chemistry

Photochemical logic gate

Photochemical logic gate is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photochemical logic gate rather than just read about it. In short: A photochemical logic gate is based on the photochemical intersystem crossing and molecular electronic transition between photochemically active molecules, leading to logic gates that can be produced. The OR gate electron–photon transfer chain The OR gate is based on the activation of molecule A, and thus pass electron / photon to molecule C's excited state orbitals (C*).

Key takeaways

Photochemical logic gate belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Photochemical logic gate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Photochemical logic gate from memory before moving on to harder problems.

Reference excerpt

The OR gate electron–photon transfer chain

The OR gate is based on the activation of molecule A, and thus pass electron / photon to molecule C's excited state orbitals (C*). The electron from molecule A inter system crosses to C* via the excited state orbitals of B, eventually utilised as a signal in the C* hνc emission. The 'OR' gate uses two inputs of light (photons) to molecule A in two separate electron transfer chains, both of which are capable of transferring to C* and thus producing the output of an OR gate. Therefore, if either electron transfer chain is activated, molecule C's excitation produces a valid/ output emission.

The 'AND' gate

Excitation A→A* by hνa photon, whereby the promoted electron is passed down to the C* molecular orbital. A second photon applied to the system (hνc2) causes the excitation of the electron in the C* molecular orbital to the C** molecular orbital -analogous pump probe spectroscopy.

Above, the energy level diagram illustrating the principle of pump probe spectroscopy –the excitation of an excited state. The AND gate is produced by the necessity of both A→A* and the C**→C excitations occurring at the same time -input hν and hν, are simultaneously required. To prevent erroneous emissions of light from a single input to the AND gate, it would be necessary to have an electron transfer series with ability accept any electrons (energy) from C* energy level. The electron transfer series would terminate with a low (non-radiative decay) of the energy The alternatives for producing an AND gate, using molecular photphysics, are two. (1) The emission produced by the electron drop from C*→C (hνc) is not a valid output frequency. The emission from the C** (hνc + hνc2, hνc3) molecular orbital is a valid output signal;. to be used in subsequent logic gates -arranged to respond to the C ∗ ∗ → c 2 C {\displaystyle C^{**}{\xrightarrow[{c2}]{}}C} emission. The second input of photon(s) to trigger the rapid conversion of a molecule used to complete the electron transfer chain. A very complex molecule like a protein can be engineered to possess high strain energies, so that in the absence of the second light frequency molecule B is inactive (B). The second photon input triggers B→B' where the forward rate constant is much smaller than the reverse. If such a molecule is used as molecule B, the transfer chain can be switched on and off.

Creating the NOT gate To stop the electron transfer chain completing, producing output signals, the input of a photon, hνc2, is used to produce a 'pump probe spectroscopy' effect by promoting an electron in an electron transfer chain. The fall of the pump probe promoted electron produces an output that is quenched down an electron transfer chain. An alternative is similar to the AND gate alternative; an input causes a change in molecule structure breaking the electron transfer chain by not allowing the smooth energy transfer of electrons.

See also Photochemistry Photochemical reaction Photohydrogen Photocatalysis Photodissociation Photoelectrolysis Photosynthesis Artificial photosynthesis

References

Worked examples

Example 1 — a first encounter with Photochemical logic gate

Start with the simplest possible case. Write down what Photochemical logic gate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photochemical logic gate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photochemical logic gate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photochemical logic gate

In research: Photochemical logic gate appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Photochemical logic gate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Photochemical logic gate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Logic gates, Molecular electronics, Photochemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Photochemical logic gate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Photochemical logic gate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Photochemical logic gate means in your own words.
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Frequently asked questions

What is Photochemical logic gate in simple terms?

A photochemical logic gate is based on the photochemical intersystem crossing and molecular electronic transition between photochemically active molecules, leading to logic gates that can be produced. The OR gate electron–photon transfer chain The OR gate is based on the activation of molecule A, a…

Why does Photochemical logic gate matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photochemical logic gate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photochemical logic gate.