 6) were 2.8–7.5%, 4.3–8.5%, and 4.2–14.6%, respectively. The high EFs of the hollow ZIF-7 coated fiber for the five biomarkers resulted from the integrated effects of the large surface area, the unique porous structure, hydrophobic interaction, gate-opening effect, and enhanced properties after etching including faster mass transport, multiple active components, and more exposed active sites. The fabricated hollow ZIF-7 coated fiber lasted at least 140 cycles of extraction/desorption/aging without obvious decrease of extraction ability and no change of crystal structure. Finally, the hollow ZIF-7 coated fiber combined with GC-FID had been successfully used to detect the five biomarkers in the headspace gas of human breast cancer cell lines (MDA-MB-231) and normal mammary cell lines (CCD-1095Sk) with the recoveries of 84–105%. These results revealed the prospect of hollow MOFs as efficient adsorbents for sample pretreatment.

Exploring the Role of Crystal Water in Potassium Manganese Hexacyanoferrate as a Cathode Material for Potassium-Ion Batteries

The Prussian Blue analogue K2−δMn[Fe(CN)6]1−ɣ∙nH2O is regarded as a key candidate for potassium-ion battery positive electrode materials due to its high specific capacity and redox potential, easy scalability, and low cost. However, various intrinsic defects, such as water in the crystal lattice, can drastically affect electrochemical performance. In this work, we varied the water content in K2−δMn[Fe(CN)6]1−ɣ∙nH2O by using a vacuum/air drying procedure and investigated its effect on the crystal structure, chemical composition and electrochemical properties. The crystal structure of K2−δMn[Fe(CN)6]1−ɣ∙nH2O was, for the first time, Rietveld-refined, based on neutron powder diffraction data at 10 and 300 K, suggesting a new structural model with the Pc space group in accordance with Mössbauer spectroscopy. The chemical composition was characterized by thermogravimetric analysis combined with mass spectroscopy, scanning transmission electron microscopy microanalysis and infrared spectroscopy. Nanosized cathode materials delivered electrochemical specific capacities of 130–134 mAh g−1 at 30 mA g−1 (C/5) in the 2.5–4.5 V (vs. K+/K) potential range. Diffusion coefficients determined by potentiostatic intermittent titration in a three-electrode cell reached 10−13 cm2 s−1 after full potassium extraction. It was shown that drying triggers no significant changes in crystal structure, iron oxidation state or electrochemical performance, though the water level clearly decreased from the pristine to air- and vacuum-dried samples.

Role of A and B site doping on antiferrodistortive phase transition in sodium bismuth titanate

We report the results of temperature-dependent powder X-ray diffraction studies on lead-free piezoelectric sodium bismuth titanate (NBT) modified by partially substituting Ba at the A site or Nb at the B site. We observed the disappearance of certain reflections and a change in the main perovskite peaks of the rhombohedral phase suggesting a structural phase transition. Detailed Rietveld refinements revealed that both the ferroelectric and the antiferrodistortive phase transitions occur together at high temperature leading to a change in crystal structure from the low-temperature ferroelectric rhombohedral phase (space group: R3c) to the high-temperature paraelectric cubic phase (space group:Pm3¯m). This suggests the suppression of the intermediate tetragonal phase of pure NBT. We found that substituting Ba onto the A site enhances the lattice strain and lowers the antiferrodistortive phase transition temperature.

Up-conversion luminescence and temperature sensing properties of Ho3+/Gd3+ co-doped YbNbO4 phosphors

Ho3+/Gd3+ co-doped YbNbO4 phosphors were successfully synthesized by the high-temperature solid-state method. The crystal structure, morphology structure, element distribution, up-conversion luminescence and relative optical temperature sensing properties were investigated. X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) analysis demonstrated that the doping of Ho3+/Gd3+ ions had no change in crystal structure and microstructure of YbNbO4 phosphors. Under the excitation of 980 nm laser radiation, the green and red UC emissions were achieved by prepared phosphors, corresponding to the transitions of (5F4, 5S2)→5I8, 5F5→5I8 of Ho3+ ions. It is observed that the UC luminescence intensity was significantly enhanced for Ho3+/Gd3+ co-doped YbNbO4 samples compared to the mere Ho3+ doped YbNbO4 sample. Moreover, Ho3+/Gd3+ co-doped YbNbO4 samples' temperature sensitivity ranging from 303 to 663 K was calculated based on the fluorescence intensity ratio (FIR) method. The maximum sensitivity reached 0.0078 K−1 at 663 K. These results indicate that the YbNbO4:Ho3+/Gd3+ samples are a promising candidate for optical temperature sensing and up-conversion luminescence.

2-3-4 TBACセミクラスレートハイドレートの合成条件による結晶構造の変化

2-3-4 TBACセミクラスレートハイドレートの合成条件による結晶構造の変化

Stepwise Li Substitution Induced Structure Evolution and Improved Nonlinear Optical Performance for Diamond-like Sulfides.

One of the key scientific issues for exploration of novel infrared nonlinear optical (NLO) crystals is to obtain ones with good hybrid NLO behaviors. Herein, we report four diamond-like Ag-based sulfides via stepwise Li substitution of Ag in Ag2ZnSnS4, including Ag2ZnSnS4 (1), (Li1.22Ag0.78)ZnSnS4 (2), (Li1.58Ag0.42)ZnSnS4 (3), and Li2ZnSnS4 (4). With the increase of Li content, the sulfide's noncentrosymmetric crystal structure changes from tetragonal I42m for 1, to orthorhombic Pmn21 for 2 and 3, and to monoclinic Pn for 4. Accordingly, their NLO responses are improved along with the increase of Li content, viz. from non-NLO-active for 1, to non-phase-matchable for 2 and 3, and to phase-matchable for 4. Their optical band gaps also increase regularly. The relationship between their chemical compositions, crystal structures, and NLO activities is investigated by means of chemical structural analysis and theoretical calculation. This work offers a new systematic case for designing promising NLO-active compounds via rarely adopted cation's stepwise partial substitution and understanding the chemical composition-structure-NLO property relationship.

Chemical and Structural Degradation of CH3NH3PbI3 Propagate from PEDOT:PSS Interface in the Presence of Humidity

AbstractUnderstanding interfacial reactions that occur between the active layer and charge‐transport layers can extend the stability of perovskite solar cells. In this study, the exposure of methylammonium lead iodide (CH3NH3PbI3) thin films prepared on poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐coated glass to 70% relative humidity (R.H.) leads to a perovskite crystal structure change from tetragonal to cubic within 2 days. Interface‐sensitive photoluminescence measurements indicate that the structural change originates at the PEDOT:PSS/perovskite interface. During exposure to 30% R.H., the same structural change occurs over a much longer time scale (>200 days), and a reflection consistent with the presence of (CH3)2NH2PbI3 is detected to coexist with the cubic phase by X‐ray diffraction pattern. The authors propose that chemical interactions at the PEDOT:PSS/perovskite interface, facilitated by humidity, promote the formation of dimethylammonium, (CH3)2NH2+. The partial A‐site substitution of CH3NH3+ for (CH3)2NH2+ to produce a cubic (CH3NH3)1−x[(CH3)2NH2]xPbI3 phase explains the structural change from tetragonal to cubic during short‐term humidity exposure. When (CH3)2NH2+ content exceeds its solubility limit in the perovskite during longer humidity exposures, a (CH3)2NH2+‐rich, hexagonal phase of (CH3NH3)1−x[(CH3)2NH2]xPbI3 emerges. These interfacial interactions may have consequences for device stability and performance beyond CH3NH3PbI3 model systems and merit close attention from the perovskite research community.

Performance and reaction process of Ba1−xCo0.7Fe0.2Nb0.1O3-δ cathode for intermediate-temperature solid oxide fuel cell

Perovskite-type cathode Ba1-xCo0.7Fe0.2Nb0.1O3-δ (B1-xCFN, x = 0.0-0.15) are proposed for intermediate-temperature solid oxide fuel cell(IT-SOFC). The changes in crystal structure, thermal expansion and electrochemical reaction through XRD, SEM, ac impedance spectroscopy and single-cell test are studied. The results show that except for the B0.95CFN has a small amount of impurity，B1-xCFN oxides present cubic perovskite structure. The porosity decreases as A-site deficiency increases, B0.9CFN has a lowest porosity. The interfacial polarization resistance of B0.9CFN drops nearly 66.2% than BCFN at 800 ◦C. The process of generating lattice oxygen is the major rate-limiting step when oxygen partial pressure is higher than 0.01 atm. Ba deficiency mainly accelerates the ionization process of oxygen atoms in the cathode bulk. The performance of single-cell B0.9CFN/SDC/Ni0.9Cu0.1-SDC is higher than other cathodes in the operation temperature, which means B0.9CFN is a better cathode for IT-SOFC.

Solid-state fluorescent switch based on the intercoversion of J-aggregation and dimer and aggregation pattern-dependent fluorescence colorimetric sensing of GSH/Zn2+/Cd2+

A phthalazinetrione derivative, 2-(benzo[d]thiazol-2-yl)-4-hydroxyphthalazin-1(2H)-one hydrate (TP) was developed based on phthalic acid and 2-hydrazinobenzothiazole in acetic acid (AcOH) solution and obtained corresponding crystal TP-A. The TP-A exhibited colorimetric fluorescence response from yellow to green through fuming with the triethylamine (TEA) vapor, resulting in the crystal structure change to TP-N. TP-A and TP-N exhibited aggregation-induced emission (AIE) in solid state due to the J-aggregation and dimer formation, respectively. And the interconversion of the J-aggregation and dimer by a external TEA/AcOH vapor stimuli successfully and repeatedly realized switching of yellow/green luminescence. In addition, TP-A and TP-N showed similar AIE effect both in aqueous solution and in solid state, and they exhibited different sensing behavior in 100% aqueous solution. TP-A with excellent selectivity and sensitivity could be employed as a fluorescent colorimetric sensor to discriminately identify Zn2+ and Cd2+. TP-N could further fluorescent colorimetric sensing glutathione (GSH). Different aggregation pattern gave different chance for Zn2+/Cd2+.and GSH to respond with the formation of new aggregates through corresponding coordination reaction and addition reaction mechanism. Further, the TP-A and TP-N were applied to detect Zn2+/Cd2+.and GSH in Hela cells.

Effect of Y3+-O2- partial substitution with Ca2+-F- on the luminescence enhancement of Y2Mo3O12:Sm3+ red-emitting phosphors

To improve the luminescence property of Sm3+ in Y2Mo3O12, partial Ca2+-F- co-substituted Y2Mo3O12:Sm3+ phosphor, namely Y2-xCaxMo3O12-xFx:Sm3+, was prepared using a solid-state method. The effect of introducing Ca2+-F- ion pairs on structure and luminescence properties of Y2Mo3O12:Sm3+ was studied in depth. XRD patterns not only manifested that all as-prepared Y2-xCaxMo3O12-xFx:Sm3+ samples had standard Y2Mo3O12 structure, but also indicated the introduction of Ca2+-F- ion pairs did not cause the change of crystal structure. Under the near ultraviolet excitation of 404 nm, the emission peaks of Y2Mo3O12:Sm3+ were located at 567 nm, 605 nm and 652 nm, respectively, resulting from the 4f→4f electron transitions of Sm3+ ions. Furthermore, the luminescence intensity of Sm3+ was obviously enhanced through the co-substitution of Y3+-O2- ions with Ca2+-F- ions in Y2Mo3O12 structure, and the chromaticity coordinates moved towards red region, which due to the environmental effect of crystal field around Sm3+. Besides, the red LED device was manufactured for suitable chromaticity parameters. All results indicated that the as-prepared Y1.84Ca0.06Mo3O11.94F0.06:0.10Sm3+ red-emitting phosphor could become a promising candidate for application of white light-emitting diodes and plant illumination.

Green and High Effective Scale Inhibitor Based on Ring-Opening Graft Modification of Polyaspartic Acid

Polyaspartic acid (PASP)-based green scale inhibitor has great potential application in water treatment. Here, we first synthesized PASP in ionic liquid. Then, an effective PASP-based green scale inhibitor was synthesized by ring-opening graft modification of PASP with both aspartic acid (ASP) and monoethanolamine (MEA). Its chemical composition was characterized by gel chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and 1H nuclear magnetic resonance (1H NMR). Scale inhibition efficiency was measured by static scale inhibition tests. The results showed that the new PASP-based scale inhibitor has high scale inhibition to both CaCO3 and Ca3(PO4)2. When the concentration was increased to 2 mg/L, the inhibition efficiency of the new PASP-based scale inhibitor was 99% for CaCO3, while when the concentration was raised to only 4 mg/L, its inhibition efficiency increased to 100% for Ca3(PO4)2. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the changes of crystal structure for CaCO3 and Ca3(PO4)2 after adding the new PASP-based scale inhibitor. The crystal size of CaCO3 and Ca3(PO4)2 became smaller and the crystal form became amorphous after adding the modified PASPs compared with adding pure PASP. Moreover, the modified PASP showed good biodegradation performance.

Changes in the crystal structure of SnO2 nanoparticles and improved H2S gas-sensing characteristics by Al doping

Pristine and Al-doped SnO2 nanoparticles with different amounts of Al dopant were synthesized using a conventional hydrothermal process. The existing SnO2 exhibited simple interstitial physical bonding (SnO2–Al (1:0.16)) with the Al dopant; however, with an increase in the Al concentration, the bonding changed to substitutional chemical bonding (SnO2–Al (1:0.33)). We found that this crystal structural change is strongly interrelated with surface reactivity; the optimized Al-doped SnO2 nanoparticles-based sensor exhibited a significantly improved response of 17.38 – 20 ppm H2S gas with a response time of 35 s. The enhanced gas response was related to the high surface area of the optimal gas sensor (BET surface area = 78.087 m3/g) as well as the beneficial effects of Al doping. It is highlighted that this simple technique of engineering the bonding characteristics can be widely applied to other semiconducting metal oxides.