” Remember, great power
brings with it great responsibility .”
Uncle Ben’s Message to Peter Parker in Spiderman Movie.
If we all as youth aware of the essence of the message conveyed Ben’s uncle, certainly the ideals of Indonesia as a country that is advanced, prosperous, and abundant no longer nonsense.
We all know that Indonesia is a very rich country, even the slogan “Indonesia rich country” has become a doctrine since elementary school. The IPS SD lessons state that Indonesia is rich in natural resources (gas and minerals), rich in flora and fauna diversity, rich in demography (the 4th largest in the world), etc.
Even the legendary band Koes Plus also made a song that one of the lyrics is “People say our land is heaven land, Wooden sticks and stones so plants”.
But does the wealth bring prosperity to the Indonesian people?
These assets are of course a very big force, so it should also bring a great responsibility, not to wear.
The responsibility is of course the responsibility to manage the wealth as best as possible in order to improve the lives of the Indonesian people. Manage by giving it added value and manage without destroying nature, 2 things that require high scholarship.
The responsibility of managing the natural resources is a very difficult task, can not be borne by 1 or 2 people only. But that does not mean impossible. For students and youth, these responsibilities can be started by studying seriously and in real work to manage Indonesia’s wealth.
One of Indonesia’s riches to be proud of is Timah.
By 2015, tin reserves in Indonesia are the second largest in the world after China, which is about 800,000 tons . Besides having the largest tin reserves, tin production is also the second largest and PT Timah in 2017 is the world’s third largest company in terms of tin exporters  .
The largest tin producing regions in Indonesia are the islands of Bangka and Belitung. About 90 percent of tin produced by Indonesia comes from the two islands . We also have many who know because the novel and film Laskar Pelangi also has told the potential.
(Left) The price of tin bar is Rp. 260.000 / kg (right) The price of tin nanoparticles (size <150 nm) is Rp. 960,000,000 / kg or 1 billion less 40 million (source: Sigma Aldrich ).
The tin industry is certainly very profitable, because tin is used very widely in the field of electronics (all electronic devices must have tin), metal food packaging, etc. However, did you know that tin is a key ingredient in the manufacture of gas sensors?
Gas sensor works like a nose, the tool can detect various types of gas. But not only does it detect, the gas sensor can also measure how much the gas content is, monitor the type and content of a gas, and can be an input so that other gases such as perfume gas can be sprayed automatically ( discriminate odor ).
The gas sensor was first created by a Japanese inventor named Naoyoshi Taguchi in 1968 . The gas sensor is based on tin (IV) oxide or SnO 2 . Remember, tin has 2 oxidation states ie +2 and +4. In the case of utilization of gas sensor used is tin with +4 oxidation number, therefore the way of writing is Tin (IV) oxide. Tin (IV) oxide is also a n- type semiconductor , meaning it has an electron advantage over a hole.
The simple principle of a gas sensor made from SnO 2 is the change in the resistance value (or conductance, remember the conductance = 1 / resistance) of the sensor surface against the absorbed gas.
There are interesting things in the process of gas sensor discovery. Naoyoshi Taguchi was inspired while reading a newspaper about a propane gas explosion on the Yamanaka lake. After the news of the explosion, Taguchi realized that the presence of gas leak detectors is very important .
The newspaper read Taguchi in 1962, meaning it took 6 years to find a gas sensor that is still in use today. The time is not short. Even Naoyoshi Taguchi also created a company called Figaro Engineering and leading in producing gas sensors to date .
Once the gas sensor patents created by Naoyoshi Taguchi are approved by US Patent 3,631,436 and British ( British Patent 1,257,155), researchers are vying to continue developing gas sensors .
This time researchers have applied various kinds of metal oxides as gas sensors such as Cr 2 O 3 , Mn 2 O 3 , Co 3 O 4 , NiO, CuO, SrO, In 2 O 3 , WO 3 , TiO 2 , V 2 O 3 , Fe 2 O 3 , GeO 2, Nb 2 O 5 , MoO 3 , Ta 2 O 5 , La 2 O 3 , CeO 2 , Nd 2 O 3, ZnO, Fe 2 O 3 , NiO, Cr 2 O 3 , etc. .
But among the various metal oxides, SnO 2 is the star (superstar). In addition to the initial invention of gas sensors using SnO 2 , various studies have also revealed that SnO 2can be used to detect and measure various gases.
Beginning of the invention, the gas sensor made by Taguchi is used to detect leakage of flammable gases such as methane, LPG, etc., as well as undesirable reducing gas such as carbon monoxide (CO) and hydrogen (H 2 ).
However SnO 2 continues to be developed so it can also detect alcohol gases (ethanol) , oxygen , nitrogen oxide (NO 2 ) , hydrogen sulfide (H 2 S) , formaldehyde (HCHO) [11 ], carbon dioxide (CO 2 ) , and does not rule out the possibility of being used as a sensor for various other gases.
Imagine if the SnO 2 sensor is divided into areas such as maps, area 1 can detect methane gas, area 2 can detect carbon monoxide, area 3 can detect carbon dioxide gas, area 4 can detect hydrogen sulphide gas, area 5 can detect oxygen, and so on , then we can create an artificial nose called integrated electronic nose ( Integrated Electronic Nose ) .
Why SnO 2 can be a superstar material in gas sensors?
Some important parameters in the application of a metal oxide as a gas sensor are band gaps , electrical and optical conductivity, material structure, and catalytic activity. SnO 2 excels at these parameters, other than that SnO 2 is also relatively cheap, not easy to react with chemicals (inert), and large surface area.
If interested in deepening SnO2 applications as sensors, the authors recommend a review paper entitled ” SnO 2 : A comprehensive review on structures and gas sensors ” .
Given the availability of tin in Indonesia is the second largest after China, then in addition to the Tin Museum of Indonesia which has been established in Pangkalpinang, tin research center is also considered very necessary. In addition to increasing the selling value of tin, research on tin is very prospective especially on applications as gas sensors.
 US Geological Survey . 2015. Retrieved on March 2, 2018.
 Top Tin Exporters . 2016. Retrieved on March 3, 2018.
 Types of Mining Goods in Indonesia . 2018. Retrieved on March 2, 2018.
 The History of Figato Engineering . 2018. Retrieved on March 3, 2018.
 J. Watson. 1984. The tin oxide gas sensor and its applications. Sensors and Actuators, Volume 5, Issue 1. Pages 29-42.
 Chengxiang Wang, Longwei Yin, Luyuan Zhang, Dong Xiang, and Rui Gao. 2010. Metal Oxide Gas Sensors: Sensitivity and Influencing Factors. Sensors (Basel). 10 (3): 2088-2106.
 Zhan, S., Li, D., Liang, S., Chen, X., Li, X., 2013. A Novel Flexible Room Temperature Ethanol Gas Sensor Based on SnO2 Doped Poly-Diallyldimethylammonium Chloride. Sensors 13, 4378-4389.
 Kolmakov, A., Zhang, Y., Cheng, G., Moskovits, M., 2003. Detection of CO and O2 Using Tin Oxide Nanowire Sensors. Advanced Materials 15, 997-1000.
 Anjali Sharma, Monika Tomar, Vinay Gupta. 2011. SnO2 thin film sensor with enhanced response for NO2 gas at lower temperatures. Sensors and Actuators B: Chemical, Volume 156, Issue 2, Pages 743-752.
 G Sarala Devi, S Manorama, VJ Rao, 1995. High sensitivity and selectivity of SnO2 sensors to H2S at around 100 ° C,
Sensors and Actuators B: Chemical. Volume 28, Issue 1. Pages 31-37.
 Wei Zhang, XiaoLi Cheng, Xianfa Zhang, Yingming Xu, Shan Gao, Hui Zhao, Lihua Huo. 2017. High selectivity to ppb-level HCHO sensor based on mesoporous tubular SnO2 at low temperature, Sensors and Actuators B: Chemical,
Volume 247, Pages 664-672.
 Ulrich Hoefer, Gerd Kühner, Werner Schweizer, Gerd Sulz, Klaus Steiner. 1994. CO and CO2 thin-film SnO2 gas sensors on Si substrates, Sensors and Actuators B: Chemical, Volume 22, Issue 2. Pages 115-119.
 Chiu, S.-W., & Tang, K.-T. 2013. Towards a Chemiresistive Sensor-Integrated Electronic Nose: A Review. Sensors (Basel, Switzerland) , 13 (10), 14214-14247.
 Soumen Das, V. Jayaraman. 2014. SnO2: A comprehensive review on structures and gas sensors. Progress in Materials Science. Volume 66, Pages 112-255.
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